{
 "instance": {
  "a10k2019.htm exhibit99110k2019.htm": {
   "axisCustom": 0,
   "axisStandard": 35,
   "contextCount": 914,
   "dts": {
    "calculationLink": {
     "local": [
      "sum-20191228_cal.xml"
     ]
    },
    "definitionLink": {
     "local": [
      "us-gaap-eedm-def-2019-01-31.xml",
      "srt-eedm1-def-2019-01-31.xml",
      "sum-20191228_def.xml"
     ]
    },
    "inline": {
     "local": [
      "a10k2019.htm",
      "exhibit99110k2019.htm"
     ]
    },
    "labelLink": {
     "local": [
      "sum-20191228_lab.xml",
      "dei-doc-2019-01-31.xml",
      "srt-doc-2019-01-31.xml",
      "us-gaap-doc-2019-01-31.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "sum-20191228_pre.xml"
     ]
    },
    "referenceLink": {
     "local": [
      "dei-ref-2019-01-31.xml",
      "us-gaap-ref-2019-01-31.xml",
      "srt-ref-2019-01-31.xml"
     ]
    },
    "schema": {
     "local": [
      "sum-20191228.xsd",
      "srt-types-2019-01-31.xsd",
      "xbrl-instance-2003-12-31.xsd",
      "xbrl-linkbase-2003-12-31.xsd",
      "xl-2003-12-31.xsd",
      "xlink-2003-12-31.xsd",
      "numeric-2009-12-16.xsd",
      "nonNumeric-2009-12-16.xsd",
      "ref-2006-02-27.xsd",
      "srt-2019-01-31.xsd",
      "xbrldt-2005.xsd",
      "us-gaap-2019-01-31.xsd",
      "us-roles-2019-01-31.xsd",
      "srt-roles-2019-01-31.xsd",
      "country-2017-01-31.xsd",
      "us-types-2019-01-31.xsd",
      "factExplanatory-2009-12-16.xsd",
      "negated-2009-12-16.xsd",
      "net-2009-12-16.xsd",
      "currency-2019-01-31.xsd",
      "dei-2019-01-31.xsd",
      "exch-2019-01-31.xsd",
      "invest-2013-01-31.xsd",
      "naics-2017-01-31.xsd",
      "sic-2011-01-31.xsd",
      "stpr-2018-01-31.xsd",
      "deprecated-2009-12-16.xsd",
      "reference-2009-12-16.xsd",
      "us-parts-codification-2019-01-31.xsd"
     ]
    }
   },
   "elementCount": 929,
   "entityCount": 1,
   "hidden": {
    "http://fasb.org/us-gaap/2019-01-31": 131,
    "http://xbrl.sec.gov/dei/2019-01-31": 10,
    "total": 141
   },
   "keyCustom": 96,
   "keyStandard": 536,
   "memberCustom": 66,
   "memberStandard": 64,
   "nsprefix": "sum",
   "nsuri": "http://www.summitmaterials.com/20191228",
   "report": {
    "R1": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:DocumentType",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "document",
     "isDefault": "true",
     "longName": "0001000 - Document - Cover",
     "role": "http://www.summitmaterials.com/role/Cover",
     "shortName": "Cover",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:DocumentType",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R10": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:BusinessCombinationDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2102100 - Disclosure - Acquisitions",
     "role": "http://www.summitmaterials.com/role/Acquisitions",
     "shortName": "Acquisitions",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:BusinessCombinationDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R100": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:RoyaltyAgreementFutureMinimumPaymentsDueCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2417404 - Disclosure - Leases - Schedule of Minimum Contractual Agreements Under Royalty Agreements (Details)",
     "role": "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
     "shortName": "Leases - Schedule of Minimum Contractual Agreements Under Royalty Agreements (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:RoyaltyAgreementFutureMinimumPaymentsDueCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R101": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_DebtInstrumentAxis_sum_SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyTwoMember_us-gaap_DerivativeInstrumentRiskAxis_us-gaap_InterestRateContractMember_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_us-gaap_CashFlowHedgingMember",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeAmountOfHedgedItem",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2418402 - Disclosure - Fair Value of Financial Instruments - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
     "shortName": "Fair Value of Financial Instruments - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_DebtInstrumentAxis_sum_SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyTwoMember_us-gaap_DerivativeInstrumentRiskAxis_us-gaap_InterestRateContractMember_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_us-gaap_CashFlowHedgingMember",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeAmountOfHedgedItem",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R102": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Member",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:BusinessCombinationContingentConsiderationLiabilityCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2418403 - Disclosure - Fair Value of Financial Instruments - Fair Value Measurements (Details)",
     "role": "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
     "shortName": "Fair Value of Financial Instruments - Fair Value Measurements (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Member",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:BusinessCombinationContingentConsiderationLiabilityCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R103": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LongTermDebtCurrent",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2418404 - Disclosure - Fair Value of Financial Instruments - Carrying Value and Fair Value of Financial Instruments (Details)",
     "role": "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
     "shortName": "Fair Value of Financial Instruments - Carrying Value and Fair Value of Financial Instruments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel2Member",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:LongTermDebtCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R104": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:NumberOfOperatingSegments",
      "reportCount": 1,
      "unitRef": "segment",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2419402 - Disclosure - Segment Information - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
     "shortName": "Segment Information - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R105": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4QTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2419403 - Disclosure - Segment Information - Financial Data (Details)",
     "role": "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
     "shortName": "Segment Information - Financial Data (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfSegmentReportingInformationBySegmentTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DepreciationDepletionAndAmortization",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R106": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2421402 - Disclosure - Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Balance Sheets (Details)",
     "role": "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
     "shortName": "Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Balance Sheets (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "srt:ScheduleOfCondensedBalanceSheetTableTextBlock",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FI2019Q4_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": "-3",
      "lang": null,
      "name": "sum:IntercompanyReceivablesAssetsCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R107": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4QTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2421403 - Disclosure - Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Operations and Comprehensive Income (Details)",
     "role": "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
     "shortName": "Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Operations and Comprehensive Income (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "srt:ScheduleOfCondensedIncomeStatementTableTextBlock",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": "-3",
      "lang": null,
      "name": "sum:GeneralAdministrativeAndOtherExpenses",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R108": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:NetCashProvidedByUsedInOperatingActivities",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2421404 - Disclosure - Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Cash Flows (Details)",
     "role": "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
     "shortName": "Senior Notes' Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Cash Flows (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "srt:ScheduleOfCondensedCashFlowStatementTableTextBlock",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": "-3",
      "lang": null,
      "name": "sum:ProceedsFromRepaymentsOfPartnershipContribution",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R109": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4QTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429402 - Disclosure - Supplementary Data (Unaudited) - Supplemental Financial Information (Detail)",
     "role": "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail",
     "shortName": "Supplementary Data (Unaudited) - Supplemental Financial Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R11": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:GoodwillDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2103100 - Disclosure - Goodwill",
     "role": "http://www.summitmaterials.com/role/Goodwill",
     "shortName": "Goodwill",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:GoodwillDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R12": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2104100 - Disclosure - Revenue Recognition",
     "role": "http://www.summitmaterials.com/role/RevenueRecognition",
     "shortName": "Revenue Recognition",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R13": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:InventoryDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2105100 - Disclosure - Inventories",
     "role": "http://www.summitmaterials.com/role/Inventories",
     "shortName": "Inventories",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:InventoryDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R14": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentAndIntangibleAssetsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2106100 - Disclosure - Property, Plant and Equipment, net and Intangibles, net",
     "role": "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
     "shortName": "Property, Plant and Equipment, net and Intangibles, net",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentAndIntangibleAssetsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R15": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2107100 - Disclosure - Accrued Expenses",
     "role": "http://www.summitmaterials.com/role/AccruedExpenses",
     "shortName": "Accrued Expenses",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R16": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DebtDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2108100 - Disclosure - Debt",
     "role": "http://www.summitmaterials.com/role/Debt",
     "shortName": "Debt",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DebtDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R17": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:IncomeTaxDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2109100 - Disclosure - Income Taxes",
     "role": "http://www.summitmaterials.com/role/IncomeTaxes",
     "shortName": "Income Taxes",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:IncomeTaxDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R18": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2110100 - Disclosure - Earnings Per Share",
     "role": "http://www.summitmaterials.com/role/EarningsPerShare",
     "shortName": "Earnings Per Share",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R19": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2111100 - Disclosure - Stockholder's Equity/Members' Interest",
     "role": "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
     "shortName": "Stockholder's Equity/Members' Interest",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R2": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1001000 - Statement - Consolidated Balance Sheets",
     "role": "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
     "shortName": "Consolidated Balance Sheets",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DeferredIncomeTaxAssetsNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R20": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CashFlowSupplementalDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2112100 - Disclosure - Supplemental Cash Flow Information",
     "role": "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
     "shortName": "Supplemental Cash Flow Information",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CashFlowSupplementalDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R21": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ShareholdersEquityAndShareBasedPaymentsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2113100 - Disclosure - Stock-Based Compensation",
     "role": "http://www.summitmaterials.com/role/StockBasedCompensation",
     "shortName": "Stock-Based Compensation",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ShareholdersEquityAndShareBasedPaymentsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R22": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CompensationAndEmployeeBenefitPlansTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2114100 - Disclosure - Employee Benefit Plans",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
     "shortName": "Employee Benefit Plans",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CompensationAndEmployeeBenefitPlansTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R23": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AssetRetirementObligationDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2115100 - Disclosure - Accrued Mining and Landfill Reclamation",
     "role": "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
     "shortName": "Accrued Mining and Landfill Reclamation",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AssetRetirementObligationDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R24": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2116100 - Disclosure - Commitments and Contingencies",
     "role": "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
     "shortName": "Commitments and Contingencies",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R25": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LesseeOperatingLeasesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2117100 - Disclosure - Leases",
     "role": "http://www.summitmaterials.com/role/Leases",
     "shortName": "Leases",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LesseeOperatingLeasesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R26": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2118100 - Disclosure - Fair Value of Financial Instruments",
     "role": "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
     "shortName": "Fair Value of Financial Instruments",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R27": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2119100 - Disclosure - Segment Information",
     "role": "http://www.summitmaterials.com/role/SegmentInformation",
     "shortName": "Segment Information",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R28": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "srt:CondensedFinancialStatementsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2121100 - Disclosure - Senior Notes' Guarantor and Non-Guarantor Financial Information",
     "role": "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
     "shortName": "Senior Notes' Guarantor and Non-Guarantor Financial Information",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "srt:CondensedFinancialStatementsTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R29": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:QuarterlyFinancialInformationTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2129100 - Disclosure - Supplementary Data (Unaudited)",
     "role": "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
     "shortName": "Supplementary Data (Unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:QuarterlyFinancialInformationTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R3": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CommonStockSharesAuthorized",
      "reportCount": 1,
      "unitRef": "shares",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1001501 - Statement - Consolidated Balance Sheets (Parenthetical)",
     "role": "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
     "shortName": "Consolidated Balance Sheets (Parenthetical)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": null
    },
    "R30": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ConsolidationPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2201201 - Disclosure - Summary of Organization and Significant Accounting Policies (Policies)",
     "role": "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies",
     "shortName": "Summary of Organization and Significant Accounting Policies (Policies)",
     "subGroupType": "policies",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ConsolidationPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R31": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:ScheduleOfBusinessAcquisitionsNumberOfAcquisitionsByRegionTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2302301 - Disclosure - Acquisitions (Tables)",
     "role": "http://www.summitmaterials.com/role/AcquisitionsTables",
     "shortName": "Acquisitions (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:ScheduleOfBusinessAcquisitionsNumberOfAcquisitionsByRegionTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R32": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfGoodwillTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2303301 - Disclosure - Goodwill (Tables)",
     "role": "http://www.summitmaterials.com/role/GoodwillTables",
     "shortName": "Goodwill (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfGoodwillTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R33": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisaggregationOfRevenueTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2304301 - Disclosure - Revenue Recognition (Tables)",
     "role": "http://www.summitmaterials.com/role/RevenueRecognitionTables",
     "shortName": "Revenue Recognition (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisaggregationOfRevenueTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R34": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfInventoryCurrentTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2305301 - Disclosure - Inventories (Tables)",
     "role": "http://www.summitmaterials.com/role/InventoriesTables",
     "shortName": "Inventories (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfInventoryCurrentTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R35": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2306301 - Disclosure - Property, Plant and Equipment, net and Intangibles, net (Tables)",
     "role": "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables",
     "shortName": "Property, Plant and Equipment, net and Intangibles, net (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R36": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2307301 - Disclosure - Accrued Expenses (Tables)",
     "role": "http://www.summitmaterials.com/role/AccruedExpensesTables",
     "shortName": "Accrued Expenses (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R37": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfDebtTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2308301 - Disclosure - Debt (Tables)",
     "role": "http://www.summitmaterials.com/role/DebtTables",
     "shortName": "Debt (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfDebtTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R38": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2309301 - Disclosure - Income Taxes (Tables)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesTables",
     "shortName": "Income Taxes (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R39": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2310301 - Disclosure - Earnings Per Share (Tables)",
     "role": "http://www.summitmaterials.com/role/EarningsPerShareTables",
     "shortName": "Earnings Per Share (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R4": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:DisaggregationOfRevenueTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1002000 - Statement - Consolidated Statements of Operations",
     "role": "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
     "shortName": "Consolidated Statements of Operations",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:GeneralAndAdministrativeExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R40": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2311301 - Disclosure - Stockholder's Equity/Members' Interest (Tables)",
     "role": "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
     "shortName": "Stockholder's Equity/Members' Interest (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R41": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2312301 - Disclosure - Supplemental Cash Flow Information (Tables)",
     "role": "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables",
     "shortName": "Supplemental Cash Flow Information (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R42": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2313301 - Disclosure - Stock-Based Compensation (Tables)",
     "role": "http://www.summitmaterials.com/role/StockBasedCompensationTables",
     "shortName": "Stock-Based Compensation (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R43": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNetFundedStatusTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2314301 - Disclosure - Employee Benefit Plans (Tables)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
     "shortName": "Employee Benefit Plans (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNetFundedStatusTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R44": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfChangeInAssetRetirementObligationTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2315301 - Disclosure - Accrued Mining and Landfill Reclamation (Tables)",
     "role": "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables",
     "shortName": "Accrued Mining and Landfill Reclamation (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfChangeInAssetRetirementObligationTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R45": {
     "firstAnchor": {
      "ancestors": [
       "us-gaap:LesseeOperatingLeaseLiabilityMaturityTableTextBlock",
       "us-gaap:FinanceLeaseLiabilityMaturityTableTextBlock",
       "sum:AssetsAndLiabilitiesLesseeTableTextBlock",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LeaseCostTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2317301 - Disclosure - Leases (Tables)",
     "role": "http://www.summitmaterials.com/role/LeasesTables",
     "shortName": "Leases (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "us-gaap:LesseeOperatingLeaseLiabilityMaturityTableTextBlock",
       "us-gaap:FinanceLeaseLiabilityMaturityTableTextBlock",
       "sum:AssetsAndLiabilitiesLesseeTableTextBlock",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LeaseCostTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R46": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2318301 - Disclosure - Fair Value (Tables)",
     "role": "http://www.summitmaterials.com/role/FairValueTables",
     "shortName": "Fair Value (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R47": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSegmentReportingInformationBySegmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2319301 - Disclosure - Segment Information (Tables)",
     "role": "http://www.summitmaterials.com/role/SegmentInformationTables",
     "shortName": "Segment Information (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSegmentReportingInformationBySegmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R48": {
     "firstAnchor": {
      "ancestors": [
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "srt:ScheduleOfCondensedBalanceSheetTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2321301 - Disclosure - Senior Notes' Guarantor and Non-Guarantor Financial Information (Tables)",
     "role": "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables",
     "shortName": "Senior Notes' Guarantor and Non-Guarantor Financial Information (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "srt:ScheduleOfCondensedBalanceSheetTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R49": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2329301 - Disclosure - Supplementary Data (Unaudited) (Tables)",
     "role": "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables",
     "shortName": "Supplementary Data (Unaudited) (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R5": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1003000 - Statement - Consolidated Statements of Comprehensive Income",
     "role": "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
     "shortName": "Consolidated Statements of Comprehensive Income",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R50": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:NumberOfOperatingSegments",
      "reportCount": 1,
      "unitRef": "segment",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2401402 - Disclosure - Summary of Organization and Significant Accounting Policies - General Information and Equity Offerings (Details)",
     "role": "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails",
     "shortName": "Summary of Organization and Significant Accounting Policies - General Information and Equity Offerings (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "us-gaap:ConcentrationRiskCreditRisk",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:NumberOfStatesInWhichEntityOperates",
      "reportCount": 1,
      "unique": true,
      "unitRef": "state",
      "xsiNil": "false"
     }
    },
    "R51": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseRightOfUseAsset",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2401403 - Disclosure - Summary of Organization and Significant Accounting Policies - New Accounting Standards (Details)",
     "role": "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails",
     "shortName": "Summary of Organization and Significant Accounting Policies - New Accounting Standards (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "us-gaap:NewAccountingPronouncementsPolicyPolicyTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "I2019Q1Dec30_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_us-gaap_AccountingStandardsUpdate201602Member",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:OperatingLeaseRightOfUseAsset",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R52": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_StatementBusinessSegmentsAxis_sum_WestMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:NumberOfBusinessesAcquired",
      "reportCount": 1,
      "unique": true,
      "unitRef": "acquistiion",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2402402 - Disclosure - Acquisitions - Acquisitions by Region (Details)",
     "role": "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
     "shortName": "Acquisitions - Acquisitions by Region (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_StatementBusinessSegmentsAxis_sum_WestMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:NumberOfBusinessesAcquired",
      "reportCount": 1,
      "unique": true,
      "unitRef": "acquistiion",
      "xsiNil": "false"
     }
    },
    "R53": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:Goodwill",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2402403 - Disclosure - Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail)",
     "role": "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail",
     "shortName": "Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_BusinessAcquisitionAxis_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R54": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2018Q4YTD_srt_RangeAxis_srt_MinimumMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:DeferredConsiderationPaymentTerm",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2402404 - Disclosure - Acquisitions - Contractual Obligations (Details)",
     "role": "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
     "shortName": "Acquisitions - Contractual Obligations (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2018Q4YTD_srt_RangeAxis_srt_MinimumMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:DeferredConsiderationPaymentTerm",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R55": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "sum:NumberOfReportingUnitsBeingSubjectedToGoodwillImpairmentTest",
      "reportCount": 1,
      "unique": true,
      "unitRef": "reporting_unit",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2403402 - Disclosure - Goodwill - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
     "shortName": "Goodwill - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "sum:NumberOfReportingUnitsBeingSubjectedToGoodwillImpairmentTest",
      "reportCount": 1,
      "unique": true,
      "unitRef": "reporting_unit",
      "xsiNil": "false"
     }
    },
    "R56": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:Goodwill",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2403403 - Disclosure - Goodwill - Summary of Goodwill by Reportable Segments (Details)",
     "role": "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
     "shortName": "Goodwill - Summary of Goodwill by Reportable Segments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfGoodwillTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:GoodwillAcquiredDuringPeriod",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R57": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4QTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2404402 - Disclosure - Revenue Recognition - By Product (Details)",
     "role": "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
     "shortName": "Revenue Recognition - By Product (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:DisaggregationOfRevenueTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_srt_ProductOrServiceAxis_sum_AggregatesMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R58": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ContractWithCustomerAssetAndLiabilityTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ContractWithCustomerAssetNetCurrent",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2404403 - Disclosure - Revenue Recognition - Contract Assets and Liabilities (Details)",
     "role": "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
     "shortName": "Revenue Recognition - Contract Assets and Liabilities (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ContractWithCustomerAssetAndLiabilityTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "sum:ContractWithCustomerAssetIncreaseDecreaseForOtherActivity",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R59": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:TradeAccountsReceivable",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2404404 - Disclosure - Revenue Recognition - Summary of Accounts Receivable, Net (Details)",
     "role": "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
     "shortName": "Revenue Recognition - Summary of Accounts Receivable, Net (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:TradeAccountsReceivable",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R6": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1005000 - Statement - Consolidated Statements of Cash Flows",
     "role": "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
     "shortName": "Consolidated Statements of Cash Flows",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "sum:DepreciationDepletionAmortizationAndAccretionOnAssetRetirementObligation",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R60": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InventoryOreStockpilesOnLeachPads",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2405402 - Disclosure - Inventories - Components of Inventories (Details)",
     "role": "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
     "shortName": "Inventories - Components of Inventories (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InventoryOreStockpilesOnLeachPads",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R61": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:PropertyPlantAndEquipmentGross",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2406402 - Disclosure - Property, Plant and Equipment, net and Intangibles, net - Components of Property, Plant and Equipment (Details)",
     "role": "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
     "shortName": "Property, Plant and Equipment, net and Intangibles, net - Components of Property, Plant and Equipment (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:PropertyPlantAndEquipmentGross",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R62": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:FinanceLeaseRightOfUseAssetGross",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2406403 - Disclosure - Property, Plant and Equipment, net and Intangibles, net - Capital and Finance Leases (Details)",
     "role": "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
     "shortName": "Property, Plant and Equipment, net and Intangibles, net - Capital and Finance Leases (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_IncomeStatementLocationAxis_us-gaap_GeneralAndAdministrativeExpenseMember",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:GainLossOnSaleOfPropertyPlantEquipment",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R63": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:IntangibleAssetsGrossExcludingGoodwill",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2406404 - Disclosure - Property, Plant and Equipment, net and Intangibles, net - Intangible Assets (Details)",
     "role": "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails",
     "shortName": "Property, Plant and Equipment, net and Intangibles, net - Intangible Assets (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:IntangibleAssetsGrossExcludingGoodwill",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R64": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestPayableCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2407402 - Disclosure - Accrued Expenses - Components of Accrued Expenses (Details)",
     "role": "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
     "shortName": "Accrued Expenses - Components of Accrued Expenses (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestPayableCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R65": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LongTermDebt",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408402 - Disclosure - Debt - Schedule of Debt (Details)",
     "role": "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
     "shortName": "Debt - Schedule of Debt (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:LongTermDebtNoncurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R66": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfMaturitiesOfLongTermDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408403 - Disclosure - Debt - Schedule of Contractual Payments of Long-Term Debt (Details)",
     "role": "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
     "shortName": "Debt - Schedule of Contractual Payments of Long-Term Debt (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfMaturitiesOfLongTermDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R67": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LongTermDebt",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408404 - Disclosure - Debt - Senior Notes (Details)",
     "role": "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
     "shortName": "Debt - Senior Notes (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "I2015Q4Nov30_us-gaap_DebtInstrumentAxis_sum_TenPointZeroFivePercentageSeniorNotesDueTwentyTwentyMember",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:DebtInstrumentRepurchasedFaceAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R68": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfMaturitiesOfLongTermDebtTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DebtInstrumentCarryingAmount",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408405 - Disclosure - Debt - Senior Secured Credit Facilities (Details)",
     "role": "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
     "shortName": "Debt - Senior Secured Credit Facilities (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "FI2019Q4_dei_LegalEntityAxis_sum_SummitMaterialsLlcMember_us-gaap_DebtInstrumentAxis_sum_SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyFourMember",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:DebtInstrumentFaceAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R69": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DeferredFinanceCostsNet",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408406 - Disclosure - Debt - Summary of Activity for Deferred Financing Fees (Details)",
     "role": "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails",
     "shortName": "Debt - Summary of Activity for Deferred Financing Fees (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2017Q4",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DeferredFinanceCostsNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R7": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2016Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1006000 - Statement - Consolidated Statements of Changes in Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest",
     "role": "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
     "shortName": "Consolidated Statements of Changes in Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2016Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R70": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "I2015Q1Jan15_us-gaap_DebtInstrumentAxis_sum_CanadianSubsidiaryCreditAgreementOperatingActivitiesMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity",
      "reportCount": 1,
      "unique": true,
      "unitRef": "cad",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408407 - Disclosure - Debt - Other Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
     "shortName": "Debt - Other Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "I2015Q1Jan15_us-gaap_DebtInstrumentAxis_sum_CanadianSubsidiaryCreditAgreementOperatingActivitiesMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity",
      "reportCount": 1,
      "unique": true,
      "unitRef": "cad",
      "xsiNil": "false"
     }
    },
    "R71": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CurrentIncomeTaxExpenseBenefit",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409402 - Disclosure - Income Taxes - Components of Income Tax Benefit (Detail)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
     "shortName": "Income Taxes - Components of Income Tax Benefit (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CurrentIncomeTaxExpenseBenefit",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R72": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409403 - Disclosure - Income Taxes - Schedule of Income Tax Benefit (Expense) (Details)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails",
     "shortName": "Income Taxes - Schedule of Income Tax Benefit (Expense) (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R73": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:DeferredTaxAssetsIntangibleAssetsExcludingGoodwill",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409404 - Disclosure - Income Taxes - Components of Net Deferred Income Tax Assets and Liabilities (Detail)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
     "shortName": "Income Taxes - Components of Net Deferred Income Tax Assets and Liabilities (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:DeferredTaxAssetsIntangibleAssetsExcludingGoodwill",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R74": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "sum:EffectiveIncomeTaxRateReconciliationUncertainTaxPositions",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409405 - Disclosure - Income Taxes - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
     "shortName": "Income Taxes - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-5",
      "lang": null,
      "name": "sum:DeferredTaxAssetsSubjectToTaxReceivableAgreement",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R75": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:UnrecognizedTaxBenefits",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409406 - Disclosure - Income Taxes - Unrecognized Tax Benefits (Details)",
     "role": "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails",
     "shortName": "Income Taxes - Unrecognized Tax Benefits (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R76": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DeferredTaxAssetsValuationAllowance",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2409407 - Disclosure - Incomes Taxes - Deferred Tax Asset Valuation Allowance (Details)",
     "role": "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails",
     "shortName": "Incomes Taxes - Deferred Tax Asset Valuation Allowance (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:SummaryOfValuationAllowanceTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "sum:ValuationAllowanceDeferredTaxAssetIncreaseDecreaseForExchangeOfLPUnits",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R77": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfQuarterlyFinancialInformationTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4QTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2410402 - Disclosure - Earnings Per Share - Schedule of Basic to Diluted Income Per Share (Details)",
     "role": "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
     "shortName": "Earnings Per Share - Schedule of Basic to Diluted Income Per Share (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:NetIncomeLossAttributableToParentDiluted",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R78": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CommonStockSharesAuthorized",
      "reportCount": 1,
      "unitRef": "shares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2411402 - Disclosure - Stockholders' Equity/Members' Interest - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails",
     "shortName": "Stockholders' Equity/Members' Interest - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "exhibit99110k2019.htm",
      "contextRef": "D2017Q1Jan10-Jan10_us-gaap_StatementClassOfStockAxis_us-gaap_CommonClassAMember_us-gaap_SubsidiarySaleOfStockAxis_sum_FollowOnPublicOfferingMember",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:ProceedsFromIssuanceOfCommonStock",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R79": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised",
      "reportCount": 1,
      "unitRef": "shares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2411403 - Disclosure - Stockholders' Equity/Members' Interest - Change in Ownership (Details)",
     "role": "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
     "shortName": "Stockholders' Equity/Members' Interest - Change in Ownership (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_dei_LegalEntityAxis_sum_SummitMaterialsIncorporatedAndSummitHoldingsLPMember",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:StockIssuedDuringPeriodSharesConversionOfUnits",
      "reportCount": 1,
      "unique": true,
      "unitRef": "shares",
      "xsiNil": "false"
     }
    },
    "R8": {
     "firstAnchor": null,
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1006001 - Statement - Consolidated Statements of Changes in Redeemable Noncontrolling Interest and Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest (Parenthetical)",
     "role": "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInRedeemableNoncontrollingInterestAndStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterestParenthetical",
     "shortName": "Consolidated Statements of Changes in Redeemable Noncontrolling Interest and Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest (Parenthetical)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": null
    },
    "R80": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2411404 - Disclosure - Stockholders' Equity/Members' Interest - Accumulated Other Comprehensive Income (Loss) (Details)",
     "role": "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails",
     "shortName": "Stockholders' Equity/Members' Interest - Accumulated Other Comprehensive Income (Loss) (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R81": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestPaidNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2412402 - Disclosure - Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details)",
     "role": "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
     "shortName": "Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestPaidNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R82": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:AllocatedShareBasedCompensationExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2413402 - Disclosure - Stock-Based Compensation - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
     "shortName": "Stock-Based Compensation - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:AllocatedShareBasedCompensationExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R83": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised",
      "reportCount": 1,
      "unitRef": "shares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2413403 - Disclosure - Stock-Based Compensation - Summary of Award Activity (Details)",
     "role": "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
     "shortName": "Stock-Based Compensation - Summary of Award Activity (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_AwardTypeAxis_us-gaap_EmployeeStockOptionMember",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod",
      "reportCount": 1,
      "unique": true,
      "unitRef": "shares",
      "xsiNil": "false"
     }
    },
    "R84": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2017Q4YTD_us-gaap_AwardTypeAxis_us-gaap_EmployeeStockOptionMember",
      "decimals": "2",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2413404 - Disclosure - Stock-Based Compensation - Weighted Average Assumptions Used to Estimate the Fair Value of Grants (Details)",
     "role": "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
     "shortName": "Stock-Based Compensation - Weighted Average Assumptions Used to Estimate the Fair Value of Grants (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2017Q4YTD_us-gaap_AwardTypeAxis_us-gaap_EmployeeStockOptionMember",
      "decimals": "2",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     }
    },
    "R85": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedContributionPlanCostRecognized",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414402 - Disclosure - Employee Benefit Plans - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
     "shortName": "Employee Benefit Plans - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedContributionPlanCostRecognized",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R86": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanFairValueOfPlanAssets",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414403 - Disclosure - Employee Benefit Plans - Obligations and Funded Status (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
     "shortName": "Employee Benefit Plans - Obligations and Funded Status (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanActuarialGainLoss",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R87": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAmountsRecognizedInOtherComprehensiveIncomeLossTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414404 - Disclosure - Employee Benefit Plans - Amounts Recognized in Other Comprehensive (Gain) Loss (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
     "shortName": "Employee Benefit Plans - Amounts Recognized in Other Comprehensive (Gain) Loss (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAmountsRecognizedInOtherComprehensiveIncomeLossTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R88": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfNetBenefitCostsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanServiceCost",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414405 - Disclosure - Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
     "shortName": "Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfNetBenefitCostsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R89": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "4",
      "first": true,
      "lang": null,
      "name": "sum:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationsExpectedLongTermReturnOnAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414406 - Disclosure - Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Benefit Obligations (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
     "shortName": "Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Benefit Obligations (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "4",
      "first": true,
      "lang": null,
      "name": "sum:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationsExpectedLongTermReturnOnAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     }
    },
    "R9": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2101100 - Disclosure - Summary of Organization and Significant Accounting Policies",
     "role": "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
     "shortName": "Summary of Organization and Significant Accounting Policies",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R90": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "4",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414407 - Disclosure - Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
     "shortName": "Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "4",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "number",
      "xsiNil": "false"
     }
    },
    "R91": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414408 - Disclosure - Employee Benefit Plans - Effects of One Percentage-Point Change in Assumed Health Care Cost Trend Rates (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
     "shortName": "Employee Benefit Plans - Effects of One Percentage-Point Change in Assumed Health Care Cost Trend Rates (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R92": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAllocationOfPlanAssetsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanFairValueOfPlanAssets",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414409 - Disclosure - Employee Benefit Plans - Fair Value of Company's Pension Plans' Assets (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
     "shortName": "Employee Benefit Plans - Fair Value of Company's Pension Plans' Assets (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfAllocationOfPlanAssetsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_sum_IntermediateGovernmentSecuritiesMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanFairValueOfPlanAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R93": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfExpectedBenefitPaymentsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414410 - Disclosure - Employee Benefit Plans - Estimated Benefit Payments (Detail)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
     "shortName": "Employee Benefit Plans - Estimated Benefit Payments (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfExpectedBenefitPaymentsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R94": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfMultiemployerPlansTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:MultiemployerPlansPlanContributions1",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414411 - Disclosure - Employee Benefit Plans - Multiemployer Plans (Details)",
     "role": "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails",
     "shortName": "Employee Benefit Plans - Multiemployer Plans (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "us-gaap:ScheduleOfMultiemployerPlansTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:MultiemployerPlansPlanContributions1",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R95": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "sum:AssetRetirementObligationAnticipatedCosts",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2415402 - Disclosure - Accrued Mining and Landfill Reclamation - Narrative (Detail)",
     "role": "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
     "shortName": "Accrued Mining and Landfill Reclamation - Narrative (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2019Q4",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "sum:AssetRetirementObligationAnticipatedCosts",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R96": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AssetRetirementObligation",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2415403 - Disclosure - Accrued Mining and Landfill Reclamation - Activity for Asset Retirement Obligations (Details)",
     "role": "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
     "shortName": "Accrued Mining and Landfill Reclamation - Activity for Asset Retirement Obligations (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "lang": null,
      "name": "sum:AssetRetirementObligationLiabilitiesAcquired",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R97": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:PurchaseCommitmentTerms",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2416401 - Disclosure - Commitments and Contingencies - Narrative (Details)",
     "role": "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails",
     "shortName": "Commitments and Contingencies - Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "sum:PurchaseCommitmentTerms",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R98": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2417402 - Disclosure - Leases - Operating and Finance Leases (Details)",
     "role": "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
     "shortName": "Leases - Operating and Finance Leases (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R99": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:RoyaltyExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2417403 - Disclosure - Leases - Narrative (Detail)",
     "role": "http://www.summitmaterials.com/role/LeasesNarrativeDetail",
     "shortName": "Leases - Narrative (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "a10k2019.htm",
      "contextRef": "FD2019Q4YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:RoyaltyExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    }
   },
   "segmentCount": 134,
   "tag": {
    "dei_AmendmentFlag": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.",
        "label": "Amendment Flag",
        "terseLabel": "Amendment Flag"
       }
      }
     },
     "localname": "AmendmentFlag",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_CityAreaCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Area code of city",
        "label": "City Area Code",
        "terseLabel": "City Area Code"
       }
      }
     },
     "localname": "CityAreaCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_CoverAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cover page.",
        "label": "Cover page."
       }
      }
     },
     "localname": "CoverAbstract",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "dei_CurrentFiscalYearEndDate": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "End date of current fiscal year in the format --MM-DD.",
        "label": "Current Fiscal Year End Date",
        "terseLabel": "Current Fiscal Year End Date"
       }
      }
     },
     "localname": "CurrentFiscalYearEndDate",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "gMonthDayItemType"
    },
    "dei_DocumentAnnualReport": {
     "auth_ref": [
      "r535"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true only for a form used as an annual report.",
        "label": "Document Annual Report",
        "terseLabel": "Document Annual Report"
       }
      }
     },
     "localname": "DocumentAnnualReport",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_DocumentFiscalPeriodFocus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fiscal period values are FY, Q1, Q2, and Q3.  1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY.",
        "label": "Document Fiscal Period Focus",
        "terseLabel": "Document Fiscal Period Focus"
       }
      }
     },
     "localname": "DocumentFiscalPeriodFocus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "fiscalPeriodItemType"
    },
    "dei_DocumentFiscalYearFocus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.",
        "label": "Document Fiscal Year Focus",
        "terseLabel": "Document Fiscal Year Focus"
       }
      }
     },
     "localname": "DocumentFiscalYearFocus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "gYearItemType"
    },
    "dei_DocumentInformationLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Document Information [Line Items]",
        "terseLabel": "Document Information [Line Items]"
       }
      }
     },
     "localname": "DocumentInformationLineItems",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "stringItemType"
    },
    "dei_DocumentInformationTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Container to support the formal attachment of each official or unofficial, public or private document as part of a submission package.",
        "label": "Document Information [Table]",
        "terseLabel": "Document Information [Table]"
       }
      }
     },
     "localname": "DocumentInformationTable",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "stringItemType"
    },
    "dei_DocumentPeriodEndDate": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented.  If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.",
        "label": "Document Period End Date",
        "terseLabel": "Document Period End Date"
       }
      }
     },
     "localname": "DocumentPeriodEndDate",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "dateItemType"
    },
    "dei_DocumentTransitionReport": {
     "auth_ref": [
      "r534"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true only for a form used as a transition report.",
        "label": "Document Transition Report",
        "terseLabel": "Document Transition Report"
       }
      }
     },
     "localname": "DocumentTransitionReport",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_DocumentType": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.",
        "label": "Document Type",
        "terseLabel": "Document Type"
       }
      }
     },
     "localname": "DocumentType",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "submissionTypeItemType"
    },
    "dei_DocumentsIncorporatedByReferenceTextBlock": {
     "auth_ref": [
      "r532"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Documents incorporated by reference.",
        "label": "Documents Incorporated by Reference [Text Block]",
        "terseLabel": "Documents Incorporated by Reference"
       }
      }
     },
     "localname": "DocumentsIncorporatedByReferenceTextBlock",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "textBlockItemType"
    },
    "dei_EntitiesTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Container to assemble all relevant information about each entity associated with the document instance",
        "label": "Entities [Table]",
        "terseLabel": "Entities [Table]"
       }
      }
     },
     "localname": "EntitiesTable",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "stringItemType"
    },
    "dei_EntityAddressAddressLine1": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Address Line 1 such as Attn, Building Name, Street Name",
        "label": "Entity Address, Address Line One",
        "terseLabel": "Entity Address, Address Line One"
       }
      }
     },
     "localname": "EntityAddressAddressLine1",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressAddressLine2": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Address Line 2 such as Street or Suite number",
        "label": "Entity Address, Address Line Two",
        "terseLabel": "Entity Address, Address Line Two"
       }
      }
     },
     "localname": "EntityAddressAddressLine2",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressCityOrTown": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the City or Town",
        "label": "Entity Address, City or Town",
        "terseLabel": "Entity Address, City or Town"
       }
      }
     },
     "localname": "EntityAddressCityOrTown",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressPostalZipCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Code for the postal or zip code",
        "label": "Entity Address, Postal Zip Code",
        "terseLabel": "Entity Address, Postal Zip Code"
       }
      }
     },
     "localname": "EntityAddressPostalZipCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressStateOrProvince": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the state or province.",
        "label": "Entity Address, State or Province",
        "terseLabel": "Entity Address, State or Province"
       }
      }
     },
     "localname": "EntityAddressStateOrProvince",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "stateOrProvinceItemType"
    },
    "dei_EntityCentralIndexKey": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.",
        "label": "Entity Central Index Key",
        "terseLabel": "Entity Central Index Key"
       }
      }
     },
     "localname": "EntityCentralIndexKey",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "centralIndexKeyItemType"
    },
    "dei_EntityCommonStockSharesOutstanding": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.",
        "label": "Entity Common Stock, Shares Outstanding",
        "terseLabel": "Entity Common Stock, Shares Outstanding (in shares)"
       }
      }
     },
     "localname": "EntityCommonStockSharesOutstanding",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "sharesItemType"
    },
    "dei_EntityCurrentReportingStatus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure.",
        "label": "Entity Current Reporting Status",
        "terseLabel": "Entity Current Reporting Status"
       }
      }
     },
     "localname": "EntityCurrentReportingStatus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_EntityDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "All the names of the entities being reported upon in a document. Any legal structure used to conduct activities or to hold assets. Some examples of such structures are corporations, partnerships, limited liability companies, grantor trusts, and other trusts. This item does not include business and geographical segments which are included in the geographical or business segments domains.",
        "label": "Entity [Domain]",
        "terseLabel": "Entity [Domain]"
       }
      }
     },
     "localname": "EntityDomain",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses",
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/AccruedExpensesTables",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables",
      "http://www.summitmaterials.com/role/Acquisitions",
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail",
      "http://www.summitmaterials.com/role/AcquisitionsTables",
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/Debt",
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails",
      "http://www.summitmaterials.com/role/DebtTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
      "http://www.summitmaterials.com/role/FairValueTables",
      "http://www.summitmaterials.com/role/Goodwill",
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/GoodwillTables",
      "http://www.summitmaterials.com/role/IncomeTaxes",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesTables",
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails",
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails",
      "http://www.summitmaterials.com/role/Inventories",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/InventoriesTables",
      "http://www.summitmaterials.com/role/Leases",
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
      "http://www.summitmaterials.com/role/LeasesTables",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables",
      "http://www.summitmaterials.com/role/RevenueRecognition",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionTables",
      "http://www.summitmaterials.com/role/SegmentInformation",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationTables",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensation",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables",
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "domainItemType"
    },
    "dei_EntityEmergingGrowthCompany": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate if registrant meets the emerging growth company criteria.",
        "label": "Entity Emerging Growth Company",
        "terseLabel": "Entity Emerging Growth Company"
       }
      }
     },
     "localname": "EntityEmergingGrowthCompany",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntityFileNumber": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.",
        "label": "Entity File Number",
        "terseLabel": "Entity File Number"
       }
      }
     },
     "localname": "EntityFileNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "fileNumberItemType"
    },
    "dei_EntityFilerCategory": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.",
        "label": "Entity Filer Category",
        "terseLabel": "Entity Filer Category"
       }
      }
     },
     "localname": "EntityFilerCategory",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "filerCategoryItemType"
    },
    "dei_EntityIncorporationStateCountryCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two-character EDGAR code representing the state or country of incorporation.",
        "label": "Entity Incorporation, State or Country Code",
        "terseLabel": "Entity Incorporation, State or Country Code"
       }
      }
     },
     "localname": "EntityIncorporationStateCountryCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "edgarStateCountryItemType"
    },
    "dei_EntityInformationLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Entity Information [Line Items]",
        "terseLabel": "Company Information"
       }
      }
     },
     "localname": "EntityInformationLineItems",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "stringItemType"
    },
    "dei_EntityInteractiveDataCurrent": {
     "auth_ref": [
      "r537"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).",
        "label": "Entity Interactive Data Current",
        "terseLabel": "Entity Interactive Data Current"
       }
      }
     },
     "localname": "EntityInteractiveDataCurrent",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_EntityPublicFloat": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter.",
        "label": "Entity Public Float",
        "terseLabel": "Entity Public Float"
       }
      }
     },
     "localname": "EntityPublicFloat",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "monetaryItemType"
    },
    "dei_EntityRegistrantName": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.",
        "label": "Entity Registrant Name",
        "terseLabel": "Entity Registrant Name"
       }
      }
     },
     "localname": "EntityRegistrantName",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityShellCompany": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.",
        "label": "Entity Shell Company",
        "terseLabel": "Entity Shell Company"
       }
      }
     },
     "localname": "EntityShellCompany",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntitySmallBusiness": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicates that the company is a Smaller Reporting Company (SRC).",
        "label": "Entity Small Business",
        "terseLabel": "Entity Small Business"
       }
      }
     },
     "localname": "EntitySmallBusiness",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntityTaxIdentificationNumber": {
     "auth_ref": [
      "r536"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.",
        "label": "Entity Tax Identification Number",
        "terseLabel": "Entity Tax Identification Number"
       }
      }
     },
     "localname": "EntityTaxIdentificationNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "employerIdItemType"
    },
    "dei_EntityVoluntaryFilers": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate 'Yes' or 'No' if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.",
        "label": "Entity Voluntary Filers",
        "terseLabel": "Entity Voluntary Filers"
       }
      }
     },
     "localname": "EntityVoluntaryFilers",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_EntityWellKnownSeasonedIssuer": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate 'Yes' or 'No' if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Is used on Form Type: 10-K, 10-Q, 8-K, 20-F, 6-K, 10-K/A, 10-Q/A, 20-F/A, 6-K/A, N-CSR, N-Q, N-1A.",
        "label": "Entity Well-known Seasoned Issuer",
        "terseLabel": "Entity Well-known Seasoned Issuer"
       }
      }
     },
     "localname": "EntityWellKnownSeasonedIssuer",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_LegalEntityAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The set of legal entities associated with a report.",
        "label": "Legal Entity [Axis]",
        "terseLabel": "Legal Entity [Axis]"
       }
      }
     },
     "localname": "LegalEntityAxis",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses",
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/AccruedExpensesTables",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables",
      "http://www.summitmaterials.com/role/Acquisitions",
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail",
      "http://www.summitmaterials.com/role/AcquisitionsTables",
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/Debt",
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails",
      "http://www.summitmaterials.com/role/DebtTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
      "http://www.summitmaterials.com/role/FairValueTables",
      "http://www.summitmaterials.com/role/Goodwill",
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/GoodwillTables",
      "http://www.summitmaterials.com/role/IncomeTaxes",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesTables",
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails",
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails",
      "http://www.summitmaterials.com/role/Inventories",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/InventoriesTables",
      "http://www.summitmaterials.com/role/Leases",
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
      "http://www.summitmaterials.com/role/LeasesTables",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables",
      "http://www.summitmaterials.com/role/RevenueRecognition",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionTables",
      "http://www.summitmaterials.com/role/SegmentInformation",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationTables",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensation",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables",
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "stringItemType"
    },
    "dei_LocalPhoneNumber": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Local phone number for entity.",
        "label": "Local Phone Number",
        "terseLabel": "Local Phone Number"
       }
      }
     },
     "localname": "LocalPhoneNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_Security12bTitle": {
     "auth_ref": [
      "r531"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Title of a 12(b) registered security.",
        "label": "Title of 12(b) Security",
        "terseLabel": "Title of 12(b) Security"
       }
      }
     },
     "localname": "Security12bTitle",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "securityTitleItemType"
    },
    "dei_SecurityExchangeName": {
     "auth_ref": [
      "r533"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the Exchange on which a security is registered.",
        "label": "Security Exchange Name",
        "terseLabel": "Security Exchange Name"
       }
      }
     },
     "localname": "SecurityExchangeName",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "edgarExchangeCodeItemType"
    },
    "dei_TradingSymbol": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Trading symbol of an instrument as listed on an exchange.",
        "label": "Trading Symbol",
        "terseLabel": "Trading Symbol"
       }
      }
     },
     "localname": "TradingSymbol",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Cover"
     ],
     "xbrltype": "tradingSymbolItemType"
    },
    "srt_CondensedFinancialInformationOfParentCompanyOnlyDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Condensed Financial Information Disclosure [Abstract]"
       }
      }
     },
     "localname": "CondensedFinancialInformationOfParentCompanyOnlyDisclosureAbstract",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "srt_CondensedFinancialStatementsCaptionsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Condensed Financial Statements, Captions [Line Items]",
        "terseLabel": "Condensed Financial Statements, Captions [Line Items]"
       }
      }
     },
     "localname": "CondensedFinancialStatementsCaptionsLineItems",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_CondensedFinancialStatementsTextBlock": {
     "auth_ref": [
      "r127",
      "r539",
      "r541",
      "r544",
      "r545",
      "r546"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for condensed financial statements.",
        "label": "Condensed Financial Statements [Text Block]",
        "terseLabel": "Senior Notes' Guarantor and Non-Guarantor Financial Information"
       }
      }
     },
     "localname": "CondensedFinancialStatementsTextBlock",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "srt_CondensedIncomeStatementTable": {
     "auth_ref": [
      "r127",
      "r414",
      "r539"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about condensed income statement including, but not limited to, income statements of consolidated entities and consolidation eliminations.",
        "label": "Condensed Income Statement [Table]",
        "terseLabel": "Condensed Income Statement [Table]"
       }
      }
     },
     "localname": "CondensedIncomeStatementTable",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_CondensedIncomeStatementsCaptionsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Condensed Income Statements, Captions [Line Items]",
        "terseLabel": "Condensed Income Statements, Captions [Line Items]"
       }
      }
     },
     "localname": "CondensedIncomeStatementsCaptionsLineItems",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ConsolidatedEntitiesAxis": {
     "auth_ref": [
      "r530",
      "r538"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by consolidated entity or group of entities.",
        "label": "Consolidated Entities [Axis]",
        "terseLabel": "Consolidated Entities [Axis]"
       }
      }
     },
     "localname": "ConsolidatedEntitiesAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ConsolidatedEntitiesDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Entity or group of entities consolidated into reporting entity.",
        "label": "Consolidated Entities [Domain]",
        "terseLabel": "Consolidated Entities [Domain]"
       }
      }
     },
     "localname": "ConsolidatedEntitiesDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ConsolidationEliminationsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Eliminating entries used in consolidating a parent entity and its subsidiaries.",
        "label": "Consolidation, Eliminations [Member]",
        "terseLabel": "Eliminations"
       }
      }
     },
     "localname": "ConsolidationEliminationsMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ConsolidationItemsAxis": {
     "auth_ref": [
      "r167",
      "r174"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by components, eliminations, non-segment corporate-level activity and reconciling items used in consolidating a parent entity and its subsidiaries or its operating segments.",
        "label": "Consolidation Items [Axis]",
        "terseLabel": "Consolidation Items [Axis]"
       }
      }
     },
     "localname": "ConsolidationItemsAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ConsolidationItemsDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Components, elimination, non-segment corporate-level activity and reconciling items used in consolidating a parent entity and its subsidiaries or its operating segments.",
        "label": "Consolidation Items [Domain]",
        "terseLabel": "Consolidation Items [Domain]"
       }
      }
     },
     "localname": "ConsolidationItemsDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_GuarantorSubsidiariesMember": {
     "auth_ref": [
      "r250",
      "r542"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Entity owned or controlled by another entity which has guaranteed the issue of securities by another subsidiary of the parent or has guaranteed the issue of securities by the parent.",
        "label": "Guarantor Subsidiaries [Member]",
        "terseLabel": "100% Owned Guarantors"
       }
      }
     },
     "localname": "GuarantorSubsidiariesMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_MaximumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Upper limit of the provided range.",
        "label": "Maximum [Member]",
        "terseLabel": "Maximum"
       }
      }
     },
     "localname": "MaximumMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_MinimumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lower limit of the provided range.",
        "label": "Minimum [Member]",
        "terseLabel": "Minimum"
       }
      }
     },
     "localname": "MinimumMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_NonGuarantorSubsidiariesMember": {
     "auth_ref": [
      "r251",
      "r543"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Entity owned or controlled by another entity which has not guaranteed the issue of securities by another subsidiary of the parent or has not guaranteed the issue of securities by the parent.",
        "label": "Non-Guarantor Subsidiaries [Member]",
        "terseLabel": "Non-Guarantors"
       }
      }
     },
     "localname": "NonGuarantorSubsidiariesMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_OwnershipAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by name of entity in which ownership interest is disclosed. Excludes equity method investee and named security investment.",
        "label": "Ownership [Axis]",
        "terseLabel": "Ownership [Axis]"
       }
      }
     },
     "localname": "OwnershipAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_OwnershipDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of entity in which ownership interest is disclosed. Excludes equity method investee and named security investment.",
        "label": "Ownership [Domain]",
        "terseLabel": "Ownership [Domain]"
       }
      }
     },
     "localname": "OwnershipDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ProductOrServiceAxis": {
     "auth_ref": [
      "r177",
      "r272",
      "r274",
      "r524",
      "r525"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by product and service, or group of similar products and similar services.",
        "label": "Product and Service [Axis]",
        "terseLabel": "Product and Service [Axis]"
       }
      }
     },
     "localname": "ProductOrServiceAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ProductsAndServicesDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Product or service, or a group of similar products or similar services.",
        "label": "Product and Service [Domain]",
        "terseLabel": "Product and Service [Domain]"
       }
      }
     },
     "localname": "ProductsAndServicesDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_RangeAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by statistical measurement. Includes, but is not limited to, minimum, maximum, weighted average, arithmetic average, and median.",
        "label": "Statistical Measurement [Axis]",
        "terseLabel": "Statistical Measurement [Axis]"
       }
      }
     },
     "localname": "RangeAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_RangeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Statistical measurement. Includes, but is not limited to, minimum, maximum, weighted average, arithmetic average, and median.",
        "label": "Statistical Measurement [Domain]",
        "terseLabel": "Statistical Measurement [Domain]"
       }
      }
     },
     "localname": "RangeMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ReportableLegalEntitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Legal entities of the consolidated entity reporting separate financial information in the entity's financial statements.",
        "label": "Reportable Legal Entities [Member]",
        "terseLabel": "Reportable Legal Entities"
       }
      }
     },
     "localname": "ReportableLegalEntitiesMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ScheduleOfCondensedBalanceSheetTableTextBlock": {
     "auth_ref": [
      "r547"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of condensed balance sheet, including, but not limited to, balance sheets of consolidated entities and consolidation eliminations.",
        "label": "Condensed Balance Sheet [Table Text Block]",
        "terseLabel": "Condensed Consolidating Balance Sheets"
       }
      }
     },
     "localname": "ScheduleOfCondensedBalanceSheetTableTextBlock",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "srt_ScheduleOfCondensedCashFlowStatementTableTextBlock": {
     "auth_ref": [
      "r547"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of condensed cash flow statement, including, but not limited to, cash flow statements of consolidated entities and consolidation eliminations.",
        "label": "Condensed Cash Flow Statement [Table Text Block]",
        "terseLabel": "Condensed Consolidating Statements of Cash Flows"
       }
      }
     },
     "localname": "ScheduleOfCondensedCashFlowStatementTableTextBlock",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "srt_ScheduleOfCondensedFinancialStatementsTable": {
     "auth_ref": [
      "r127",
      "r414",
      "r539",
      "r548",
      "r549",
      "r550"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about condensed financial statements, including, but not limited to, the balance sheet, income statement, and statement of cash flows.",
        "label": "Condensed Financial Statements [Table]",
        "terseLabel": "Condensed Financial Statements [Table]"
       }
      }
     },
     "localname": "ScheduleOfCondensedFinancialStatementsTable",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ScheduleOfCondensedIncomeStatementTableTextBlock": {
     "auth_ref": [
      "r547"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of condensed income statement, including, but not limited to, income statements of consolidated entities and consolidation eliminations.",
        "label": "Condensed Income Statement [Table Text Block]",
        "terseLabel": "Condensed Consolidating Statements of Operations and Comprehensive Loss"
       }
      }
     },
     "localname": "ScheduleOfCondensedIncomeStatementTableTextBlock",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "srt_SubsidiaryIssuerMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A company controlled, directly or indirectly, by its parent, which has issued securities and those securities are guaranteed by its parent and another subsidiary of the parent.",
        "label": "Subsidiary Issuer [Member]",
        "terseLabel": "Issuers"
       }
      }
     },
     "localname": "SubsidiaryIssuerMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ValuationAndQualifyingAccountsDisclosureLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]",
        "terseLabel": "SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]"
       }
      }
     },
     "localname": "ValuationAndQualifyingAccountsDisclosureLineItems",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ValuationAndQualifyingAccountsDisclosureTable": {
     "auth_ref": [
      "r129",
      "r540"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of valuation and qualifying accounts and reserves.",
        "label": "SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table]",
        "terseLabel": "SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table]"
       }
      }
     },
     "localname": "ValuationAndQualifyingAccountsDisclosureTable",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_AccruedExpensesTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accrued Expenses [Table]",
        "label": "Accrued Expenses [Table]",
        "terseLabel": "Accrued Expenses [Table]"
       }
      }
     },
     "localname": "AccruedExpensesTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses",
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/AccruedExpensesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_AcquisitionRelatedLiabilitiesCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of consideration for a business acquisition due in the current period.",
        "label": "Acquisition Related Liabilities Current",
        "terseLabel": "Current portion of acquisition-related liabilities"
       }
      }
     },
     "localname": "AcquisitionRelatedLiabilitiesCurrent",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AcquisitionRelatedLiabilitiesNonCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 3.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of consideration for a business acquisition that is not due in the next twelve months.",
        "label": "Acquisition Related Liabilities Non Current",
        "terseLabel": "Acquisition-related liabilities"
       }
      }
     },
     "localname": "AcquisitionRelatedLiabilitiesNonCurrent",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AdjustedEarningsBeforeInterestIncomeTaxesDepreciationAndAmortization": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Adjusted earnings before interest, income taxes, depreciation and amortization (Adjusted EBITDA).",
        "label": "Adjusted Earnings Before Interest Income Taxes Depreciation And Amortization",
        "verboseLabel": "Total Adjusted EBITDA"
       }
      }
     },
     "localname": "AdjustedEarningsBeforeInterestIncomeTaxesDepreciationAndAmortization",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AdjustmentsToAdditionalPaidInCapitalPurchaseOfNoncontrollingInterest": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase to additional paid-in-capital attributable to the purchase of a noncontrolling interest.",
        "label": "Adjustments To Additional Paid in Capital Purchase of Noncontrolling Interest",
        "terseLabel": "Purchase of noncontrolling interest"
       }
      }
     },
     "localname": "AdjustmentsToAdditionalPaidInCapitalPurchaseOfNoncontrollingInterest",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AggregatesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregates.",
        "label": "Aggregates [Member]",
        "terseLabel": "Aggregates"
       }
      }
     },
     "localname": "AggregatesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_AsphaltMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Asphalt.",
        "label": "Asphalt [Member]",
        "terseLabel": "Asphalt"
       }
      }
     },
     "localname": "AsphaltMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_AssetRetirementObligationAnticipatedCosts": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total undiscounted anticipated costs for site reclamation.",
        "label": "Asset Retirement Obligation, Anticipated Costs",
        "terseLabel": "Anticipated costs"
       }
      }
     },
     "localname": "AssetRetirementObligationAnticipatedCosts",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AssetRetirementObligationLiabilitiesAcquired": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of asset retirement obligations acquired during the period.",
        "label": "Asset Retirement Obligation, Liabilities Acquired",
        "terseLabel": "Acquired obligations"
       }
      }
     },
     "localname": "AssetRetirementObligationLiabilitiesAcquired",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_AssetRetirementObligationsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Asset Retirement Obligations [Line Items]",
        "label": "Asset Retirement Obligations [Line Items]",
        "terseLabel": "Asset Retirement Obligations [Line Items]"
       }
      }
     },
     "localname": "AssetRetirementObligationsLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_AssetRetirementObligationsTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Asset Retirement Obligations [Table]",
        "label": "Asset Retirement Obligations [Table]",
        "terseLabel": "Asset Retirement Obligations [Table]"
       }
      }
     },
     "localname": "AssetRetirementObligationsTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_AssetsAndLiabilitiesLesseeTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Assets And Liabilities, Lessee [Table Text Block]",
        "label": "Assets And Liabilities, Lessee [Table Text Block]",
        "terseLabel": "Schedule of Lease Assets and Liabilities"
       }
      }
     },
     "localname": "AssetsAndLiabilitiesLesseeTableTextBlock",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "sum_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAdjustedOtherAssets": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 5.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Business combination recognized identifiable assets acquired and liabilities assumed adjusted other assets.",
        "label": "Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Adjusted Other Assets",
        "terseLabel": "Other assets"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAdjustedOtherAssets",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_CanadianSubsidiaryCreditAgreementCapitalEquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents information pertaining to credit agreement of wholly-owned Canadian subsidiary to be used for capital equipment.",
        "label": "Canadian Subsidiary Credit Agreement Capital Equipment [Member]",
        "terseLabel": "Canadian subsidiary credit agreement, Capital equipment"
       }
      }
     },
     "localname": "CanadianSubsidiaryCreditAgreementCapitalEquipmentMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CanadianSubsidiaryCreditAgreementGuaranteesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents information pertaining to credit agreement of wholly-owned Canadian subsidiary to provide guarantees on behalf of that subsidiary.",
        "label": "Canadian Subsidiary Credit Agreement Guarantees [Member]",
        "terseLabel": "Canadian subsidiary credit agreement, Guarantees"
       }
      }
     },
     "localname": "CanadianSubsidiaryCreditAgreementGuaranteesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CanadianSubsidiaryCreditAgreementMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents information pertaining to credit agreement of wholly-owned Canadian subsidiary.",
        "label": "Canadian Subsidiary Credit Agreement [Member]",
        "terseLabel": "Canadian subsidiary credit agreement"
       }
      }
     },
     "localname": "CanadianSubsidiaryCreditAgreementMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CanadianSubsidiaryCreditAgreementOperatingActivitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents information pertaining to credit agreement of wholly-owned Canadian subsidiary to be used for operating activities.",
        "label": "Canadian Subsidiary Credit Agreement Operating Activities [Member]",
        "terseLabel": "Canadian subsidiary credit agreement, Operating activities"
       }
      }
     },
     "localname": "CanadianSubsidiaryCreditAgreementOperatingActivitiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CementMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the cement segment of the reporting entity.",
        "label": "Cement [Member]",
        "terseLabel": "Cement"
       }
      }
     },
     "localname": "CementMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CementPlantMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cement plant facility.",
        "label": "Cement Plant [Member]",
        "terseLabel": "Cement Plant"
       }
      }
     },
     "localname": "CementPlantMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_CollectionAndBillingPeriodRetentionReceivables": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The general collection and billing period for retention receivables.",
        "label": "Collection and Billing Period, Retention Receivables",
        "terseLabel": "General collection and billing period for retention receivables"
       }
      }
     },
     "localname": "CollectionAndBillingPeriodRetentionReceivables",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "sum_ComprehensiveIncomeLossNetOfTaxAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 3.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests, excluding portion attributable to noncontrolling interest of the wholly owned indirect subsidiary of the registrant.",
        "label": "Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest, Excluding Portion Attributable To Noncontrolling Interest Of Wholly Owned Indirect Subsidiary Of Registrant",
        "terseLabel": "Less comprehensive income attributable to Summit Holdings"
       }
      }
     },
     "localname": "ComprehensiveIncomeLossNetOfTaxAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ComprehensiveIncomeLossNetOfTaxAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 2.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests of the wholly owned indirect subsidiary of the registrant.",
        "label": "Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest Of Wholly Owned Indirect Subsidiary Of Registrant",
        "terseLabel": "Less comprehensive income attributable to the noncontrolling interest in consolidated subsidiaries"
       }
      }
     },
     "localname": "ComprehensiveIncomeLossNetOfTaxAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ConstructionIndustryLaborersPensionFundMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Construction Industry Laborers Pension Fund [Member]",
        "label": "Construction Industry Laborers Pension Fund [Member]",
        "terseLabel": "Construction Industry Laborers Pension Fund"
       }
      }
     },
     "localname": "ConstructionIndustryLaborersPensionFundMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ContinentalCementCompanyLLCMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Continental Cement Company L.L.C., formerly an non-wholly owned indirect subsidiary, which became a wholly owned indirect subsidiary following parent's purchase of the noncontrolling interest.",
        "label": "Continental Cement Company L L C [Member]",
        "terseLabel": "Continental Cement"
       }
      }
     },
     "localname": "ContinentalCementCompanyLLCMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ContractWithCustomerAssetCumulativeCatchupAdjustmentToRevenueChangeInRevenueBilledContractPriceOrEstimates": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 10.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in revenue billed, contract price or cost estimates which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.",
        "label": "Contract With Customer, Asset, Cumulative Catch-up Adjustment To Revenue, Change In Revenue Billed, Contract Price Or Estimates",
        "negatedLabel": "Costs and estimated earnings in excess of billings",
        "terseLabel": "Changes in revenue billed, contract price or cost estimates"
       }
      }
     },
     "localname": "ContractWithCustomerAssetCumulativeCatchupAdjustmentToRevenueChangeInRevenueBilledContractPriceOrEstimates",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ContractWithCustomerAssetIncreaseDecreaseForOtherActivity": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, from other activities.",
        "label": "Contract with Customer, Asset, Increase (Decrease) for Other Activity",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "ContractWithCustomerAssetIncreaseDecreaseForOtherActivity",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ContractWithCustomerLiabilityCumulativeCatchupAdjustmentToRevenueChangeInRevenueBilledContractPriceOrCostEstimates": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 15.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in revenue billed, contract pric or cost estimates which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due. Includes, but is not limited to, change in assessment of whether estimate of variable consideration is constrained.",
        "label": "Contract With Customer, Liability, Cumulative Catch-up Adjustment To Revenue, Change In Revenue Billed, Contract Price Or Cost Estimates",
        "terseLabel": "Changes in revenue billed, contract price or cost estimates",
        "verboseLabel": "Billings in excess of costs and estimated earnings"
       }
      }
     },
     "localname": "ContractWithCustomerLiabilityCumulativeCatchupAdjustmentToRevenueChangeInRevenueBilledContractPriceOrCostEstimates",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ContractWithCustomerLiabilityIncreaseDecreaseForOtherActivities": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration from customer has been received or is due, from other activities.",
        "label": "Contract with Customer, Liability, Increase (Decrease) for Other Activities",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "ContractWithCustomerLiabilityIncreaseDecreaseForOtherActivities",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ContractualObligationsPresentValue": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of contractual obligations.",
        "label": "Contractual Obligations, Present Value",
        "terseLabel": "Total noncompete obligations and deferred consideration"
       }
      }
     },
     "localname": "ContractualObligationsPresentValue",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ContributionToMembersEquity": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Capital contributed to limited liability company (LLC).",
        "label": "Contribution To Members Equity",
        "terseLabel": "Net contributed capital"
       }
      }
     },
     "localname": "ContributionToMembersEquity",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DebtInstrumentPrepaymentPremium": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of fee for an early repayment of debt.",
        "label": "Debt Instrument, Prepayment Premium",
        "terseLabel": "Prepayment premium"
       }
      }
     },
     "localname": "DebtInstrumentPrepaymentPremium",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DebtInstrumentRedemptionCharge": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Debt instrument redemption charge. May include prepayment premium and write-off of deferred financing fees.",
        "label": "Debt Instrument Redemption Charge",
        "terseLabel": "Charges on redemption"
       }
      }
     },
     "localname": "DebtInstrumentRedemptionCharge",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DebtInstrumentReferenceRateAdditionalPercentage": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage points added to the base rate to determine reference rate.",
        "label": "Debt Instrument, Reference Rate, Additional Percentage",
        "terseLabel": "Percentage added to base rate"
       }
      }
     },
     "localname": "DebtInstrumentReferenceRateAdditionalPercentage",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "sum_DecreaseInNetDeferredTaxAssetsDueToChangeInFederalStatutoryTaxRate": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Reduction of net deferred tax assets due to change in federal statutory rate.",
        "label": "Decrease in Net Deferred Tax Assets Due to Change in Federal Statutory Tax Rate",
        "terseLabel": "Reduction of net deferred tax assets due to change in statutory rate"
       }
      }
     },
     "localname": "DecreaseInNetDeferredTaxAssetsDueToChangeInFederalStatutoryTaxRate",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredConsiderationAndNoncompeteObligationsCurrentFairValueDisclosure": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred consideration and noncompete obligations current fair value.",
        "label": "Deferred Consideration and Noncompete Obligations Current Fair Value Disclosure",
        "terseLabel": "Current portion of deferred consideration and noncompete obligations"
       }
      }
     },
     "localname": "DeferredConsiderationAndNoncompeteObligationsCurrentFairValueDisclosure",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredConsiderationAndNoncompeteObligationsNoncurrentFairValueDisclosure": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred consideration and noncompete obligations noncurrent fair value.",
        "label": "Deferred Consideration and Noncompete Obligations Noncurrent Fair Value Disclosure",
        "terseLabel": "Long term portion of deferred consideration and noncompete obligations"
       }
      }
     },
     "localname": "DeferredConsiderationAndNoncompeteObligationsNoncurrentFairValueDisclosure",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredConsiderationPaymentTerm": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Term of payment for deferred consideration associated with a business acquisition.",
        "label": "Deferred Consideration, Payment Term",
        "terseLabel": "Term of payment for deferred consideration"
       }
      }
     },
     "localname": "DeferredConsiderationPaymentTerm",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "sum_DeferredTaxAssetsDeemedProbable": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefit associated with a deferred tax asset that is deemed probable.",
        "label": "Deferred Tax Assets, Deemed Probable",
        "terseLabel": "Tax benefit deemed probable"
       }
      }
     },
     "localname": "DeferredTaxAssetsDeemedProbable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsIntangibleAssetsExcludingGoodwill": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets excluding goodwill.",
        "label": "Deferred Tax Assets, Intangible Assets Excluding Goodwill",
        "terseLabel": "Net intangible assets"
       }
      }
     },
     "localname": "DeferredTaxAssetsIntangibleAssetsExcludingGoodwill",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsLiabilitiesNetBeforeValuationAllowances": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred Tax Assets Liabilities Net Before Valuation Allowances",
        "label": "Deferred Tax Assets Liabilities Net Before Valuation Allowances",
        "totalLabel": "Deferred tax liabilities, net"
       }
      }
     },
     "localname": "DeferredTaxAssetsLiabilitiesNetBeforeValuationAllowances",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsLiabilitiesNetIncludedInNoncurrentLiabilities": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after allocation of valuation allowances, deferred tax liability and foreign deferred tax liability.",
        "label": "Deferred Tax Assets Liabilities, Net, Included in Noncurrent Liabilities",
        "totalLabel": "Net deferred tax asset"
       }
      }
     },
     "localname": "DeferredTaxAssetsLiabilitiesNetIncludedInNoncurrentLiabilities",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsLiabilitiesWorkingCapital": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 6.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred Tax Assets Liabilities Working Capital",
        "label": "Deferred Tax Assets Liabilities Working Capital",
        "terseLabel": "Working capital (e.g., accrued compensation, prepaid assets)"
       }
      }
     },
     "localname": "DeferredTaxAssetsLiabilitiesWorkingCapital",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsMiningReclamationReserve": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 5.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred tax assets mining reclamation reserve.",
        "label": "Deferred Tax Assets, Mining Reclamation Reserve",
        "terseLabel": "Mining reclamation reserve"
       }
      }
     },
     "localname": "DeferredTaxAssetsMiningReclamationReserve",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxAssetsSubjectToTaxReceivableAgreement": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred tax assets subject to Tax Receivable Agreement.",
        "label": "Deferred Tax Assets Subject to Tax Receivable Agreement",
        "terseLabel": "Deferred tax assets subject to TRA"
       }
      }
     },
     "localname": "DeferredTaxAssetsSubjectToTaxReceivableAgreement",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxLiabilityGoodwillAndIntangibleAssetsIntangibleAssets": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred tax liabilities attributable to taxable temporary differences from intangible assets other than goodwill.",
        "label": "Deferred Tax Liability, Intangible Assets",
        "negatedLabel": "Net intangible assets"
       }
      }
     },
     "localname": "DeferredTaxLiabilityGoodwillAndIntangibleAssetsIntangibleAssets",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxLiabilityIncludedInOtherNoncurrentLiabilities": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 2.0,
       "parentTag": "sum_DeferredTaxAssetsLiabilitiesNetIncludedInNoncurrentLiabilities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred tax liability included in other non-current liabilities.",
        "label": "Deferred Tax Liability, Included in Other Noncurrent Liabilities",
        "negatedTerseLabel": "Less foreign deferred tax liability (included in other noncurrent liabilities)"
       }
      }
     },
     "localname": "DeferredTaxLiabilityIncludedInOtherNoncurrentLiabilities",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DeferredTaxLiabilityInvestmentInPartnership": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 4.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred tax liability attributable to investment in limited partnership.",
        "label": "Deferred Tax Liability, Investment in Partnership",
        "negatedLabel": "Investment in limited partnership"
       }
      }
     },
     "localname": "DeferredTaxLiabilityInvestmentInPartnership",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationsExpectedLongTermReturnOnAssets": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to determine the benefit obligation.",
        "label": "Defined Benefit Plan, Assumptions Used Calculating Benefit Obligations, Expected Long-term Return on Assets",
        "terseLabel": "Expected long-term rate of return on plan assets, benefit obligation"
       }
      }
     },
     "localname": "DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationsExpectedLongTermReturnOnAssets",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesCommoditiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, Commodities [Member]",
        "label": "Defined Benefit Plan, Equity Securities, Commodities [Member]",
        "terseLabel": "Commodities Broad Basket"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesCommoditiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, Emerging Markets [Member]",
        "label": "Defined Benefit Plan, Equity Securities, Emerging Markets [Member]",
        "terseLabel": "Emerging Markets"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSLargeCapGrowthMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Large Cap, Growth [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Large Cap, Growth [Member]",
        "terseLabel": "U.S. Large cap growth"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSLargeCapGrowthMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSLargeCapValueMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Large Cap, Value [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Large Cap, Value [Member]",
        "terseLabel": "U.S. Large cap value"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSLargeCapValueMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSMidCapGrowthMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Mid Cap, Growth [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Mid Cap, Growth [Member]",
        "terseLabel": "U.S. Mid cap growth"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSMidCapGrowthMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSMidCapValueMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Mid Cap, Value [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Mid Cap, Value [Member]",
        "terseLabel": "U.S. Mid cap value"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSMidCapValueMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSSmallCapGrowthMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Small Cap, Growth [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Small Cap, Growth [Member]",
        "terseLabel": "U.S. Small cap growth"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSSmallCapGrowthMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DefinedBenefitPlanEquitySecuritiesUSSmallCapValueMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined Benefit Plan, Equity Securities, US, Small Cap, Value [Member]",
        "label": "Defined Benefit Plan, Equity Securities, US, Small Cap, Value [Member]",
        "terseLabel": "U.S. Small cap value"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesUSSmallCapValueMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_DepreciationDepletionAmortizationAndAccretion": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 4.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, depleting assets or accretion of asset retirement obligations to periods that benefit from use of the related assets.",
        "label": "Depreciation Depletion Amortization And Accretion",
        "terseLabel": "Depreciation, depletion, amortization and accretion",
        "verboseLabel": "Total depreciation, depletion, amortization and accretion"
       }
      }
     },
     "localname": "DepreciationDepletionAmortizationAndAccretion",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DepreciationDepletionAmortizationAndAccretionOnAssetRetirementObligation": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Depreciation depletion amortization and accretion on asset retirement obligation.",
        "label": "Depreciation Depletion Amortization And Accretion On Asset Retirement Obligation",
        "terseLabel": "Depreciation, depletion, amortization and accretion"
       }
      }
     },
     "localname": "DepreciationDepletionAmortizationAndAccretionOnAssetRetirementObligation",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_DisclosureSelectedQuarterlyFinancialDataAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure Selected Quarterly Financial Data [Abstract]",
        "label": "Disclosure Selected Quarterly Financial Data [Abstract]"
       }
      }
     },
     "localname": "DisclosureSelectedQuarterlyFinancialDataAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "xbrltype": "stringItemType"
    },
    "sum_EastMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the east region segment of the reporting entity.",
        "label": "East [Member]",
        "terseLabel": "East"
       }
      }
     },
     "localname": "EastMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]",
        "label": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]",
        "terseLabel": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]"
       }
      }
     },
     "localname": "EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Table]",
        "label": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Table]",
        "terseLabel": "Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Table]"
       }
      }
     },
     "localname": "EffectiveIncomeTaxRateContinuingOperationsTaxRateReconciliationTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_EffectiveIncomeTaxRateReconciliationUncertainTaxPositions": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Effective Income Tax Rate Reconciliation, Uncertain Tax Positions",
        "label": "Effective Income Tax Rate Reconciliation, Uncertain Tax Positions",
        "terseLabel": "Unrecognized tax benefits"
       }
      }
     },
     "localname": "EffectiveIncomeTaxRateReconciliationUncertainTaxPositions",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ExcludingShippingAndHandlingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Excluding Shipping And Handling [Member]",
        "label": "Excluding Shipping And Handling [Member]",
        "terseLabel": "Excluding delivery and subcontract revenue"
       }
      }
     },
     "localname": "ExcludingShippingAndHandlingMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_FinanceLeaseCost1Abstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Finance Lease Cost1 [Abstract]",
        "label": "Finance Lease Cost1 [Abstract]",
        "terseLabel": "Financing lease cost:"
       }
      }
     },
     "localname": "FinanceLeaseCost1Abstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_FinanceLeaseRightOfUseAssetAccumulatedAmortization": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_FinanceLeaseRightOfUseAsset",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Finance Lease, Right-Of-Use Asset, Accumulated Amortization",
        "label": "Finance Lease, Right-Of-Use Asset, Accumulated Amortization",
        "negatedTerseLabel": "Less accumulated depreciation",
        "terseLabel": "Finance lease, ROU asset, accumulated amortization"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAssetAccumulatedAmortization",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_FinanceLeaseRightOfUseAssetGross": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_FinanceLeaseRightOfUseAsset",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Finance Lease, Right-Of-Use Asset, Gross",
        "label": "Finance Lease, Right-Of-Use Asset, Gross",
        "terseLabel": "Property and equipment, gross",
        "verboseLabel": "Finance lease ROU assets included in property, plant and equipment, gross"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAssetGross",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_FinanceLeasesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Finance Leases [Abstract]",
        "label": "Finance Leases [Abstract]",
        "terseLabel": "Finance leases:"
       }
      }
     },
     "localname": "FinanceLeasesAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_FirstLienLeverageRatio": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "First lien leverage ratio as defined in the terms of the agreement.",
        "label": "First Lien Leverage Ratio",
        "terseLabel": "First lien leverage ratio"
       }
      }
     },
     "localname": "FirstLienLeverageRatio",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "pureItemType"
    },
    "sum_FivePointOneTwoFivePercentageSeniorNotesDueTwentyTwentyFiveMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the 5.125 percent senior notes of the entity due in 2025.",
        "label": "Five Point One Two Five Percentage Senior Notes Due Twenty Twenty Five [Member]",
        "terseLabel": "5 1/8% Senior Notes, due 2025"
       }
      }
     },
     "localname": "FivePointOneTwoFivePercentageSeniorNotesDueTwentyTwentyFiveMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_FixedIncomeSecuritiesNonUSMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fixed Income Securities, Non-US [Member]",
        "label": "Fixed Income Securities, Non-US [Member]",
        "terseLabel": "International"
       }
      }
     },
     "localname": "FixedIncomeSecuritiesNonUSMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_FollowOnPublicOfferingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Follow on public offering of stock by the company that is subsequent to its initial public offering.",
        "label": "Follow On Public Offering [Member]",
        "terseLabel": "Follow on Public Offering"
       }
      }
     },
     "localname": "FollowOnPublicOfferingMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_GainLossOnDebtFinancing": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 3.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gain loss on debt financing.",
        "label": "Gain Loss On Debt Financing",
        "negatedTerseLabel": "Loss on debt financings"
       }
      }
     },
     "localname": "GainLossOnDebtFinancing",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_GeneralAdministrativeAndOtherExpenses": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "General, administrative and other expenses.",
        "label": "General Administrative And Other Expenses",
        "terseLabel": "General and administrative expenses"
       }
      }
     },
     "localname": "GeneralAdministrativeAndOtherExpenses",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IncomeTaxReconciliationEffectOfLpUnitOwnershipChange": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 9.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to the impact of LP unit ownership change.",
        "label": "Income Tax Reconciliation, Effect of LP Unit Ownership Change",
        "terseLabel": "Impact of LP Unit ownership change"
       }
      }
     },
     "localname": "IncomeTaxReconciliationEffectOfLpUnitOwnershipChange",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IncomeTaxReconciliationEffectOfTraExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) TRA expense.",
        "label": "Income Tax Reconciliation, Effect of TRA Expense",
        "terseLabel": "Tax receivable agreement (benefit) expense"
       }
      }
     },
     "localname": "IncomeTaxReconciliationEffectOfTraExpense",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IncomeTaxReconciliationPermanentDifference": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Income Tax Reconciliation Permanent Difference",
        "label": "Income Tax Reconciliation Permanent Difference",
        "terseLabel": "Permanent differences"
       }
      }
     },
     "localname": "IncomeTaxReconciliationPermanentDifference",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IncomeTaxesLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Income Taxes [Line Items]",
        "label": "Income Taxes [Line Items]",
        "terseLabel": "Income Taxes [Line Items]"
       }
      }
     },
     "localname": "IncomeTaxesLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxes",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_IncomeTaxesTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Income Taxes [Table]",
        "label": "Income Taxes [Table]",
        "terseLabel": "Income Taxes [Table]"
       }
      }
     },
     "localname": "IncomeTaxesTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxes",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_IncreaseDecreaseInTaxReceivableAgreementLiability": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 16.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in tax receivable agreement liability.",
        "label": "Increase (Decrease) in Tax Receivable Agreement Liability",
        "terseLabel": "Tax receivable agreement liability"
       }
      }
     },
     "localname": "IncreaseDecreaseInTaxReceivableAgreementLiability",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IntercompanyPayablesLiabilitiesCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intercompany Payables Liabilities Current",
        "label": "Intercompany Payables Liabilities Current",
        "terseLabel": "Intercompany payables"
       }
      }
     },
     "localname": "IntercompanyPayablesLiabilitiesCurrent",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IntercompanyReceivablesAssetsCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intercompany Receivables Assets Current",
        "label": "Intercompany Receivables Assets Current",
        "terseLabel": "Intercompany receivables"
       }
      }
     },
     "localname": "IntercompanyReceivablesAssetsCurrent",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_IntermediateCorporateSecuritiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intermediate corporate securities.",
        "label": "Intermediate Corporate Securities [Member]",
        "terseLabel": "Intermediate\u2014corporate"
       }
      }
     },
     "localname": "IntermediateCorporateSecuritiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_IntermediateGovernmentSecuritiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intermediate government securities.",
        "label": "Intermediate Government Securities [Member]",
        "terseLabel": "Intermediate\u2014government"
       }
      }
     },
     "localname": "IntermediateGovernmentSecuritiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LandAndAssetRetirementCostsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Land and asset retirement costs.",
        "label": "Land And Asset Retirement Costs [Member]",
        "terseLabel": "Land (mineral bearing) and asset retirement costs"
       }
      }
     },
     "localname": "LandAndAssetRetirementCostsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LandfillAirspaceAndImprovementsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Landfill airspace and improvements.",
        "label": "Landfill Airspace And Improvements [Member]",
        "terseLabel": "Landfill airspace and improvements"
       }
      }
     },
     "localname": "LandfillAirspaceAndImprovementsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LeaseDiscountRateAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Discount Rate [Abstract]",
        "label": "Lease Discount Rate [Abstract]",
        "terseLabel": "Discount Rate"
       }
      }
     },
     "localname": "LeaseDiscountRateAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_LeaseTermAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Term [Abstract]",
        "label": "Lease Term [Abstract]",
        "terseLabel": "Lease Term"
       }
      }
     },
     "localname": "LeaseTermAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_LeverageRestorationOptionsTimeVestingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Leverage restoration options issued to holders of Class D interests in the limited partnership, which are not employee stock options, and which are subject to a time-vesting requirement.",
        "label": "Leverage Restoration Options Time Vesting [Member]",
        "terseLabel": "Leverage restoration options, time-vesting"
       }
      }
     },
     "localname": "LeverageRestorationOptionsTimeVestingMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LimitedPartnersCapitalAccountUnitsExchanged": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of limited partner units exchanged.",
        "label": "Limited Partners' Capital Account, Units Exchanged",
        "negatedTerseLabel": "Number of LP Units exchanged"
       }
      }
     },
     "localname": "LimitedPartnersCapitalAccountUnitsExchanged",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "sum_LimitedPartnershipUnitsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Units representing ownership interest in a limited partnership (LP).",
        "label": "Limited Partnership Units [Member]",
        "terseLabel": "LP Units"
       }
      }
     },
     "localname": "LimitedPartnershipUnitsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LondonInterbankOfferedRateLiborPlusOnePercentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest rate at which a bank borrows funds from other banks in the London interbank market plus one percent.",
        "label": "London Interbank Offered Rate Libor Plus One Percent [Member]",
        "terseLabel": "LIBOR Plus 1%"
       }
      }
     },
     "localname": "LondonInterbankOfferedRateLiborPlusOnePercentMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_LongTermDebtNet": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount of long-term debt, net of unamortized discount or premium and debt issuance costs, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.",
        "label": "Long-term Debt, Net",
        "totalLabel": "Total debt"
       }
      }
     },
     "localname": "LongTermDebtNet",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_LongTermDebtNoncurrentNet": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 2.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount of long-term debt, after unamortized (discount) premium and debt issuance costs, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities).",
        "label": "Long Term Debt Noncurrent, Net",
        "terseLabel": "Long-term debt"
       }
      }
     },
     "localname": "LongTermDebtNoncurrentNet",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_LpUnitsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lp Units [Member]",
        "label": "Lp Units [Member]",
        "terseLabel": "LP Units"
       }
      }
     },
     "localname": "LpUnitsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_MiscellaneousOtherIncomeExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 9.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Miscellaneous other income (expense).",
        "label": "Miscellaneous Other Income (Expense)",
        "negatedLabel": "Other"
       }
      }
     },
     "localname": "MiscellaneousOtherIncomeExpense",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_MobileEquipmentAndBargesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Mobile equipment and barges.",
        "label": "Mobile Equipment And Barges [Member]",
        "terseLabel": "Mobile equipment and barges"
       }
      }
     },
     "localname": "MobileEquipmentAndBargesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_MovementinContractAssetsandContractLiabilitiesRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Movement in Contract Assets and Contract Liabilities",
        "label": "Movement in Contract Assets and Contract Liabilities [Roll Forward]",
        "terseLabel": "Movement in Contract Assets and Contract Liabilities [Roll Forward]"
       }
      }
     },
     "localname": "MovementinContractAssetsandContractLiabilitiesRollForward",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_NetBenefitFromWriteOffOriginalIssuancePremiumAndDiscount": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Net benefit from write off original issuance premium and discount.",
        "label": "Net Benefit From Write Off Original Issuance Premium And Discount",
        "terseLabel": "Net benefit from the write-off the original issuance premium and discount"
       }
      }
     },
     "localname": "NetBenefitFromWriteOffOriginalIssuancePremiumAndDiscount",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_NetIncomeLossAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 3.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of Net Income (Loss) attributable to noncontrolling interest, excluding portion attributable to noncontrolling interest of the wholly owned indirect subsidiary of the registrant.",
        "label": "Net Income Loss Attributable To Noncontrolling Interest, Excluding Portion Attributable To Noncontrolling Interest Of Wholly Owned Indirect Subsidiary Of Registrant",
        "terseLabel": "Net income attributable to Summit Holdings"
       }
      }
     },
     "localname": "NetIncomeLossAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_NetIncomeLossAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 2.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of Net Income (Loss) attributable to noncontrolling interest of the wholly owned indirect subsidiary of the registrant.",
        "label": "Net Income Loss Attributable To Noncontrolling Interest Of Wholly Owned Indirect Subsidiary Of Registrant",
        "terseLabel": "Net income attributable to noncontrolling interest in subsidiaries"
       }
      }
     },
     "localname": "NetIncomeLossAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_NonCashCompensationExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 8.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Non Cash Compensation Expense",
        "label": "Non Cash Compensation Expense",
        "terseLabel": "Non-cash compensation"
       }
      }
     },
     "localname": "NonCashCompensationExpense",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_NonCashFinancingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Non Cash Financing Activities [Abstract]",
        "label": "Non Cash Financing Activities [Abstract]",
        "terseLabel": "Non cash financing activities:"
       }
      }
     },
     "localname": "NonCashFinancingActivitiesAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_NonCashGainLossOnDebtRefinancing": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 5.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Non-cash loss on debt refinancing.",
        "label": "Non Cash Gain Loss On Debt Refinancing",
        "negatedLabel": "Non-cash loss on debt financings"
       }
      }
     },
     "localname": "NonCashGainLossOnDebtRefinancing",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_NoncompeteAndDeferredConsiderationAgreementsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information pertaining to noncompete and deferred consideration agreements associated with business acquisitions.",
        "label": "Noncompete And Deferred Consideration Agreements [Member]",
        "terseLabel": "Noncompete and Deferred Consideration Agreements"
       }
      }
     },
     "localname": "NoncompeteAndDeferredConsiderationAgreementsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_NoncontrollingInterestInLlcMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Noncontrolling interest attributable to the 20% minority ownership in Ohio Valley Asphalt, LLC.",
        "label": "Noncontrolling Interest In Llc [Member]",
        "terseLabel": "Noncontrolling Interest in subsidiaries"
       }
      }
     },
     "localname": "NoncontrollingInterestInLlcMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_NoncontrollingInterestInLpMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Noncontrolling interest attributable to the ownership in Summit Materials Holdings, L.P., of which Summit Materials, LLC is a an indirect wholly owned subsidiary.",
        "label": "Noncontrolling Interest In Lp [Member]",
        "terseLabel": "Noncontrolling Interest"
       }
      }
     },
     "localname": "NoncontrollingInterestInLpMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_NoncurrentLiabilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Noncurrent Liabilities [Member]",
        "label": "Noncurrent Liabilities [Member]",
        "terseLabel": "Noncurrent liabilities"
       }
      }
     },
     "localname": "NoncurrentLiabilitiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_NumberOfNoncontributoryDefinedBenefitPensionPlans": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number Of Noncontributory Defined Benefit Pension Plans",
        "label": "Number Of Noncontributory Defined Benefit Pension Plans",
        "terseLabel": "Number of noncontributory defined benefit pension plans"
       }
      }
     },
     "localname": "NumberOfNoncontributoryDefinedBenefitPensionPlans",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_NumberOfPlantsOwnedAndOperated": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of plants owned and operated by the entity.",
        "label": "Number of Plants Owned and Operated",
        "terseLabel": "Number of plants"
       }
      }
     },
     "localname": "NumberOfPlantsOwnedAndOperated",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_NumberOfReportingUnitsAfterIntegration": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number Of Reporting Units After Integration",
        "label": "Number Of Reporting Units After Integration",
        "terseLabel": "Number of reporting units after Austin and Houston integration"
       }
      }
     },
     "localname": "NumberOfReportingUnitsAfterIntegration",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_NumberOfReportingUnitsBeingSubjectedToGoodwillImpairmentTest": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the number of reporting units subject to goodwill impairment testing.",
        "label": "Number Of Reporting Units Being Subjected To Goodwill Impairment Test",
        "terseLabel": "Number of reporting units with goodwill"
       }
      }
     },
     "localname": "NumberOfReportingUnitsBeingSubjectedToGoodwillImpairmentTest",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_NumberOfUnfundedHealthcareAndLifeInsuranceBenefitPlans": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number Of Unfunded Healthcare And Life Insurance Benefit Plans",
        "label": "Number Of Unfunded Healthcare And Life Insurance Benefit Plans",
        "terseLabel": "Number of unfunded healthcare and life insurance benefit plans"
       }
      }
     },
     "localname": "NumberOfUnfundedHealthcareAndLifeInsuranceBenefitPlans",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_NumberOfUnfundedHealthcarePlansForBenefitsPriorToMedicareEligibility": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number Of Unfunded Healthcare Plans For Benefits Prior To Medicare Eligibility",
        "label": "Number Of Unfunded Healthcare Plans For Benefits Prior To Medicare Eligibility",
        "terseLabel": "Number of unfunded healthcare plans for benefits prior to medicare eligibility"
       }
      }
     },
     "localname": "NumberOfUnfundedHealthcarePlansForBenefitsPriorToMedicareEligibility",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "sum_OhioValleyAsphaltMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Ohio Valley Asphalt , LLC, a majority owned indirect subsidiary of Summit Materials, LLC.",
        "label": "Ohio Valley Asphalt [Member]",
        "terseLabel": "Ohio Valley Asphalt"
       }
      }
     },
     "localname": "OhioValleyAsphaltMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_OperatingEngineersLocal101PensionPlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Operating Engineers Local 101 Pension Plan [Member]",
        "label": "Operating Engineers Local 101 Pension Plan [Member]",
        "terseLabel": "Operating Engineers Local 101 Pension Plan"
       }
      }
     },
     "localname": "OperatingEngineersLocal101PensionPlanMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_OperatingLeasesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Operating Leases [Abstract]",
        "label": "Operating Leases [Abstract]",
        "terseLabel": "Operating leases:"
       }
      }
     },
     "localname": "OperatingLeasesAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_OtherComprehensiveIncomeLossAdjustmentToPlanBenefitsNetOfTax": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 6.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of gain (loss) adjustment to other comprehensive income (loss) resulting from adjustment of plan benefits of defined benefit pension and other postretirement defined benefit plans.",
        "label": "Other Comprehensive Income (Loss), Adjustment to Plan Benefits, Net of Tax",
        "negatedLabel": "Adjustment to plan benefits"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAdjustmentToPlanBenefitsNetOfTax",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAociPensionAndOtherPostretirementBenefitPlansOtherThanNetPriorServiceCostCreditNetOfTax": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 5.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of reclassification adjustment from accumulated other comprehensive (income) loss other than net prior service cost (credit) related to pension and other postretirement benefit plans.",
        "label": "Other Comprehensive Income (Loss), Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Other Than Net Prior Service (Cost) Credit, Net of Tax",
        "negatedLabel": "Amortization of gain"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAmortizationAdjustmentFromAociPensionAndOtherPostretirementBenefitPlansOtherThanNetPriorServiceCostCreditNetOfTax",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_OtherEquityActivityShares": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents other stockholder equity activity, in shares.",
        "label": "Other Equity Activity, Shares",
        "terseLabel": "Shares redeemed to settle taxes and other (in shares)",
        "verboseLabel": "Other equity transactions (in shares)"
       }
      }
     },
     "localname": "OtherEquityActivityShares",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "sum_OtherEquityActivityValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents other stockholder equity activity.",
        "label": "Other Equity Activity, Value",
        "terseLabel": "Shares redeemed to settle taxes and other"
       }
      }
     },
     "localname": "OtherEquityActivityValue",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_OtherNonoperatingIncomeExpenseNet": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other Nonoperating Income Expense Net",
        "label": "Other Nonoperating Income Expense Net",
        "negatedLabel": "Other (income) loss, net"
       }
      }
     },
     "localname": "OtherNonoperatingIncomeExpenseNet",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_OtherProductsOrServicesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other products or services.",
        "label": "Other Products Or Services [Member]",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "OtherProductsOrServicesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_PavingAndRelatedServicesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Paving and related services.",
        "label": "Paving And Related Services [Member]",
        "terseLabel": "Paving and related services"
       }
      }
     },
     "localname": "PavingAndRelatedServicesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_PercentageOfParValueOnSeniorNotes": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage of par value on senior notes.",
        "label": "Percentage Of Par Value On Senior Notes",
        "terseLabel": "Percentage of par value of senior notes"
       }
      }
     },
     "localname": "PercentageOfParValueOnSeniorNotes",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "sum_PercentageOfTaxReceivableAgreement": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage of benefits related to tax receivable agreement paid by entity.",
        "label": "Percentage Of Tax Receivable Agreement",
        "terseLabel": "Percentage of benefits to be paid on tax receivable agreement"
       }
      }
     },
     "localname": "PercentageOfTaxReceivableAgreement",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "sum_PreciousMetalsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Precious metals.",
        "label": "Precious Metals [Member]",
        "terseLabel": "Precious metals"
       }
      }
     },
     "localname": "PreciousMetalsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ProceedsFromRepaymentsOfPartnershipContribution": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow (outflow) from capital received or paid in cash from a partner in a partnership during the period.",
        "label": "Proceeds from (Repayments) of Partnership Contribution",
        "terseLabel": "Proceeds from investment by member"
       }
      }
     },
     "localname": "ProceedsFromRepaymentsOfPartnershipContribution",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAccumulatedDepreciationAndAmortization": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": 2.0,
       "parentTag": "sum_PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAfterAccumulatedDepreciationAndAmortization",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, Accumulated Depreciation And Amortization",
        "label": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, Accumulated Depreciation And Amortization",
        "negatedLabel": "Less accumulated depreciation, depletion and amortization"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAccumulatedDepreciationAndAmortization",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAfterAccumulatedDepreciationAndAmortization": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 2.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, After Accumulated Depreciation And Amortization",
        "label": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, After Accumulated Depreciation And Amortization",
        "terseLabel": "Property, plant and equipment including finance lease right-of-use assets, net",
        "totalLabel": "Property, plant and equipment, net",
        "verboseLabel": "Property, plant and equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAfterAccumulatedDepreciationAndAmortization",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetBeforeAccumulatedDepreciationAndAmortization": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": 1.0,
       "parentTag": "sum_PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetAfterAccumulatedDepreciationAndAmortization",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, Before Accumulated Depreciation And Amortization",
        "label": "Property, Plant, And Equipment And Finance Lease Right-of-Use Asset, Before Accumulated Depreciation And Amortization",
        "terseLabel": "Property, plant and equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAndFinanceLeaseRightofUseAssetBeforeAccumulatedDepreciationAndAmortization",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_PurchaseCommitmentTerms": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Term of purchase commitment, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Purchase Commitment Terms",
        "terseLabel": "Term of purchase commitments"
       }
      }
     },
     "localname": "PurchaseCommitmentTerms",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "sum_QuarterlyFinancialInformationLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "[Line Items] for Quarterly Financial Information [Table]",
        "label": "Quarterly Financial Information [Line Items]",
        "terseLabel": "Quarterly Financial Information [Line Items]"
       }
      }
     },
     "localname": "QuarterlyFinancialInformationLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_QuarterlyFinancialInformationTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Quarterly Financial Information [Table]",
        "label": "Quarterly Financial Information [Table]",
        "terseLabel": "Quarterly Financial Information [Table]"
       }
      }
     },
     "localname": "QuarterlyFinancialInformationTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ReadyMixedConcreteMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Ready mixed concrete.",
        "label": "Ready Mixed Concrete [Member]",
        "terseLabel": "Ready-mix concrete"
       }
      }
     },
     "localname": "ReadyMixedConcreteMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ReserveRightsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Reserve rights.",
        "label": "Reserve Rights [Member]",
        "terseLabel": "Reserve rights"
       }
      }
     },
     "localname": "ReserveRightsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_RetentionReceivables": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_AccountsReceivableGrossCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amounts earned by entity but held by customers until projects have been fully completed or near completion and are expected to be billed and collected within one year of the balance sheet date (or the normal operating cycle, whichever is longer).",
        "label": "Retention Receivables",
        "terseLabel": "Retention receivables"
       }
      }
     },
     "localname": "RetentionReceivables",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RevenueFromContractWithCustomerCollectionTerms": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Revenue From Contract With Customer, Collection Terms",
        "label": "Revenue From Contract With Customer, Collection Terms",
        "terseLabel": "Collection terms"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerCollectionTerms",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "sum_RoyaltyAgreementFutureMinimumPaymentsDueCurrent": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty agreement future minimum payments due current.",
        "label": "Royalty Agreement Future Minimum Payments Due Current",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "RoyaltyAgreementFutureMinimumPaymentsDueCurrent",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RoyaltyAgreementFutureMinimumPaymentsDueInFiveYears": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty agreement future minimum payments due in five years.",
        "label": "Royalty Agreement Future Minimum Payments Due In Five Years",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "RoyaltyAgreementFutureMinimumPaymentsDueInFiveYears",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RoyaltyAgreementFutureMinimumPaymentsDueInFourYears": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty agreement future minimum payments due in four years.",
        "label": "Royalty Agreement Future Minimum Payments Due In Four Years",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "RoyaltyAgreementFutureMinimumPaymentsDueInFourYears",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RoyaltyAgreementFutureMinimumPaymentsDueInThreeYears": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty agreement future minimum payments due in three years.",
        "label": "Royalty Agreement Future Minimum Payments Due In Three Years",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "RoyaltyAgreementFutureMinimumPaymentsDueInThreeYears",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RoyaltyAgreementFutureMinimumPaymentsDueInTwoYears": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty agreement future minimum payments due in two years.",
        "label": "Royalty Agreement Future Minimum Payments Due In Two Years",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "RoyaltyAgreementFutureMinimumPaymentsDueInTwoYears",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_RoyaltyAgreementLiabilitiesPaymentsDueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Royalty Agreement Liabilities Payments Due [Abstract]",
        "label": "Royalty Agreement Liabilities Payments Due [Abstract]",
        "terseLabel": "Royalty Agreements"
       }
      }
     },
     "localname": "RoyaltyAgreementLiabilitiesPaymentsDueAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ScheduleOfAccruedExpensesLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule Of Accrued Expenses [Line Items]",
        "label": "Schedule Of Accrued Expenses [Line Items]",
        "terseLabel": "Schedule Of Accrued Expenses [Line Items]"
       }
      }
     },
     "localname": "ScheduleOfAccruedExpensesLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses",
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/AccruedExpensesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ScheduleOfBusinessAcquisitionsByAcquisitionNoncompeteAndDeferredConsiderationMaturityTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of acquisition related liabilities, including deferred consideration and noncompete arrangements.",
        "label": "Schedule of Business Acquisitions by Acquisition, Noncompete and Deferred Consideration [Table Text Block]",
        "terseLabel": "Schedule of remaining payments under noncompete and deferred consideration agreements"
       }
      }
     },
     "localname": "ScheduleOfBusinessAcquisitionsByAcquisitionNoncompeteAndDeferredConsiderationMaturityTableTextBlock",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "sum_ScheduleOfBusinessAcquisitionsNumberOfAcquisitionsByRegionTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the number of business acquisitions by region",
        "label": "Schedule of Business Acquisitions, Number of Acquisitions by Region [Table Text Block]",
        "terseLabel": "Summary of Acquisitions by Region"
       }
      }
     },
     "localname": "ScheduleOfBusinessAcquisitionsNumberOfAcquisitionsByRegionTableTextBlock",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "sum_ScheduleOfCashFlowSupplementalLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Schedule Of Cash Flow Supplemental [Line Items]",
        "terseLabel": "Schedule Of Cash Flow Supplemental [Line Items]"
       }
      }
     },
     "localname": "ScheduleOfCashFlowSupplementalLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ScheduleOfCashFlowSupplementalTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule Of Cash Flow Supplemental [Table]",
        "label": "Schedule Of Cash Flow Supplemental [Table]",
        "terseLabel": "Schedule Of Cash Flow Supplemental [Table]"
       }
      }
     },
     "localname": "ScheduleOfCashFlowSupplementalTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ScheduleOfDeferredFinancingFeesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of deferred financing fees.",
        "label": "Schedule Of Deferred Financing Fees [Table Text Block]",
        "terseLabel": "Summary of Activity for Deferred Financing Fees"
       }
      }
     },
     "localname": "ScheduleOfDeferredFinancingFeesTableTextBlock",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "sum_ScheduleOfDeferredIncomeTaxAssetsAndLiabilitiesTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule Of Deferred Income Tax Assets And Liabilities [Table]",
        "label": "Schedule Of Deferred Income Tax Assets And Liabilities [Table]",
        "terseLabel": "Schedule Of Deferred Income Tax Assets And Liabilities [Table]"
       }
      }
     },
     "localname": "ScheduleOfDeferredIncomeTaxAssetsAndLiabilitiesTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_ScheduleOfSummaryOfSignificantAccountingPoliciesAndRecentAccountingPronouncementsTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule Of Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Table]",
        "label": "Schedule Of Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Table]",
        "terseLabel": "Schedule Of Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Table]"
       }
      }
     },
     "localname": "ScheduleOfSummaryOfSignificantAccountingPoliciesAndRecentAccountingPronouncementsTable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_SeniorNotes8.5PercentDue2022Member": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents 8.5 percent senior notes of the entity due in 2022.",
        "label": "Senior Notes8.5 Percent Due2022 [Member]",
        "terseLabel": "8 1/2% Senior Notes, due 2022"
       }
      }
     },
     "localname": "SeniorNotes8.5PercentDue2022Member",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SeniorSecuredCreditFacilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents Senior Secured Credit Facilities of the entity.",
        "label": "Senior Secured Credit Facilities [Member]",
        "terseLabel": "Senior Secured Credit Facilities"
       }
      }
     },
     "localname": "SeniorSecuredCreditFacilitiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SeniorSecuredCreditFacilityLetterOfCreditMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents letters of credit under the entity's Senior Secured Credit Facility.",
        "label": "Senior Secured Credit Facility Letter Of Credit [Member]",
        "terseLabel": "Letter of Credit"
       }
      }
     },
     "localname": "SeniorSecuredCreditFacilityLetterOfCreditMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SeniorSecuredCreditFacilityRevolvingCreditFacilityMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents revolving credit facility under the entity's Senior Secured Credit Facility.",
        "label": "Senior Secured Credit Facility Revolving Credit Facility [Member]",
        "terseLabel": "Revolving Credit Facility"
       }
      }
     },
     "localname": "SeniorSecuredCreditFacilityRevolvingCreditFacilityMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyFourMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents term loan of the entity due in 2024 under the entity's Senior Secured Credit Facility.",
        "label": "Senior Secured Credit Facility Term Loan Due Two Thousand Twenty Four [Member]",
        "terseLabel": "Term Loan, due 2024"
       }
      }
     },
     "localname": "SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyFourMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyTwoMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents term loan of the entity due in 2022 under the entity's Senior Secured Credit Facility.",
        "label": "Senior Secured Credit Facility Term Loan Due Two Thousand Twenty Two [Member]",
        "terseLabel": "Term Loan, due 2022"
       }
      }
     },
     "localname": "SeniorSecuredCreditFacilityTermLoanDueTwoThousandTwentyTwoMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriod": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of equity-based payment instruments, excluding stock (or unit) options, exercised during the reporting period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Exercised in Period",
        "negatedLabel": "Number of units, Exercised (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriod",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "sum_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriodWeightedAverageGrantDateFairValue": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to exercise shares or units, other instruments, or cash in accordance with the terms of the arrangement.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Exercised in Period, Weighted Average Grant Date Fair Value",
        "terseLabel": "Number of units, Exercised (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriodWeightedAverageGrantDateFairValue",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "sum_ShortTermCorporateSecuritiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Short term corporate securities.",
        "label": "Short Term Corporate Securities [Member]",
        "terseLabel": "Short-term\u2014corporate"
       }
      }
     },
     "localname": "ShortTermCorporateSecuritiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ShortTermGovernmentSecuritiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Short term government securities.",
        "label": "Short Term Government Securities [Member]",
        "terseLabel": "Short-term\u2014government"
       }
      }
     },
     "localname": "ShortTermGovernmentSecuritiesMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SixPointFivePercentageSeniorNotesDueTwentyTwentySevenMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Six Point Five Percentage Senior Notes Due Twenty Twenty Seven [Member]",
        "label": "Six Point Five Percentage Senior Notes Due Twenty Twenty Seven [Member]",
        "terseLabel": "6 1\u20442% Senior Notes, due 2027"
       }
      }
     },
     "localname": "SixPointFivePercentageSeniorNotesDueTwentyTwentySevenMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeIssuedAt99.375PercentOfParMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents 6.125 percent senior notes of the entity due in 2023, issued at 99.375 percent of par.",
        "label": "Six Point One Two Five Percentage Senior Notes Due Twenty Twenty Three Issued At99.375 Percent Of Par [Member]",
        "terseLabel": "6 1/8% Senior Notes, due 2023, , issued at 99.375% of par"
       }
      }
     },
     "localname": "SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeIssuedAt99.375PercentOfParMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeIssuedAtParMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents 6.125 percent senior notes of the entity due in 2023, issued at par.",
        "label": "Six Point One Two Five Percentage Senior Notes Due Twenty Twenty Three Issued At Par [Member]",
        "terseLabel": "6 1/8% Senior Notes, due 2023, issued at par"
       }
      }
     },
     "localname": "SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeIssuedAtParMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents 6.125 percent senior notes of the entity due in 2023.",
        "label": "Six Point One Two Five Percentage Senior Notes Due Twenty Twenty Three [Member]",
        "terseLabel": "6 1/8% Senior Notes, due 2023"
       }
      }
     },
     "localname": "SixPointOneTwoFivePercentageSeniorNotesDueTwentyTwentyThreeMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_StockWarrantsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Stock Warrants [Member]",
        "label": "Stock Warrants [Member]",
        "terseLabel": "Warrants"
       }
      }
     },
     "localname": "StockWarrantsMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_StockholdersEquityAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 2.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest), excluding portion attributable to noncontrolling interest of the wholly owned indirect subsidiary of the registrant.",
        "label": "Stockholders' Equity Attributable to Noncontrolling Interest, Excluding Portion Attributable To Noncontrolling Interest Of Wholly Owned Indirect Subsidiary Of Registrant",
        "terseLabel": "Noncontrolling interest in Summit Holdings"
       }
      }
     },
     "localname": "StockholdersEquityAttributableToNoncontrollingInterestExcludingPortionAttributableToNoncontrollingInterestOfWhollyOwnedIndirectSubsidiaryOfRegistrant",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_SubsidiaryEntityParentVotingControlPercentage": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The percentage of the the subsidiary's voting power that is controlled by the parent registrant.",
        "label": "Subsidiary Entity Parent Voting Control Percentage",
        "terseLabel": "Voting power (as a percent)"
       }
      }
     },
     "localname": "SubsidiaryEntityParentVotingControlPercentage",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "sum_SummaryOfSignificantAccountingPoliciesAndRecentAccountingPronouncementsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]",
        "label": "Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]",
        "terseLabel": "Summary Of Significant Accounting Policies And Recent Accounting Pronouncements"
       }
      }
     },
     "localname": "SummaryOfSignificantAccountingPoliciesAndRecentAccountingPronouncementsLineItems",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_SummitHoldingsLpMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summit Materials Holdings L.P., a non-wholly owned subsidiary of the registrant.",
        "label": "Summit Holdings Lp [Member]",
        "terseLabel": "Summit Holdings LP"
       }
      }
     },
     "localname": "SummitHoldingsLpMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SummitMaterialsIncMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summit Materials Inc [Member]",
        "label": "Summit Materials Inc [Member]",
        "terseLabel": "Summit Materials Inc"
       }
      }
     },
     "localname": "SummitMaterialsIncMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SummitMaterialsIncorporatedAndSummitHoldingsLPMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information pertaining to Summit Materials, Inc. and Summit Holdings, LP.",
        "label": "Summit Materials Incorporated And Summit Holdings L P [Member]",
        "terseLabel": "Summit Materials Incorporated And Summit Holdings LP"
       }
      }
     },
     "localname": "SummitMaterialsIncorporatedAndSummitHoldingsLPMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SummitMaterialsLlcAndSummitMaterialsFinanceCorpMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information pertaining to Summit Materials, LLC and Summit Materials Finance Corp. (collectively, the \"Issuers\").",
        "label": "Summit Materials Llc And Summit Materials Finance Corp [Member]",
        "terseLabel": "Issuers"
       }
      }
     },
     "localname": "SummitMaterialsLlcAndSummitMaterialsFinanceCorpMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_SummitMaterialsLlcMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summit Materials, LLC, a wholly owned indirect subsidiary of the registrant.",
        "label": "Summit Materials Llc [Member]",
        "terseLabel": "Summit Materials, LLC"
       }
      }
     },
     "localname": "SummitMaterialsLlcMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses",
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/AccruedExpensesTables",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables",
      "http://www.summitmaterials.com/role/Acquisitions",
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail",
      "http://www.summitmaterials.com/role/AcquisitionsTables",
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/Debt",
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails",
      "http://www.summitmaterials.com/role/DebtTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
      "http://www.summitmaterials.com/role/FairValueTables",
      "http://www.summitmaterials.com/role/Goodwill",
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/GoodwillTables",
      "http://www.summitmaterials.com/role/IncomeTaxes",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesTables",
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails",
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails",
      "http://www.summitmaterials.com/role/Inventories",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/InventoriesTables",
      "http://www.summitmaterials.com/role/Leases",
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
      "http://www.summitmaterials.com/role/LeasesTables",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables",
      "http://www.summitmaterials.com/role/RevenueRecognition",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionTables",
      "http://www.summitmaterials.com/role/SegmentInformation",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationTables",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformation",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensation",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails",
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables",
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_TaxReceivableAgreementExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 4.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expense recognized for the period related to the tax receivable agreement.",
        "label": "Tax Receivable Agreement Expense",
        "terseLabel": "Tax receivable agreement expense (benefit)"
       }
      }
     },
     "localname": "TaxReceivableAgreementExpense",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_TaxReceivableAgreementLiability": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 4.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the liability due to former holders of LP Units related to the Tax Receivable Agreement.",
        "label": "Tax Receivable Agreement Liability",
        "verboseLabel": "Tax receivable agreement liability"
       }
      }
     },
     "localname": "TaxReceivableAgreementLiability",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_TaxReceivableAgreementMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information pertaining to the tax receivable agreement.",
        "label": "Tax Receivable Agreement [Member]",
        "terseLabel": "Tax Receivable Agreement"
       }
      }
     },
     "localname": "TaxReceivableAgreementMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_TaxReceivableAgreementPolicyTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for tax receivable agreement.",
        "label": "Tax Receivable Agreement [Policy Text Block]",
        "terseLabel": "Tax Receivable Agreement"
       }
      }
     },
     "localname": "TaxReceivableAgreementPolicyTextBlock",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "sum_TenPointZeroFivePercentageSeniorNotesDueTwentyTwentyMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents 10.5 percent senior notes of the entity due in 2020.",
        "label": "Ten Point Zero Five Percentage Senior Notes Due Twenty Twenty [Member]",
        "terseLabel": "10 1/2% Senior Notes, due 2020"
       }
      }
     },
     "localname": "TenPointZeroFivePercentageSeniorNotesDueTwentyTwentyMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_TradeAccountsReceivable": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AccountsReceivableGrossCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Trade receivable amounts due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer) for goods or services.",
        "label": "Trade Accounts Receivable",
        "terseLabel": "Trade accounts receivable"
       }
      }
     },
     "localname": "TradeAccountsReceivable",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_TruckAndAutoFleetMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Truck and auto fleet.",
        "label": "Truck And Auto Fleet [Member]",
        "terseLabel": "Truck and auto fleet"
       }
      }
     },
     "localname": "TruckAndAutoFleetMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_TwoThousandFifteenOmnibusEquityIncentivePlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two Thousand Fifteen Omnibus Equity Incentive Plan [Member]",
        "label": "Two Thousand Fifteen Omnibus Equity Incentive Plan [Member]",
        "terseLabel": "2015 Omnibus Equity Incentive Plan"
       }
      }
     },
     "localname": "TwoThousandFifteenOmnibusEquityIncentivePlanMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "sum_ValuationAllowanceDeferredTaxAssetDecreaseDueToReleaseOfAllowance": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of decrease in the valuation allowance due to release of allowance for specific deferred tax assets.",
        "label": "Valuation Allowance, Deferred Tax Asset, Decrease due to Release of Allowance",
        "terseLabel": "Current year decreases (increases) from operations"
       }
      }
     },
     "localname": "ValuationAllowanceDeferredTaxAssetDecreaseDueToReleaseOfAllowance",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_ValuationAllowanceDeferredTaxAssetIncreaseDecreaseForExchangeOfLPUnits": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in the valuation allowance for deferred tax asset associated with exchange of L.P. Units.",
        "label": "Valuation Allowance, Deferred Tax Asset, Increase (Decrease) for Exchange of L P Units",
        "terseLabel": "Additional basis from exchanged LP Units"
       }
      }
     },
     "localname": "ValuationAllowanceDeferredTaxAssetIncreaseDecreaseForExchangeOfLPUnits",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "sum_WeightedAverageLeaseTermAndDiscountRateAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted Average Lease Term And Discount Rate [Abstract]",
        "label": "Weighted Average Lease Term And Discount Rate [Abstract]",
        "terseLabel": "Weighted average:"
       }
      }
     },
     "localname": "WeightedAverageLeaseTermAndDiscountRateAbstract",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "sum_WestMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the west region segment of the reporting entity.",
        "label": "West [Member]",
        "terseLabel": "West"
       }
      }
     },
     "localname": "WestMember",
     "nsuri": "http://www.summitmaterials.com/20191228",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AOCIAttributableToParentNetOfTaxRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "AOCI Attributable to Parent, Net of Tax [Roll Forward]",
        "terseLabel": "Changes in each component of accumulated other comprehensive loss"
       }
      }
     },
     "localname": "AOCIAttributableToParentNetOfTaxRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccountingPoliciesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Accounting Policies [Abstract]"
       }
      }
     },
     "localname": "AccountingPoliciesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccountingStandardsUpdate201602Member": {
     "auth_ref": [
      "r470"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accounting Standards Update 2016-02 Leases (Topic 842).",
        "label": "Accounting Standards Update 2016-02 [Member]",
        "terseLabel": "Accounting Standards Update 2016-02"
       }
      }
     },
     "localname": "AccountingStandardsUpdate201602Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccountsNotesAndLoansReceivableLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Accounts, Notes, Loans and Financing Receivable [Line Items]",
        "terseLabel": "Accounts, Notes, Loans and Financing Receivable [Line Items]"
       }
      }
     },
     "localname": "AccountsNotesAndLoansReceivableLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock": {
     "auth_ref": [
      "r39"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for accounts payable and accrued liabilities at the end of the reporting period.",
        "label": "Accounts Payable and Accrued Liabilities Disclosure [Text Block]",
        "verboseLabel": "Accrued Expenses"
       }
      }
     },
     "localname": "AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpenses"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_AccountsPayableAndAccruedLiabilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing accounts payable and accrued liabilities.",
        "label": "Accounts Payable and Accrued Liabilities [Member]",
        "terseLabel": "Accrued expenses."
       }
      }
     },
     "localname": "AccountsPayableAndAccruedLiabilitiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccountsPayableCurrent": {
     "auth_ref": [
      "r38"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accounts Payable, Current",
        "terseLabel": "Accounts payable"
       }
      }
     },
     "localname": "AccountsPayableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccountsReceivableGrossCurrent": {
     "auth_ref": [
      "r179",
      "r180"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AccountsReceivableNetCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.",
        "label": "Accounts Receivable, before Allowance for Credit Loss, Current",
        "totalLabel": "Accounts receivable"
       }
      }
     },
     "localname": "AccountsReceivableGrossCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccountsReceivableNetCurrent": {
     "auth_ref": [
      "r3",
      "r20",
      "r179",
      "r180",
      "r273"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.",
        "label": "Accounts Receivable, after Allowance for Credit Loss, Current",
        "terseLabel": "Accounts receivable, net",
        "totalLabel": "Accounts receivable, net"
       }
      }
     },
     "localname": "AccountsReceivableNetCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccountsReceivableRelatedParties": {
     "auth_ref": [
      "r19",
      "r123",
      "r491",
      "r492",
      "r493",
      "r519"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_AccountsReceivableGrossCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "For an unclassified balance sheet, amount of receivables arising from transactions with related parties.",
        "label": "Accounts Receivable, Related Parties",
        "terseLabel": "Receivables from related parties"
       }
      }
     },
     "localname": "AccountsReceivableRelatedParties",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent": {
     "auth_ref": [
      "r7",
      "r43",
      "r362"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of obligations incurred and payable for real and property taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accrual for Taxes Other than Income Taxes, Current",
        "terseLabel": "Non-income taxes"
       }
      }
     },
     "localname": "AccrualForTaxesOtherThanIncomeTaxesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccruedEmployeeBenefitsCurrent": {
     "auth_ref": [
      "r6",
      "r7",
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accrued Employee Benefits, Current",
        "terseLabel": "Payroll and benefits"
       }
      }
     },
     "localname": "AccruedEmployeeBenefitsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccruedInsuranceCurrent": {
     "auth_ref": [
      "r6",
      "r7",
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of obligations incurred through that date and payable to insurance entities to mitigate potential loss from various risks or to satisfy a promise to provide certain coverage's to employees. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accrued Insurance, Current",
        "terseLabel": "Insurance"
       }
      }
     },
     "localname": "AccruedInsuranceCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccruedLiabilitiesCurrent": {
     "auth_ref": [
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accrued Liabilities, Current",
        "terseLabel": "Accrued expenses",
        "totalLabel": "Total"
       }
      }
     },
     "localname": "AccruedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccruedLiabilitiesMember": {
     "auth_ref": [
      "r43"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This item represents obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered.",
        "label": "Accrued Liabilities [Member]",
        "terseLabel": "Accrued expenses"
       }
      }
     },
     "localname": "AccruedLiabilitiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccruedProfessionalFeesCurrent": {
     "auth_ref": [
      "r6",
      "r7",
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accrued Professional Fees, Current",
        "terseLabel": "Professional fees"
       }
      }
     },
     "localname": "AccruedProfessionalFeesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember": {
     "auth_ref": [
      "r61",
      "r67",
      "r70",
      "r305",
      "r424"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive (income) loss related to defined benefit plans attributable to the parent.",
        "label": "Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]",
        "terseLabel": "Change in retirement plans"
       }
      }
     },
     "localname": "AccumulatedDefinedBenefitPlansAdjustmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment": {
     "auth_ref": [
      "r36",
      "r219"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_PropertyPlantAndEquipmentNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.",
        "label": "Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment",
        "negatedLabel": "Less accumulated depreciation, depletion and amortization",
        "verboseLabel": "Property, plant and equipment, accumulated depreciation, depletion and amortization"
       }
      }
     },
     "localname": "AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember": {
     "auth_ref": [
      "r67",
      "r78",
      "r423"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive income (loss) from gain (loss) of derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness, attributable to parent.",
        "label": "Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]",
        "terseLabel": "Cash flow hedge adjustments"
       }
      }
     },
     "localname": "AccumulatedGainLossNetCashFlowHedgeParentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember": {
     "auth_ref": [
      "r59",
      "r67",
      "r70",
      "r423"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive income (loss) resulting from gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges, attributable to the parent.",
        "label": "Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]",
        "terseLabel": "Cash flow hedge adjustments"
       }
      }
     },
     "localname": "AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Accumulated Other Comprehensive Income (Loss) [Line Items]",
        "terseLabel": "Accumulated Other Comprehensive Income (Loss) [Line Items]"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeLossLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax": {
     "auth_ref": [
      "r65",
      "r66",
      "r67"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 3.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.",
        "label": "Accumulated Other Comprehensive Income (Loss), Net of Tax",
        "terseLabel": "Accumulated other comprehensive income"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeLossTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about components of accumulated other comprehensive income (loss).",
        "label": "Accumulated Other Comprehensive Income (Loss) [Table]",
        "terseLabel": "Accumulated Other Comprehensive Income (Loss) [Table]"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeLossTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeMember": {
     "auth_ref": [
      "r64",
      "r67",
      "r70",
      "r424"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated increase (decrease) in equity from transactions and other events and circumstances from non-owner sources, attributable to the parent. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners.",
        "label": "AOCI Attributable to Parent [Member]",
        "terseLabel": "Accumulated Other Comprehensive Income (Loss)"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedTranslationAdjustmentMember": {
     "auth_ref": [
      "r58",
      "r67",
      "r70",
      "r424"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive income (loss) resulting from foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to the parent.",
        "label": "Accumulated Foreign Currency Adjustment Attributable to Parent [Member]",
        "terseLabel": "Foreign currency translation adjustment"
       }
      }
     },
     "localname": "AccumulatedTranslationAdjustmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdditionalPaidInCapitalCommonStock": {
     "auth_ref": [
      "r21"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 1.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.",
        "label": "Additional Paid in Capital, Common Stock",
        "terseLabel": "Additional paid-in capital"
       }
      }
     },
     "localname": "AdditionalPaidInCapitalCommonStock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AdditionalPaidInCapitalMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders.",
        "label": "Additional Paid-in Capital [Member]",
        "terseLabel": "Additional Paid-in Capital"
       }
      }
     },
     "localname": "AdditionalPaidInCapitalMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdjustmentsForNewAccountingPronouncementsAxis": {
     "auth_ref": [
      "r131"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by new accounting pronouncement.",
        "label": "Adjustments for New Accounting Pronouncements [Axis]",
        "terseLabel": "Adjustments for New Accounting Pronouncements [Axis]"
       }
      }
     },
     "localname": "AdjustmentsForNewAccountingPronouncementsAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue": {
     "auth_ref": [
      "r330",
      "r332",
      "r359",
      "r360"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase to additional paid-in capital (APIC) for recognition of cost for award under share-based payment arrangement.",
        "label": "APIC, Share-based Payment Arrangement, Increase for Cost Recognition",
        "terseLabel": "Share-based compensation"
       }
      }
     },
     "localname": "AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]",
        "verboseLabel": "Adjustments to reconcile net income to net cash provided by operating activities:"
       }
      }
     },
     "localname": "AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AllocatedShareBasedCompensationExpense": {
     "auth_ref": [
      "r332",
      "r353",
      "r358"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.",
        "label": "Share-based Payment Arrangement, Expense",
        "terseLabel": "Share-based compensation expense"
       }
      }
     },
     "localname": "AllocatedShareBasedCompensationExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent": {
     "auth_ref": [
      "r26",
      "r182",
      "r188"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_AccountsReceivableNetCurrent",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of allowance for credit loss on accounts receivable, classified as current.",
        "label": "Accounts Receivable, Allowance for Credit Loss, Current",
        "negatedLabel": "Less: Allowance for doubtful accounts"
       }
      }
     },
     "localname": "AllowanceForDoubtfulAccountsReceivableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AmortizationOfFinancingCosts": {
     "auth_ref": [
      "r83",
      "r109",
      "r464"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense attributable to debt issuance costs.",
        "label": "Amortization of Debt Issuance Costs",
        "negatedLabel": "Amortization"
       }
      }
     },
     "localname": "AmortizationOfFinancingCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AmortizationOfIntangibleAssets": {
     "auth_ref": [
      "r109",
      "r207",
      "r213"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.",
        "label": "Amortization of Intangible Assets",
        "terseLabel": "Amortization expense"
       }
      }
     },
     "localname": "AmortizationOfIntangibleAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount": {
     "auth_ref": [
      "r145"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.",
        "label": "Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount",
        "terseLabel": "Anti dilutive shares excluded from calculation of earnings per share"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis": {
     "auth_ref": [
      "r145"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of antidilutive security.",
        "label": "Antidilutive Securities [Axis]",
        "terseLabel": "Antidilutive Securities [Axis]"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AntidilutiveSecuritiesNameDomain": {
     "auth_ref": [
      "r145"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Incremental common shares attributable to securities that were not included in diluted earnings per share (EPS) because to do so would increase EPS amounts or decrease loss per share amounts for the period presented.",
        "label": "Antidilutive Securities, Name [Domain]",
        "terseLabel": "Antidilutive Securities, Name [Domain]"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ArrangementsAndNonarrangementTransactionsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations.",
        "label": "Collaborative Arrangement and Arrangement Other than Collaborative [Domain]",
        "terseLabel": "Collaborative Arrangement and Arrangement Other than Collaborative [Domain]"
       }
      }
     },
     "localname": "ArrangementsAndNonarrangementTransactionsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AssetRetirementObligation": {
     "auth_ref": [
      "r226"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.",
        "label": "Asset Retirement Obligation",
        "periodEndLabel": "Ending balance",
        "periodStartLabel": "Beginning balance"
       }
      }
     },
     "localname": "AssetRetirementObligation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetRetirementObligationAccretionExpense": {
     "auth_ref": [
      "r225",
      "r228"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.",
        "label": "Asset Retirement Obligation, Accretion Expense",
        "terseLabel": "Accretion",
        "verboseLabel": "Accretion expense"
       }
      }
     },
     "localname": "AssetRetirementObligationAccretionExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetRetirementObligationCurrent": {
     "auth_ref": [
      "r226"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.",
        "label": "Asset Retirement Obligation, Current",
        "terseLabel": "Asset retirement obligation, current"
       }
      }
     },
     "localname": "AssetRetirementObligationCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetRetirementObligationDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Asset Retirement Obligation Disclosure [Abstract]"
       }
      }
     },
     "localname": "AssetRetirementObligationDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetRetirementObligationDisclosureTextBlock": {
     "auth_ref": [
      "r231"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.",
        "label": "Asset Retirement Obligation Disclosure [Text Block]",
        "terseLabel": "Accrued Mining and Landfill Reclamation"
       }
      }
     },
     "localname": "AssetRetirementObligationDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_AssetRetirementObligationLiabilitiesSettled": {
     "auth_ref": [
      "r227"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.",
        "label": "Asset Retirement Obligation, Liabilities Settled",
        "negatedLabel": "Settlement of reclamation obligations"
       }
      }
     },
     "localname": "AssetRetirementObligationLiabilitiesSettled",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetRetirementObligationRevisionOfEstimate": {
     "auth_ref": [
      "r224",
      "r229"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.",
        "label": "Asset Retirement Obligation, Revision of Estimate",
        "terseLabel": "Change in cost estimate"
       }
      }
     },
     "localname": "AssetRetirementObligationRevisionOfEstimate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]",
        "terseLabel": "Asset Retirement Obligation, Activity"
       }
      }
     },
     "localname": "AssetRetirementObligationRollForwardAnalysisRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationActivityForAssetRetirementObligationsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetRetirementObligationsAndEnvironmentalCostPolicyTextBlock": {
     "auth_ref": [
      "r118",
      "r230",
      "r233",
      "r234"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for legal obligation associated with retirement of long-lived asset that results from acquisition, construction, or development or from normal operation of long-lived asset, and environmental remediation liability from improper or other-than-normal operation of long-lived asset. Includes, but is not limited to, timing of recognition and whether obligation is measured on discounted basis.",
        "label": "Asset Retirement Obligation and Environmental Cost [Policy Text Block]",
        "terseLabel": "Accrued Mining and Landfill Reclamation"
       }
      }
     },
     "localname": "AssetRetirementObligationsAndEnvironmentalCostPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_Assets": {
     "auth_ref": [
      "r171",
      "r500",
      "r514"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.",
        "label": "Assets",
        "terseLabel": "Total assets",
        "totalLabel": "Total assets"
       }
      }
     },
     "localname": "Assets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets [Abstract]",
        "terseLabel": "Assets"
       }
      }
     },
     "localname": "AssetsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsAndLiabilitiesLesseeAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets and Liabilities, Lessee [Abstract]",
        "terseLabel": "Supplemental balance sheet information related to leases:"
       }
      }
     },
     "localname": "AssetsAndLiabilitiesLesseeAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsCurrent": {
     "auth_ref": [
      "r4",
      "r5",
      "r55"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 1.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.",
        "label": "Assets, Current",
        "totalLabel": "Total current assets"
       }
      }
     },
     "localname": "AssetsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsCurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets, Current [Abstract]",
        "terseLabel": "Current assets:"
       }
      }
     },
     "localname": "AssetsCurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsHeldUnderCapitalLeasesMember": {
     "auth_ref": [
      "r468"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Long lived property, plant or equipment assets held by a lessee through a capital lease arrangement.",
        "label": "Assets Held under Capital Leases [Member]",
        "terseLabel": "Capital leases for equipment and building"
       }
      }
     },
     "localname": "AssetsHeldUnderCapitalLeasesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AwardTypeAxis": {
     "auth_ref": [
      "r333",
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of award under share-based payment arrangement.",
        "label": "Award Type [Axis]",
        "terseLabel": "Award Type [Axis]"
       }
      }
     },
     "localname": "AwardTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BalanceSheetLocationAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by location on balance sheet (statement of financial position).",
        "label": "Balance Sheet Location [Axis]",
        "terseLabel": "Balance Sheet Location [Axis]"
       }
      }
     },
     "localname": "BalanceSheetLocationAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BalanceSheetLocationDomain": {
     "auth_ref": [
      "r436",
      "r439"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Location in the balance sheet (statement of financial position).",
        "label": "Balance Sheet Location [Domain]",
        "terseLabel": "Balance Sheet Location [Domain]"
       }
      }
     },
     "localname": "BalanceSheetLocationDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationNarrativeDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BilledContractReceivables": {
     "auth_ref": [
      "r50"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_AccountsReceivableGrossCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the balance sheet date.",
        "label": "Billed Contracts Receivable",
        "terseLabel": "Construction contract receivables"
       }
      }
     },
     "localname": "BilledContractReceivables",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BuildingImprovementsMember": {
     "auth_ref": [
      "r218"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Addition, improvement, or renovation to a facility held for productive use including, but not limited to, office, production, storage and distribution facilities.",
        "label": "Building Improvements [Member]",
        "terseLabel": "Buildings and improvements"
       }
      }
     },
     "localname": "BuildingImprovementsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BuildingMember": {
     "auth_ref": [
      "r218"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Facility held for productive use including, but not limited to, office, production, storage and distribution facilities.",
        "label": "Building [Member]",
        "terseLabel": "Building"
       }
      }
     },
     "localname": "BuildingMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BusinessAcquisitionAcquireeDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Identification of the acquiree in a material business combination (or series of individually immaterial business combinations), which may include the name or other type of identification of the acquiree.",
        "label": "Business Acquisition, Acquiree [Domain]",
        "terseLabel": "Business Acquisition, Acquiree [Domain]"
       }
      }
     },
     "localname": "BusinessAcquisitionAcquireeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BusinessAcquisitionAxis": {
     "auth_ref": [
      "r398",
      "r399"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by business combination or series of individually immaterial business combinations.",
        "label": "Business Acquisition [Axis]",
        "terseLabel": "Business Acquisition [Axis]"
       }
      }
     },
     "localname": "BusinessAcquisitionAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BusinessAcquisitionLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Business Acquisition [Line Items]",
        "terseLabel": "Business Acquisition [Line Items]"
       }
      }
     },
     "localname": "BusinessAcquisitionLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BusinessCombinationAcquisitionRelatedCosts": {
     "auth_ref": [
      "r397"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 5.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.",
        "label": "Business Combination, Acquisition Related Costs",
        "verboseLabel": "Transaction costs"
       }
      }
     },
     "localname": "BusinessCombinationAcquisitionRelatedCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationConsiderationTransferred1": {
     "auth_ref": [
      "r407",
      "r408",
      "r410"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.",
        "label": "Business Combination, Consideration Transferred",
        "terseLabel": "Net cash paid for acquisitions"
       }
      }
     },
     "localname": "BusinessCombinationConsiderationTransferred1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred": {
     "auth_ref": [
      "r405",
      "r407",
      "r408",
      "r411"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.",
        "label": "Business Combination, Consideration Transferred, Liabilities Incurred",
        "negatedLabel": "Acquisition-related liabilities"
       }
      }
     },
     "localname": "BusinessCombinationConsiderationTransferredLiabilitiesIncurred",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent": {
     "auth_ref": [
      "r406",
      "r409"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer.",
        "label": "Business Combination, Contingent Consideration, Liability, Current",
        "terseLabel": "Current portion of acquisition-related liabilities and Accrued expenses - Contingent consideration"
       }
      }
     },
     "localname": "BusinessCombinationContingentConsiderationLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput": {
     "auth_ref": [
      "r449"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of input used to measure contingent consideration liability from business combination.",
        "label": "Business Combination, Contingent Consideration, Liability, Measurement Input",
        "terseLabel": "Discount rate"
       }
      }
     },
     "localname": "BusinessCombinationContingentConsiderationLiabilityMeasurementInput",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "decimalItemType"
    },
    "us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent": {
     "auth_ref": [
      "r406",
      "r409"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer.",
        "label": "Business Combination, Contingent Consideration, Liability, Noncurrent",
        "terseLabel": "Acquisition-related liabilities and Other noncurrent liabilities - Contingent consideration"
       }
      }
     },
     "localname": "BusinessCombinationContingentConsiderationLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationDisclosureTextBlock": {
     "auth_ref": [
      "r412"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).",
        "label": "Business Combination Disclosure [Text Block]",
        "terseLabel": "Acquisitions"
       }
      }
     },
     "localname": "BusinessCombinationDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Acquisitions"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets": {
     "auth_ref": [
      "r400",
      "r401",
      "r457"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of financial assets (as defined) recognized as of the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets",
        "terseLabel": "Financial assets"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialLiabilities": {
     "auth_ref": [
      "r400",
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 6.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of financial liabilities assumed (as defined) which have been recognized as of the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities",
        "negatedLabel": "Financial liabilities"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill": {
     "auth_ref": [
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 4.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of intangible assets, excluding goodwill, acquired at the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill",
        "terseLabel": "Intangible assets"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory": {
     "auth_ref": [
      "r400",
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of inventory recognized as of the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory",
        "terseLabel": "Inventories"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet": {
     "auth_ref": [
      "r400",
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net",
        "totalLabel": "Net assets acquired"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther": {
     "auth_ref": [
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 7.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other",
        "negatedLabel": "Other long-term liabilities"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment": {
     "auth_ref": [
      "r400",
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 3.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of property, plant, and equipment recognized as of the acquisition date.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment",
        "terseLabel": "Property, plant and equipment"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet": {
     "auth_ref": [
      "r401"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.",
        "label": "Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net",
        "totalLabel": "Purchase price"
       }
      }
     },
     "localname": "BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_BusinessCombinationsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Business Combinations [Abstract]"
       }
      }
     },
     "localname": "BusinessCombinationsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CapitalLeaseObligationsCurrent": {
     "auth_ref": [
      "r12",
      "r467",
      "r469"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 8.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of capital lease obligation due within one year or the normal operating cycle, if longer.",
        "label": "Capital Lease Obligations, Current",
        "terseLabel": "Finance lease obligations",
        "verboseLabel": "Capital lease obligations, current"
       }
      }
     },
     "localname": "CapitalLeaseObligationsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CapitalLeaseObligationsNoncurrent": {
     "auth_ref": [
      "r46",
      "r467",
      "r469"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal, through the balance sheet date and due to be paid more than one year (or one operating cycle, if longer) after the balance sheet date.",
        "label": "Capital Lease Obligations, Noncurrent",
        "verboseLabel": "Capital lease obligations, noncurrent"
       }
      }
     },
     "localname": "CapitalLeaseObligationsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CapitalUnitClassDomain": {
     "auth_ref": [
      "r527"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Description of the type or class of capital units or capital shares.",
        "label": "Capital Unit, Class [Domain]",
        "terseLabel": "Capital Unit, Class [Domain]"
       }
      }
     },
     "localname": "CapitalUnitClassDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CapitalUnitsByClassAxis": {
     "auth_ref": [
      "r526",
      "r528"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type or class of the entity's capital units.",
        "label": "Capital Units by Class [Axis]",
        "terseLabel": "Capital Units by Class [Axis]"
       }
      }
     },
     "localname": "CapitalUnitsByClassAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_CarryingReportedAmountFairValueDisclosureMember": {
     "auth_ref": [
      "r455",
      "r456"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measured as reported on the statement of financial position (balance sheet).",
        "label": "Reported Value Measurement [Member]",
        "terseLabel": "Carrying Value"
       }
      }
     },
     "localname": "CarryingReportedAmountFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CashAndCashEquivalentsAtCarryingValue": {
     "auth_ref": [
      "r1",
      "r33",
      "r111"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.",
        "label": "Cash and Cash Equivalents, at Carrying Value",
        "terseLabel": "Cash and cash equivalents"
       }
      }
     },
     "localname": "CashAndCashEquivalentsAtCarryingValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents": {
     "auth_ref": [
      "r105",
      "r111",
      "r116"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.",
        "label": "Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents",
        "periodEndLabel": "Cash and cash equivalents\u2014end of period",
        "periodStartLabel": "Cash and cash equivalents\u2014beginning of period"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect": {
     "auth_ref": [
      "r105",
      "r459"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in cash, cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; including effect from exchange rate change. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.",
        "label": "Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect",
        "totalLabel": "Net increase (decrease) in cash"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashFlowHedgingMember": {
     "auth_ref": [
      "r434"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Hedge of the exposure to variability in the cash flows of a recognized asset or liability, or of a forecasted transaction, that is attributable to a particular risk.",
        "label": "Cash Flow Hedging [Member]",
        "terseLabel": "Cash flow hedges"
       }
      }
     },
     "localname": "CashFlowHedgingMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CashFlowSupplementalDisclosuresTextBlock": {
     "auth_ref": [
      "r117"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for supplemental cash flow activities, including cash, noncash, and part noncash transactions, for the period. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. \"Part noncash\" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.",
        "label": "Cash Flow, Supplemental Disclosures [Text Block]",
        "terseLabel": "Supplemental Cash Flow Information"
       }
      }
     },
     "localname": "CashFlowSupplementalDisclosuresTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ChangeInContractWithCustomerAssetAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Change in Contract with Customer, Asset [Abstract]",
        "terseLabel": "Change in Contract with Customer, Asset [Abstract]"
       }
      }
     },
     "localname": "ChangeInContractWithCustomerAssetAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ChangeInContractWithCustomerLiabilityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Change in Contract with Customer, Liability [Abstract]",
        "terseLabel": "Change in Contract with Customer, Liability [Abstract]"
       }
      }
     },
     "localname": "ChangeInContractWithCustomerLiabilityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ClassOfStockDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share of stock differentiated by the voting rights the holder receives. Examples include, but are not limited to, common stock, redeemable preferred stock, nonredeemable preferred stock, and convertible stock.",
        "label": "Class of Stock [Domain]",
        "terseLabel": "Class of Stock [Domain]"
       }
      }
     },
     "localname": "ClassOfStockDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ClassOfWarrantOrRightAxis": {
     "auth_ref": [
      "r126",
      "r265",
      "r331"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of warrant or right issued.",
        "label": "Class of Warrant or Right [Axis]",
        "terseLabel": "Class of Warrant or Right [Axis]"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ClassOfWarrantOrRightDomain": {
     "auth_ref": [
      "r122"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the class or type of warrant or right outstanding. Warrants and rights represent derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months.",
        "label": "Class of Warrant or Right [Domain]",
        "terseLabel": "Class of Warrant or Right [Domain]"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommitmentsAndContingencies": {
     "auth_ref": [
      "r48",
      "r238",
      "r505",
      "r521"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 3.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the caption on the face of the balance sheet to indicate that the entity has entered into (1) purchase or supply arrangements that will require expending a portion of its resources to meet the terms thereof, and (2) is exposed to potential losses or, less frequently, gains, arising from (a) possible claims against a company's resources due to future performance under contract terms, and (b) possible losses or likely gains from uncertainties that will ultimately be resolved when one or more future events that are deemed likely to occur do occur or fail to occur.",
        "label": "Commitments and Contingencies",
        "terseLabel": "Commitments and contingencies (see note 16)"
       }
      }
     },
     "localname": "CommitmentsAndContingencies",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CommitmentsAndContingenciesDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Commitments and Contingencies Disclosure [Abstract]"
       }
      }
     },
     "localname": "CommitmentsAndContingenciesDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CommitmentsAndContingenciesDisclosureTextBlock": {
     "auth_ref": [
      "r237",
      "r245"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for commitments and contingencies.",
        "label": "Commitments and Contingencies Disclosure [Text Block]",
        "terseLabel": "Commitments and Contingencies"
       }
      }
     },
     "localname": "CommitmentsAndContingenciesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CommonClassAMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Classification of common stock representing ownership interest in a corporation.",
        "label": "Common Class A [Member]",
        "terseLabel": "Common Class A"
       }
      }
     },
     "localname": "CommonClassAMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonClassBMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Classification of common stock that has different rights than Common Class A, representing ownership interest in a corporation.",
        "label": "Common Class B [Member]",
        "terseLabel": "Common Class B"
       }
      }
     },
     "localname": "CommonClassBMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonStockDividendsPerShareDeclared": {
     "auth_ref": [
      "r262"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate dividends declared during the period for each share of common stock outstanding.",
        "label": "Common Stock, Dividends, Per Share, Declared",
        "terseLabel": "Dividends (in dollars per share)"
       }
      }
     },
     "localname": "CommonStockDividendsPerShareDeclared",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInRedeemableNoncontrollingInterestAndStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterestParenthetical"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_CommonStockDividendsShares": {
     "auth_ref": [
      "r257"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares of common stock issued as dividends during the period. Excludes stock splits.",
        "label": "Common Stock Dividends, Shares",
        "terseLabel": "Dividend (in shares)"
       }
      }
     },
     "localname": "CommonStockDividendsShares",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Stock that is subordinate to all other stock of the issuer.",
        "label": "Common Stock [Member]",
        "terseLabel": "Common Stock"
       }
      }
     },
     "localname": "CommonStockMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonStockParOrStatedValuePerShare": {
     "auth_ref": [
      "r18"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Face amount or stated value per share of common stock.",
        "label": "Common Stock, Par or Stated Value Per Share",
        "terseLabel": "Common stock, par value (USD per share)"
       }
      }
     },
     "localname": "CommonStockParOrStatedValuePerShare",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_CommonStockSharesAuthorized": {
     "auth_ref": [
      "r18"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The maximum number of common shares permitted to be issued by an entity's charter and bylaws.",
        "label": "Common Stock, Shares Authorized",
        "terseLabel": "Common stock, shares authorized (in shares)"
       }
      }
     },
     "localname": "CommonStockSharesAuthorized",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesIssued": {
     "auth_ref": [
      "r18"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.",
        "label": "Common Stock, Shares, Issued",
        "periodEndLabel": "Ending balance stockholders' equity (in shares)",
        "periodStartLabel": "Beginning balance stockholders' equity (in shares)",
        "terseLabel": "Common stock, shares issued (in shares)"
       }
      }
     },
     "localname": "CommonStockSharesIssued",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesOutstanding": {
     "auth_ref": [
      "r18",
      "r257"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.",
        "label": "Common Stock, Shares, Outstanding",
        "terseLabel": "Common stock, shares outstanding (in shares)"
       }
      }
     },
     "localname": "CommonStockSharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockValue": {
     "auth_ref": [
      "r18"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 4.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.",
        "label": "Common Stock, Value, Issued",
        "terseLabel": "Common stock"
       }
      }
     },
     "localname": "CommonStockValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CompensationAndEmployeeBenefitPlansTextBlock": {
     "auth_ref": [
      "r276",
      "r279",
      "r329",
      "r361"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for an entity's employee compensation and benefit plans, including, but not limited to, postemployment and postretirement benefit plans, defined benefit pension plans, defined contribution plans, non-qualified and supplemental benefit plans, deferred compensation, share-based compensation, life insurance, severance, health care, unemployment and other benefit plans.",
        "label": "Compensation and Employee Benefit Plans [Text Block]",
        "terseLabel": "Employee Benefit Plans"
       }
      }
     },
     "localname": "CompensationAndEmployeeBenefitPlansTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CompensationAndRetirementDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Retirement Benefits [Abstract]"
       }
      }
     },
     "localname": "CompensationAndRetirementDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_ComponentsOfDeferredTaxLiabilitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Components of Deferred Tax Liabilities [Abstract]",
        "terseLabel": "Deferred tax assets (liabilities):"
       }
      }
     },
     "localname": "ComponentsOfDeferredTaxLiabilitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ComponentsOfIncomeTaxExpenseBenefitContinuingOperationsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]",
        "terseLabel": "Provision for income taxes:"
       }
      }
     },
     "localname": "ComponentsOfIncomeTaxExpenseBenefitContinuingOperationsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ComprehensiveIncomeNetOfTax": {
     "auth_ref": [
      "r73",
      "r75",
      "r76"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.",
        "label": "Comprehensive Income (Loss), Net of Tax, Attributable to Parent",
        "terseLabel": "Comprehensive income (loss) income attributable to member of Summit Materials, LLC",
        "totalLabel": "Comprehensive income attributable to Summit Materials, Inc. / Summit Materials, LLC"
       }
      }
     },
     "localname": "ComprehensiveIncomeNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r73",
      "r75",
      "r417",
      "r429"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 1.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.",
        "label": "Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest",
        "totalLabel": "Comprehensive income"
       }
      }
     },
     "localname": "ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ConcentrationRiskCreditRisk": {
     "auth_ref": [
      "r159",
      "r512"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for credit risk.",
        "label": "Concentration Risk, Credit Risk, Policy [Policy Text Block]",
        "terseLabel": "Business and Credit Concentrations"
       }
      }
     },
     "localname": "ConcentrationRiskCreditRisk",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTextBlock": {
     "auth_ref": [
      "r425",
      "r430"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The tabular disclosure of the effects of any changes in a parent's ownership interest in a subsidiary on the equity attributable to the parent if the ownership interests in a subsidiary changes during the period. The changes represented by this element did not result in the deconsolidation of the subsidiary.",
        "label": "Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table Text Block]",
        "terseLabel": "Schedule of Changes in Ownership of Summit Holdings"
       }
      }
     },
     "localname": "ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ConsolidationPolicyTextBlock": {
     "auth_ref": [
      "r118",
      "r419",
      "r431",
      "r432"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting.  The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.",
        "label": "Consolidation, Policy [Policy Text Block]",
        "terseLabel": "Principles of Consolidation"
       }
      }
     },
     "localname": "ConsolidationPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ConstructionInProgressMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.",
        "label": "Construction in Progress [Member]",
        "terseLabel": "Construction in progress"
       }
      }
     },
     "localname": "ConstructionInProgressMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock": {
     "auth_ref": [
      "r270"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of contract balances and changes in contract balances.",
        "label": "Contract with Customer, Asset and Liability [Table Text Block]",
        "terseLabel": "Summary of Contract Assets and Liabilities"
       }
      }
     },
     "localname": "ContractWithCustomerAssetAndLiabilityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ContractWithCustomerAssetNetCurrent": {
     "auth_ref": [
      "r267",
      "r269",
      "r273"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.",
        "label": "Contract with Customer, Asset, Net, Current",
        "periodEndLabel": "Balance\u2014December 28, 2019",
        "periodStartLabel": "Balance\u2014December 29, 2018",
        "terseLabel": "Costs and estimated earnings in excess of billings"
       }
      }
     },
     "localname": "ContractWithCustomerAssetNetCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractWithCustomerLiabilityCurrent": {
     "auth_ref": [
      "r267",
      "r268",
      "r273"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.",
        "label": "Contract with Customer, Liability, Current",
        "periodEndLabel": "Balance\u2014December 28, 2019",
        "periodStartLabel": "Balance\u2014December 29, 2018",
        "terseLabel": "Billings in excess of costs and estimated earnings"
       }
      }
     },
     "localname": "ContractWithCustomerLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligation": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.",
        "label": "Contractual Obligation",
        "totalLabel": "Total scheduled payments"
       }
      }
     },
     "localname": "ContractualObligation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueAfterFifthYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due after Fifth Year",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "ContractualObligationDueAfterFifthYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueInFifthYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due in Fifth Year",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "ContractualObligationDueInFifthYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueInFourthYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due in Fourth Year",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "ContractualObligationDueInFourthYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueInNextTwelveMonths": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due in Next Fiscal Year",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "ContractualObligationDueInNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueInSecondYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due in Second Year",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "ContractualObligationDueInSecondYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationDueInThirdYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_ContractualObligation",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contractual obligation due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Contractual Obligation, Due in Third Year",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "ContractualObligationDueInThirdYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ContractualObligationFiscalYearMaturityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Contractual Obligation, Fiscal Year Maturity [Abstract]",
        "terseLabel": "Remaining payments on contractual obligations"
       }
      }
     },
     "localname": "ContractualObligationFiscalYearMaturityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ConversionOfStockAmountConverted1": {
     "auth_ref": [
      "r113",
      "r114",
      "r115"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The value of the stock converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. \"Part noncash\" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.",
        "label": "Conversion of Stock, Amount Converted",
        "terseLabel": "Exchange of LP Units to shares of Class A common stock"
       }
      }
     },
     "localname": "ConversionOfStockAmountConverted1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CorporateNonSegmentMember": {
     "auth_ref": [
      "r176"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Corporate headquarters or functional department that may not earn revenues or may earn revenues that are only incidental to the activities of the entity and is not considered an operating segment.",
        "label": "Corporate, Non-Segment [Member]",
        "terseLabel": "Corporate and other"
       }
      }
     },
     "localname": "CorporateNonSegmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CostOfGoodsAndServicesSold": {
     "auth_ref": [
      "r84"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.",
        "label": "Cost of Goods and Services Sold",
        "terseLabel": "Cost of revenue"
       }
      }
     },
     "localname": "CostOfGoodsAndServicesSold",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CostOfGoodsAndServicesSoldAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Cost of Goods and Services Sold [Abstract]",
        "terseLabel": "Cost of revenue (excluding items shown separately below):"
       }
      }
     },
     "localname": "CostOfGoodsAndServicesSoldAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_CurrentIncomeTaxExpenseBenefit": {
     "auth_ref": [
      "r121",
      "r389",
      "r393"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.",
        "label": "Current Income Tax Expense (Benefit)",
        "terseLabel": "Current"
       }
      }
     },
     "localname": "CurrentIncomeTaxExpenseBenefit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtCurrent": {
     "auth_ref": [
      "r41"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.",
        "label": "Debt, Current",
        "terseLabel": "Current portion of debt"
       }
      }
     },
     "localname": "DebtCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Debt Disclosure [Abstract]"
       }
      }
     },
     "localname": "DebtDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DebtDisclosureTextBlock": {
     "auth_ref": [
      "r256"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.",
        "label": "Debt Disclosure [Text Block]",
        "terseLabel": "Debt"
       }
      }
     },
     "localname": "DebtDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Debt"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DebtInstrumentAxis": {
     "auth_ref": [
      "r12",
      "r13",
      "r14",
      "r501",
      "r503",
      "r513"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of debt instrument, including, but not limited to, draws against credit facilities.",
        "label": "Debt Instrument [Axis]",
        "terseLabel": "Debt Instrument [Axis]"
       }
      }
     },
     "localname": "DebtInstrumentAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DebtInstrumentBasisSpreadOnVariableRate1": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage points added to the reference rate to compute the variable rate on the debt instrument.",
        "label": "Debt Instrument, Basis Spread on Variable Rate",
        "terseLabel": "Basis spread on variable rate",
        "verboseLabel": "Basis spread on variable rate"
       }
      }
     },
     "localname": "DebtInstrumentBasisSpreadOnVariableRate1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DebtInstrumentCarryingAmount": {
     "auth_ref": [
      "r14",
      "r252",
      "r503",
      "r513"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 1.0,
       "parentTag": "sum_LongTermDebtNet",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.",
        "label": "Long-term Debt, Gross",
        "terseLabel": "Gross amount",
        "totalLabel": "Total",
        "verboseLabel": "Outstanding principal amount"
       }
      }
     },
     "localname": "DebtInstrumentCarryingAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtInstrumentFaceAmount": {
     "auth_ref": [
      "r463",
      "r465"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Face (par) amount of debt instrument at time of issuance.",
        "label": "Debt Instrument, Face Amount",
        "terseLabel": "Debt instrument, face amount"
       }
      }
     },
     "localname": "DebtInstrumentFaceAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtInstrumentInterestRateStatedPercentage": {
     "auth_ref": [
      "r45"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Contractual interest rate for funds borrowed, under the debt agreement.",
        "label": "Debt Instrument, Interest Rate, Stated Percentage",
        "terseLabel": "Debt instrument interest rate (as a percent)",
        "verboseLabel": "Senior notes, interest rate (as a percent)"
       }
      }
     },
     "localname": "DebtInstrumentInterestRateStatedPercentage",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DebtInstrumentLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Debt Instrument [Line Items]",
        "terseLabel": "Debt",
        "verboseLabel": "Debt Instrument [Line Items]"
       }
      }
     },
     "localname": "DebtInstrumentLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DebtInstrumentNameDomain": {
     "auth_ref": [
      "r46"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The name for the particular debt instrument or borrowing that distinguishes it from other debt instruments or borrowings, including draws against credit facilities.",
        "label": "Debt Instrument, Name [Domain]",
        "terseLabel": "Debt Instrument, Name [Domain]"
       }
      }
     },
     "localname": "DebtInstrumentNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DebtInstrumentRepurchasedFaceAmount": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Face (par) amount of the original debt instrument that was repurchased.",
        "label": "Debt Instrument, Repurchased Face Amount",
        "terseLabel": "Senior notes, aggregate principal amount redeemed"
       }
      }
     },
     "localname": "DebtInstrumentRepurchasedFaceAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtInstrumentTable": {
     "auth_ref": [
      "r46",
      "r124",
      "r258",
      "r259",
      "r260",
      "r261",
      "r462",
      "r463",
      "r465",
      "r511"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A table or schedule providing information pertaining to long-term debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the company, if longer.",
        "label": "Schedule of Long-term Debt Instruments [Table]",
        "terseLabel": "Schedule of Long-term Debt Instruments [Table]"
       }
      }
     },
     "localname": "DebtInstrumentTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DebtInstrumentUnamortizedDiscount": {
     "auth_ref": [
      "r462",
      "r465"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 2.0,
       "parentTag": "sum_LongTermDebtNet",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after accumulated amortization, of debt discount.",
        "label": "Debt Instrument, Unamortized Discount",
        "negatedLabel": "Less: Original issue net discount",
        "terseLabel": "Debt discount"
       }
      }
     },
     "localname": "DebtInstrumentUnamortizedDiscount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails",
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredCostsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Deferred Costs [Abstract]",
        "terseLabel": "Deferred finance costs"
       }
      }
     },
     "localname": "DeferredCostsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DeferredCostsCurrentAndNoncurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 3.0,
       "parentTag": "sum_LongTermDebtNet",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The carrying amount of deferred costs.",
        "label": "Deferred Costs",
        "negatedLabel": "Less: Capitalized loan costs"
       }
      }
     },
     "localname": "DeferredCostsCurrentAndNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredFinanceCostsNet": {
     "auth_ref": [
      "r37",
      "r464"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.",
        "label": "Debt Issuance Costs, Net",
        "periodEndLabel": "Ending balance",
        "periodStartLabel": "Beginning balance"
       }
      }
     },
     "localname": "DeferredFinanceCostsNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredIncomeTaxAssetsNet": {
     "auth_ref": [
      "r384"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 5.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.",
        "label": "Deferred Income Tax Assets, Net",
        "terseLabel": "Deferred tax assets"
       }
      }
     },
     "localname": "DeferredIncomeTaxAssetsNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredIncomeTaxExpenseBenefit": {
     "auth_ref": [
      "r109",
      "r121",
      "r390",
      "r393"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.",
        "label": "Deferred Income Tax Expense (Benefit)",
        "terseLabel": "Deferred"
       }
      }
     },
     "localname": "DeferredIncomeTaxExpenseBenefit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredIncomeTaxesAndTaxCredits": {
     "auth_ref": [
      "r110"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 6.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred income tax expense (benefit) and income tax credits.",
        "label": "Deferred Income Taxes and Tax Credits",
        "terseLabel": "Change in deferred tax asset, net"
       }
      }
     },
     "localname": "DeferredIncomeTaxesAndTaxCredits",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsInvestments": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from investments (excludes investments in subsidiaries and equity method investments).",
        "label": "Deferred Tax Assets, Investments",
        "terseLabel": "Deferred tax asset, Investment in limited partnership"
       }
      }
     },
     "localname": "DeferredTaxAssetsInvestments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsLiabilitiesNet": {
     "auth_ref": [
      "r384"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 1.0,
       "parentTag": "sum_DeferredTaxAssetsLiabilitiesNetIncludedInNoncurrentLiabilities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.",
        "label": "Deferred Tax Assets, Net",
        "totalLabel": "Deferred tax assets"
       }
      }
     },
     "localname": "DeferredTaxAssetsLiabilitiesNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsOperatingLossCarryforwards": {
     "auth_ref": [
      "r363",
      "r387",
      "r388"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 3.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.",
        "label": "Deferred Tax Assets, Operating Loss Carryforwards",
        "terseLabel": "Net operating loss"
       }
      }
     },
     "localname": "DeferredTaxAssetsOperatingLossCarryforwards",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.",
        "label": "Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration",
        "terseLabel": "Net operating loss carryforwards"
       }
      }
     },
     "localname": "DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpiration",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsOtherTaxCarryforwards": {
     "auth_ref": [
      "r364",
      "r387",
      "r388"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 8.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax carryforwards, classified as other.",
        "label": "Deferred Tax Assets, Other Tax Carryforwards",
        "terseLabel": "Interest expense limitation carryforward"
       }
      }
     },
     "localname": "DeferredTaxAssetsOtherTaxCarryforwards",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax": {
     "auth_ref": [
      "r386",
      "r387",
      "r388"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before allocation of valuation allowances of deferred tax asset attributable to deductible alternative minimum tax credit carryforwards.",
        "label": "Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax",
        "terseLabel": "Alternative minimum tax credit"
       }
      }
     },
     "localname": "DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsValuationAllowance": {
     "auth_ref": [
      "r383"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 7.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.",
        "label": "Deferred Tax Assets, Valuation Allowance",
        "negatedPeriodEndLabel": "Ending balance",
        "negatedPeriodStartLabel": "Beginning balance",
        "negatedTerseLabel": "Less valuation allowance",
        "terseLabel": "Deferred tax asset, valuation allowance"
       }
      }
     },
     "localname": "DeferredTaxAssetsValuationAllowance",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxLiabilities": {
     "auth_ref": [
      "r370",
      "r384"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.",
        "label": "Deferred Tax Liabilities, Net",
        "negatedTotalLabel": "Net deferred tax liability, net"
       }
      }
     },
     "localname": "DeferredTaxLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment": {
     "auth_ref": [
      "r364",
      "r387",
      "r388"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_DeferredTaxAssetsLiabilitiesNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.",
        "label": "Deferred Tax Liabilities, Property, Plant and Equipment",
        "negatedLabel": "Accelerated depreciation"
       }
      }
     },
     "localname": "DeferredTaxLiabilitiesPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsAndLiabilitiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax": {
     "auth_ref": [
      "r62",
      "r67"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).",
        "label": "Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax",
        "totalLabel": "Total amount recognized"
       }
      }
     },
     "localname": "DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossAfterTaxAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax [Abstract]",
        "terseLabel": "Amounts recognized in accumulated other comprehensive income:"
       }
      }
     },
     "localname": "DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossAfterTaxAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax": {
     "auth_ref": [
      "r67",
      "r305"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.",
        "label": "Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax",
        "negatedTerseLabel": "Net actuarial (gain) loss"
       }
      }
     },
     "localname": "DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax": {
     "auth_ref": [
      "r67",
      "r305"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).",
        "label": "Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax",
        "terseLabel": "Prior service cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets": {
     "auth_ref": [
      "r288",
      "r323"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.",
        "label": "Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)",
        "terseLabel": "Actual return on plan assets"
       }
      }
     },
     "localname": "DefinedBenefitPlanActualReturnOnPlanAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanActuarialGainLoss": {
     "auth_ref": [
      "r285"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.",
        "label": "Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)",
        "negatedLabel": "Actuarial (gain) loss"
       }
      }
     },
     "localname": "DefinedBenefitPlanActuarialGainLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses": {
     "auth_ref": [
      "r302",
      "r320",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": 3.0,
       "parentTag": "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.",
        "label": "Defined Benefit Plan, Amortization of Gain (Loss)",
        "negatedLabel": "Amortization of gain"
       }
      }
     },
     "localname": "DefinedBenefitPlanAmortizationOfGainsLosses",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit": {
     "auth_ref": [
      "r303",
      "r321",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": 5.0,
       "parentTag": "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.",
        "label": "Defined Benefit Plan, Amortization of Prior Service Cost (Credit)",
        "terseLabel": "Amortization of prior service credit"
       }
      }
     },
     "localname": "DefinedBenefitPlanAmortizationOfPriorServiceCostCredit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate": {
     "auth_ref": [
      "r307"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.",
        "label": "Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate",
        "terseLabel": "Discount rate"
       }
      }
     },
     "localname": "DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate": {
     "auth_ref": [
      "r307"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.",
        "label": "Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate",
        "terseLabel": "Discount rate"
       }
      }
     },
     "localname": "DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets": {
     "auth_ref": [
      "r308"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.",
        "label": "Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets",
        "terseLabel": "Expected long-term rate of return on plan assets, net periodic benefit cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlanBenefitObligation": {
     "auth_ref": [
      "r282"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_DefinedBenefitPlanFundedStatusOfPlan",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.",
        "label": "Defined Benefit Plan, Benefit Obligation",
        "periodEndLabel": "End of period",
        "periodStartLabel": "Beginning of period"
       }
      }
     },
     "localname": "DefinedBenefitPlanBenefitObligation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid": {
     "auth_ref": [
      "r286",
      "r324"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.",
        "label": "Defined Benefit Plan, Benefit Obligation, Benefits Paid",
        "negatedTerseLabel": "Benefits paid"
       }
      }
     },
     "localname": "DefinedBenefitPlanBenefitObligationBenefitsPaid",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis": {
     "auth_ref": [
      "r294",
      "r295",
      "r311",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by defined benefit plan asset investment.",
        "label": "Defined Benefit Plan, Plan Assets, Category [Axis]",
        "terseLabel": "Defined Benefit Plan, Plan Assets, Category [Axis]"
       }
      }
     },
     "localname": "DefinedBenefitPlanByPlanAssetCategoriesAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanCashMember": {
     "auth_ref": [
      "r294",
      "r295",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash in which defined benefit plan asset is invested.",
        "label": "Defined Benefit Plan, Cash [Member]",
        "terseLabel": "Cash"
       }
      }
     },
     "localname": "DefinedBenefitPlanCashMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]",
        "terseLabel": "Change in benefit obligations:"
       }
      }
     },
     "localname": "DefinedBenefitPlanChangeInBenefitObligationRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]",
        "terseLabel": "Change in fair value of plan assets:"
       }
      }
     },
     "localname": "DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanContributionsByEmployer": {
     "auth_ref": [
      "r289",
      "r294",
      "r295",
      "r322",
      "r323"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contribution received by defined benefit plan from employer which increases plan assets.",
        "label": "Defined Benefit Plan, Plan Assets, Contributions by Employer",
        "terseLabel": "Employer contributions"
       }
      }
     },
     "localname": "DefinedBenefitPlanContributionsByEmployer",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanDerivativeMember": {
     "auth_ref": [
      "r294"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Financial instrument or other contract with one or more underlyings, notional amount or payment provision or both; can be settled net by means outside contract or delivery of asset; and with minimal or no initial net investment, in which defined benefit plan asset is invested.",
        "label": "Defined Benefit Plan, Derivative [Member]",
        "terseLabel": "Managed Futures"
       }
      }
     },
     "localname": "DefinedBenefitPlanDerivativeMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DefinedBenefitPlanDisclosureLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Defined Benefit Plan Disclosure [Line Items]",
        "terseLabel": "Defined Benefit Plan Disclosure [Line Items]"
       }
      }
     },
     "localname": "DefinedBenefitPlanDisclosureLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1": {
     "auth_ref": [
      "r310"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.",
        "label": "Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation",
        "negatedLabel": "APBO, Decrease"
       }
      }
     },
     "localname": "DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1": {
     "auth_ref": [
      "r310"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.",
        "label": "Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components",
        "negatedLabel": "Total service cost and interest cost components, Decrease"
       }
      }
     },
     "localname": "DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation": {
     "auth_ref": [
      "r310"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.",
        "label": "Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation",
        "terseLabel": "APBO, Increase"
       }
      }
     },
     "localname": "DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents": {
     "auth_ref": [
      "r310"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.",
        "label": "Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components",
        "terseLabel": "Total service cost and interest cost components, Increase"
       }
      }
     },
     "localname": "DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanEquitySecuritiesMember": {
     "auth_ref": [
      "r294",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Security representing ownership in corporation or other legal entity for which ownership is represented by share of stock, in which defined benefit plan asset is invested. Includes, but is not limited to, common stock, preferred stock, convertible security, stock right and stock warrant.",
        "label": "Defined Benefit Plan, Equity Securities [Member]",
        "terseLabel": "Equity Securities"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DefinedBenefitPlanEquitySecuritiesNonUsMember": {
     "auth_ref": [
      "r294",
      "r295",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Security representing ownership in corporation or other legal entity, not domiciled in United States of America (US), for which ownership is represented by share of stock; in which defined benefit plan asset is invested. Includes, but is not limited to, common stock, preferred stock, convertible security, stock right and stock warrant.",
        "label": "Defined Benefit Plan, Equity Securities, Non-US [Member]",
        "terseLabel": "International"
       }
      }
     },
     "localname": "DefinedBenefitPlanEquitySecuritiesNonUsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter",
        "terseLabel": "2025 - 2029"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Year Five",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Year Four",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Year Three",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo": {
     "auth_ref": [
      "r296"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Benefit Payment, Year Two",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear": {
     "auth_ref": [
      "r297"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year",
        "terseLabel": "Expected contributions in 2020"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets": {
     "auth_ref": [
      "r301",
      "r319",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": 4.0,
       "parentTag": "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.",
        "label": "Defined Benefit Plan, Expected Return (Loss) on Plan Assets",
        "negatedLabel": "Expected return on plan assets"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedReturnOnPlanAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanFairValueOfPlanAssets": {
     "auth_ref": [
      "r287",
      "r294",
      "r295",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_DefinedBenefitPlanFundedStatusOfPlan",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.",
        "label": "Defined Benefit Plan, Plan Assets, Amount",
        "periodEndLabel": "End of period",
        "periodStartLabel": "Beginning of period",
        "terseLabel": "Total fair value"
       }
      }
     },
     "localname": "DefinedBenefitPlanFairValueOfPlanAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanFundedStatusOfPlan": {
     "auth_ref": [
      "r280",
      "r291"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetailCalc2": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.",
        "label": "Defined Benefit Plan, Funded (Unfunded) Status of Plan",
        "totalLabel": "Funded status of plans"
       }
      }
     },
     "localname": "DefinedBenefitPlanFundedStatusOfPlan",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear": {
     "auth_ref": [
      "r309"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.",
        "label": "Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year",
        "terseLabel": "Assumed health care cost trend rates"
       }
      }
     },
     "localname": "DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlanInterestCost": {
     "auth_ref": [
      "r284",
      "r300",
      "r318",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost recognized for passage of time related to defined benefit plan.",
        "label": "Defined Benefit Plan, Interest Cost",
        "terseLabel": "Interest cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanInterestCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost": {
     "auth_ref": [
      "r298",
      "r316",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of net periodic benefit cost (credit) for defined benefit plan.",
        "label": "Defined Benefit Plan, Net Periodic Benefit Cost (Credit)",
        "totalLabel": "Net periodic (expense) benefit cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanNetPeriodicBenefitCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]",
        "terseLabel": "Components of net periodic benefit cost:"
       }
      }
     },
     "localname": "DefinedBenefitPlanNetPeriodicBenefitCostAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid": {
     "auth_ref": [
      "r290",
      "r324"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.",
        "label": "Defined Benefit Plan, Plan Assets, Benefits Paid",
        "negatedLabel": "Benefits paid"
       }
      }
     },
     "localname": "DefinedBenefitPlanPlanAssetsBenefitsPaid",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage": {
     "auth_ref": [
      "r293",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.",
        "label": "Defined Benefit Plan, Plan Assets, Target Allocation, Percentage",
        "terseLabel": "Target allocation"
       }
      }
     },
     "localname": "DefinedBenefitPlanPlanAssetsTargetAllocationPercentage",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlanServiceCost": {
     "auth_ref": [
      "r283",
      "r299",
      "r317",
      "r323"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.",
        "label": "Defined Benefit Plan, Service Cost",
        "terseLabel": "Service cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanServiceCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1": {
     "auth_ref": [
      "r309"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Ultimate trend rate for health care cost for defined benefit postretirement plan.",
        "label": "Defined Benefit Plan, Ultimate Health Care Cost Trend Rate",
        "terseLabel": "Assumed health care cost, grading"
       }
      }
     },
     "localname": "DefinedBenefitPlanUltimateHealthCareCostTrendRate1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable": {
     "auth_ref": [
      "r312",
      "r313",
      "r314",
      "r315",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosures and provisions pertaining to defined benefit pension plans or other postretirement defined benefit plans. The arrangements are generally based on terms and conditions stipulated by the entity, and which contain a promise by the employer to pay certain amounts or awards at designated future dates, including a period after retirement, upon compliance with stipulated requirements. Excludes disclosures pertaining to defined contribution plans.",
        "label": "Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table]",
        "terseLabel": "Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table]"
       }
      }
     },
     "localname": "DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]",
        "terseLabel": "Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]"
       }
      }
     },
     "localname": "DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEffectsOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedContributionPlanCostRecognized": {
     "auth_ref": [
      "r325"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost for defined contribution plan.",
        "label": "Defined Contribution Plan, Cost",
        "terseLabel": "Expense for defined contribution plans"
       }
      }
     },
     "localname": "DefinedContributionPlanCostRecognized",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_Depreciation": {
     "auth_ref": [
      "r109",
      "r217"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.",
        "label": "Depreciation",
        "verboseLabel": "Depreciation, depletion and amortization expense"
       }
      }
     },
     "localname": "Depreciation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DepreciationDepletionAndAmortization": {
     "auth_ref": [
      "r109",
      "r169"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.",
        "label": "Depreciation, Depletion and Amortization",
        "terseLabel": "Depreciation, depletion and amortization"
       }
      }
     },
     "localname": "DepreciationDepletionAndAmortization",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeAmountOfHedgedItem": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of hedged item in hedging relationship. Excludes hedged asset or liability.",
        "label": "Derivative, Amount of Hedged Item",
        "terseLabel": "Term loan borrowings hedged by derivatives"
       }
      }
     },
     "localname": "DerivativeAmountOfHedgedItem",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeContractTypeDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Financial instrument or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.",
        "label": "Derivative Contract [Domain]",
        "terseLabel": "Derivative Contract [Domain]"
       }
      }
     },
     "localname": "DerivativeContractTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DerivativeInstrumentRiskAxis": {
     "auth_ref": [
      "r437",
      "r438",
      "r440",
      "r442"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of derivative contract.",
        "label": "Derivative Instrument [Axis]",
        "terseLabel": "Derivative Instrument [Axis]"
       }
      }
     },
     "localname": "DerivativeInstrumentRiskAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis": {
     "auth_ref": [
      "r435",
      "r437",
      "r440"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of hedging relationship.",
        "label": "Hedging Relationship [Axis]",
        "terseLabel": "Hedging Relationship [Axis]"
       }
      }
     },
     "localname": "DerivativeInstrumentsGainLossByHedgingRelationshipAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeLiabilitiesCurrent": {
     "auth_ref": [
      "r56"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.",
        "label": "Derivative Liability, Current",
        "terseLabel": "Current portion of acquisition-related liabilities and Accrued expenses - Cash flow hedge"
       }
      }
     },
     "localname": "DerivativeLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeLiabilitiesNoncurrent": {
     "auth_ref": [
      "r56"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.",
        "label": "Derivative Liability, Noncurrent",
        "terseLabel": "Acquisition-related liabilities and Other noncurrent liabilities - Cash flow hedge"
       }
      }
     },
     "localname": "DerivativeLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisaggregationOfRevenueTableTextBlock": {
     "auth_ref": [
      "r272"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of disaggregation of revenue into categories depicting how nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factor.",
        "label": "Disaggregation of Revenue [Table Text Block]",
        "terseLabel": "Summary of Revenue by Products"
       }
      }
     },
     "localname": "DisaggregationOfRevenueTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Share-based Payment Arrangement [Abstract]"
       }
      }
     },
     "localname": "DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock": {
     "auth_ref": [
      "r333",
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of share-based payment arrangement.",
        "label": "Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]",
        "terseLabel": "Summary of Information for the Equity Awards Granted"
       }
      }
     },
     "localname": "DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DistributionMadeToLimitedLiabilityCompanyLLCMemberCashDistributionsDeclared": {
     "auth_ref": [
      "r154",
      "r155",
      "r262"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of equity impact of cash distributions declared to unit-holder of limited liability company (LLC).",
        "label": "Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared",
        "negatedLabel": "Distributions"
       }
      }
     },
     "localname": "DistributionMadeToLimitedLiabilityCompanyLLCMemberCashDistributionsDeclared",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DividendsCash": {
     "auth_ref": [
      "r262",
      "r510"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of paid and unpaid cash dividends declared for classes of stock, for example, but not limited to, common and preferred.",
        "label": "Dividends, Cash",
        "negatedLabel": "Dividend"
       }
      }
     },
     "localname": "DividendsCash",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DomesticCountryMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Designated tax department of the government that is entitled to levy and collect income taxes from the entity in its country of domicile.",
        "label": "Domestic Tax Authority [Member]",
        "terseLabel": "Federal"
       }
      }
     },
     "localname": "DomesticCountryMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EarningsPerShareAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Earnings Per Share [Abstract]",
        "terseLabel": "Income per share of Class A common stock:"
       }
      }
     },
     "localname": "EarningsPerShareAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareBasic": {
     "auth_ref": [
      "r81",
      "r132",
      "r138",
      "r142",
      "r143",
      "r144",
      "r148",
      "r507",
      "r522"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.",
        "label": "Earnings Per Share, Basic",
        "terseLabel": "Basic (USD per share)",
        "verboseLabel": "Basic earnings (loss) per share attributable to Summit Inc. (USD per share)"
       }
      }
     },
     "localname": "EarningsPerShareBasic",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_EarningsPerShareBasicLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]",
        "terseLabel": "Reconciliation of basic to diluted loss per share"
       }
      }
     },
     "localname": "EarningsPerShareBasicLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareDiluted": {
     "auth_ref": [
      "r81",
      "r132",
      "r138",
      "r142",
      "r143",
      "r144",
      "r148",
      "r507",
      "r522"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.",
        "label": "Earnings Per Share, Diluted",
        "terseLabel": "Diluted (USD per share)",
        "verboseLabel": "Diluted earnings (loss) per share attributable to Summit Inc. (USD per share)"
       }
      }
     },
     "localname": "EarningsPerShareDiluted",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_EarningsPerSharePolicyTextBlock": {
     "auth_ref": [
      "r118",
      "r145",
      "r146",
      "r147"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.",
        "label": "Earnings Per Share, Policy [Policy Text Block]",
        "terseLabel": "Earnings per Share"
       }
      }
     },
     "localname": "EarningsPerSharePolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_EarningsPerShareTextBlock": {
     "auth_ref": [
      "r149"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for earnings per share.",
        "label": "Earnings Per Share [Text Block]",
        "verboseLabel": "Earnings Per Share"
       }
      }
     },
     "localname": "EarningsPerShareTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShare"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents": {
     "auth_ref": [
      "r459"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 4.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) from effect of exchange rate changes on cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; held in foreign currencies. Excludes amounts for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.",
        "label": "Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents",
        "terseLabel": "Impact of foreign currency on cash"
       }
      }
     },
     "localname": "EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions": {
     "auth_ref": [
      "r354"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost to be recognized for option under share-based payment arrangement.",
        "label": "Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount",
        "terseLabel": "Unrecognized compensation cost"
       }
      }
     },
     "localname": "EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EmployeeStockOptionMember": {
     "auth_ref": [
      "r352"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share-based payment arrangement granting right, subject to vesting and other restrictions, to purchase or sell certain number of shares at predetermined price for specified period of time.",
        "label": "Share-based Payment Arrangement, Option [Member]",
        "terseLabel": "Options"
       }
      }
     },
     "localname": "EmployeeStockOptionMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Revenue from External Customer [Line Items]",
        "terseLabel": "Revenue from External Customer [Line Items]"
       }
      }
     },
     "localname": "EntityWideInformationRevenueFromExternalCustomerLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognition",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tangible personal property used to produce goods and services.",
        "label": "Equipment [Member]",
        "terseLabel": "Equipment"
       }
      }
     },
     "localname": "EquipmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Equity [Abstract]"
       }
      }
     },
     "localname": "EquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_EquityComponentDomain": {
     "auth_ref": [
      "r257"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Components of equity are the parts of the total Equity balance including that which is allocated to common, preferred, treasury stock, retained earnings, etc.",
        "label": "Equity Component [Domain]",
        "terseLabel": "Equity Component [Domain]"
       }
      }
     },
     "localname": "EquityComponentDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EstimateOfFairValueFairValueDisclosureMember": {
     "auth_ref": [
      "r454"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measured as an estimate of fair value.",
        "label": "Estimate of Fair Value Measurement [Member]",
        "terseLabel": "Fair Value"
       }
      }
     },
     "localname": "EstimateOfFairValueFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]",
        "terseLabel": "Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]"
       }
      }
     },
     "localname": "FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
      "http://www.summitmaterials.com/role/FairValueTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable": {
     "auth_ref": [
      "r445",
      "r446",
      "r447",
      "r451"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about asset and liability measured at fair value on recurring and nonrecurring basis.",
        "label": "Fair Value, Recurring and Nonrecurring [Table]",
        "terseLabel": "Fair Value, Recurring and Nonrecurring [Table]"
       }
      }
     },
     "localname": "FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails",
      "http://www.summitmaterials.com/role/FairValueTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]",
        "terseLabel": "Financial Instruments"
       }
      }
     },
     "localname": "FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByBalanceSheetGroupingTable": {
     "auth_ref": [
      "r445",
      "r455",
      "r456"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about the fair value of financial instruments, including financial assets and financial liabilities, and the measurements of those instruments, assets, and liabilities.",
        "label": "Fair Value, by Balance Sheet Grouping [Table]",
        "terseLabel": "Fair Value, by Balance Sheet Grouping [Table]"
       }
      }
     },
     "localname": "FairValueByBalanceSheetGroupingTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByBalanceSheetGroupingTextBlock": {
     "auth_ref": [
      "r445",
      "r455"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the fair value of financial instruments, including financial assets and financial liabilities, and the measurements of those instruments, assets, and liabilities.",
        "label": "Fair Value, by Balance Sheet Grouping [Table Text Block]",
        "terseLabel": "Schedule of Carrying Value and Fair Value of Financial Instruments"
       }
      }
     },
     "localname": "FairValueByBalanceSheetGroupingTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FairValueByFairValueHierarchyLevelAxis": {
     "auth_ref": [
      "r294",
      "r295",
      "r323",
      "r446",
      "r494"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by level within fair value hierarchy and fair value measured at net asset value per share as practical expedient.",
        "label": "Fair Value Hierarchy and NAV [Axis]",
        "terseLabel": "Fair Value Hierarchy and NAV [Axis]"
       }
      }
     },
     "localname": "FairValueByFairValueHierarchyLevelAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByMeasurementBasisAxis": {
     "auth_ref": [
      "r445",
      "r452"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by measurement basis.",
        "label": "Measurement Basis [Axis]",
        "terseLabel": "Measurement Basis [Axis]"
       }
      }
     },
     "localname": "FairValueByMeasurementBasisAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueDisclosureItemAmountsDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measurement basis, for example, but not limited to, reported value, fair value, portion at fair value, portion at other than fair value.",
        "label": "Fair Value Measurement [Domain]",
        "terseLabel": "Fair Value Measurement [Domain]"
       }
      }
     },
     "localname": "FairValueDisclosureItemAmountsDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueDisclosuresAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Fair Value Disclosures [Abstract]"
       }
      }
     },
     "localname": "FairValueDisclosuresAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueDisclosuresTextBlock": {
     "auth_ref": [
      "r450"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.",
        "label": "Fair Value Disclosures [Text Block]",
        "terseLabel": "Fair Value of Financial Instruments"
       }
      }
     },
     "localname": "FairValueDisclosuresTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstruments"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FairValueInputsLevel1Member": {
     "auth_ref": [
      "r294",
      "r295",
      "r323",
      "r446",
      "r495"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Quoted prices in active markets for identical assets or liabilities that the reporting entity can access at the measurement date.",
        "label": "Fair Value, Inputs, Level 1 [Member]",
        "terseLabel": "Quoted Prices in Active Markets for Identical Assets (Level 1)"
       }
      }
     },
     "localname": "FairValueInputsLevel1Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueInputsLevel2Member": {
     "auth_ref": [
      "r294",
      "r295",
      "r323",
      "r446",
      "r496"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Inputs other than quoted prices included within level 1 that are observable for an asset or liability, either directly or indirectly, including, but not limited to, quoted prices for similar assets or liabilities in active markets, or quoted prices for identical or similar assets or liabilities in inactive markets.",
        "label": "Fair Value, Inputs, Level 2 [Member]",
        "terseLabel": "Observable Inputs (Level 2)",
        "verboseLabel": "Level 2"
       }
      }
     },
     "localname": "FairValueInputsLevel2Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueInputsLevel3Member": {
     "auth_ref": [
      "r294",
      "r295",
      "r323",
      "r446",
      "r497"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.",
        "label": "Fair Value, Inputs, Level 3 [Member]",
        "terseLabel": "Level 3"
       }
      }
     },
     "localname": "FairValueInputsLevel3Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock": {
     "auth_ref": [
      "r445",
      "r446"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of liabilities measured at fair value measured on a recurring or nonrecurring basis. Includes, but is not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2.",
        "label": "Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis [Table Text Block]",
        "terseLabel": "Schedule of Contingent Consideration and Derivatives Measured at Fair Value"
       }
      }
     },
     "localname": "FairValueLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FairValueMeasurementsFairValueHierarchyDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Categories used to prioritize the inputs to valuation techniques to measure fair value.",
        "label": "Fair Value Hierarchy and NAV [Domain]",
        "terseLabel": "Fair Value Hierarchy and NAV [Domain]"
       }
      }
     },
     "localname": "FairValueMeasurementsFairValueHierarchyDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FederalFundsEffectiveSwapRateMember": {
     "auth_ref": [
      "r443"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fixed rate on U.S. dollar, constant-notional interest rate swap having its variable-rate leg referenced to Federal Funds effective rate with no additional spread over Federal Funds effective rate on that variable-rate leg.",
        "label": "Fed Funds Effective Rate Overnight Index Swap Rate [Member]",
        "terseLabel": "Federal funds rate"
       }
      }
     },
     "localname": "FederalFundsEffectiveSwapRateMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations": {
     "auth_ref": [
      "r125",
      "r371"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of current and deferred federal income tax expense (benefit) attributable to income (loss) from continuing operations.",
        "label": "Federal Income Tax Expense (Benefit), Continuing Operations",
        "terseLabel": "Less: Income tax benefit at federal statutory tax rate for LLC entities"
       }
      }
     },
     "localname": "FederalIncomeTaxExpenseBenefitContinuingOperations",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseInterestExpense": {
     "auth_ref": [
      "r473",
      "r479",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_LeaseCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of interest expense on finance lease liability.",
        "label": "Finance Lease, Interest Expense",
        "terseLabel": "Interest on lease liabilities"
       }
      }
     },
     "localname": "FinanceLeaseInterestExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseInterestPaymentOnLiability": {
     "auth_ref": [
      "r475",
      "r483"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of interest paid on finance lease liability.",
        "label": "Finance Lease, Interest Payment on Liability",
        "terseLabel": "Operating cash payments on finance leases"
       }
      }
     },
     "localname": "FinanceLeaseInterestPaymentOnLiability",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Finance Lease, Liability, Payment, Due [Abstract]",
        "terseLabel": "Finance Leases"
       }
      }
     },
     "localname": "FinanceLeaseLiabilitiesPaymentsDueAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FinanceLeaseLiability": {
     "auth_ref": [
      "r472",
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": 2.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from finance lease.",
        "label": "Finance Lease, Liability",
        "totalLabel": "Total finance lease liabilities"
       }
      }
     },
     "localname": "FinanceLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityCurrent": {
     "auth_ref": [
      "r472"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_FinanceLeaseLiability",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.",
        "label": "Finance Lease, Liability, Current",
        "terseLabel": "Current finance lease liabilities",
        "verboseLabel": "Finance lease obligations"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock": {
     "auth_ref": [
      "r488"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of undiscounted cash flows of finance lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to finance lease liability recognized in statement of financial position.",
        "label": "Finance Lease, Liability, Maturity [Table Text Block]",
        "terseLabel": "Schedule of Finance Lease Liability Maturities"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityMaturityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FinanceLeaseLiabilityNoncurrent": {
     "auth_ref": [
      "r472"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_FinanceLeaseLiability",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.",
        "label": "Finance Lease, Liability, Noncurrent",
        "terseLabel": "Long-term finance lease liabilities"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDue": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease.",
        "label": "Finance Lease, Liability, Payment, Due",
        "totalLabel": "Total lease payments"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due after fifth fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due after Year Five",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueAfterYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in next fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due Next Twelve Months",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in fifth fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due Year Five",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in fourth fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due Year Four",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearFour",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in third fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due Year Three",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearThree",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in second fiscal year following latest fiscal year.",
        "label": "Finance Lease, Liability, Payments, Due Year Two",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": 1.0,
       "parentTag": "us-gaap_FinanceLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for finance lease.",
        "label": "Finance Lease, Liability, Undiscounted Excess Amount",
        "negatedTerseLabel": "Less imputed interest"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityUndiscountedExcessAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeasePrincipalPayments": {
     "auth_ref": [
      "r474",
      "r483"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow for principal payment on finance lease.",
        "label": "Finance Lease, Principal Payments",
        "terseLabel": "Finance cash payments on finance leases"
       }
      }
     },
     "localname": "FinanceLeasePrincipalPayments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseRightOfUseAsset": {
     "auth_ref": [
      "r471"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's right to use underlying asset under finance lease.",
        "label": "Finance Lease, Right-of-Use Asset",
        "totalLabel": "Property and equipment, net"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAsset",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseRightOfUseAssetAmortization": {
     "auth_ref": [
      "r473",
      "r479",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_LeaseCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense attributable to right-of-use asset from finance lease.",
        "label": "Finance Lease, Right-of-Use Asset, Amortization",
        "terseLabel": "Amortization of right-of-use assets"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAssetAmortization",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent": {
     "auth_ref": [
      "r486",
      "r489"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average discount rate for finance lease calculated at point in time.",
        "label": "Finance Lease, Weighted Average Discount Rate, Percent",
        "terseLabel": "Finance lease"
       }
      }
     },
     "localname": "FinanceLeaseWeightedAverageDiscountRatePercent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_FinanceLeaseWeightedAverageRemainingLeaseTerm1": {
     "auth_ref": [
      "r485",
      "r489"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining lease term for finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Finance Lease, Weighted Average Remaining Lease Term",
        "terseLabel": "Finance lease"
       }
      }
     },
     "localname": "FinanceLeaseWeightedAverageRemainingLeaseTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization": {
     "auth_ref": [
      "r212"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_IntangibleAssetsNetExcludingGoodwill",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.",
        "label": "Finite-Lived Intangible Assets, Accumulated Amortization",
        "negatedLabel": "Accumulated Amortization"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAccumulatedAmortization",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, after Year Five",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths": {
     "auth_ref": [
      "r214"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive": {
     "auth_ref": [
      "r214"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, Year Five",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour": {
     "auth_ref": [
      "r214"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, Year Four",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseYearFour",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree": {
     "auth_ref": [
      "r214"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, Year Three",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseYearThree",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo": {
     "auth_ref": [
      "r214"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_FiniteLivedIntangibleAssetsNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Finite-Lived Intangible Assets, Amortization Expense, Year Two",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis": {
     "auth_ref": [
      "r208",
      "r209",
      "r212",
      "r215",
      "r498"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by major type or class of finite-lived intangible assets.",
        "label": "Finite-Lived Intangible Assets by Major Class [Axis]",
        "terseLabel": "Finite-Lived Intangible Assets by Major Class [Axis]"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsByMajorClassAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]",
        "terseLabel": "Estimated amortization expense"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Finite-Lived Intangible Assets [Line Items]",
        "terseLabel": "Finite-Lived Intangible Assets [Line Items]"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain": {
     "auth_ref": [
      "r208",
      "r211"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The major class of finite-lived intangible asset (for example, patents, trademarks, copyrights, etc.) A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.",
        "label": "Finite-Lived Intangible Assets, Major Class Name [Domain]",
        "terseLabel": "Finite-Lived Intangible Assets, Major Class Name [Domain]"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsMajorClassNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FiniteLivedIntangibleAssetsNet": {
     "auth_ref": [
      "r212"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 4.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.",
        "label": "Finite-Lived Intangible Assets, Net",
        "terseLabel": "Intangible assets",
        "totalLabel": "Total",
        "verboseLabel": "Intangible assets, net"
       }
      }
     },
     "localname": "FiniteLivedIntangibleAssetsNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FixedIncomeSecuritiesMember": {
     "auth_ref": [
      "r294",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Investment that provides a return in the form of fixed periodic payments and eventual return of principal at maturity.",
        "label": "Fixed Income Securities [Member]",
        "terseLabel": "Fixed Income Securities"
       }
      }
     },
     "localname": "FixedIncomeSecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_GainLossOnDispositionOfAssets1": {
     "auth_ref": [
      "r109"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.",
        "label": "Gain (Loss) on Disposition of Assets",
        "negatedLabel": "Net gain on asset disposals"
       }
      }
     },
     "localname": "GainLossOnDispositionOfAssets1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GainLossOnSaleOfBusiness": {
     "auth_ref": [
      "r109",
      "r426"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 6.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 10.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.",
        "label": "Gain (Loss) on Disposition of Business",
        "negatedLabel": "Gain on sale of business",
        "negatedTerseLabel": "Gain on sale of business"
       }
      }
     },
     "localname": "GainLossOnSaleOfBusiness",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GainLossOnSaleOfPropertyPlantEquipment": {
     "auth_ref": [
      "r109"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.",
        "label": "Gain (Loss) on Disposition of Property Plant Equipment",
        "terseLabel": "Net gain from asset dispositions"
       }
      }
     },
     "localname": "GainLossOnSaleOfPropertyPlantEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GainsLossesOnExtinguishmentOfDebt": {
     "auth_ref": [
      "r109",
      "r254",
      "r255"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.",
        "label": "Gain (Loss) on Extinguishment of Debt",
        "terseLabel": "Loss on extinguishment of debt"
       }
      }
     },
     "localname": "GainsLossesOnExtinguishmentOfDebt",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GeneralAndAdministrativeExpense": {
     "auth_ref": [
      "r87"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 3.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.",
        "label": "General and Administrative Expense",
        "terseLabel": "General and administrative expenses"
       }
      }
     },
     "localname": "GeneralAndAdministrativeExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GeneralAndAdministrativeExpenseMember": {
     "auth_ref": [
      "r82"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing general and administrative expense.",
        "label": "General and Administrative Expense [Member]",
        "terseLabel": "General and administrative expenses"
       }
      }
     },
     "localname": "GeneralAndAdministrativeExpenseMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Goodwill": {
     "auth_ref": [
      "r194",
      "r196"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 3.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.",
        "label": "Goodwill",
        "periodEndLabel": "Ending balance",
        "periodStartLabel": "Beginning balance",
        "terseLabel": "Goodwill"
       }
      }
     },
     "localname": "Goodwill",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GoodwillAcquiredDuringPeriod": {
     "auth_ref": [
      "r198"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.",
        "label": "Goodwill, Acquired During Period",
        "terseLabel": "Acquisitions"
       }
      }
     },
     "localname": "GoodwillAcquiredDuringPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Goodwill and Intangible Assets Disclosure [Abstract]"
       }
      }
     },
     "localname": "GoodwillAndIntangibleAssetsDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_GoodwillAndIntangibleAssetsGoodwillPolicy": {
     "auth_ref": [
      "r118",
      "r202"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for goodwill. This accounting policy also may address how an entity assesses and measures impairment of goodwill, how reporting units are determined, how goodwill is allocated to such units, and how the fair values of the reporting units are determined.",
        "label": "Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]",
        "terseLabel": "Goodwill"
       }
      }
     },
     "localname": "GoodwillAndIntangibleAssetsGoodwillPolicy",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_GoodwillDisclosureTextBlock": {
     "auth_ref": [
      "r205"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for goodwill.",
        "label": "Goodwill Disclosure [Text Block]",
        "terseLabel": "Goodwill"
       }
      }
     },
     "localname": "GoodwillDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Goodwill"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_GoodwillForeignCurrencyTranslationGainLoss": {
     "auth_ref": [
      "r200"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.",
        "label": "Goodwill, Foreign Currency Translation Gain (Loss)",
        "terseLabel": "Foreign currency translation adjustments"
       }
      }
     },
     "localname": "GoodwillForeignCurrencyTranslationGainLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GoodwillImpairedAccumulatedImpairmentLoss": {
     "auth_ref": [
      "r197",
      "r201"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.",
        "label": "Goodwill, Impaired, Accumulated Impairment Loss",
        "terseLabel": "Accumulated impairment losses"
       }
      }
     },
     "localname": "GoodwillImpairedAccumulatedImpairmentLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GoodwillImpairmentLoss": {
     "auth_ref": [
      "r109",
      "r195",
      "r199",
      "r203"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.",
        "label": "Goodwill, Impairment Loss",
        "terseLabel": "Goodwill, impairment loss"
       }
      }
     },
     "localname": "GoodwillImpairmentLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GoodwillLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Goodwill [Line Items]",
        "terseLabel": "Goodwill"
       }
      }
     },
     "localname": "GoodwillLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_GoodwillRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Goodwill [Roll Forward]",
        "terseLabel": "Goodwill [Roll Forward]"
       }
      }
     },
     "localname": "GoodwillRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_HedgingRelationshipDomain": {
     "auth_ref": [
      "r435"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Nature or intent of a hedge.",
        "label": "Hedging Relationship [Domain]",
        "terseLabel": "Hedging Relationship [Domain]"
       }
      }
     },
     "localname": "HedgingRelationshipDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest": {
     "auth_ref": [
      "r80",
      "r132",
      "r499",
      "r506",
      "r523"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 1.0,
       "parentTag": "us-gaap_ProfitLoss",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.",
        "label": "Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest",
        "totalLabel": "Income (loss) from operations before taxes"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeStatementAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Income Statement [Abstract]"
       }
      }
     },
     "localname": "IncomeStatementAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeStatementLocationAxis": {
     "auth_ref": [
      "r221"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by location in the income statement.",
        "label": "Income Statement Location [Axis]",
        "terseLabel": "Income Statement Location [Axis]"
       }
      }
     },
     "localname": "IncomeStatementLocationAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeStatementLocationDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Location in the income statement.",
        "label": "Income Statement Location [Domain]",
        "terseLabel": "Income Statement Location [Domain]"
       }
      }
     },
     "localname": "IncomeStatementLocationDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeTaxAuthorityAxis": {
     "auth_ref": [
      "r375"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by tax jurisdiction.",
        "label": "Income Tax Authority [Axis]",
        "terseLabel": "Income Tax Authority [Axis]"
       }
      }
     },
     "localname": "IncomeTaxAuthorityAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeTaxAuthorityDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Agency, division or body classification that levies income taxes, examines tax returns for compliance, or grants exemptions from or makes other decisions pertaining to income taxes.",
        "label": "Income Tax Authority [Domain]",
        "terseLabel": "Income Tax Authority [Domain]"
       }
      }
     },
     "localname": "IncomeTaxAuthorityDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeTaxContingencyLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Income Tax Contingency [Line Items]",
        "terseLabel": "Income Tax Contingency [Line Items]"
       }
      }
     },
     "localname": "IncomeTaxContingencyLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeTaxContingencyTable": {
     "auth_ref": [
      "r376",
      "r380",
      "r382",
      "r392"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about tax positions taken in the tax returns filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities and other income tax contingencies. Includes, but is not limited to, interest and penalties, reconciliation of unrecognized tax benefits, unrecognized tax benefits that would affect the effective tax rate, tax years that remain subject to examination by tax jurisdictions, and information about positions for which it is reasonably possible that amounts unrecognized will significantly change within 12 months.",
        "label": "Income Tax Contingency [Table]",
        "terseLabel": "Income Tax Contingency [Table]"
       }
      }
     },
     "localname": "IncomeTaxContingencyTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeTaxDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Income Tax Disclosure [Abstract]"
       }
      }
     },
     "localname": "IncomeTaxDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeTaxDisclosureTextBlock": {
     "auth_ref": [
      "r396"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.",
        "label": "Income Tax Disclosure [Text Block]",
        "terseLabel": "Income Taxes"
       }
      }
     },
     "localname": "IncomeTaxDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxes"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense": {
     "auth_ref": [
      "r374"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.",
        "label": "Income Tax Examination, Penalties and Interest Expense",
        "terseLabel": "Penalties and interest expense"
       }
      }
     },
     "localname": "IncomeTaxExaminationPenaltiesAndInterestExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxExpenseBenefit": {
     "auth_ref": [
      "r121",
      "r170",
      "r394"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 2.0,
       "parentTag": "us-gaap_ProfitLoss",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.",
        "label": "Income Tax Expense (Benefit)",
        "terseLabel": "Income tax expense (benefit)",
        "totalLabel": "Income tax expense (benefit)",
        "verboseLabel": "Income tax expense (benefit)"
       }
      }
     },
     "localname": "IncomeTaxExpenseBenefit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/IncomeTaxesComponentsOfIncomeTaxBenefitDetail",
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxPolicyTextBlock": {
     "auth_ref": [
      "r77",
      "r118",
      "r368",
      "r369",
      "r381",
      "r382",
      "r385",
      "r395",
      "r529"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.",
        "label": "Income Tax, Policy [Policy Text Block]",
        "terseLabel": "Income Taxes"
       }
      }
     },
     "localname": "IncomeTaxPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance": {
     "auth_ref": [
      "r367",
      "r372",
      "r373"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 8.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.",
        "label": "Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount",
        "verboseLabel": "Change in valuation allowance"
       }
      }
     },
     "localname": "IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate": {
     "auth_ref": [
      "r366",
      "r372",
      "r373"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.",
        "label": "Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount",
        "terseLabel": "Effective tax rate change"
       }
      }
     },
     "localname": "IncomeTaxReconciliationChangeInEnactedTaxRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate": {
     "auth_ref": [
      "r120",
      "r372",
      "r373"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.",
        "label": "Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount",
        "terseLabel": "Income tax expense (benefit) at federal statutory tax rate"
       }
      }
     },
     "localname": "IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationOtherReconcilingItems": {
     "auth_ref": [
      "r372",
      "r373"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 10.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.",
        "label": "Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "IncomeTaxReconciliationOtherReconcilingItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes": {
     "auth_ref": [
      "r120",
      "r372",
      "r373"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_IncomeTaxExpenseBenefit",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit).",
        "label": "Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount",
        "terseLabel": "State and local income taxes"
       }
      }
     },
     "localname": "IncomeTaxReconciliationStateAndLocalIncomeTaxes",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitExpenseDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxesPaidNet": {
     "auth_ref": [
      "r112"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.",
        "label": "Income Taxes Paid, Net",
        "terseLabel": "(Refund) payments for income taxes, net"
       }
      }
     },
     "localname": "IncomeTaxesPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInAccountsPayable": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 13.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.",
        "label": "Increase (Decrease) in Accounts Payable",
        "terseLabel": "Accounts payable"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccountsPayable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInAccountsReceivable": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 8.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.",
        "label": "Increase (Decrease) in Accounts Receivable",
        "negatedLabel": "Accounts receivable, net"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccountsReceivable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInAccruedLiabilities": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 14.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the aggregate amount of expenses incurred but not yet paid.",
        "label": "Increase (Decrease) in Accrued Liabilities",
        "terseLabel": "Accrued expenses"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccruedLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInInventories": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 9.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the aggregate value of all inventory held by the reporting entity, associated with underlying transactions that are classified as operating activities.",
        "label": "Increase (Decrease) in Inventories",
        "negatedLabel": "Inventories"
       }
      }
     },
     "localname": "IncreaseDecreaseInInventories",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOperatingAssetsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Increase (Decrease) in Operating Assets [Abstract]",
        "terseLabel": "(Increase) decrease in operating assets, net of acquisitions and dispositions:"
       }
      }
     },
     "localname": "IncreaseDecreaseInOperatingAssetsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Increase (Decrease) in Operating Liabilities [Abstract]",
        "terseLabel": "(Decrease) increase in operating liabilities, net of acquisitions and dispositions:"
       }
      }
     },
     "localname": "IncreaseDecreaseInOperatingLiabilitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherCurrentAssets": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 11.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in current assets classified as other.",
        "label": "Increase (Decrease) in Other Current Assets",
        "negatedLabel": "Other current assets"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherCurrentAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherNoncurrentAssets": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 12.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in noncurrent assets classified as other.",
        "label": "Increase (Decrease) in Other Noncurrent Assets",
        "negatedLabel": "Other assets"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherNoncurrentAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherOperatingLiabilities": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 17.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in operating liabilities classified as other.",
        "label": "Increase (Decrease) in Other Operating Liabilities",
        "terseLabel": "Other liabilities"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherOperatingLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInStockholdersEquityRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Increase (Decrease) in Stockholders' Equity [Roll Forward]",
        "terseLabel": "Increase (Decrease) In Stockholders' Equity [Rollforward]"
       }
      }
     },
     "localname": "IncreaseDecreaseInStockholdersEquityRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants": {
     "auth_ref": [
      "r144"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of call options and warrants using the treasury stock method.",
        "label": "Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants",
        "terseLabel": "Add: warrants"
       }
      }
     },
     "localname": "IncrementalCommonSharesAttributableToCallOptionsAndWarrants",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements": {
     "auth_ref": [
      "r139",
      "r146"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.",
        "label": "Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements",
        "terseLabel": "Add: Share-based payment arrangements"
       }
      }
     },
     "localname": "IncrementalCommonSharesAttributableToShareBasedPaymentArrangements",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_IntangibleAssetsGrossExcludingGoodwill": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_IntangibleAssetsNetExcludingGoodwill",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before accumulated amortization of intangible assets, excluding goodwill.",
        "label": "Intangible Assets, Gross (Excluding Goodwill)",
        "verboseLabel": "Gross Carrying Amount"
       }
      }
     },
     "localname": "IntangibleAssetsGrossExcludingGoodwill",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IntangibleAssetsNetExcludingGoodwill": {
     "auth_ref": [
      "r206",
      "r210"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.",
        "label": "Intangible Assets, Net (Excluding Goodwill)",
        "totalLabel": "Net Carrying Amount"
       }
      }
     },
     "localname": "IntangibleAssetsNetExcludingGoodwill",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestExpense": {
     "auth_ref": [
      "r79",
      "r168",
      "r461",
      "r464",
      "r509"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 5.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of the cost of borrowed funds accounted for as interest expense.",
        "label": "Interest Expense",
        "terseLabel": "Interest expense"
       }
      }
     },
     "localname": "InterestExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestIncomeExpenseNet": {
     "auth_ref": [
      "r508"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The net amount of operating interest income (expense).",
        "label": "Interest Income (Expense), Net",
        "negatedLabel": "Interest expense (income)"
       }
      }
     },
     "localname": "InterestIncomeExpenseNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestPaidNet": {
     "auth_ref": [
      "r103",
      "r106",
      "r112"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.",
        "label": "Interest Paid, Excluding Capitalized Interest, Operating Activities",
        "verboseLabel": "Interest"
       }
      }
     },
     "localname": "InterestPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestPayableCurrent": {
     "auth_ref": [
      "r7",
      "r8",
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Interest Payable, Current",
        "terseLabel": "Interest"
       }
      }
     },
     "localname": "InterestPayableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestRateContractMember": {
     "auth_ref": [
      "r294",
      "r441"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Derivative instrument whose primary underlying risk is tied to the right to receive or pay a sum of money at a given interest rate.",
        "label": "Interest Rate Contract [Member]",
        "terseLabel": "Interest rate derivatives"
       }
      }
     },
     "localname": "InterestRateContractMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_InventoryCurrentTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about inventory expected to be sold or consumed within one year or operating cycle, if longer.",
        "label": "Inventory, Current [Table]",
        "terseLabel": "Inventory, Current [Table]"
       }
      }
     },
     "localname": "InventoryCurrentTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Inventories",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/InventoriesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_InventoryDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Inventory Disclosure [Abstract]"
       }
      }
     },
     "localname": "InventoryDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_InventoryDisclosureTextBlock": {
     "auth_ref": [
      "r193"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for inventory. Includes, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the classes of inventory, and the nature of the cost elements included in inventory.",
        "label": "Inventory Disclosure [Text Block]",
        "terseLabel": "Inventories"
       }
      }
     },
     "localname": "InventoryDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Inventories"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_InventoryFinishedGoodsNetOfReserves": {
     "auth_ref": [
      "r27",
      "r192"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.",
        "label": "Inventory, Finished Goods, Net of Reserves",
        "terseLabel": "Finished goods"
       }
      }
     },
     "localname": "InventoryFinishedGoodsNetOfReserves",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InventoryLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Inventory [Line Items]",
        "terseLabel": "Inventory [Line Items]"
       }
      }
     },
     "localname": "InventoryLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Inventories",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/InventoriesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_InventoryNet": {
     "auth_ref": [
      "r2",
      "r52",
      "r189"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.",
        "label": "Inventory, Net",
        "terseLabel": "Inventories",
        "totalLabel": "Total"
       }
      }
     },
     "localname": "InventoryNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InventoryOreStockpilesOnLeachPads": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before last-in first-out (LIFO) and valuation reserves of ore stockpile material contained on a leach pad, for example, but not limited to, copper or gold ore.",
        "label": "Inventory, Ore Stockpiles on Leach Pads, Gross",
        "terseLabel": "Aggregate stockpiles"
       }
      }
     },
     "localname": "InventoryOreStockpilesOnLeachPads",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InventoryPolicyTextBlock": {
     "auth_ref": [
      "r9",
      "r53",
      "r118",
      "r150",
      "r190",
      "r191"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of inventory accounting policy for inventory classes, including, but not limited to, basis for determining inventory amounts, methods by which amounts are added and removed from inventory classes, loss recognition on impairment of inventories, and situations in which inventories are stated above cost.",
        "label": "Inventory, Policy [Policy Text Block]",
        "terseLabel": "Inventories"
       }
      }
     },
     "localname": "InventoryPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_InventoryRawMaterialsNetOfReserves": {
     "auth_ref": [
      "r29",
      "r192"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process.",
        "label": "Inventory, Raw Materials, Net of Reserves",
        "terseLabel": "Raw materials"
       }
      }
     },
     "localname": "InventoryRawMaterialsNetOfReserves",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InventoryWorkInProcessNetOfReserves": {
     "auth_ref": [
      "r28",
      "r192"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.",
        "label": "Inventory, Work in Process, Net of Reserves",
        "terseLabel": "Work in process"
       }
      }
     },
     "localname": "InventoryWorkInProcessNetOfReserves",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/InventoriesComponentsOfInventoriesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LandMember": {
     "auth_ref": [
      "r274"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Part of earth's surface not covered by water.",
        "label": "Land [Member]",
        "terseLabel": "Land (non-mineral bearing)"
       }
      }
     },
     "localname": "LandMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_LeaseAgreementsMember": {
     "auth_ref": [
      "r404"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Contractual agreement that stipulates the lessee pay the lessor for use of an asset.",
        "label": "Lease Agreements [Member]",
        "terseLabel": "Mineral leases"
       }
      }
     },
     "localname": "LeaseAgreementsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_LeaseCost": {
     "auth_ref": [
      "r487",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease cost recognized by lessee for lease contract.",
        "label": "Lease, Cost",
        "totalLabel": "Total lease cost"
       }
      }
     },
     "localname": "LeaseCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LeaseCostAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Lease, Cost [Abstract]",
        "terseLabel": "Lease, Cost [Abstract]"
       }
      }
     },
     "localname": "LeaseCostAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LeaseCostTableTextBlock": {
     "auth_ref": [
      "r487"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income.",
        "label": "Lease, Cost [Table Text Block]",
        "terseLabel": "Schedule of Lease Cost"
       }
      }
     },
     "localname": "LeaseCostTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LeasesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Leases [Abstract]"
       }
      }
     },
     "localname": "LeasesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeFinanceLeaseTermOfContract1": {
     "auth_ref": [
      "r477"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Term of lessee's finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Lessee, Finance Lease, Term of Contract",
        "terseLabel": "Equipment lease term"
       }
      }
     },
     "localname": "LesseeFinanceLeaseTermOfContract1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_LesseeFinanceLeasesTextBlock": {
     "auth_ref": [
      "r490"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for finance leases of lessee. Includes, but is not limited to, description of lessee's finance lease and maturity analysis of finance lease liability.",
        "label": "Lessee, Finance Leases [Text Block]",
        "terseLabel": "Leases"
       }
      }
     },
     "localname": "LesseeFinanceLeasesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Leases"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LesseeLeaseDescriptionLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Lessee, Lease, Description [Line Items]",
        "terseLabel": "Lessee, Lease, Description [Line Items]"
       }
      }
     },
     "localname": "LesseeLeaseDescriptionLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Leases",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeLeaseDescriptionTable": {
     "auth_ref": [
      "r478"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about lessee's leases.",
        "label": "Lessee, Lease, Description [Table]",
        "terseLabel": "Lessee, Lease, Description [Table]"
       }
      }
     },
     "localname": "LesseeLeaseDescriptionTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Leases",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/LeasesScheduleOfMinimumContractualAgreementsUnderRoyaltyAgreementsDetails",
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock": {
     "auth_ref": [
      "r488"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position.",
        "label": "Lessee, Operating Lease, Liability, Maturity [Table Text Block]",
        "terseLabel": "Schedule of Operating Lease Liability Maturities"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityMaturityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due",
        "totalLabel": "Total lease payments"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due after fifth fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due after Year Five",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due in next fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fifth fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due Year Five",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fourth fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due Year Four",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearFour",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due in third fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due Year Three",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearThree",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease, due in second fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Due Year Two",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount": {
     "auth_ref": [
      "r488"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": 1.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.",
        "label": "Lessee, Operating Lease, Liability, Undiscounted Excess Amount",
        "negatedTerseLabel": "Less imputed interest"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityUndiscountedExcessAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeasesTextBlock": {
     "auth_ref": [
      "r490"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for operating leases of lessee. Includes, but is not limited to, description of operating lease and maturity analysis of operating lease liability.",
        "label": "Lessee, Operating Leases [Text Block]",
        "terseLabel": "Leases"
       }
      }
     },
     "localname": "LesseeOperatingLeasesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Leases"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_Liabilities": {
     "auth_ref": [
      "r42"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 2.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.",
        "label": "Liabilities",
        "terseLabel": "Total liabilities",
        "totalLabel": "Total liabilities"
       }
      }
     },
     "localname": "Liabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquity": {
     "auth_ref": [
      "r25",
      "r504",
      "r518"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liabilities and equity items, including the portion of equity attributable to noncontrolling interests, if any.",
        "label": "Liabilities and Equity",
        "totalLabel": "Total liabilities and stockholders' equity / member's interest"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities and Equity [Abstract]",
        "terseLabel": "Liabilities and Stockholders' Equity / Member's Interest"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesCurrent": {
     "auth_ref": [
      "r44"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 1.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer.",
        "label": "Liabilities, Current",
        "totalLabel": "Total current liabilities"
       }
      }
     },
     "localname": "LiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesCurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities, Current [Abstract]",
        "terseLabel": "Current liabilities:"
       }
      }
     },
     "localname": "LiabilitiesCurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesFairValueAdjustment": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of addition (reduction) to the amount at which a liability could be incurred (settled) in a current transaction between willing parties.",
        "label": "Liabilities, Fair Value Adjustment",
        "negatedLabel": "Present value adjustments"
       }
      }
     },
     "localname": "LiabilitiesFairValueAdjustment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilityForUncertainTaxPositionsNoncurrent": {
     "auth_ref": [
      "r47"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount recognized for uncertainty in income taxes classified as noncurrent.",
        "label": "Liability for Uncertainty in Income Taxes, Noncurrent",
        "terseLabel": "Liability for uncertainty in income taxes"
       }
      }
     },
     "localname": "LiabilityForUncertainTaxPositionsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r154",
      "r155",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of ownership interest in a limited liability company (LLC), including portions attributable to both the parent and noncontrolling interests.",
        "label": "Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest",
        "periodEndLabel": "Ending balance members' interest",
        "periodStartLabel": "Beginning balance members' interest",
        "totalLabel": "Total member's interest",
        "verboseLabel": "Total member's interest"
       }
      }
     },
     "localname": "LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LimitedPartnersCapitalAccountDistributionAmount": {
     "auth_ref": [
      "r154",
      "r263"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total amount of distributions to limited partners.",
        "label": "Limited Partners' Capital Account, Distribution Amount",
        "terseLabel": "Distributions to LP Unitholders"
       }
      }
     },
     "localname": "LimitedPartnersCapitalAccountDistributionAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding": {
     "auth_ref": [
      "r154",
      "r264"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of limited partner units outstanding.",
        "label": "Limited Partners' Capital Account, Units Outstanding",
        "periodEndLabel": "Number of LP Units outstanding (in shares)",
        "periodStartLabel": "Number of LP Units outstanding (in shares)"
       }
      }
     },
     "localname": "LimitedPartnersCapitalAccountUnitsOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_LineOfCredit": {
     "auth_ref": [
      "r14",
      "r503",
      "r513"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.",
        "label": "Long-term Line of Credit",
        "terseLabel": "Amount outstanding"
       }
      }
     },
     "localname": "LineOfCredit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity": {
     "auth_ref": [
      "r40"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.",
        "label": "Line of Credit Facility, Maximum Borrowing Capacity",
        "terseLabel": "Revolving credit commitment",
        "verboseLabel": "Maximum borrowing capacity"
       }
      }
     },
     "localname": "LineOfCreditFacilityMaximumBorrowingCapacity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity": {
     "auth_ref": [
      "r40"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).",
        "label": "Line of Credit Facility, Remaining Borrowing Capacity",
        "terseLabel": "Remaining borrowing capacity"
       }
      }
     },
     "localname": "LineOfCreditFacilityRemainingBorrowingCapacity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LoansNotesTradeAndOtherReceivablesDisclosureTextBlock": {
     "auth_ref": [
      "r184"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.",
        "label": "Loans, Notes, Trade and Other Receivables Disclosure [Text Block]",
        "verboseLabel": "Revenue Recognition"
       }
      }
     },
     "localname": "LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognition"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LondonInterbankOfferedRateLIBORMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest rate at which a bank borrows funds from other banks in the London interbank market.",
        "label": "London Interbank Offered Rate (LIBOR) [Member]",
        "terseLabel": "LIBOR"
       }
      }
     },
     "localname": "LondonInterbankOfferedRateLIBORMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_LongTermDebt": {
     "auth_ref": [
      "r14",
      "r253",
      "r503",
      "r516"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.",
        "label": "Long-term Debt",
        "terseLabel": "Long-term debt",
        "totalLabel": "Total debt"
       }
      }
     },
     "localname": "LongTermDebt",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtByMaturityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Long-term Debt, Fiscal Year Maturity [Abstract]",
        "terseLabel": "Contractual payments of long-term debt"
       }
      }
     },
     "localname": "LongTermDebtByMaturityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LongTermDebtCurrent": {
     "auth_ref": [
      "r41"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_LongTermDebt",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.",
        "label": "Long-term Debt, Current Maturities",
        "terseLabel": "Current portion of debt",
        "verboseLabel": "Current portion of long-term debt"
       }
      }
     },
     "localname": "LongTermDebtCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtFairValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.",
        "label": "Long-term Debt, Fair Value",
        "verboseLabel": "Long-term debt"
       }
      }
     },
     "localname": "LongTermDebtFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal after Year Five",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal in Year Five",
        "terseLabel": "2024"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal in Year Four",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal in Year Three",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo": {
     "auth_ref": [
      "r128",
      "r248"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_DebtInstrumentCarryingAmount",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.",
        "label": "Long-term Debt, Maturities, Repayments of Principal in Year Two",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfContractualPaymentsOfLongTermDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtNoncurrent": {
     "auth_ref": [
      "r46"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_LongTermDebt",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.",
        "label": "Long-term Debt, Excluding Current Maturities",
        "terseLabel": "Long-term debt"
       }
      }
     },
     "localname": "LongTermDebtNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongtermDebtTypeAxis": {
     "auth_ref": [
      "r46"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of long-term debt.",
        "label": "Long-term Debt, Type [Axis]",
        "terseLabel": "Long-term Debt, Type [Axis]"
       }
      }
     },
     "localname": "LongtermDebtTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LongtermDebtTypeDomain": {
     "auth_ref": [
      "r46",
      "r249"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Type of long-term debt arrangement, such as notes, line of credit, commercial paper, asset-based financing, project financing, letter of credit financing. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the company, if longer.",
        "label": "Long-term Debt, Type [Domain]",
        "terseLabel": "Long-term Debt, Type [Domain]"
       }
      }
     },
     "localname": "LongtermDebtTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_LossContingenciesLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Loss Contingencies [Line Items]",
        "terseLabel": "Loss Contingencies [Line Items]"
       }
      }
     },
     "localname": "LossContingenciesLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LossContingenciesTable": {
     "auth_ref": [
      "r238",
      "r239",
      "r240",
      "r241",
      "r242",
      "r243",
      "r244",
      "r246",
      "r247"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Discloses the specific components (such as the nature, name, and date) of the loss contingency and gives an estimate of the possible loss or range of loss, or states that a reasonable estimate cannot be made. Excludes environmental contingencies, warranties and unconditional purchase obligations.",
        "label": "Loss Contingencies [Table]",
        "terseLabel": "Loss Contingencies [Table]"
       }
      }
     },
     "localname": "LossContingenciesTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/CommitmentsAndContingencies",
      "http://www.summitmaterials.com/role/CommitmentsAndContingenciesNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MachineryAndEquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.",
        "label": "Machinery and Equipment [Member]",
        "terseLabel": "Plants, machinery and equipment"
       }
      }
     },
     "localname": "MachineryAndEquipmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MeasurementInputDiscountRateMember": {
     "auth_ref": [
      "r448"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measurement input using interest rate to determine present value of future cash flows.",
        "label": "Measurement Input, Discount Rate [Member]",
        "terseLabel": "Discount Rate"
       }
      }
     },
     "localname": "MeasurementInputDiscountRateMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MeasurementInputTypeAxis": {
     "auth_ref": [
      "r448"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of measurement input used to determine value of asset and liability.",
        "label": "Measurement Input Type [Axis]",
        "terseLabel": "Measurement Input Type [Axis]"
       }
      }
     },
     "localname": "MeasurementInputTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MeasurementInputTypeDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measurement input used to determine value of asset and liability.",
        "label": "Measurement Input Type [Domain]",
        "terseLabel": "Measurement Input Type [Domain]"
       }
      }
     },
     "localname": "MeasurementInputTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MemberUnitsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Ownership interest in limited liability company (LLC).",
        "label": "Member Units [Member]",
        "terseLabel": "Members' equity"
       }
      }
     },
     "localname": "MemberUnitsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MembersCapital": {
     "auth_ref": [
      "r154",
      "r155",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of member capital in limited liability company (LLC).",
        "label": "Members' Capital",
        "terseLabel": "Member's equity"
       }
      }
     },
     "localname": "MembersCapital",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_MembersEquityNotesDisclosureTextBlock": {
     "auth_ref": [
      "r156"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for the formation, structure, control and ownership of a limited liability company (LLC).",
        "label": "Members' Equity Notes Disclosure [Text Block]",
        "terseLabel": "Members' Interest"
       }
      }
     },
     "localname": "MembersEquityNotesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.",
        "label": "Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners",
        "verboseLabel": "Noncontrolling interest elimination (as a percent)"
       }
      }
     },
     "localname": "MinorityInterestOwnershipPercentageByNoncontrollingOwners",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_MinorityInterestOwnershipPercentageByParent": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The parent entity's interest in net assets of the subsidiary, expressed as a percentage.",
        "label": "Noncontrolling Interest, Ownership Percentage by Parent",
        "verboseLabel": "Summit Inc. Ownership Percentage"
       }
      }
     },
     "localname": "MinorityInterestOwnershipPercentageByParent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_MovementInValuationAllowancesAndReservesRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]",
        "terseLabel": "Valuation Allowance:"
       }
      }
     },
     "localname": "MovementInValuationAllowancesAndReservesRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomesTaxesDeferredTaxAssetValuationAllowanceDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MultiemployerPlanNameAxis": {
     "auth_ref": [
      "r326"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by legal name of a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.",
        "label": "Multiemployer Plan Name [Axis]",
        "terseLabel": "Multiemployer Plan Name [Axis]"
       }
      }
     },
     "localname": "MultiemployerPlanNameAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MultiemployerPlanNameDomain": {
     "auth_ref": [
      "r326"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Legal names of pension or postretirement benefit plans to which two or more unrelated employers contribute to the same plan where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.",
        "label": "Multiemployer Plan Name [Domain]",
        "terseLabel": "Multiemployer Plan Name [Domain]"
       }
      }
     },
     "localname": "MultiemployerPlanNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MultiemployerPlansLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Multiemployer Plans [Line Items]",
        "terseLabel": "Multiemployer Plans [Line Items]"
       }
      }
     },
     "localname": "MultiemployerPlansLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MultiemployerPlansPlanContributions1": {
     "auth_ref": [
      "r328"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contributions made to multiemployer plan by all employers who participate in plan.",
        "label": "Multiemployer Plans, Plan Contributions",
        "terseLabel": "Contributions of Company"
       }
      }
     },
     "localname": "MultiemployerPlansPlanContributions1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInFinancingActivities": {
     "auth_ref": [
      "r105"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 3.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.",
        "label": "Net Cash Provided by (Used in) Financing Activities",
        "totalLabel": "Net cash provided by (used in) financing activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInFinancingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Financing Activities [Abstract]",
        "terseLabel": "Cash flow from financing activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInFinancingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivities": {
     "auth_ref": [
      "r105"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 2.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.",
        "label": "Net Cash Provided by (Used in) Investing Activities",
        "terseLabel": "Net cash used for investing activities",
        "totalLabel": "Net cash used for investing activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Investing Activities [Abstract]",
        "terseLabel": "Cash flow from investing activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivities": {
     "auth_ref": [
      "r105",
      "r107",
      "r110"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 1.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.",
        "label": "Net Cash Provided by (Used in) Operating Activities",
        "terseLabel": "Net cash (used in) provided by operating activities",
        "totalLabel": "Net cash provided by operating activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Operating Activities [Abstract]",
        "terseLabel": "Cash flow from operating activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetIncomeLossAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r71",
      "r74",
      "r421",
      "r428"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of Net Income (Loss) attributable to noncontrolling interest.",
        "label": "Net Income (Loss) Attributable to Noncontrolling Interest",
        "terseLabel": "Net income attributable to noncontrolling interest",
        "verboseLabel": "Net income (loss) attributable to noncontrolling interest"
       }
      }
     },
     "localname": "NetIncomeLossAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetIncomeLossAttributableToParentDiluted": {
     "auth_ref": [
      "r137"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The portion of profit or loss for the period, net of income taxes, which is attributable to the parent, and includes adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.",
        "label": "Net Income (Loss) Attributable to Parent, Diluted",
        "terseLabel": "Diluted net income attributable to Summit Inc."
       }
      }
     },
     "localname": "NetIncomeLossAttributableToParentDiluted",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic": {
     "auth_ref": [
      "r132",
      "r136"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.",
        "label": "Net Income (Loss) Available to Common Stockholders, Basic",
        "terseLabel": "Net income attributable to Summit Inc.",
        "totalLabel": "Net income attributable to Summit Inc.",
        "verboseLabel": "Net income (loss) attributable to Summit Inc."
       }
      }
     },
     "localname": "NetIncomeLossAvailableToCommonStockholdersBasic",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NewAccountingPronouncementEarlyAdoptionLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "New Accounting Pronouncement, Early Adoption [Line Items]",
        "terseLabel": "New Accounting Standards"
       }
      }
     },
     "localname": "NewAccountingPronouncementEarlyAdoptionLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NewAccountingPronouncementEarlyAdoptionTable": {
     "auth_ref": [
      "r131",
      "r133"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule detailing the financial statement line items and the effect of the guidance on financial statement line items by guidance implemented if the entity elects earlier application.",
        "label": "New Accounting Pronouncement, Early Adoption [Table]",
        "terseLabel": "New Accounting Pronouncement, Early Adoption [Table]"
       }
      }
     },
     "localname": "NewAccountingPronouncementEarlyAdoptionTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact.",
        "label": "New Accounting Pronouncements, Policy [Policy Text Block]",
        "terseLabel": "New Accounting Standards"
       }
      }
     },
     "localname": "NewAccountingPronouncementsPolicyPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_NoncashOrPartNoncashAcquisitionNetNonmonetaryAssetsAcquiredLiabilitiesAssumed1": {
     "auth_ref": [
      "r113",
      "r114",
      "r115"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The net book value of a nonmonetary asset transferred or exchanged in connection with the acquisition of a business or asset in a noncash transaction. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. \"Part noncash\" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Nonmonetary assets and liabilities are assets and liabilities that will not result in cash receipts or cash payments in the future.",
        "label": "Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed)",
        "negatedLabel": "Purchase of noncontrolling interest"
       }
      }
     },
     "localname": "NoncashOrPartNoncashAcquisitionNetNonmonetaryAssetsAcquiredLiabilitiesAssumed1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NumberOfBusinessesAcquired": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of businesses acquired by the entity during the period.",
        "label": "Number of Businesses Acquired",
        "terseLabel": "Number of business acquisitions"
       }
      }
     },
     "localname": "NumberOfBusinessesAcquired",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "us-gaap_NumberOfOperatingSegments": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.",
        "label": "Number of Operating Segments",
        "terseLabel": "Number of operating segments"
       }
      }
     },
     "localname": "NumberOfOperatingSegments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "us-gaap_NumberOfReportableSegments": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.",
        "label": "Number of Reportable Segments",
        "terseLabel": "Number of reportable segments"
       }
      }
     },
     "localname": "NumberOfReportableSegments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "us-gaap_NumberOfStatesInWhichEntityOperates": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of states the entity operates in as of the balance sheet date.",
        "label": "Number of States in which Entity Operates",
        "terseLabel": "Number of states in which the entity operates"
       }
      }
     },
     "localname": "NumberOfStatesInWhichEntityOperates",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "us-gaap_OfficeEquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tangible personal property used in an office setting. Examples include, but are not limited to, computers, copiers and fax machine.",
        "label": "Office Equipment [Member]",
        "terseLabel": "Office equipment"
       }
      }
     },
     "localname": "OfficeEquipmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OperatingIncomeLoss": {
     "auth_ref": [],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The net result for the period of deducting operating expenses from operating revenues.",
        "label": "Operating Income (Loss)",
        "terseLabel": "Operating income (loss)",
        "totalLabel": "Operating income"
       }
      }
     },
     "localname": "OperatingIncomeLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseCost": {
     "auth_ref": [
      "r480",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_LeaseCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.",
        "label": "Operating Lease, Cost",
        "terseLabel": "Operating lease cost"
       }
      }
     },
     "localname": "OperatingLeaseCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Lessee, Operating Lease, Liability, Payment, Due [Abstract]",
        "terseLabel": "Operating Leases"
       }
      }
     },
     "localname": "OperatingLeaseLiabilitiesPaymentsDueAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingLeaseLiability": {
     "auth_ref": [
      "r472"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetailsCalc2": {
       "order": 2.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from operating lease.",
        "label": "Operating Lease, Liability",
        "terseLabel": "Operating lease liability",
        "totalLabel": "Total operating lease liabilities"
       }
      }
     },
     "localname": "OperatingLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilityCurrent": {
     "auth_ref": [
      "r472"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_OperatingLeaseLiability",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.",
        "label": "Operating Lease, Liability, Current",
        "terseLabel": "Current operating lease liabilities",
        "verboseLabel": "Current operating lease liabilities"
       }
      }
     },
     "localname": "OperatingLeaseLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilityNoncurrent": {
     "auth_ref": [
      "r472"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 5.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingLeaseLiability",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.",
        "label": "Operating Lease, Liability, Noncurrent",
        "terseLabel": "Noncurrent operating lease liabilities",
        "verboseLabel": "Noncurrent operating lease liabilities"
       }
      }
     },
     "localname": "OperatingLeaseLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasePayments": {
     "auth_ref": [
      "r476",
      "r483"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.",
        "label": "Operating Lease, Payments",
        "terseLabel": "Operating cash payments on operating leases"
       }
      }
     },
     "localname": "OperatingLeasePayments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseRightOfUseAsset": {
     "auth_ref": [
      "r471"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 6.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's right to use underlying asset under operating lease.",
        "label": "Operating Lease, Right-of-Use Asset",
        "terseLabel": "Operating lease right-of-use assets",
        "verboseLabel": "Operating lease right-of-use assets"
       }
      }
     },
     "localname": "OperatingLeaseRightOfUseAsset",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent": {
     "auth_ref": [
      "r486",
      "r489"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average discount rate for operating lease calculated at point in time.",
        "label": "Operating Lease, Weighted Average Discount Rate, Percent",
        "terseLabel": "Operating leases"
       }
      }
     },
     "localname": "OperatingLeaseWeightedAverageDiscountRatePercent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1": {
     "auth_ref": [
      "r485",
      "r489"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Operating Lease, Weighted Average Remaining Lease Term",
        "terseLabel": "Operating leases"
       }
      }
     },
     "localname": "OperatingLeaseWeightedAverageRemainingLeaseTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_OperatingLeasedAssetsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Operating Leased Assets [Line Items]",
        "terseLabel": "Operating Leased Assets [Line Items]"
       }
      }
     },
     "localname": "OperatingLeasedAssetsLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingSegmentsMember": {
     "auth_ref": [
      "r167",
      "r174"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Identifies components of an entity that engage in business activities from which they may earn revenue and incur expenses, including transactions with other components of the same entity.",
        "label": "Operating Segments [Member]",
        "terseLabel": "Operating segment"
       }
      }
     },
     "localname": "OperatingSegmentsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock": {
     "auth_ref": [
      "r130",
      "r134",
      "r165",
      "r433"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for the general note to the financial statements for the reporting entity which may include, descriptions of the basis of presentation, business description, significant accounting policies, consolidations, reclassifications, new pronouncements not yet adopted and changes in accounting principles.",
        "label": "Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]",
        "terseLabel": "Summary of Organization and Significant Accounting Policies"
       }
      }
     },
     "localname": "OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_OtherAccruedLiabilitiesCurrent": {
     "auth_ref": [
      "r6",
      "r7",
      "r8",
      "r43"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.",
        "label": "Other Accrued Liabilities, Current",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "OtherAccruedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesComponentsOfAccruedExpensesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherAssetsCurrent": {
     "auth_ref": [
      "r54"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of current assets classified as other.",
        "label": "Other Assets, Current",
        "terseLabel": "Other current assets"
       }
      }
     },
     "localname": "OtherAssetsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherAssetsNoncurrent": {
     "auth_ref": [
      "r37"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 7.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of noncurrent assets classified as other.",
        "label": "Other Assets, Noncurrent",
        "terseLabel": "Other assets"
       }
      }
     },
     "localname": "OtherAssetsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherCommitmentsAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of other commitment.",
        "label": "Other Commitments [Axis]",
        "terseLabel": "Other Commitments [Axis]"
       }
      }
     },
     "localname": "OtherCommitmentsAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherCommitmentsDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other future obligation.",
        "label": "Other Commitments [Domain]",
        "terseLabel": "Other Commitments [Domain]"
       }
      }
     },
     "localname": "OtherCommitmentsDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax": {
     "auth_ref": [
      "r63",
      "r65",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax",
        "terseLabel": "Prior service cost"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]",
        "terseLabel": "Amounts recognized in other comprehensive (income) loss:"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax": {
     "auth_ref": [
      "r60",
      "r65",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.",
        "label": "Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax",
        "negatedLabel": "Net actuarial loss (gain)"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent": {
     "auth_ref": [
      "r417",
      "r418",
      "r423"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss), attributable to parent entity.",
        "label": "Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent",
        "negatedLabel": "Income on cash flow hedges, net of tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent": {
     "auth_ref": [
      "r417",
      "r418",
      "r423"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.",
        "label": "Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent",
        "terseLabel": "Foreign currency translation adjustment, net of tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax": {
     "auth_ref": [
      "r65",
      "r68",
      "r69",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 2.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax",
        "terseLabel": "Postretirement liability adjustment"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax": {
     "auth_ref": [
      "r65",
      "r68",
      "r69",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 3.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax",
        "negatedLabel": "Amortization of prior year service cost"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax": {
     "auth_ref": [
      "r59",
      "r65"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 5.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.",
        "label": "Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax",
        "terseLabel": "Income (loss) on cash flow hedges"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax": {
     "auth_ref": [
      "r65",
      "r68"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.",
        "label": "Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax",
        "negatedTerseLabel": "Income on cash flow hedges, net of tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax": {
     "auth_ref": [
      "r65",
      "r68",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 1.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.",
        "label": "Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax",
        "terseLabel": "Postretirement curtailment adjustment"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax": {
     "auth_ref": [
      "r65",
      "r68",
      "r304"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": 4.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.",
        "label": "Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax",
        "negatedLabel": "Curtailment benefit"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax": {
     "auth_ref": [
      "r57",
      "r65",
      "r458",
      "r460"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 3.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.",
        "label": "Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax",
        "terseLabel": "Foreign currency translation adjustment"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossNetOfTax": {
     "auth_ref": [
      "r72",
      "r75",
      "r78",
      "r257"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 2.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax and reclassification adjustments of other comprehensive income (loss).",
        "label": "Other Comprehensive Income (Loss), Net of Tax",
        "terseLabel": "Other comprehensive income (loss), net of tax",
        "totalLabel": "Other comprehensive income (loss)"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Other Comprehensive Income (Loss), Net of Tax [Abstract]",
        "terseLabel": "Other comprehensive income (loss):"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax": {
     "auth_ref": [
      "r62",
      "r65"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax",
        "totalLabel": "Total amount recognized"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax": {
     "auth_ref": [
      "r65",
      "r68",
      "r69",
      "r304"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of reclassification adjustment from accumulated other comprehensive (income) loss for net periodic benefit cost (credit) of defined benefit plan.",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax",
        "terseLabel": "Postretirement liability adjustment, net of tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1": {
     "auth_ref": [
      "r417",
      "r418",
      "r423"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 4.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.",
        "label": "Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent",
        "negatedLabel": "Less tax effect of other comprehensive income items"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossTaxPortionAttributableToParent1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax": {
     "auth_ref": [
      "r59",
      "r65",
      "r444"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 6.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).",
        "label": "Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax",
        "terseLabel": "Income (loss) on cash flow hedges"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherIntangibleAssetsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intangible assets classified as other.",
        "label": "Other Intangible Assets [Member]",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "OtherIntangibleAssetsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OtherLiabilitiesNoncurrent": {
     "auth_ref": [
      "r47"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 6.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.",
        "label": "Other Liabilities, Noncurrent",
        "terseLabel": "Other noncurrent liabilities"
       }
      }
     },
     "localname": "OtherLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNoncashIncomeExpense": {
     "auth_ref": [
      "r110"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 7.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of income (expense) included in net income that results in no cash inflow (outflow), classified as other.",
        "label": "Other Noncash Income (Expense)",
        "negatedLabel": "Other"
       }
      }
     },
     "localname": "OtherNoncashIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNoncurrentLiabilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing other noncurrent liabilities.",
        "label": "Other Noncurrent Liabilities [Member]",
        "terseLabel": "Other noncurrent liabilities"
       }
      }
     },
     "localname": "OtherNoncurrentLiabilitiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OtherNonoperatingIncomeExpense": {
     "auth_ref": [
      "r89"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of income (expense) related to nonoperating activities, classified as other.",
        "label": "Other Nonoperating Income (Expense)",
        "negatedLabel": "Other income, net"
       }
      }
     },
     "localname": "OtherNonoperatingIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember": {
     "auth_ref": [
      "r278",
      "r312",
      "r313",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Plan designed to provide other postretirement benefits. Includes, but is not limited to, defined benefit and defined contribution plans. Excludes pension benefits.",
        "label": "Other Postretirement Benefits Plan [Member]",
        "terseLabel": "Healthcare &amp; Life Ins"
       }
      }
     },
     "localname": "OtherPostretirementBenefitPlansDefinedBenefitMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PartnersCapitalAccountDistributions": {
     "auth_ref": [
      "r262",
      "r264"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total distributions to each class of partners (i.e., general, limited and preferred partners).",
        "label": "Partners' Capital Account, Distributions",
        "negatedLabel": "Distributions from partnership"
       }
      }
     },
     "localname": "PartnersCapitalAccountDistributions",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PayablesAndAccrualsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Payables and Accruals [Abstract]"
       }
      }
     },
     "localname": "PayablesAndAccrualsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PaymentsForProceedsFromOtherInvestingActivities": {
     "auth_ref": [
      "r92",
      "r95",
      "r127"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 5.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash (inflow) outflow from investing activities classified as other.",
        "label": "Payments for (Proceeds from) Other Investing Activities",
        "negatedLabel": "Other"
       }
      }
     },
     "localname": "PaymentsForProceedsFromOtherInvestingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfDebtIssuanceCosts": {
     "auth_ref": [
      "r101"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.",
        "label": "Payments of Debt Issuance Costs",
        "verboseLabel": "Loan origination fees"
       }
      }
     },
     "localname": "PaymentsOfDebtIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfDistributionsToAffiliates": {
     "auth_ref": [
      "r99"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 8.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 9.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The distributions of earnings to an entity that is affiliated with the reporting entity by means of direct or indirect ownership.",
        "label": "Payments of Distributions to Affiliates",
        "negatedTerseLabel": "Distributions from partnership"
       }
      }
     },
     "localname": "PaymentsOfDistributionsToAffiliates",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfFinancingCosts": {
     "auth_ref": [
      "r102"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 8.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow for loan and debt issuance costs.",
        "label": "Payments of Financing Costs",
        "negatedLabel": "Debt issuance costs"
       }
      }
     },
     "localname": "PaymentsOfFinancingCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfMergerRelatedCostsFinancingActivities": {
     "auth_ref": [
      "r102"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 7.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow for financing costs associated with business combinations.",
        "label": "Payments of Merger Related Costs, Financing Activities",
        "negatedLabel": "Payments on acquisition-related liabilities"
       }
      }
     },
     "localname": "PaymentsOfMergerRelatedCostsFinancingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfStockIssuanceCosts": {
     "auth_ref": [
      "r102"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow for cost incurred directly with the issuance of an equity security.",
        "label": "Payments of Stock Issuance Costs",
        "negatedLabel": "Capital issuance costs"
       }
      }
     },
     "localname": "PaymentsOfStockIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired": {
     "auth_ref": [
      "r93"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.",
        "label": "Payments to Acquire Businesses, Net of Cash Acquired",
        "negatedLabel": "Acquisitions, net of cash acquired"
       }
      }
     },
     "localname": "PaymentsToAcquireBusinessesNetOfCashAcquired",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquirePropertyPlantAndEquipment": {
     "auth_ref": [
      "r94"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.",
        "label": "Payments to Acquire Property, Plant, and Equipment",
        "negatedLabel": "Purchase of property, plant and equipment",
        "negatedTerseLabel": "Purchases of property, plant and equipment",
        "terseLabel": "Total purchases of property, plant and equipment"
       }
      }
     },
     "localname": "PaymentsToAcquirePropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToMinorityShareholders": {
     "auth_ref": [
      "r102"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 6.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.",
        "label": "Payments to Noncontrolling Interests",
        "negatedLabel": "Purchase of noncontrolling interests"
       }
      }
     },
     "localname": "PaymentsToMinorityShareholders",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities": {
     "auth_ref": [
      "r13",
      "r280",
      "r281",
      "r291"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 1.0,
       "parentTag": "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetailCalc2": {
       "order": 1.0,
       "parentTag": "us-gaap_DefinedBenefitPlanFundedStatusOfPlan",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as current.",
        "label": "Liability, Defined Benefit Plan, Current",
        "negatedLabel": "Current liabilities"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent": {
     "auth_ref": [
      "r280",
      "r291",
      "r502",
      "r515"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.",
        "label": "Liability, Defined Benefit Plan",
        "negatedTotalLabel": "Liability recognized"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent": {
     "auth_ref": [
      "r15",
      "r280",
      "r281",
      "r291"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail": {
       "order": 2.0,
       "parentTag": "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesCurrentAndNoncurrent",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetailCalc2": {
       "order": 2.0,
       "parentTag": "us-gaap_DefinedBenefitPlanFundedStatusOfPlan",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.",
        "label": "Liability, Defined Benefit Plan, Noncurrent",
        "negatedLabel": "Noncurrent liabilities"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionPlansDefinedBenefitMember": {
     "auth_ref": [
      "r277",
      "r312",
      "r313",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Plan designed to provide participant with pension benefits. Includes, but is not limited to, defined benefit and defined contribution plans. Excludes other postretirement benefits.",
        "label": "Pension Plan [Member]",
        "terseLabel": "Pension Benefits"
       }
      }
     },
     "localname": "PensionPlansDefinedBenefitMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PerformanceSharesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share-based payment arrangement awarded for meeting performance target.",
        "label": "Performance Shares [Member]",
        "terseLabel": "Performance Stock Units"
       }
      }
     },
     "localname": "PerformanceSharesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PlanAssetCategoriesDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Defined benefit plan asset investment.",
        "label": "Defined Benefit Plan, Plan Assets, Category [Domain]",
        "terseLabel": "Defined Benefit Plan, Plan Assets, Category [Domain]"
       }
      }
     },
     "localname": "PlanAssetCategoriesDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansFairValueOfCompanysPensionPlansAssetsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PlanNameAxis": {
     "auth_ref": [
      "r333",
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by plan name for share-based payment arrangement.",
        "label": "Plan Name [Axis]",
        "terseLabel": "Plan Name [Axis]"
       }
      }
     },
     "localname": "PlanNameAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PlanNameDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Plan name for share-based payment arrangement.",
        "label": "Plan Name [Domain]",
        "terseLabel": "Plan Name [Domain]"
       }
      }
     },
     "localname": "PlanNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PortionAtFairValueFairValueDisclosureMember": {
     "auth_ref": [
      "r453"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measured at fair value for financial reporting purposes.",
        "label": "Portion at Fair Value Measurement [Member]",
        "terseLabel": "Portion at Fair Value Measurement [Member]"
       }
      }
     },
     "localname": "PortionAtFairValueFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/FairValueOfFinancialInstrumentsCarryingValueAndFairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PostemploymentBenefitsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Postemployment Benefits [Abstract]"
       }
      }
     },
     "localname": "PostemploymentBenefitsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PrimeRateMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest rate charged by financial institutions to their most creditworthy borrowers.",
        "label": "Prime Rate [Member]",
        "terseLabel": "Prime rate"
       }
      }
     },
     "localname": "PrimeRateMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ProceedsFromDebtNetOfIssuanceCosts": {
     "auth_ref": [
      "r97"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.",
        "label": "Proceeds from Debt, Net of Issuance Costs",
        "terseLabel": "Proceeds net of related fees and expenses"
       }
      }
     },
     "localname": "ProceedsFromDebtNetOfIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromDivestitureOfBusinesses": {
     "auth_ref": [
      "r90"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.",
        "label": "Proceeds from Divestiture of Businesses",
        "terseLabel": "Proceeds from sale of business"
       }
      }
     },
     "localname": "ProceedsFromDivestitureOfBusinesses",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromIssuanceOfCommonStock": {
     "auth_ref": [
      "r96"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from the additional capital contribution to the entity.",
        "label": "Proceeds from Issuance of Common Stock",
        "terseLabel": "Proceeds from sale of common stock, net of underwriting discounts",
        "verboseLabel": "Proceeds from equity offerings"
       }
      }
     },
     "localname": "ProceedsFromIssuanceOfCommonStock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromIssuanceOfDebt": {
     "auth_ref": [
      "r97"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.",
        "label": "Proceeds from Issuance of Debt",
        "terseLabel": "Net proceeds from debt issuance",
        "verboseLabel": "Proceeds from debt issuances"
       }
      }
     },
     "localname": "ProceedsFromIssuanceOfDebt",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromPartnershipContribution": {
     "auth_ref": [
      "r98"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 11.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from the capital received in cash from a partner in a partnership during the period.",
        "label": "Proceeds from Partnership Contribution",
        "terseLabel": "Capital contributions by member"
       }
      }
     },
     "localname": "ProceedsFromPartnershipContribution",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromPaymentsForOtherFinancingActivities": {
     "auth_ref": [
      "r98",
      "r102",
      "r127"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 10.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 10.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from financing activities classified as other.",
        "label": "Proceeds from (Payments for) Other Financing Activities",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "ProceedsFromPaymentsForOtherFinancingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromRepaymentsOfRelatedPartyDebt": {
     "auth_ref": [
      "r127"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from long-term debt by a related party. Related parties, include, but are not limited to, affiliates, owners or officers and their immediate families, and pension trusts.",
        "label": "Proceeds from (Repayments of) Related Party Debt",
        "terseLabel": "Loans received from and payments made on loans from other Summit Companies"
       }
      }
     },
     "localname": "ProceedsFromRepaymentsOfRelatedPartyDebt",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment": {
     "auth_ref": [
      "r91"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.",
        "label": "Proceeds from Sale of Property, Plant, and Equipment",
        "terseLabel": "Proceeds from the sale of property, plant and equipment",
        "verboseLabel": "Proceeds from the sale of property, plant, and equipment"
       }
      }
     },
     "localname": "ProceedsFromSaleOfPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromStockOptionsExercised": {
     "auth_ref": [
      "r96",
      "r356"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 9.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow from exercise of option under share-based payment arrangement.",
        "label": "Proceeds from Stock Options Exercised",
        "terseLabel": "Proceeds from stock option exercises"
       }
      }
     },
     "localname": "ProceedsFromStockOptionsExercised",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProductMember": {
     "auth_ref": [
      "r274"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Article or substance produced by nature, labor or machinery.",
        "label": "Product [Member]",
        "terseLabel": "Product"
       }
      }
     },
     "localname": "ProductMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ProfitLoss": {
     "auth_ref": [
      "r71",
      "r74",
      "r104",
      "r171",
      "r175",
      "r417",
      "r420",
      "r422",
      "r428",
      "r429"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome": {
       "order": 1.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 1.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.",
        "label": "Net Income (Loss), Including Portion Attributable to Noncontrolling Interest",
        "terseLabel": "Net income",
        "totalLabel": "Net income",
        "verboseLabel": "Net (loss) income"
       }
      }
     },
     "localname": "ProfitLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Property, Plant and Equipment [Abstract]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentAndIntangibleAssetsTextBlock": {
     "auth_ref": [
      "r216",
      "r223"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for intangible assets and long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.",
        "label": "Property, Plant, and Equipment and Intangible Assets [Text Block]",
        "terseLabel": "Property, Plant and Equipment, net and Intangibles, net"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAndIntangibleAssetsTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentByTypeAxis": {
     "auth_ref": [
      "r36",
      "r220"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of long-lived, physical assets used to produce goods and services and not intended for resale.",
        "label": "Property, Plant and Equipment, Type [Axis]",
        "terseLabel": "Property, Plant and Equipment, Type [Axis]",
        "verboseLabel": "Long-Lived Intangible Asset [Axis]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentByTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentGross": {
     "auth_ref": [
      "r35",
      "r218"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_PropertyPlantAndEquipmentNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.",
        "label": "Property, Plant and Equipment, Gross",
        "terseLabel": "Property, plant and equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentGross",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Property, Plant and Equipment [Line Items]",
        "terseLabel": "Property, Plant and Equipment [Line Items]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentNet": {
     "auth_ref": [
      "r10",
      "r11",
      "r220",
      "r520"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 8.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.",
        "label": "Property, Plant and Equipment, Net",
        "terseLabel": "Property, plant and equipment",
        "totalLabel": "Property, plant and equipment, net",
        "verboseLabel": "Property, plant and equipment, net"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingBalanceSheetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentOtherTypesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Long-lived, physical assets used to produce goods and services and not intended for resale, classified as other.",
        "label": "Property, Plant and Equipment, Other Types [Member]",
        "terseLabel": "Other"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentOtherTypesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentPolicyTextBlock": {
     "auth_ref": [
      "r34",
      "r118",
      "r220"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, basis of assets, depreciation and depletion methods used, including composite deprecation, estimated useful lives, capitalization policy, accounting treatment for costs incurred for repairs and maintenance, capitalized interest and the method it is calculated, disposals and impairments.",
        "label": "Property, Plant and Equipment, Policy [Policy Text Block]",
        "terseLabel": "Property, Plant and Equipment, net"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentTextBlock": {
     "auth_ref": [
      "r10",
      "r220"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.",
        "label": "Property, Plant and Equipment [Table Text Block]",
        "terseLabel": "Summary of Property, Plant and Equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentTypeDomain": {
     "auth_ref": [
      "r10",
      "r218"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Listing of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.",
        "label": "Property, Plant and Equipment, Type [Domain]",
        "terseLabel": "Property, Plant and Equipment, Type [Domain]",
        "verboseLabel": "Long-Lived Tangible Asset [Domain]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentUsefulLife": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.",
        "label": "Property, Plant and Equipment, Useful Life",
        "terseLabel": "Estimated useful life"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentUsefulLife",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_QuarterlyFinancialInformationDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Quarterly Financial Information Disclosure [Abstract]"
       }
      }
     },
     "localname": "QuarterlyFinancialInformationDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_QuarterlyFinancialInformationTextBlock": {
     "auth_ref": [
      "r153"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for quarterly financial data. Includes, but is not limited to, tabular presentation of financial information for fiscal quarters, effect of year-end adjustments, and an explanation of matters or transactions that affect comparability of the information.",
        "label": "Quarterly Financial Information [Text Block]",
        "terseLabel": "Supplementary Data (Unaudited)"
       }
      }
     },
     "localname": "QuarterlyFinancialInformationTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnaudited"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ReceivablesPolicyTextBlock": {
     "auth_ref": [
      "r118",
      "r181",
      "r185",
      "r186",
      "r187"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for receivable. Includes, but is not limited to, accounts receivable and financing receivable.",
        "label": "Receivable [Policy Text Block]",
        "terseLabel": "Accounts Receivable"
       }
      }
     },
     "localname": "ReceivablesPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]",
        "terseLabel": "Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]"
       }
      }
     },
     "localname": "ReconciliationOfUnrecognizedTaxBenefitsExcludingAmountsPertainingToExaminedTaxReturnsRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RepaymentsOfDebt": {
     "auth_ref": [
      "r100"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 5.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.",
        "label": "Repayments of Debt",
        "negatedLabel": "Payments on debt",
        "negatedTerseLabel": "Payments on long-term debt"
       }
      }
     },
     "localname": "RepaymentsOfDebt",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfCashFlowsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestrictedStockUnitsRSUMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share instrument which is convertible to stock or an equivalent amount of cash, after a specified period of time or when specified performance conditions are met.",
        "label": "Restricted Stock Units (RSUs) [Member]",
        "terseLabel": "Restricted stock"
       }
      }
     },
     "localname": "RestrictedStockUnitsRSUMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RetainedEarningsAccumulatedDeficit": {
     "auth_ref": [
      "r22",
      "r262",
      "r517"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 2.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cumulative amount of the reporting entity's undistributed earnings or deficit.",
        "label": "Retained Earnings (Accumulated Deficit)",
        "terseLabel": "Accumulated earnings"
       }
      }
     },
     "localname": "RetainedEarningsAccumulatedDeficit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RetainedEarningsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cumulative amount of the reporting entity's undistributed earnings or deficit.",
        "label": "Retained Earnings [Member]",
        "terseLabel": "Accumulated Earnings/Deficit"
       }
      }
     },
     "localname": "RetainedEarningsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RetirementPlanTypeAxis": {
     "auth_ref": [
      "r277",
      "r278",
      "r312",
      "r313",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of retirement benefit plan. Includes, but is not limited to, retirement benefit arrangement for defined benefit pension and other postretirement plans, retirement benefit arrangement for defined contribution pension and other postretirement plans, and special and contractual termination benefits payable upon retirement.",
        "label": "Retirement Plan Type [Axis]",
        "terseLabel": "Retirement Plan Type [Axis]"
       }
      }
     },
     "localname": "RetirementPlanTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RetirementPlanTypeDomain": {
     "auth_ref": [
      "r277",
      "r278",
      "r312",
      "r313",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Type of plan designed to provide participants with retirement benefits. Includes, but is not limited to, retirement benefit arrangement for defined benefit pension and other postretirement plans, retirement benefit arrangement for defined contribution pension and other postretirement plans, and special and contractual termination benefits payable upon retirement.",
        "label": "Retirement Plan Type [Domain]",
        "terseLabel": "Retirement Plan Type [Domain]"
       }
      }
     },
     "localname": "RetirementPlanTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansEstimatedBenefitPaymentsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RevenueFromContractWithCustomerAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Revenue from Contract with Customer [Abstract]"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax": {
     "auth_ref": [
      "r271",
      "r272"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations": {
       "order": 1.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": 1.0
      },
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.",
        "label": "Revenue from Contract with Customer, Excluding Assessed Tax",
        "terseLabel": "Revenue",
        "verboseLabel": "Net revenue"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerExcludingAssessedTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SeniorNotesGuarantorAndNonGuarantorFinancialInformationScheduleOfCondensedConsolidatingStatementsOfOperationsAndComprehensiveIncomeDetails",
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedSupplementalFinancialInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RevenueFromContractWithCustomerPolicyTextBlock": {
     "auth_ref": [
      "r119",
      "r275"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for revenue from contract with customer.",
        "label": "Revenue from Contract with Customer [Policy Text Block]",
        "terseLabel": "Revenue Recognition"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_RevenuesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Revenues [Abstract]",
        "terseLabel": "Revenue:"
       }
      }
     },
     "localname": "RevenuesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability": {
     "auth_ref": [
      "r484",
      "r489"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in right-of-use asset obtained in exchange for finance lease liability.",
        "label": "Right-of-Use Asset Obtained in Exchange for Finance Lease Liability",
        "terseLabel": "Right of use assets obtained in exchange for finance leases obligations"
       }
      }
     },
     "localname": "RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability": {
     "auth_ref": [
      "r484",
      "r489"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in right-of-use asset obtained in exchange for operating lease liability.",
        "label": "Right-of-Use Asset Obtained in Exchange for Operating Lease Liability",
        "terseLabel": "Right of use assets obtained in exchange for operating lease obligations"
       }
      }
     },
     "localname": "RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RoyaltyExpense": {
     "auth_ref": [
      "r86"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expense related to royalty payments under a contractual arrangement such as payment for mineral and drilling rights and use of technology or intellectual property.",
        "label": "Royalty Expense",
        "terseLabel": "Royalty expense recorded in cost of revenue"
       }
      }
     },
     "localname": "RoyaltyExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_SaleOfStockNameOfTransactionDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sale of the entity's stock, including, but not limited to, initial public offering (IPO) and private placement.",
        "label": "Sale of Stock [Domain]",
        "terseLabel": "Sale of Stock [Domain]"
       }
      }
     },
     "localname": "SaleOfStockNameOfTransactionDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable": {
     "auth_ref": [
      "r51"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule itemizing specific types of trade accounts and notes receivable, and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables.",
        "label": "Schedule of Accounts, Notes, Loans and Financing Receivable [Table]",
        "terseLabel": "Schedule of Accounts, Notes, Loans and Financing Receivable [Table]"
       }
      }
     },
     "localname": "ScheduleOfAccountsNotesLoansAndFinancingReceivableTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionSummaryOfAccountsReceivableNetDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock": {
     "auth_ref": [
      "r51"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the various types of trade accounts and notes receivable and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables.",
        "label": "Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]",
        "terseLabel": "Summary of Accounts Receivable, Net"
       }
      }
     },
     "localname": "ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognitionTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the components of accrued liabilities.",
        "label": "Schedule of Accrued Liabilities [Table Text Block]",
        "terseLabel": "Components of Accrued Expenses"
       }
      }
     },
     "localname": "ScheduleOfAccruedLiabilitiesTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedExpensesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock": {
     "auth_ref": [
      "r67"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the components of accumulated other comprehensive income (loss).",
        "label": "Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]",
        "terseLabel": "Schedule of Changes in Each Component of Accumulated Other Comprehensive Income (Loss)"
       }
      }
     },
     "localname": "ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAllocationOfPlanAssetsTableTextBlock": {
     "auth_ref": [
      "r292"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans.  This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall.",
        "label": "Schedule of Allocation of Plan Assets [Table Text Block]",
        "terseLabel": "Fair Value of Company's Pension Plans' Assets"
       }
      }
     },
     "localname": "ScheduleOfAllocationOfPlanAssetsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAmountsRecognizedInOtherComprehensiveIncomeLossTableTextBlock": {
     "auth_ref": [
      "r304"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the net gain (loss) and net prior service cost or credit recognized in other comprehensive income (loss) for the period for pension plans and/or other employee benefit plans, and reclassification adjustments of other comprehensive income (loss) for the period, as those amounts, including amortization of the net transition asset or obligation, are recognized as components of net periodic benefit cost.",
        "label": "Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]",
        "terseLabel": "Amounts Recognized in Other Comprehensive (Gain) Loss"
       }
      }
     },
     "localname": "ScheduleOfAmountsRecognizedInOtherComprehensiveIncomeLossTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock": {
     "auth_ref": [
      "r145"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would increase EPS amounts or decrease loss per share amounts for the period presented, by antidilutive securities.",
        "label": "Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]",
        "terseLabel": "Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share"
       }
      }
     },
     "localname": "ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAssumptionsUsedTableTextBlock": {
     "auth_ref": [
      "r306"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of assumption used to determine benefit obligation and net periodic benefit cost of defined benefit plan. Includes, but is not limited to, discount rate, rate of compensation increase, expected long-term rate of return on plan assets and interest crediting rate.",
        "label": "Defined Benefit Plan, Assumptions [Table Text Block]",
        "terseLabel": "Schedule of Assumptions Used"
       }
      }
     },
     "localname": "ScheduleOfAssumptionsUsedTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable": {
     "auth_ref": [
      "r398",
      "r399"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule reflecting each material business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities.",
        "label": "Schedule of Business Acquisitions, by Acquisition [Table]",
        "terseLabel": "Schedule of Business Acquisitions, by Acquisition [Table]"
       }
      }
     },
     "localname": "ScheduleOfBusinessAcquisitionsByAcquisitionTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/AcquisitionsContractualObligationsDetails",
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfCapitalizationEquityLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Schedule of Capitalization, Equity [Line Items]",
        "terseLabel": "Schedule of Capitalization, Equity [Line Items]"
       }
      }
     },
     "localname": "ScheduleOfCapitalizationEquityLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfCapitalizationEquityTable": {
     "auth_ref": [
      "r152"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summarization of information required and determined to be disclosed concerning the equity component of the capitalization of the entity. The table may be detailed by subsidiary (legal entity) (if applicable) and include information by component of equity as may be included in the Statement of Changes in Shareholders' Equity.",
        "label": "Schedule of Capitalization, Equity [Table]",
        "terseLabel": "Schedule of Capitalization, Equity [Table]"
       }
      }
     },
     "localname": "ScheduleOfCapitalizationEquityTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of supplemental cash flow information for the periods presented.",
        "label": "Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]",
        "terseLabel": "Schedule of Supplemental Cash Flow Information"
       }
      }
     },
     "localname": "ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfChangeInAssetRetirementObligationTableTextBlock": {
     "auth_ref": [
      "r232"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation.",
        "label": "Schedule of Change in Asset Retirement Obligation [Table Text Block]",
        "terseLabel": "Activity for Asset Retirement Obligations"
       }
      }
     },
     "localname": "ScheduleOfChangeInAssetRetirementObligationTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AccruedMiningAndLandfillReclamationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock": {
     "auth_ref": [
      "r391"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the components of income tax expense attributable to continuing operations for each year presented including, but not limited to: current tax expense (benefit), deferred tax expense (benefit), investment tax credits, government grants, the benefits of operating loss carryforwards, tax expense that results from allocating certain tax benefits either directly to contributed capital or to reduce goodwill or other noncurrent intangible assets of an acquired entity, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity, and adjustments of the beginning-of-the-year balances of a valuation allowance because of a change in circumstances that causes a change in judgment about the realizability of the related deferred tax asset in future years.",
        "label": "Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]",
        "terseLabel": "Components of Income Tax Benefit"
       }
      }
     },
     "localname": "ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfDebtTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of information pertaining to short-term and long-debt instruments or arrangements, including but not limited to identification of terms, features, collateral requirements and other information necessary to a fair presentation.",
        "label": "Schedule of Debt [Table Text Block]",
        "terseLabel": "Schedule of Debt"
       }
      }
     },
     "localname": "ScheduleOfDebtTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock": {
     "auth_ref": [
      "r384"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets.",
        "label": "Schedule of Deferred Tax Assets and Liabilities [Table Text Block]",
        "terseLabel": "Components of Net Deferred Income Tax Liability"
       }
      }
     },
     "localname": "ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable": {
     "auth_ref": [
      "r312",
      "r313",
      "r314",
      "r315",
      "r323"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosures about an individual defined benefit pension plan or an other postretirement defined benefit plan. It may be appropriate to group certain similar plans.  Also includes schedule for fair value of plan assets by major categories of plan assets by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets or liabilities (Level 1), Significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).",
        "label": "Schedule of Defined Benefit Plans Disclosures [Table]",
        "terseLabel": "Schedule of Defined Benefit Plans Disclosures [Table]"
       }
      }
     },
     "localname": "ScheduleOfDefinedBenefitPlansDisclosuresTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlans",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansAmountsRecognizedInOtherComprehensiveGainLossDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansComponentsOfNetPeriodicBenefitCostDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansNarrativeDetails",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansObligationsAndFundedStatusDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineBenefitObligationsDetail",
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansWeightedAverageAssumptionsUsedToDetermineNetPeriodicBenefitCostDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock": {
     "auth_ref": [
      "r146"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations.",
        "label": "Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]",
        "terseLabel": "Schedule of Basic Earnings Per Share"
       }
      }
     },
     "localname": "ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable": {
     "auth_ref": [
      "r85",
      "r138",
      "r140",
      "r141",
      "r144",
      "r148"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Complete disclosure pertaining to an entity's diluted earnings per share.",
        "label": "Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table]",
        "terseLabel": "Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table]"
       }
      }
     },
     "localname": "ScheduleOfEarningsPerShareDilutedByCommonClassTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfEffectOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesTableTextBlock": {
     "auth_ref": [
      "r310"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the effect of a one-percentage-point increase and the effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs and the accumulated postretirement benefit obligation for health care benefits.",
        "label": "Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]",
        "terseLabel": "Effects of One Percentage-Point Change in Assumed Health Care Cost Trend Rates"
       }
      }
     },
     "localname": "ScheduleOfEffectOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock": {
     "auth_ref": [
      "r372"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations.",
        "label": "Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]",
        "terseLabel": "Schedule of Reconciliation of Income Tax (Benefit) Expense"
       }
      }
     },
     "localname": "ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable": {
     "auth_ref": [
      "r177"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular presentation of the description and amount of revenues from a product or service, or a group of similar products or similar services, reported from external customers during the period, if the information is not provided as part of the reportable operating segment information.",
        "label": "Revenue from External Customers by Products and Services [Table]",
        "terseLabel": "Revenue from External Customers by Products and Services [Table]"
       }
      }
     },
     "localname": "ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/RevenueRecognition",
      "http://www.summitmaterials.com/role/RevenueRecognitionByProductDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionContractAssetsAndLiabilitiesDetails",
      "http://www.summitmaterials.com/role/RevenueRecognitionTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfExpectedBenefitPaymentsTableTextBlock": {
     "auth_ref": [
      "r296"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter.",
        "label": "Schedule of Expected Benefit Payments [Table Text Block]",
        "terseLabel": "Estimated Benefit Payments"
       }
      }
     },
     "localname": "ScheduleOfExpectedBenefitPaymentsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable": {
     "auth_ref": [
      "r208",
      "r211"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.",
        "label": "Schedule of Finite-Lived Intangible Assets [Table]",
        "terseLabel": "Schedule of Finite-Lived Intangible Assets [Table]"
       }
      }
     },
     "localname": "ScheduleOfFiniteLivedIntangibleAssetsTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock": {
     "auth_ref": [
      "r208",
      "r211"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance with a finite life, by either major class or business segment.",
        "label": "Schedule of Finite-Lived Intangible Assets [Table Text Block]",
        "terseLabel": "Intangible Assets by Type and in Total"
       }
      }
     },
     "localname": "ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock": {
     "auth_ref": [
      "r466"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of future minimum payments required in the aggregate and for each of the five succeeding fiscal years for operating leases having initial or remaining noncancelable lease terms in excess of one year and the total minimum rentals to be received in the future under noncancelable subleases as of the balance sheet date.",
        "label": "Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]",
        "terseLabel": "Schedule of Future Minimum Rental Payments for Operating Leases"
       }
      }
     },
     "localname": "ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfGoodwillTable": {
     "auth_ref": [
      "r202",
      "r204"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of goodwill and the changes during the year due to acquisition, sale, impairment or for other reasons.",
        "label": "Schedule of Goodwill [Table]",
        "terseLabel": "Schedule of Goodwill [Table]"
       }
      }
     },
     "localname": "ScheduleOfGoodwillTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillNarrativeDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfGoodwillTextBlock": {
     "auth_ref": [
      "r202",
      "r204"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.",
        "label": "Schedule of Goodwill [Table Text Block]",
        "terseLabel": "Goodwill by Reportable Segment and in Total"
       }
      }
     },
     "localname": "ScheduleOfGoodwillTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/GoodwillTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfInventoryCurrentTableTextBlock": {
     "auth_ref": [
      "r9",
      "r30",
      "r31",
      "r32"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.",
        "label": "Schedule of Inventory, Current [Table Text Block]",
        "terseLabel": "Components of Inventories"
       }
      }
     },
     "localname": "ScheduleOfInventoryCurrentTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/InventoriesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock": {
     "auth_ref": [
      "r248"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the combined aggregate amount of maturities and sinking fund requirements for all long-term borrowings for each of the five years following the date of the latest balance sheet date presented.",
        "label": "Schedule of Maturities of Long-term Debt [Table Text Block]",
        "terseLabel": "Schedule of Contractual Payments of Long-Term Debt"
       }
      }
     },
     "localname": "ScheduleOfMaturitiesOfLongTermDebtTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfMultiemployerPlansTable": {
     "auth_ref": [
      "r327"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of the quantitative and qualitative information related to multiemployer plans in which the employer participates. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.",
        "label": "Schedule of Multiemployer Plans [Table]",
        "terseLabel": "Schedule of Multiemployer Plans [Table]"
       }
      }
     },
     "localname": "ScheduleOfMultiemployerPlansTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansMultiemployerPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfMultiemployerPlansTableTextBlock": {
     "auth_ref": [
      "r327"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the quantitative and qualitative information related to multiemployer  plans in which the employer participates. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.",
        "label": "Schedule of Multiemployer Plans [Table Text Block]",
        "terseLabel": "Schedule of Multiemployer Plans"
       }
      }
     },
     "localname": "ScheduleOfMultiemployerPlansTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfNetBenefitCostsTableTextBlock": {
     "auth_ref": [
      "r298"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments.",
        "label": "Schedule of Net Benefit Costs [Table Text Block]",
        "terseLabel": "Schedule of Net Benefit Costs"
       }
      }
     },
     "localname": "ScheduleOfNetBenefitCostsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfNetFundedStatusTableTextBlock": {
     "auth_ref": [
      "r291"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of net funded status of pension plans and/or other employee benefit plans.",
        "label": "Schedule of Net Funded Status [Table Text Block]",
        "terseLabel": "Obligations and Funded Status"
       }
      }
     },
     "localname": "ScheduleOfNetFundedStatusTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfOperatingLeasedAssetsTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of long-lived, depreciable assets that are subject to a operating lease agreements and are used in the normal conduct of business to produce goods and services. Examples may include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.",
        "label": "Schedule of Operating Leased Assets [Table]"
       }
      }
     },
     "localname": "ScheduleOfOperatingLeasedAssetsTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesNarrativeDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfPropertyPlantAndEquipmentTable": {
     "auth_ref": [
      "r36",
      "r220"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.",
        "label": "Property, Plant and Equipment [Table]",
        "terseLabel": "Property, Plant and Equipment [Table]"
       }
      }
     },
     "localname": "ScheduleOfPropertyPlantAndEquipmentTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNet",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetCapitalAndFinanceLeasesDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetComponentsOfPropertyPlantAndEquipmentDetails",
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock": {
     "auth_ref": [
      "r151"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of quarterly financial data. Includes, but is not limited to, financial information for fiscal quarters, cumulative effect of a change in accounting principle and earnings per share data.",
        "label": "Quarterly Financial Information [Table Text Block]",
        "terseLabel": "Summary of Quarterly Data (Unaudited)"
       }
      }
     },
     "localname": "ScheduleOfQuarterlyFinancialInformationTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementaryDataUnauditedTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock": {
     "auth_ref": [
      "r402"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree.",
        "label": "Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]",
        "terseLabel": "Summary of Assets Acquired and Liabilities Assumed"
       }
      }
     },
     "localname": "ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable": {
     "auth_ref": [
      "r166",
      "r171",
      "r172",
      "r173",
      "r202"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A table disclosing the profit or loss and total assets for each reportable segment of the entity. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.",
        "label": "Schedule of Segment Reporting Information, by Segment [Table]",
        "terseLabel": "Schedule of Segment Reporting Information, by Segment [Table]"
       }
      }
     },
     "localname": "ScheduleOfSegmentReportingInformationBySegmentTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformation",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock": {
     "auth_ref": [
      "r166",
      "r171",
      "r172",
      "r173",
      "r202"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.",
        "label": "Schedule of Segment Reporting Information, by Segment [Table Text Block]",
        "terseLabel": "Summary of Financial Data for Company's Reportable Business Segments"
       }
      }
     },
     "localname": "ScheduleOfSegmentReportingInformationBySegmentTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable": {
     "auth_ref": [
      "r333",
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about share-based payment arrangement.",
        "label": "Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]",
        "terseLabel": "Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]"
       }
      }
     },
     "localname": "ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensation",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock": {
     "auth_ref": [
      "r348"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.",
        "label": "Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]",
        "terseLabel": "Weighted Average Assumptions Used to Estimate the Fair Value of Grants"
       }
      }
     },
     "localname": "ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock": {
     "auth_ref": [
      "r380",
      "r392"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the change in unrecognized tax benefits.",
        "label": "Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]",
        "terseLabel": "Schedule of Unrecognized Tax Benefits Roll Forward"
       }
      }
     },
     "localname": "ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock": {
     "auth_ref": [
      "r211"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for finite-lived intangible assets.",
        "label": "Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]",
        "terseLabel": "Estimated Amortization Expense for Intangible Assets"
       }
      }
     },
     "localname": "ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SegmentDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Components of an entity that engage in business activities from which they may earn revenue and incur expenses, including transactions with other components of the same entity.",
        "label": "Segments [Domain]",
        "terseLabel": "Segments [Domain]"
       }
      }
     },
     "localname": "SegmentDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_SegmentReportingAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Segment Reporting [Abstract]"
       }
      }
     },
     "localname": "SegmentReportingAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_SegmentReportingDisclosureTextBlock": {
     "auth_ref": [
      "r178"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.",
        "label": "Segment Reporting Disclosure [Text Block]",
        "terseLabel": "Segment Information"
       }
      }
     },
     "localname": "SegmentReportingDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SegmentReportingInformationLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Segment Reporting Information [Line Items]",
        "terseLabel": "Segment Reporting Information [Line Items]"
       }
      }
     },
     "localname": "SegmentReportingInformationLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SegmentInformation",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails",
      "http://www.summitmaterials.com/role/SegmentInformationNarrativeDetails",
      "http://www.summitmaterials.com/role/SegmentInformationTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SeniorNotesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Bond that takes priority over other debt securities sold by the issuer. In the event the issuer goes bankrupt, senior debt holders receive priority for (must receive) repayment prior to (relative to) junior and unsecured (general) creditors.",
        "label": "Senior Notes [Member]",
        "terseLabel": "Senior Notes"
       }
      }
     },
     "localname": "SeniorNotesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtScheduleOfDebtDetails",
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember": {
     "auth_ref": [
      "r399"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Represents the aggregation and reporting of combined amounts of individually immaterial business combinations that were completed during the period.",
        "label": "Series of Individually Immaterial Business Acquisitions [Member]",
        "terseLabel": "Series of Individually Immaterial Business Acquisitions"
       }
      }
     },
     "localname": "SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsSummaryOfAssetsAcquiredAndLiabilitiesAssumedDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ServiceMember": {
     "auth_ref": [
      "r274"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Assistance, including, but not limited to, technology, license and maintenance, license and service, maintenance, oil and gas, and financial service.",
        "label": "Service [Member]",
        "terseLabel": "Service"
       }
      }
     },
     "localname": "ServiceMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ShareBasedCompensation": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of noncash expense for share-based payment arrangement.",
        "label": "Share-based Payment Arrangement, Noncash Expense",
        "terseLabel": "Share-based compensation expense"
       }
      }
     },
     "localname": "ShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1": {
     "auth_ref": [
      "r334"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period",
        "terseLabel": "Award vesting period"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod": {
     "auth_ref": [
      "r341"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period",
        "negatedLabel": "Number of units, Forfeited/Canceled (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r345"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value",
        "terseLabel": "Number of units, Forfeited/Canceled (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod": {
     "auth_ref": [
      "r343"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period",
        "terseLabel": "Awards granted during the period (in shares)",
        "verboseLabel": "Number of units, granted (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r343"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value",
        "terseLabel": "Number of units, Granted (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber": {
     "auth_ref": [
      "r342"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number",
        "periodEndLabel": "Number of units, Ending balance (in shares)",
        "periodStartLabel": "Number of units, Beginning balance (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]",
        "terseLabel": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r342"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value",
        "periodEndLabel": "Number of units, Ending balance (in dollars per share)",
        "periodStartLabel": "Number of units, Beginning balance (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]",
        "terseLabel": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod": {
     "auth_ref": [
      "r344"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period",
        "negatedLabel": "Number of units, Vested (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r344"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value",
        "terseLabel": "Number of units, Vested (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate": {
     "auth_ref": [
      "r350"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate",
        "terseLabel": "Volatility (as a percent)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate": {
     "auth_ref": [
      "r351"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The risk-free interest rate assumption that is used in valuing an option on its own shares.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate",
        "terseLabel": "Risk-free interest rate (as a percent)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum",
        "terseLabel": "Risk-free interest rate, Maximum"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum",
        "terseLabel": "Risk-free interest rate, Minimum"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award [Line Items]",
        "terseLabel": "Share-based Compensation Arrangement by Share-based Payment Award [Line Items]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensation",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationTables",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized": {
     "auth_ref": [
      "r335"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares authorized for issuance under share-based payment arrangement.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized",
        "terseLabel": "Number of shares authorized (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant": {
     "auth_ref": [
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant",
        "terseLabel": "Shares available for grant (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber": {
     "auth_ref": [
      "r339"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number",
        "terseLabel": "Exercisable (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod": {
     "auth_ref": [
      "r341"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period",
        "negatedLabel": "Options, Forfeited/Canceled (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gross number of share options (or share units) granted during the period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross",
        "terseLabel": "Options, Granted (in shares)",
        "verboseLabel": "Options, granted (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue": {
     "auth_ref": [
      "r355"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value",
        "terseLabel": "Intrinsic value, options outstanding"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber": {
     "auth_ref": [
      "r338",
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of options outstanding, including both vested and non-vested options.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number",
        "periodEndLabel": "Options, Ending balance (in shares)",
        "periodStartLabel": "Options, Beginning balance (in shares)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]",
        "terseLabel": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice": {
     "auth_ref": [
      "r337"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price",
        "periodEndLabel": "Options, Ending balance (in dollars per share)",
        "periodStartLabel": "Options, Beginning balance (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]",
        "terseLabel": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice": {
     "auth_ref": [
      "r347"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price",
        "terseLabel": "Weighted average strike price, exercisable (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice": {
     "auth_ref": [
      "r346"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price",
        "terseLabel": "Weighted average strike price, outstanding (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain": {
     "auth_ref": [
      "r331",
      "r336"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Award under share-based payment arrangement.",
        "label": "Award Type [Domain]",
        "terseLabel": "Award Type [Domain]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which option holders acquired shares when converting their stock options into shares.",
        "label": "Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price",
        "terseLabel": "Options, Exercised (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.",
        "label": "Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price",
        "terseLabel": "Options, Forfeited/Canceled (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.",
        "label": "Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price",
        "terseLabel": "Options, Granted (in dollars per share)"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding",
        "terseLabel": "Intrinsic value, units outstanding"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1": {
     "auth_ref": [
      "r349",
      "r357"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term",
        "terseLabel": "Expected term"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationWeightedAverageAssumptionsUsedToEstimateFairValueOfGrantsDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1": {
     "auth_ref": [
      "r355"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value",
        "terseLabel": "Intrinsic value, exercisable stock options"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1": {
     "auth_ref": [
      "r355"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term",
        "terseLabel": "Weighed average remaining contractual term, exercisable"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1": {
     "auth_ref": [
      "r347"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining contractual term for fully vested and expected to vest exercisable or convertible options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term",
        "terseLabel": "Weighted average remaining contractual term"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1": {
     "auth_ref": [
      "r346"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term",
        "terseLabel": "Weighted average contractual term, unrecognized compensation cost"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of options vested.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares",
        "negatedLabel": "Options, Vested"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average grant-date fair value of options vested.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value",
        "terseLabel": "Options, Vested (in dollars per share)"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareholdersEquityAndShareBasedPaymentsTextBlock": {
     "auth_ref": [
      "r266",
      "r361"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for shareholders' equity and share-based payment arrangement. Includes, but is not limited to, disclosure of policy and terms of share-based payment arrangement, deferred compensation arrangement, and employee stock purchase plan (ESPP).",
        "label": "Shareholders' Equity and Share-based Payments [Text Block]",
        "terseLabel": "Stock-Based Compensation"
       }
      }
     },
     "localname": "ShareholdersEquityAndShareBasedPaymentsTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockBasedCompensation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SharesIssuedPricePerShare": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Per share or per unit amount of equity securities issued.",
        "label": "Shares Issued, Price Per Share",
        "terseLabel": "Offering price (in dollars per share)"
       }
      }
     },
     "localname": "SharesIssuedPricePerShare",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShippingAndHandlingMember": {
     "auth_ref": [
      "r274"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Packing and transport of product.",
        "label": "Shipping and Handling [Member]",
        "terseLabel": "Delivery and subcontract revenue"
       }
      }
     },
     "localname": "ShippingAndHandlingMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ShortTermLeaseCost": {
     "auth_ref": [
      "r481",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_LeaseCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of short-term lease cost, excluding expense for lease with term of one month or less.",
        "label": "Short-term Lease, Cost",
        "terseLabel": "Short-term lease cost"
       }
      }
     },
     "localname": "ShortTermLeaseCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StatementBusinessSegmentsAxis": {
     "auth_ref": [
      "r0",
      "r171",
      "r202",
      "r222",
      "r235",
      "r236",
      "r524"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by business segments.",
        "label": "Segments [Axis]",
        "terseLabel": "Segments [Axis]"
       }
      }
     },
     "localname": "StatementBusinessSegmentsAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/AcquisitionsAcquisitionsByRegionDetails",
      "http://www.summitmaterials.com/role/GoodwillSummaryOfGoodwillByReportableSegmentsDetails",
      "http://www.summitmaterials.com/role/SegmentInformationFinancialDataDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementClassOfStockAxis": {
     "auth_ref": [
      "r16",
      "r17",
      "r18",
      "r257"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by the different classes of stock of the entity.",
        "label": "Class of Stock [Axis]",
        "terseLabel": "Class of Stock [Axis]"
       }
      }
     },
     "localname": "StatementClassOfStockAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Cover",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails",
      "http://www.summitmaterials.com/role/StockBasedCompensationNarrativeDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementEquityComponentsAxis": {
     "auth_ref": [
      "r49",
      "r257"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by component of equity.",
        "label": "Equity Components [Axis]",
        "terseLabel": "Equity Components [Axis]"
       }
      }
     },
     "localname": "StatementEquityComponentsAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Statement [Line Items]",
        "terseLabel": "Statement [Line Items]"
       }
      }
     },
     "localname": "StatementLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Acquisitions",
      "http://www.summitmaterials.com/role/AcquisitionsTables",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Debt",
      "http://www.summitmaterials.com/role/DebtTables",
      "http://www.summitmaterials.com/role/Goodwill",
      "http://www.summitmaterials.com/role/GoodwillTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfCashFlowsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement of Cash Flows [Abstract]"
       }
      }
     },
     "localname": "StatementOfCashFlowsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfFinancialPositionAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement of Financial Position [Abstract]"
       }
      }
     },
     "localname": "StatementOfFinancialPositionAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement of Comprehensive Income [Abstract]"
       }
      }
     },
     "localname": "StatementOfIncomeAndComprehensiveIncomeAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfStockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement of Stockholders' Equity [Abstract]"
       }
      }
     },
     "localname": "StatementOfStockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule reflecting a Statement of Income, Statement of Cash Flows, Statement of Financial Position, Statement of Shareholders' Equity and Other Comprehensive Income, or other statement as needed.",
        "label": "Statement [Table]",
        "terseLabel": "Statement [Table]"
       }
      }
     },
     "localname": "StatementTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/Acquisitions",
      "http://www.summitmaterials.com/role/AcquisitionsTables",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheetsParenthetical",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfCashFlows",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfComprehensiveIncome",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/Debt",
      "http://www.summitmaterials.com/role/DebtTables",
      "http://www.summitmaterials.com/role/Goodwill",
      "http://www.summitmaterials.com/role/GoodwillTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits": {
     "auth_ref": [
      "r17",
      "r18",
      "r257",
      "r258",
      "r262"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).",
        "label": "Stock Issued During Period, Shares, Conversion of Units",
        "terseLabel": "LP Unit exchanges (in shares)",
        "verboseLabel": "Exchanges during period (in shares)"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesConversionOfUnits",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesNewIssues": {
     "auth_ref": [
      "r17",
      "r18",
      "r257",
      "r262"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of new stock issued during the period.",
        "label": "Stock Issued During Period, Shares, New Issues",
        "terseLabel": "Common stock issued (in shares)",
        "verboseLabel": "Issuance of shares (in shares)"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesNewIssues",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised": {
     "auth_ref": [
      "r17",
      "r18",
      "r257",
      "r262",
      "r340"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of share options (or share units) exercised during the current period.",
        "label": "Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period",
        "negatedLabel": "Options, Exercised (in shares)",
        "terseLabel": "Stock option exercises (in shares)"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesStockOptionsExercised",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockBasedCompensationSummaryOfAwardActivityDetails",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestChangeInOwnershipDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueConversionOfUnits": {
     "auth_ref": [
      "r49",
      "r257",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of stock issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).",
        "label": "Stock Issued During Period, Value, Conversion of Units",
        "terseLabel": "LP Unit exchanges"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueConversionOfUnits",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueNewIssues": {
     "auth_ref": [
      "r17",
      "r18",
      "r257",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.",
        "label": "Stock Issued During Period, Value, New Issues",
        "terseLabel": "Issuance of shares"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueNewIssues",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueStockDividend": {
     "auth_ref": [
      "r49",
      "r257",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of stock issued to shareholders as a dividend during the period.",
        "label": "Stock Issued During Period, Value, Stock Dividend",
        "negatedLabel": "Stock Dividend"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueStockDividend",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised": {
     "auth_ref": [
      "r49",
      "r257",
      "r262"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of stock issued as a result of the exercise of stock options.",
        "label": "Stock Issued During Period, Value, Stock Options Exercised",
        "terseLabel": "Stock option exercises"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueStockOptionsExercised",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquity": {
     "auth_ref": [
      "r18",
      "r23",
      "r24",
      "r183"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 1.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.",
        "label": "Stockholders' Equity Attributable to Parent",
        "totalLabel": "Stockholders\u2019 equity"
       }
      }
     },
     "localname": "StockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Stockholders' Equity Attributable to Parent [Abstract]",
        "terseLabel": "Stockholders' equity / Member's interest"
       }
      }
     },
     "localname": "StockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r415",
      "r416",
      "r427"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets": {
       "order": 1.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.",
        "label": "Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest",
        "periodEndLabel": "Ending balance stockholders' equity",
        "periodStartLabel": "Beginning balance stockholders' equity",
        "totalLabel": "Total stockholders\u2019 equity"
       }
      }
     },
     "localname": "StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedBalanceSheets",
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfChangesInStockholdersEquityMembersInterestAndRedeemableNoncontrollingInterest",
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityNoteDisclosureTextBlock": {
     "auth_ref": [
      "r266"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.",
        "label": "Stockholders' Equity Note Disclosure [Text Block]",
        "terseLabel": "Stockholder's Equity"
       }
      }
     },
     "localname": "StockholdersEquityNoteDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterest"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Different names of stock transactions and the different attributes of each transaction.",
        "label": "Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table]",
        "terseLabel": "Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table]"
       }
      }
     },
     "localname": "SubsidiaryOrEquityMethodInvesteeSaleOfStockBySubsidiaryOrEquityInvesteeTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SubsidiarySaleOfStockAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of sale of the entity's stock.",
        "label": "Sale of Stock [Axis]",
        "terseLabel": "Sale of Stock [Axis]"
       }
      }
     },
     "localname": "SubsidiarySaleOfStockAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SubsidiarySaleOfStockLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Subsidiary, Sale of Stock [Line Items]",
        "terseLabel": "Subsidiary, Sale of Stock [Line Items]"
       }
      }
     },
     "localname": "SubsidiarySaleOfStockLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/StockholdersEquityMembersInterestNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SummaryOfValuationAllowanceTextBlock": {
     "auth_ref": [
      "r383"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of valuation allowances to reduce deferred tax assets to net realizable value, including identification of the deferred tax asset more likely than not will not be fully realized and the corresponding amount of the valuation allowance.",
        "label": "Summary of Valuation Allowance [Table Text Block]",
        "terseLabel": "Summary of Valuation Allowance"
       }
      }
     },
     "localname": "SummaryOfValuationAllowanceTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SupplementalCashFlowElementsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Supplemental Cash Flow Elements [Abstract]"
       }
      }
     },
     "localname": "SupplementalCashFlowElementsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_SupplementalCashFlowInformationAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Supplemental Cash Flow Information [Abstract]",
        "terseLabel": "Cash payments:"
       }
      }
     },
     "localname": "SupplementalCashFlowInformationAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SupplementalCashFlowInformationScheduleOfSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_TradeNamesMember": {
     "auth_ref": [
      "r403"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rights acquired through registration of a business name to gain or protect exclusive use thereof.",
        "label": "Trade Names [Member]",
        "terseLabel": "Trade names"
       }
      }
     },
     "localname": "TradeNamesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/PropertyPlantAndEquipmentNetAndIntangiblesNetIntangibleAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TypeOfAdoptionMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Adoption and early adoption of sources of change to generally accepted accounting principles (GAAP) in the United States. The FASB released the FASB Accounting Standards Codification as the authoritative source of literature effective for interim and annual periods ending after September 15, 2009. As part of the Codification process, the FASB issues Accounting Standards Updates to amend the Codification but otherwise the Accounting Standards Updates are not authoritative in their own right. All previous accounting standards (such as FASB Statements of Financial Accounting Standards, FASB Interpretations, FASB Staff Positions, Emerging Issues Task Force Consensuses, other pronouncements of the FASB or other designated bodies, or other forms of GAAP are considered accounting pronouncements) were superseded upon the adoption of the Codification. For an interim period, references to the superseded standards are included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.",
        "label": "Type of Adoption [Domain]",
        "terseLabel": "Type of Adoption [Domain]"
       }
      }
     },
     "localname": "TypeOfAdoptionMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesNewAccountingStandardsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TypeOfArrangementAxis": {
     "auth_ref": [
      "r413"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations.",
        "label": "Collaborative Arrangement and Arrangement Other than Collaborative [Axis]",
        "terseLabel": "Collaborative Arrangement and Arrangement Other than Collaborative [Axis]"
       }
      }
     },
     "localname": "TypeOfArrangementAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesGeneralInformationAndEquityOfferingsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_UnrecognizedTaxBenefits": {
     "auth_ref": [
      "r365",
      "r377"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of unrecognized tax benefits.",
        "label": "Unrecognized Tax Benefits",
        "periodEndLabel": "Balance\u2014December 28, 2019",
        "periodStartLabel": "Balance\u2014December 29, 2018",
        "terseLabel": "Unrecognized tax benefits"
       }
      }
     },
     "localname": "UnrecognizedTaxBenefits",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails",
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions": {
     "auth_ref": [
      "r378"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.",
        "label": "Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions",
        "terseLabel": "Additions based on tax position in 2019"
       }
      }
     },
     "localname": "UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate": {
     "auth_ref": [
      "r379"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.",
        "label": "Unrecognized Tax Benefits that Would Impact Effective Tax Rate",
        "terseLabel": "Unrecognized tax benefits that if recognized would affect the annual effective tax rate"
       }
      }
     },
     "localname": "UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/IncomeTaxesNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_UseOfEstimates": {
     "auth_ref": [
      "r157",
      "r158",
      "r160",
      "r161",
      "r162",
      "r163",
      "r164"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.",
        "label": "Use of Estimates, Policy [Policy Text Block]",
        "terseLabel": "Use of Estimates"
       }
      }
     },
     "localname": "UseOfEstimates",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/SummaryOfOrganizationAndSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_VariableLeaseCost": {
     "auth_ref": [
      "r482",
      "r489"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_LeaseCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.",
        "label": "Variable Lease, Cost",
        "terseLabel": "Variable lease cost"
       }
      }
     },
     "localname": "VariableLeaseCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/LeasesOperatingAndFinanceLeasesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_VariableRateAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of variable rate.",
        "label": "Variable Rate [Axis]",
        "terseLabel": "Variable Rate [Axis]"
       }
      }
     },
     "localname": "VariableRateAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_VariableRateDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest rate that fluctuates over time as a result of an underlying benchmark interest rate or index.",
        "label": "Variable Rate [Domain]",
        "terseLabel": "Variable Rate [Domain]"
       }
      }
     },
     "localname": "VariableRateDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtOtherNarrativeDetails",
      "http://www.summitmaterials.com/role/DebtSeniorSecuredCreditFacilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding": {
     "auth_ref": [
      "r137",
      "r144"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.",
        "label": "Weighted Average Number of Shares Outstanding, Diluted",
        "terseLabel": "Diluted (in shares)",
        "totalLabel": "Weighted average dilutive shares outstanding (in shares)"
       }
      }
     },
     "localname": "WeightedAverageNumberOfDilutedSharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Weighted Average Number of Shares Outstanding, Diluted [Abstract]",
        "terseLabel": "Weighted average shares of Class A common stock:"
       }
      }
     },
     "localname": "WeightedAverageNumberOfSharesOutstandingAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_WeightedAverageNumberOfSharesOutstandingBasic": {
     "auth_ref": [
      "r135",
      "r144"
     ],
     "calculation": {
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.",
        "label": "Weighted Average Number of Shares Outstanding, Basic",
        "terseLabel": "Basic (in shares)",
        "verboseLabel": "Weighted average shares of Class A stock outstanding (in shares)"
       }
      }
     },
     "localname": "WeightedAverageNumberOfSharesOutstandingBasic",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/ConsolidatedStatementsOfOperations",
      "http://www.summitmaterials.com/role/EarningsPerShareScheduleOfBasicToDilutedIncomePerShareDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_WriteOffOfDeferredDebtIssuanceCost": {
     "auth_ref": [
      "r88"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.",
        "label": "Write off of Deferred Debt Issuance Cost",
        "negatedLabel": "Write off of deferred financing fees",
        "terseLabel": "Write off of deferred financing fees"
       }
      }
     },
     "localname": "WriteOffOfDeferredDebtIssuanceCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.summitmaterials.com/role/DebtSeniorNotesDetails",
      "http://www.summitmaterials.com/role/DebtSummaryOfActivityForDeferredFinancingFeesDetails"
     ],
     "xbrltype": "monetaryItemType"
    }
   },
   "unitCount": 11
  }
 },
 "std_ref": {
  "r0": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=d3e1361-107760"
  },
  "r1": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r10": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(13))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r100": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  },
  "r101": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  },
  "r102": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  },
  "r103": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3367-108585"
  },
  "r104": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3000-108585"
  },
  "r105": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "24",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3521-108585"
  },
  "r106": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585"
  },
  "r107": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585"
  },
  "r108": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r109": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r11": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(14))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r110": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r111": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3044-108585"
  },
  "r112": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586"
  },
  "r113": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586"
  },
  "r114": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586"
  },
  "r115": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586"
  },
  "r116": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=98513485&loc=SL98516268-108586"
  },
  "r117": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "230",
   "URI": "http://asc.fasb.org/topic&trid=2134446"
  },
  "r118": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790"
  },
  "r119": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=84158767&loc=d3e18823-107790"
  },
  "r12": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(19))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r120": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(h)(2))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r121": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(h))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r122": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(i))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r123": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(k)(1))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r124": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(e),(f))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r125": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(h)(1))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r126": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(i))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r127": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.12-04(a))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690"
  },
  "r128": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.12-04.(a))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690"
  },
  "r129": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.12-09)",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690"
  },
  "r13": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(20))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r130": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "235",
   "URI": "http://asc.fasb.org/topic&trid=2122369"
  },
  "r131": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "250",
   "URI": "http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794"
  },
  "r132": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "250",
   "URI": "http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794"
  },
  "r133": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "250",
   "URI": "http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794"
  },
  "r134": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "250",
   "URI": "http://asc.fasb.org/topic&trid=2122394"
  },
  "r135": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1448-109256"
  },
  "r136": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1377-109256"
  },
  "r137": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "16",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1505-109256"
  },
  "r138": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1252-109256"
  },
  "r139": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1500-109256"
  },
  "r14": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(22))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r140": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1278-109256"
  },
  "r141": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1311-109256"
  },
  "r142": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "60B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=SL5780133-109256"
  },
  "r143": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1337-109256"
  },
  "r144": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257"
  },
  "r145": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257"
  },
  "r146": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257"
  },
  "r147": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=6371337&loc=d3e3630-109257"
  },
  "r148": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "52",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117327953&loc=d3e4984-109258"
  },
  "r149": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "260",
   "URI": "http://asc.fasb.org/topic&trid=2144383"
  },
  "r15": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(24))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r150": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "270",
   "URI": "http://asc.fasb.org/extlink&oid=116846552&loc=d3e543-108305"
  },
  "r151": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "270",
   "URI": "http://asc.fasb.org/extlink&oid=118952077&loc=d3e1280-108306"
  },
  "r152": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(a)(5)",
   "Topic": "270",
   "URI": "http://asc.fasb.org/extlink&oid=27015980&loc=d3e46468-122699"
  },
  "r153": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "270",
   "URI": "http://asc.fasb.org/topic&trid=2126967"
  },
  "r154": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "272",
   "URI": "http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055"
  },
  "r155": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "272",
   "URI": "http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055"
  },
  "r156": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "272",
   "URI": "http://asc.fasb.org/topic&trid=2124037"
  },
  "r157": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592"
  },
  "r158": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592"
  },
  "r159": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592"
  },
  "r16": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(27))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r160": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e6161-108592"
  },
  "r161": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e6191-108592"
  },
  "r162": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e6061-108592"
  },
  "r163": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e6132-108592"
  },
  "r164": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "275",
   "URI": "http://asc.fasb.org/extlink&oid=99393423&loc=d3e6143-108592"
  },
  "r165": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "275",
   "URI": "http://asc.fasb.org/topic&trid=2134479"
  },
  "r166": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "21",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8721-108599"
  },
  "r167": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r168": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r169": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r17": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(28))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r170": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(h)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r171": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r172": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8813-108599"
  },
  "r173": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "30",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8906-108599"
  },
  "r174": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "32",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599"
  },
  "r175": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "32",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599"
  },
  "r176": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8475-108599"
  },
  "r177": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "40",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e9031-108599"
  },
  "r178": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "280",
   "URI": "http://asc.fasb.org/topic&trid=2134510"
  },
  "r179": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522"
  },
  "r18": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(29))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r180": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=118952595&loc=d3e4531-111522"
  },
  "r181": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=118936363&loc=d3e5033-111524"
  },
  "r182": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=118936363&loc=d3e5074-111524"
  },
  "r183": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 4.E)",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707"
  },
  "r184": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/subtopic&trid=2196772"
  },
  "r185": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84159169&loc=d3e10133-111534"
  },
  "r186": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84159169&loc=d3e10149-111534"
  },
  "r187": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84159169&loc=d3e10178-111534"
  },
  "r188": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=118955202&loc=SL82895884-210446"
  },
  "r189": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "10",
   "Topic": "330",
   "URI": "http://asc.fasb.org/extlink&oid=116846819&loc=d3e3927-108312"
  },
  "r19": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(3)(a)(2))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r190": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "330",
   "URI": "http://asc.fasb.org/extlink&oid=116847112&loc=d3e4492-108314"
  },
  "r191": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "330",
   "URI": "http://asc.fasb.org/extlink&oid=116847112&loc=d3e4556-108314"
  },
  "r192": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 5.BB)",
   "Topic": "330",
   "URI": "http://asc.fasb.org/extlink&oid=27011343&loc=d3e100047-122729"
  },
  "r193": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "330",
   "URI": "http://asc.fasb.org/topic&trid=2126998"
  },
  "r194": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266"
  },
  "r195": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266"
  },
  "r196": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975"
  },
  "r197": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r198": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r199": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(e)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r2": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r20": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(3))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r200": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(f)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r201": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r202": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267"
  },
  "r203": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13854-109267"
  },
  "r204": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=108376223&loc=d3e13854-109267"
  },
  "r205": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "20",
   "Topic": "350",
   "URI": "http://asc.fasb.org/subtopic&trid=2144439"
  },
  "r206": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274"
  },
  "r207": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274"
  },
  "r208": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275"
  },
  "r209": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(d)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275"
  },
  "r21": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(30)(a)(1))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r210": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "((a)(1),(b))",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r211": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r212": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)(1)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r213": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)(2)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r214": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)(3)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r215": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(d)",
   "Topic": "350",
   "URI": "http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275"
  },
  "r216": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "350",
   "URI": "http://asc.fasb.org/topic&trid=2144416"
  },
  "r217": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229"
  },
  "r218": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229"
  },
  "r219": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229"
  },
  "r22": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(30)(a)(3))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r220": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229"
  },
  "r221": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230"
  },
  "r222": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(f)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230"
  },
  "r223": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "360",
   "URI": "http://asc.fasb.org/topic&trid=2155823"
  },
  "r224": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "20",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846"
  },
  "r225": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848"
  },
  "r226": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849"
  },
  "r227": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)(2)",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849"
  },
  "r228": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)(3)",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849"
  },
  "r229": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)(4)",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849"
  },
  "r23": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(30))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r230": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849"
  },
  "r231": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "20",
   "Topic": "410",
   "URI": "http://asc.fasb.org/subtopic&trid=2175671"
  },
  "r232": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859"
  },
  "r233": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6393242&loc=d3e13231-110859"
  },
  "r234": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "30",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6571209&loc=d3e13669-110860"
  },
  "r235": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "420",
   "URI": "http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869"
  },
  "r236": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 5.P.4(d))",
   "Topic": "420",
   "URI": "http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747"
  },
  "r237": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "440",
   "URI": "http://asc.fasb.org/topic&trid=2144648"
  },
  "r238": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349"
  },
  "r239": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14615-108349"
  },
  "r24": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(31))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r240": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14394-108349"
  },
  "r241": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14435-108349"
  },
  "r242": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14453-108349"
  },
  "r243": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14472-108349"
  },
  "r244": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14557-108349"
  },
  "r245": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "450",
   "URI": "http://asc.fasb.org/topic&trid=2127136"
  },
  "r246": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "460",
   "URI": "http://asc.fasb.org/extlink&oid=118943654&loc=d3e12021-110248"
  },
  "r247": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "460",
   "URI": "http://asc.fasb.org/extlink&oid=118943654&loc=d3e12053-110248"
  },
  "r248": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601"
  },
  "r249": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=6802200&loc=SL6230698-112601"
  },
  "r25": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(32))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r250": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.3-10(d)(4)(iii))",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=116634808&loc=d3e168853-122756"
  },
  "r251": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.3-10(d)(4)(iv))",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=116634808&loc=d3e168853-122756"
  },
  "r252": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(1)",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870"
  },
  "r253": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(3)",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870"
  },
  "r254": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "40",
   "SubTopic": "50",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629"
  },
  "r255": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "40",
   "SubTopic": "50",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629"
  },
  "r256": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "470",
   "URI": "http://asc.fasb.org/topic&trid=2208564"
  },
  "r257": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644"
  },
  "r258": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644"
  },
  "r259": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644"
  },
  "r26": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(4)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r260": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644"
  },
  "r261": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644"
  },
  "r262": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.3-04)",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770"
  },
  "r263": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB TOPIC 4.F)",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770"
  },
  "r264": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 4.F)",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770"
  },
  "r265": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "50",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=6784392&loc=d3e188667-122775"
  },
  "r266": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "505",
   "URI": "http://asc.fasb.org/topic&trid=2208762"
  },
  "r267": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118944033&loc=SL49130531-203044"
  },
  "r268": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118944033&loc=SL49130532-203044"
  },
  "r269": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118944033&loc=SL49130533-203044"
  },
  "r27": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(a)(1))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r270": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118956577&loc=SL49130551-203045"
  },
  "r271": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045"
  },
  "r272": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045"
  },
  "r273": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045"
  },
  "r274": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "91",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=118944142&loc=SL49130690-203046-203046"
  },
  "r275": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "606",
   "URI": "http://asc.fasb.org/topic&trid=49130388"
  },
  "r276": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "710",
   "URI": "http://asc.fasb.org/topic&trid=2127225"
  },
  "r277": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "15",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "712",
   "URI": "http://asc.fasb.org/extlink&oid=6410066&loc=d3e79218-111664"
  },
  "r278": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "15",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "712",
   "URI": "http://asc.fasb.org/extlink&oid=6410066&loc=d3e79218-111664"
  },
  "r279": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "712",
   "URI": "http://asc.fasb.org/topic&trid=2197446"
  },
  "r28": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(a)(3))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r280": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=109237824&loc=d3e1703-114919"
  },
  "r281": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=109237824&loc=d3e1731-114919"
  },
  "r282": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r283": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r284": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r285": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(4)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r286": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(6)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r287": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r288": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r289": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r29": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(a)(4))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r290": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r291": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r292": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r293": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(i)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r294": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(ii)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r295": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(iv)(01)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r296": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(f)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r297": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r298": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r299": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r3": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r30": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(a))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r300": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r301": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r302": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(4)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r303": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r304": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(i)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r305": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(j)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r306": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(k)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r307": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(k)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r308": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(k)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r309": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(l)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r31": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(b))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r310": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(m)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r311": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(n)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r312": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r313": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2410-114920"
  },
  "r314": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920"
  },
  "r315": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2439-114920"
  },
  "r316": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r317": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r318": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r319": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r32": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(6)(c))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r320": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(4)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r321": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r322": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920"
  },
  "r323": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921"
  },
  "r324": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "60",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964"
  },
  "r325": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "70",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942"
  },
  "r326": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "80",
   "Subparagraph": "(a)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947"
  },
  "r327": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "80",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947"
  },
  "r328": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "80",
   "Subparagraph": "(c)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=65877416&loc=SL14450678-114947"
  },
  "r329": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "715",
   "URI": "http://asc.fasb.org/topic&trid=2235017"
  },
  "r33": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.1)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r330": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116855982&loc=d3e4534-113899"
  },
  "r331": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r332": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r333": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r334": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r335": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(3)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r336": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a),(g)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r337": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r338": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(i)-(ii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r339": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(iii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r34": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.13(a))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r340": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(iv)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r341": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(iv)(3)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r342": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(i)-(ii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r343": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r344": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r345": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(3)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r346": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r347": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r348": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(f)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r349": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(f)(2)(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r35": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.13)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r350": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(f)(2)(ii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r351": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(f)(2)(iv)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r352": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(g)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r353": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(h)(1)(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r354": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r355": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r356": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=SL79508275-113901"
  },
  "r357": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 14.D.2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809"
  },
  "r358": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 14.F)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809"
  },
  "r359": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=118258462&loc=d3e11149-113907"
  },
  "r36": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.14)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r360": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=118258462&loc=d3e11178-113907"
  },
  "r361": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "718",
   "URI": "http://asc.fasb.org/topic&trid=2228938"
  },
  "r362": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "720",
   "URI": "http://asc.fasb.org/extlink&oid=6419918&loc=d3e35281-107843"
  },
  "r363": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=117330534&loc=d3e28680-109314"
  },
  "r364": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=117330534&loc=d3e28680-109314"
  },
  "r365": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=SL37586934-109318"
  },
  "r366": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=d3e32059-109318"
  },
  "r367": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=d3e32123-109318"
  },
  "r368": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=d3e32247-109318"
  },
  "r369": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=d3e32280-109318"
  },
  "r37": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.17)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r370": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116821951&loc=d3e31931-109318"
  },
  "r371": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32672-109319"
  },
  "r372": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319"
  },
  "r373": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319"
  },
  "r374": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319"
  },
  "r375": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319"
  },
  "r376": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319"
  },
  "r377": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319"
  },
  "r378": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(2)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319"
  },
  "r379": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319"
  },
  "r38": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19(a))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r380": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319"
  },
  "r381": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32809-109319"
  },
  "r382": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "19",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32840-109319"
  },
  "r383": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319"
  },
  "r384": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319"
  },
  "r385": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32847-109319"
  },
  "r386": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319"
  },
  "r387": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319"
  },
  "r388": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319"
  },
  "r389": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319"
  },
  "r39": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19(a),20,24)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r390": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319"
  },
  "r391": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319"
  },
  "r392": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "217",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=117331294&loc=d3e36027-109320"
  },
  "r393": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 6.I.7)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817"
  },
  "r394": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324"
  },
  "r395": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "05",
   "SubTopic": "30",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=65884525&loc=d3e40913-109327"
  },
  "r396": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "740",
   "URI": "http://asc.fasb.org/topic&trid=2144680"
  },
  "r397": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "23",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "10",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460"
  },
  "r398": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463"
  },
  "r399": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=79982066&loc=d3e1486-128463"
  },
  "r4": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r40": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19(b),22(b))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r400": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "37",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116868840&loc=d3e2207-128464"
  },
  "r401": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472"
  },
  "r402": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472"
  },
  "r403": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=77890550&loc=d3e5263-128473"
  },
  "r404": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "31",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=77890550&loc=d3e5419-128473"
  },
  "r405": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "30",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476"
  },
  "r406": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "30",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476"
  },
  "r407": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "30",
   "SubTopic": "30",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477"
  },
  "r408": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "30",
   "SubTopic": "30",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477"
  },
  "r409": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "30",
   "Subparagraph": "b",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478"
  },
  "r41": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19,20)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r410": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(b)",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479"
  },
  "r411": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(b)(3)",
   "Topic": "805",
   "URI": "http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479"
  },
  "r412": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "805",
   "URI": "http://asc.fasb.org/topic&trid=2303972"
  },
  "r413": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "808",
   "URI": "http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434"
  },
  "r414": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=d3e5283-111683"
  },
  "r415": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683"
  },
  "r416": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "16",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683"
  },
  "r417": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "19",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=SL4569616-111683"
  },
  "r418": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=SL4569643-111683"
  },
  "r419": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=d3e5614-111684"
  },
  "r42": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19-26)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r420": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(1)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r421": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(2)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r422": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r423": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(3)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r424": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c),(3)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r425": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684"
  },
  "r426": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=109239629&loc=SL4582445-111684"
  },
  "r427": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4I",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4590271-111686"
  },
  "r428": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4J",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4591551-111686"
  },
  "r429": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4K",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4591552-111686"
  },
  "r43": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.20)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r430": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4M",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4591554-111686"
  },
  "r431": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.3A-02)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116822174&loc=d3e355033-122828"
  },
  "r432": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.3A-03)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116822174&loc=d3e355100-122828"
  },
  "r433": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "810",
   "URI": "http://asc.fasb.org/topic&trid=2197479"
  },
  "r434": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(1)(ii)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41620-113959"
  },
  "r435": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41620-113959"
  },
  "r436": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959"
  },
  "r437": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959"
  },
  "r438": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959"
  },
  "r439": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959"
  },
  "r44": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.21)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r440": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4C",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959"
  },
  "r441": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(1)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959"
  },
  "r442": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959"
  },
  "r443": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6A",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "20",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=118875152&loc=SL5864739-113975"
  },
  "r444": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109978405&loc=d3e80720-113993"
  },
  "r445": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r446": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r447": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bb)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r448": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bbb)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r449": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bbb)(2)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r45": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.22(a)(1))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r450": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r451": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19279-110258"
  },
  "r452": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258"
  },
  "r453": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=116690757&loc=d3e13220-108610"
  },
  "r454": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611"
  },
  "r455": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=118260190&loc=d3e13467-108611"
  },
  "r456": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=118260190&loc=d3e13476-108611"
  },
  "r457": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "825",
   "URI": "http://asc.fasb.org/topic&trid=2134543"
  },
  "r458": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "20",
   "Topic": "830",
   "URI": "http://asc.fasb.org/extlink&oid=118948100&loc=d3e30304-110892"
  },
  "r459": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "230",
   "Topic": "830",
   "URI": "http://asc.fasb.org/extlink&oid=98513438&loc=d3e33268-110906"
  },
  "r46": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.22)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r460": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Subparagraph": "(b,d)",
   "Topic": "830",
   "URI": "http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900"
  },
  "r461": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391"
  },
  "r462": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399"
  },
  "r463": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399"
  },
  "r464": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399"
  },
  "r465": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "30",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400"
  },
  "r466": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717"
  },
  "r467": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=84164758&loc=d3e45023-112735"
  },
  "r468": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737"
  },
  "r469": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(b)",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737"
  },
  "r47": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.24)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r470": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "65",
   "SubTopic": "10",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=119364159&loc=SL77916155-209984"
  },
  "r471": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977"
  },
  "r472": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977"
  },
  "r473": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918638-209977"
  },
  "r474": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977"
  },
  "r475": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977"
  },
  "r476": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977"
  },
  "r477": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(3)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980"
  },
  "r478": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980"
  },
  "r479": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r48": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.25)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r480": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r481": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r482": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r483": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)(1)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r484": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)(2)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r485": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)(3)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r486": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)(4)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r487": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980"
  },
  "r488": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980"
  },
  "r489": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "53",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971"
  },
  "r49": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.29-31)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r490": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/subtopic&trid=77888251"
  },
  "r491": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864"
  },
  "r492": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864"
  },
  "r493": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864"
  },
  "r494": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r495": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(1)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r496": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(2)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r497": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(3)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r498": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "340",
   "Topic": "928",
   "URI": "http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004"
  },
  "r499": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "20",
   "Topic": "940",
   "URI": "http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953"
  },
  "r5": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6801-107765"
  },
  "r50": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.3(c))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r500": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(11))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r501": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(13))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r502": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(15))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r503": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(16))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r504": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(23))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r505": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03.17)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r506": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04(15))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260"
  },
  "r507": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04(23))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260"
  },
  "r508": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04.10)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260"
  },
  "r509": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04.9)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260"
  },
  "r51": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.3,4)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r510": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "405",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817"
  },
  "r511": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "470",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823"
  },
  "r512": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "825",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=108315417&loc=d3e61044-112788"
  },
  "r513": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(16))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r514": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(12))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r515": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(15))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r516": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(16))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r517": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(23)(a)(4))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r518": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(25))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r519": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(3))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r52": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.6(a))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r520": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(8))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r521": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03.(a),19)",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r522": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.7-04(19))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263"
  },
  "r523": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.7-04(8))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263"
  },
  "r524": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4H",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "40",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=116884468&loc=SL65671331-158438"
  },
  "r525": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13H",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "40",
   "Subparagraph": "(a)",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=117419784&loc=SL117783719-158441"
  },
  "r526": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "205",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=25866437&loc=d3e10246-115837"
  },
  "r527": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.6-04.16(a))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996"
  },
  "r528": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.6-04.16)",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996"
  },
  "r529": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "740",
   "Topic": "954",
   "URI": "http://asc.fasb.org/extlink&oid=6491622&loc=d3e9504-115650"
  },
  "r53": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.6(b))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r530": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "360",
   "Subparagraph": "(SX 210.12-28(Footnote 4))",
   "Topic": "970",
   "URI": "http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024"
  },
  "r531": {
   "Name": "Exchange Act",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b"
  },
  "r532": {
   "Name": "Exchange Act",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b-23"
  },
  "r533": {
   "Name": "Exchange Act",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "d1-1"
  },
  "r534": {
   "Name": "Forms 10-K, 10-Q, 20-F",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "13",
   "Subsection": "a-1-"
  },
  "r535": {
   "Name": "Forms 10-K, 20-F, 40-F",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "15",
   "Subsection": "d-1"
  },
  "r536": {
   "Name": "Regulation 12B",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b-2"
  },
  "r537": {
   "Name": "Regulation S-T",
   "Number": "232",
   "Publisher": "SEC",
   "Section": "405"
  },
  "r538": {
   "Footnote": "4",
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "28"
  },
  "r539": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "a",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "04"
  },
  "r54": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.8)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r540": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "09"
  },
  "r541": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "c",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "4",
   "Subsection": "10"
  },
  "r542": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "d",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "(4)(iii)",
   "Subsection": "10"
  },
  "r543": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "d",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "(4)(iv)",
   "Subsection": "10"
  },
  "r544": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "d",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "4",
   "Subsection": "10"
  },
  "r545": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "e",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "4",
   "Subsection": "10"
  },
  "r546": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "f",
   "Publisher": "SEC",
   "Section": "3",
   "Subparagraph": "4",
   "Subsection": "10"
  },
  "r547": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "i",
   "Publisher": "SEC",
   "Section": "3",
   "Subsection": "10"
  },
  "r548": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "c",
   "Publisher": "SEC",
   "Section": "5",
   "Subparagraph": "Schedule I",
   "Subsection": "04"
  },
  "r549": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Paragraph": "c",
   "Publisher": "SEC",
   "Section": "7",
   "Subparagraph": "Schedule II",
   "Subsection": "05"
  },
  "r55": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.9)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r550": {
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Publisher": "SEC",
   "Section": "9",
   "Subsection": "06"
  },
  "r56": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312"
  },
  "r57": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r58": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a),(b),(c)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r59": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r6": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6911-107765"
  },
  "r60": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(i)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r61": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(i),(j),(k)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r62": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(i-k)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r63": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(j)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r64": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r65": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580"
  },
  "r66": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e681-108580"
  },
  "r67": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580"
  },
  "r68": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e689-108580"
  },
  "r69": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL34724391-108580"
  },
  "r7": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6935-107765"
  },
  "r70": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL34724394-108580"
  },
  "r71": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580"
  },
  "r72": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580"
  },
  "r73": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580"
  },
  "r74": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580"
  },
  "r75": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580"
  },
  "r76": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e557-108580"
  },
  "r77": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116657188&loc=SL116659661-227067"
  },
  "r78": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118951672&loc=d3e1436-108581"
  },
  "r79": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(210.5-03(11))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r8": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e7018-107765"
  },
  "r80": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(10))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r81": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(21))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r82": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(4))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r83": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(8))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r84": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.2(a),(d))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r85": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.21)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r86": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.3)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r87": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.4)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r88": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.8)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r89": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.9)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r9": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766"
  },
  "r90": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585"
  },
  "r91": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585"
  },
  "r92": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585"
  },
  "r93": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585"
  },
  "r94": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585"
  },
  "r95": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585"
  },
  "r96": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585"
  },
  "r97": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585"
  },
  "r98": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585"
  },
  "r99": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  }
 },
 "version": "2.1"
}
