{
 "instance": {
  "bkh10qq12019.htm": {
   "axisCustom": 1,
   "axisStandard": 31,
   "contextCount": 465,
   "dts": {
    "calculationLink": {
     "local": [
      "bkh-20190331_cal.xml"
     ]
    },
    "definitionLink": {
     "local": [
      "bkh-20190331_def.xml"
     ],
     "remote": [
      "http://xbrl.fasb.org/srt/2018/elts/srt-eedm1-def-2018-01-31.xml",
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-eedm-def-2018-01-31.xml"
     ]
    },
    "inline": {
     "local": [
      "bkh10qq12019.htm"
     ]
    },
    "labelLink": {
     "local": [
      "bkh-20190331_lab.xml"
     ],
     "remote": [
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-doc-2018-01-31.xml",
      "http://xbrl.sec.gov/invest/2013/invest-doc-2013-01-31.xml",
      "https://xbrl.sec.gov/dei/2018/dei-doc-2018-01-31.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "bkh-20190331_pre.xml"
     ]
    },
    "referenceLink": {
     "remote": [
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-ref-2018-01-31.xml",
      "http://xbrl.sec.gov/invest/2013/invest-ref-2013-01-31.xml",
      "https://xbrl.sec.gov/dei/2018/dei-ref-2018-01-31.xml"
     ]
    },
    "schema": {
     "local": [
      "bkh-20190331.xsd"
     ],
     "remote": [
      "http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xl-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xlink-2003-12-31.xsd",
      "http://www.xbrl.org/2005/xbrldt-2005.xsd",
      "http://www.xbrl.org/2006/ref-2006-02-27.xsd",
      "http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd",
      "http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/arcrole/factExplanatory-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/deprecated-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/net-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/reference-2009-12-16.xsd",
      "http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd",
      "http://xbrl.fasb.org/srt/2018/elts/srt-roles-2018-01-31.xsd",
      "http://xbrl.fasb.org/srt/2018/elts/srt-types-2018-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-parts-codification-2018-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-roles-2018-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2018/elts/us-types-2018-01-31.xsd",
      "http://xbrl.sec.gov/country/2017/country-2017-01-31.xsd",
      "http://xbrl.sec.gov/currency/2017/currency-2017-01-31.xsd",
      "http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd",
      "http://xbrl.sec.gov/naics/2017/naics-2017-01-31.xsd",
      "http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd",
      "https://xbrl.sec.gov/dei/2018/dei-2018-01-31.xsd",
      "https://xbrl.sec.gov/exch/2018/exch-2018-01-31.xsd",
      "https://xbrl.sec.gov/stpr/2018/stpr-2018-01-31.xsd"
     ]
    }
   },
   "elementCount": 616,
   "entityCount": 1,
   "hidden": {
    "http://fasb.org/us-gaap/2018-01-31": 24,
    "http://www.blackhillscorp.com/20190331": 7,
    "http://xbrl.sec.gov/dei/2018-01-31": 11,
    "total": 42
   },
   "keyCustom": 38,
   "keyStandard": 320,
   "memberCustom": 35,
   "memberStandard": 58,
   "nsprefix": "bkh",
   "nsuri": "http://www.blackhillscorp.com/20190331",
   "report": {
    "R1": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:TradingSymbol",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "document",
     "isDefault": "true",
     "longName": "0001000 - Document - Document and Entity Information Document",
     "role": "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument",
     "shortName": "Document and Entity Information Document",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:TradingSymbol",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R10": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2106100 - Disclosure - Business Segment Information:",
     "role": "http://www.blackhillscorp.com/role/BusinessSegmentInformation",
     "shortName": "Business Segment Information:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R11": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2107100 - Disclosure - Accounts Receivable:",
     "role": "http://www.blackhillscorp.com/role/AccountsReceivable",
     "shortName": "Accounts Receivable:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R12": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfRegulatoryAssetsAndLiabilitiesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2108100 - Disclosure - Regulatory Accounting:",
     "role": "http://www.blackhillscorp.com/role/RegulatoryAccounting",
     "shortName": "Regulatory Accounting:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfRegulatoryAssetsAndLiabilitiesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R13": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:InventoryDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2110100 - Disclosure - Materials, Supplies and Fuel:",
     "role": "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuel",
     "shortName": "Materials, Supplies and Fuel:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:InventoryDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R14": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2112100 - Disclosure - Earnings Per Share:",
     "role": "http://www.blackhillscorp.com/role/EarningsPerShare",
     "shortName": "Earnings Per Share:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R15": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DebtDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2114100 - Disclosure - Notes Payable, Current Maturities and Debt:",
     "role": "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebt",
     "shortName": "Notes Payable, Current Maturities and Debt:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DebtDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R16": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2115100 - Disclosure - Equity:",
     "role": "http://www.blackhillscorp.com/role/Equity",
     "shortName": "Equity:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R17": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2116100 - Disclosure - Risk Management Activities:",
     "role": "http://www.blackhillscorp.com/role/RiskManagementActivities",
     "shortName": "Risk Management Activities:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R18": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DerivativesAndFairValueTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2117100 - Disclosure - Fair Value Measurements:",
     "role": "http://www.blackhillscorp.com/role/FairValueMeasurements",
     "shortName": "Fair Value Measurements:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DerivativesAndFairValueTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R19": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2119100 - Disclosure - Fair Value of Financial Instruments:",
     "role": "http://www.blackhillscorp.com/role/FairValueOfFinancialInstruments",
     "shortName": "Fair Value of Financial Instruments:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R2": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:Revenues",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1002000 - Statement - Condensed Consolidated Statements of Income (unaudited)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
     "shortName": "Condensed Consolidated Statements of Income (unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:TaxesExcludingIncomeAndExciseTaxes",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R20": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "td",
       "tr",
       "table",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ComprehensiveIncomeNoteTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2120100 - Disclosure - Other Comprehensive Income (Loss):",
     "role": "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLoss",
     "shortName": "Other Comprehensive Income (Loss):",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "td",
       "tr",
       "table",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ComprehensiveIncomeNoteTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R21": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CashFlowSupplementalDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2121100 - Disclosure - Supplemental Disclosure of Cash Flow Information:",
     "role": "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformation",
     "shortName": "Supplemental Disclosure of Cash Flow Information:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CashFlowSupplementalDisclosuresTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R22": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PensionAndOtherPostretirementBenefitsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2122100 - Disclosure - Employee Benefit Plans:",
     "role": "http://www.blackhillscorp.com/role/EmployeeBenefitPlans",
     "shortName": "Employee Benefit Plans:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PensionAndOtherPostretirementBenefitsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R23": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2123100 - Disclosure - Commitments and Contingencies:",
     "role": "http://www.blackhillscorp.com/role/CommitmentsAndContingencies",
     "shortName": "Commitments and Contingencies:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R24": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisposalGroupsIncludingDiscontinuedOperationsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2124100 - Disclosure - Discontinued Operations:",
     "role": "http://www.blackhillscorp.com/role/DiscontinuedOperations",
     "shortName": "Discontinued Operations:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisposalGroupsIncludingDiscontinuedOperationsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R25": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:IncomeTaxDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2126100 - Disclosure - Income Taxes:",
     "role": "http://www.blackhillscorp.com/role/IncomeTaxes",
     "shortName": "Income Taxes:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:IncomeTaxDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R26": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2127100 - Disclosure - Accrued Liabilities:",
     "role": "http://www.blackhillscorp.com/role/AccruedLiabilities",
     "shortName": "Accrued Liabilities:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R27": {
     "firstAnchor": {
      "ancestors": [
       "us-gaap:OperatingLeasesOfLessorDisclosureTextBlock",
       "us-gaap:LesseeFinanceLeasesTextBlock",
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LesseeOperatingLeasesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2129100 - Disclosure - Leases:",
     "role": "http://www.blackhillscorp.com/role/Leases",
     "shortName": "Leases:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "us-gaap:OperatingLeasesOfLessorDisclosureTextBlock",
       "us-gaap:LesseeFinanceLeasesTextBlock",
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LesseeOperatingLeasesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R28": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingPolicyPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2204201 - Disclosure - Management's Statement (Policies)",
     "role": "http://www.blackhillscorp.com/role/ManagementsStatementPolicies",
     "shortName": "Management's Statement (Policies)",
     "subGroupType": "policies",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SegmentReportingPolicyPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R29": {
     "firstAnchor": {
      "ancestors": [
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisaggregationOfRevenueTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2305301 - Disclosure - Revenue (Tables)",
     "role": "http://www.blackhillscorp.com/role/RevenueTables",
     "shortName": "Revenue (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:DisaggregationOfRevenueTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R3": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income (unaudited)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
     "shortName": "Condensed Consolidated Statements of Comprehensive Income (unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R30": {
     "firstAnchor": {
      "ancestors": [
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSegmentReportingInformationBySegmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2306301 - Disclosure - Business Segment Information (Tables)",
     "role": "http://www.blackhillscorp.com/role/BusinessSegmentInformationTables",
     "shortName": "Business Segment Information (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSegmentReportingInformationBySegmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R31": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2307301 - Disclosure - Accounts Receivable (Tables)",
     "role": "http://www.blackhillscorp.com/role/AccountsReceivableTables",
     "shortName": "Accounts Receivable (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R32": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2308301 - Disclosure - Regulatory Accounting (Tables)",
     "role": "http://www.blackhillscorp.com/role/RegulatoryAccountingTables",
     "shortName": "Regulatory Accounting (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R33": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfInventoryCurrentTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2310301 - Disclosure - Materials, Supplies and Fuel (Tables)",
     "role": "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelTables",
     "shortName": "Materials, Supplies and Fuel (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfInventoryCurrentTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R34": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2312301 - Disclosure - Earnings Per Share (Tables)",
     "role": "http://www.blackhillscorp.com/role/EarningsPerShareTables",
     "shortName": "Earnings Per Share (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R35": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfShortTermDebtTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2314301 - Disclosure - Notes Payable, Current Maturities and Debt (Tables)",
     "role": "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtTables",
     "shortName": "Notes Payable, Current Maturities and Debt (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfShortTermDebtTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R36": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfStockholdersEquityTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2315301 - Disclosure - Equity (Tables)",
     "role": "http://www.blackhillscorp.com/role/EquityTables",
     "shortName": "Equity (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfStockholdersEquityTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R37": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNotionalAmountsOfOutstandingDerivativePositionsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2316301 - Disclosure - Risk Management Activities (Tables)",
     "role": "http://www.blackhillscorp.com/role/RiskManagementActivitiesTables",
     "shortName": "Risk Management Activities (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNotionalAmountsOfOutstandingDerivativePositionsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R38": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2317301 - Disclosure - Fair Value Measurements (Tables)",
     "role": "http://www.blackhillscorp.com/role/FairValueMeasurementsTables",
     "shortName": "Fair Value Measurements (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R39": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueByBalanceSheetGroupingTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2319301 - Disclosure - Fair Value of Financial Instruments (Tables)",
     "role": "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsTables",
     "shortName": "Fair Value of Financial Instruments (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FairValueByBalanceSheetGroupingTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R4": {
     "firstAnchor": null,
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1003001 - Statement - Condensed Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
     "shortName": "Condensed Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": null
    },
    "R40": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2320301 - Disclosure - Other Comprehensive Income (Loss) (Tables)",
     "role": "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossTables",
     "shortName": "Other Comprehensive Income (Loss) (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R41": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2321301 - Disclosure - Supplemental Disclosure of Cash Flow Information (Tables)",
     "role": "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationTables",
     "shortName": "Supplemental Disclosure of Cash Flow Information (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "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",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNetBenefitCostsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2322301 - Disclosure - Employee Benefit Plans (Tables)",
     "role": "http://www.blackhillscorp.com/role/EmployeeBenefitPlansTables",
     "shortName": "Employee Benefit Plans (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfNetBenefitCostsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R43": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2324301 - Disclosure - Discontinued Operations (Tables)",
     "role": "http://www.blackhillscorp.com/role/DiscontinuedOperationsTables",
     "shortName": "Discontinued Operations (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R44": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2327301 - Disclosure - Accrued Liabilities (Tables)",
     "role": "http://www.blackhillscorp.com/role/AccruedLiabilitiesTables",
     "shortName": "Accrued Liabilities (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAccruedLiabilitiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R45": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LeaseCostTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2329301 - Disclosure - Leases (Tables)",
     "role": "http://www.blackhillscorp.com/role/LeasesTables",
     "shortName": "Leases (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:LeaseCostTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R46": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseRightOfUseAsset",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2404402 - Disclosure - Management's Statement (Details)",
     "role": "http://www.blackhillscorp.com/role/ManagementsStatementDetails",
     "shortName": "Management's Statement (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "I2019Q1SpecialDate1_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_us-gaap_AccountingStandardsUpdate201602Member",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:OperatingLeaseRightOfUseAsset",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R47": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:DisaggregationOfRevenueTableTextBlock",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2405402 - Disclosure - Revenue: Disaggregation of Revenue (Details)",
     "role": "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails",
     "shortName": "Revenue: Disaggregation of Revenue (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:DisaggregationOfRevenueTableTextBlock",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_TimingOfTransferOfGoodOrServiceAxis_us-gaap_TransferredAtPointInTimeMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R48": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:DisaggregationOfRevenueTableTextBlock",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2406402 - Disclosure - Business Segment Information: Information Relating to Segment Statement of Income (Details)",
     "role": "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
     "shortName": "Business Segment Information: Information Relating to Segment Statement of Income (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:InterestIncomeExpenseNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R49": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:Assets",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2406403 - Disclosure - Business Segment Information: Segment and Corporate Assets (Details)",
     "role": "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
     "shortName": "Business Segment Information: Segment and Corporate Assets (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_DisposalGroupClassificationAxis_us-gaap_DiscontinuedOperationsHeldforsaleMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:Assets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R5": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1004000 - Statement - Condensed Consolidated Balance Sheets (unaudited)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
     "shortName": "Condensed Consolidated Balance Sheets (unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:DerivativeAssetsCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R50": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AccountsReceivableGrossCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2407402 - Disclosure - Accounts Receivable (Details)",
     "role": "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
     "shortName": "Accounts Receivable (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AccountsReceivableGrossCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R51": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RegulatoryAssets",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408402 - Disclosure - Regulatory Accounting (Details)",
     "role": "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails",
     "shortName": "Regulatory Accounting (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:RegulatoryLiabilities",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R52": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "I2019Q2SpecialDateA_dei_LegalEntityAxis_bkh_BlackHillsEnergyNebraskaGasMember_us-gaap_PublicUtilitiesRegulatoryProceedingAxis_bkh_ApplicationFiledMember_us-gaap_RegulatoryAgencyAxis_bkh_NebraskaPublicServiceCommissionNPSCMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "bkh:PublicUtilitiesNumberofCompaniesBeingMerged",
      "reportCount": 1,
      "unique": true,
      "unitRef": "utility",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2408403 - Disclosure - Regulatory Accounting: Rate Review (Details)",
     "role": "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails",
     "shortName": "Regulatory Accounting: Rate Review (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "I2019Q2SpecialDateA_dei_LegalEntityAxis_bkh_BlackHillsEnergyNebraskaGasMember_us-gaap_PublicUtilitiesRegulatoryProceedingAxis_bkh_ApplicationFiledMember_us-gaap_RegulatoryAgencyAxis_bkh_NebraskaPublicServiceCommissionNPSCMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "bkh:PublicUtilitiesNumberofCompaniesBeingMerged",
      "reportCount": 1,
      "unique": true,
      "unitRef": "utility",
      "xsiNil": "false"
     }
    },
    "R53": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InventoryRawMaterialsAndSupplies",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2410402 - Disclosure - Materials, Supplies and Fuel (Details)",
     "role": "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails",
     "shortName": "Materials, Supplies and Fuel (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InventoryRawMaterialsAndSupplies",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R54": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2412402 - Disclosure - Earnings Per Share: Earnings Per Share Reconciliation (Details)",
     "role": "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails",
     "shortName": "Earnings Per Share: Earnings Per Share Reconciliation (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:IncrementalCommonSharesAttributableToEquityUnitPurchaseAgreements",
      "reportCount": 1,
      "unique": true,
      "unitRef": "shares",
      "xsiNil": "false"
     }
    },
    "R55": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "shares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2412403 - Disclosure - Earnings Per Share: Anti-dilutive shares (Details)",
     "role": "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails",
     "shortName": "Earnings Per Share: Anti-dilutive shares (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "shares",
      "xsiNil": "false"
     }
    },
    "R56": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShortTermBorrowings",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414402 - Disclosure - Notes Payable, Current Maturities and Debt: Schedule of Short-term Debt and Narrative (Details)",
     "role": "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails",
     "shortName": "Notes Payable, Current Maturities and Debt: Schedule of Short-term Debt and Narrative (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:LettersOfCreditOutstandingAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R57": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_srt_RangeAxis_srt_MaximumMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "bkh:DebtInstrumentConsolidatedIndebtednessToCapitalizationRatioRequirementForTheNextFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "ratio",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2414403 - Disclosure - Notes Payable, Current Maturities and Debt: Debt Covenants (Details)",
     "role": "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails",
     "shortName": "Notes Payable, Current Maturities and Debt: Debt Covenants (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_srt_RangeAxis_srt_MaximumMember",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "bkh:DebtInstrumentConsolidatedIndebtednessToCapitalizationRatioRequirementForTheNextFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "ratio",
      "xsiNil": "false"
     }
    },
    "R58": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2415402 - Disclosure - Equity: Stockholders Equity Recap (Details)",
     "role": "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
     "shortName": "Equity: Stockholders Equity Recap (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2017Q4",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R59": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "I2017Q3ATMRenewal",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "bkh:AtTheMarketEquityOfferingProgramAuthorizedAggregateValue",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2415403 - Disclosure - Equity: At-the-Market Equity Offering Program (Details)",
     "role": "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
     "shortName": "Equity: At-the-Market Equity Offering Program (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "I2017Q3ATMRenewal",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "bkh:AtTheMarketEquityOfferingProgramAuthorizedAggregateValue",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R6": {
     "firstAnchor": null,
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1004001 - Statement - Condensed Consolidated Balance Sheets (unaudited) (Parenthetical)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical",
     "shortName": "Condensed Consolidated Balance Sheets (unaudited) (Parenthetical)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": null
    },
    "R60": {
     "firstAnchor": null,
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2415404 - Disclosure - Equity: Dividends on Common Stock (Details)",
     "role": "http://www.blackhillscorp.com/role/EquityDividendsOnCommonStockDetails",
     "shortName": "Equity: Dividends on Common Stock (Details)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R61": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_EnergyAxis_bkh_NaturalGasDistributionMember",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2416402 - Disclosure - Risk Management Activities: Utilities (Details)",
     "role": "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails",
     "shortName": "Risk Management Activities: Utilities (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_EnergyAxis_bkh_NaturalGasDistributionMember",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R62": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_us-gaap_CashFlowHedgingMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2416403 - Disclosure - Risk Management Activities: Cash Flow Hedges (Details)",
     "role": "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
     "shortName": "Risk Management Activities: Cash Flow Hedges (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_us-gaap_CashFlowHedgingMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R63": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RegulatoryAssets",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2416404 - Disclosure - Risk Management Activities: Derivatives Not Designated as Hedge Instruments (Details)",
     "role": "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails",
     "shortName": "Risk Management Activities: Derivatives Not Designated as Hedge Instruments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_RegulatoryAssetAxis_us-gaap_DeferredDerivativeGainLossMember",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:RegulatoryAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R64": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_FairValueByMeasurementFrequencyAxis_us-gaap_FairValueMeasurementsRecurringMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2417402 - Disclosure - Fair Value Measurements: Schedule of Fair Values (Details)",
     "role": "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails",
     "shortName": "Fair Value Measurements: Schedule of Fair Values (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_FairValueByMeasurementFrequencyAxis_us-gaap_FairValueMeasurementsRecurringMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R65": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_HedgingDesignationAxis_us-gaap_DesignatedAsHedgingInstrumentMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2417403 - Disclosure - Fair Value Measurements: Balance Sheet Location (Details)",
     "role": "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
     "shortName": "Fair Value Measurements: Balance Sheet Location (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_HedgingDesignationAxis_us-gaap_DesignatedAsHedgingInstrumentMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R66": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2419402 - Disclosure - Fair Value of Financial Instruments (Details)",
     "role": "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails",
     "shortName": "Fair Value of Financial Instruments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_us-gaap_FairValueByMeasurementBasisAxis_us-gaap_CarryingReportedAmountFairValueDisclosureMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R67": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestCostsIncurred",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2420402 - Disclosure - Other Comprehensive Income (Loss): Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details)",
     "role": "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails",
     "shortName": "Other Comprehensive Income (Loss): Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R68": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q4",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2420403 - Disclosure - Other Comprehensive Income (Loss): Accumulated Other Comprehensive Income (Details)",
     "role": "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
     "shortName": "Other Comprehensive Income (Loss): Accumulated Other Comprehensive Income (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2017Q4",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R69": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CapitalExpendituresIncurredButNotYetPaid",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2421402 - Disclosure - Supplemental Disclosure of Cash Flow Information (Details)",
     "role": "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails",
     "shortName": "Supplemental Disclosure of Cash Flow Information (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CapitalExpendituresIncurredButNotYetPaid",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R7": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "1005000 - Statement - Condensed Consolidated Statements of Cash Flows (unaudited)",
     "role": "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
     "shortName": "Condensed Consolidated Statements of Cash Flows (unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:AmortizationOfFinancingCostsAndDiscounts",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R70": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanServiceCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2422402 - Disclosure - Employee Benefit Plans (Details)",
     "role": "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails",
     "shortName": "Employee Benefit Plans (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_us-gaap_RetirementPlanTypeAxis_us-gaap_PensionPlansDefinedBenefitMember",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DefinedBenefitPlanServiceCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R71": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_bkh_BusinessGroupAxis_bkh_UtilitiesGroupMember",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "bkh:RestrictedNetAssetsForSubsidiaries",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2423401 - Disclosure - Commitments and Contingencies: Dividend Restrictions (Details)",
     "role": "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails",
     "shortName": "Commitments and Contingencies: Dividend Restrictions (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1_bkh_BusinessGroupAxis_bkh_UtilitiesGroupMember",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "bkh:RestrictedNetAssetsForSubsidiaries",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R72": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "bkh:DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2424402 - Disclosure - Discontinued Operations (Details)",
     "role": "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails",
     "shortName": "Discontinued Operations (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "bkh:DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R73": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:IncomeTaxExpenseBenefit",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2426401 - Disclosure - Income Taxes (Details)",
     "role": "http://www.blackhillscorp.com/role/IncomeTaxesDetails",
     "shortName": "Income Taxes (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-5",
      "lang": null,
      "name": "us-gaap:IncomeTaxReconciliationTaxCreditsOther",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R74": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q1",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "us-gaap:DeferredTaxAssetsGoodwillAndIntangibleAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2426402 - Disclosure - Income Taxes: Tax Benefit Related to Legal Restructuring (Details)",
     "role": "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails",
     "shortName": "Income Taxes: Tax Benefit Related to Legal Restructuring (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2018Q1",
      "decimals": "-6",
      "first": true,
      "lang": null,
      "name": "us-gaap:DeferredTaxAssetsGoodwillAndIntangibleAssets",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R75": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:IncomeTaxReconciliationChangeInEnactedTaxRate",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2426403 - Disclosure - Income Taxes: TCJA (Details)",
     "role": "http://www.blackhillscorp.com/role/IncomeTaxesTcjaDetails",
     "shortName": "Income Taxes: TCJA (Details)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R76": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:EmployeeRelatedLiabilitiesCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2427402 - Disclosure - Accrued Liabilities (Details)",
     "role": "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails",
     "shortName": "Accrued Liabilities (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:EmployeeRelatedLiabilitiesCurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R77": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_srt_RangeAxis_srt_MinimumMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:LesseeLeaseTerm",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429402 - Disclosure - Leases: Lessee (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeDetails",
     "shortName": "Leases: Lessee (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD_srt_RangeAxis_srt_MinimumMember",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "bkh:LesseeLeaseTerm",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R78": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429403 - Disclosure - Leases: Lessee - Lease Costs (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails",
     "shortName": "Leases: Lessee - Lease Costs (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R79": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseRightOfUseAsset",
      "reportCount": 1,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429404 - Disclosure - Leases: Lessee - Supplemental Balance Sheet Information (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails",
     "shortName": "Leases: Lessee - Supplemental Balance Sheet Information (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:FinanceLeaseRightOfUseAsset",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R8": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2104100 - Disclosure - Management's Statement:",
     "role": "http://www.blackhillscorp.com/role/ManagementsStatement",
     "shortName": "Management's Statement:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R80": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeasePayments",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429405 - Disclosure - Leases: Lessee - Supplemental Cash Flow Information (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails",
     "shortName": "Leases: Lessee - Supplemental Cash Flow Information (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeasePayments",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R81": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "bkh:LesseeSupplementalWeightedAverageScheduleRelatedtoLeasesTableTextBlock",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OperatingLeaseWeightedAverageRemainingLeaseTerm1",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429406 - Disclosure - Leases: Lessee - Weighted Average Information (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeWeightedAverageInformationDetails",
     "shortName": "Leases: Lessee - Weighted Average Information (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "bkh:LesseeSupplementalWeightedAverageScheduleRelatedtoLeasesTableTextBlock",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:OperatingLeaseWeightedAverageRemainingLeaseTerm1",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R82": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429407 - Disclosure - Leases: Lessee - Future Minimum Payments (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails",
     "shortName": "Leases: Lessee - Future Minimum Payments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R83": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseLeaseIncome",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429408 - Disclosure - Leases: Lessor (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLessorDetails",
     "shortName": "Leases: Lessor (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "div",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:OperatingLeaseLeaseIncome",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R84": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2429409 - Disclosure - Leases: Lessor - Future Minimum Payments (Details)",
     "role": "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails",
     "shortName": "Leases: Lessor - Future Minimum Payments (Details)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "span",
       "div",
       "td",
       "tr",
       "table",
       "div",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FI2019Q1",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear",
      "reportCount": 1,
      "unique": true,
      "unitRef": "usd",
      "xsiNil": "false"
     }
    },
    "R9": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:RevenueFromContractWithCustomerTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "2105100 - Disclosure - Revenue:",
     "role": "http://www.blackhillscorp.com/role/Revenue",
     "shortName": "Revenue:",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "baseRef": "bkh10qq12019.htm",
      "contextRef": "FD2019Q1YTD",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:RevenueFromContractWithCustomerTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    }
   },
   "segmentCount": 95,
   "tag": {
    "bkh_AccumulatedOtherComprehensiveIncomeRollForward": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated Other Comprehensive Income [Roll Forward]",
        "label": "Accumulated Other Comprehensive Income [Roll Forward]",
        "terseLabel": "AOCI Attributable to Parent, Net of Tax [Roll Forward]"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeRollForward",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_AllowanceForFundsUsedDuringConstructionMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The offsetting entry to other income when an enterprise capitalizes, as part of the cost of plant and equipment, the cost of financing construction as financed partially by equity.",
        "label": "Allowance For Funds Used During Construction [Member]",
        "terseLabel": "Deferred taxes on AFUDC"
       }
      }
     },
     "localname": "AllowanceForFundsUsedDuringConstructionMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_ApplicationFiledMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Application Filed [Member]",
        "label": "Application Filed [Member]",
        "terseLabel": "Application Filed"
       }
      }
     },
     "localname": "ApplicationFiledMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_AtTheMarketEquityOfferingProgramAuthorizedAggregateValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "At The Market Equity Offering Program authorized an aggregate value that the Company may, through its sales agents, offer and sell from time to time shares of its common stock.",
        "label": "At The Market Equity Offering Program Authorized Aggregate Value",
        "terseLabel": "At The Market Equity Offering Program Authorized Aggregate Value"
       }
      }
     },
     "localname": "AtTheMarketEquityOfferingProgramAuthorizedAggregateValue",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_AtTheMarketEquityOfferingProgramSharesIssued": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "At The Market Equity Offering Program Shares Issued",
        "label": "At The Market Equity Offering Program Shares Issued",
        "terseLabel": "At The Market Equity Offering Program Shares Issued"
       }
      }
     },
     "localname": "AtTheMarketEquityOfferingProgramSharesIssued",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "bkh_AtTheMarketEquityProgramProceedsfromSaleofStock": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "At The Market Equity Program Proceeds from Sale of Stock",
        "label": "At The Market Equity Program Proceeds from Sale of Stock",
        "terseLabel": "At The Market Equity Program Proceeds from Sale of Stock"
       }
      }
     },
     "localname": "AtTheMarketEquityProgramProceedsfromSaleofStock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_BlackHillsEnergyColoradoGasMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Black Hills Energy, Colorado Gas [Member]",
        "label": "Black Hills Energy, Colorado Gas [Member]",
        "terseLabel": "Black Hills Energy, Colorado Gas"
       }
      }
     },
     "localname": "BlackHillsEnergyColoradoGasMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_BlackHillsEnergyNebraskaGasMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Black Hills Energy, Nebraska Gas [Member]",
        "label": "Black Hills Energy, Nebraska Gas [Member]",
        "terseLabel": "Black Hills Energy, Nebraska Gas"
       }
      }
     },
     "localname": "BlackHillsEnergyNebraskaGasMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_BlackHillsEnergyWyomingGasMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Black Hills Energy, Wyoming Gas [Member]",
        "label": "Black Hills Energy, Wyoming Gas [Member]",
        "terseLabel": "Black Hills Energy, Wyoming Gas"
       }
      }
     },
     "localname": "BlackHillsEnergyWyomingGasMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_BusinessGroupAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Business Group (grouping of segments) [Axis]",
        "label": "Business Group [Axis]",
        "terseLabel": "Business Group [Axis]"
       }
      }
     },
     "localname": "BusinessGroupAxis",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_BusinessGroupDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "[Domain] for Business Group (grouping of segments) [Axis]",
        "label": "Business Group [Domain]",
        "terseLabel": "Business Group [Domain]"
       }
      }
     },
     "localname": "BusinessGroupDomain",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_ChangesToOurSegmentPerformanceMeasureAssets": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Changes To Our Segment Performance Measure - Assets",
        "label": "Changes To Our Segment Performance Measure - Assets",
        "terseLabel": "Changes To Our Segment Performance Measure - Assets"
       }
      }
     },
     "localname": "ChangesToOurSegmentPerformanceMeasureAssets",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_ChangesToOurSegmentPerformanceMeasureOperatingIncome": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Changes To Our Segment Performance Measure - Operating Income",
        "label": "Changes To Our Segment Performance Measure - Operating Income",
        "terseLabel": "Changes To Our Segment Performance Measure - Operating Income"
       }
      }
     },
     "localname": "ChangesToOurSegmentPerformanceMeasureOperatingIncome",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_ChangesToOurSegmentPerformanceMeasureRevenues": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Changes To Our Segment Performance Measure - Revenues",
        "label": "Changes To Our Segment Performance Measure - Revenues",
        "terseLabel": "Changes To Our Segment Performance Measure - Revenues"
       }
      }
     },
     "localname": "ChangesToOurSegmentPerformanceMeasureRevenues",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_ColoradoPublicUtilitiesCommissionCPUCMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Colorado Public Utilities Commission (CPUC) [Member]",
        "label": "Colorado Public Utilities Commission (CPUC) [Member]",
        "terseLabel": "Colorado Public Utilities Commission (CPUC)"
       }
      }
     },
     "localname": "ColoradoPublicUtilitiesCommissionCPUCMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_CommercialPaperMaximumBorrowingCapacity": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Commercial Paper, Maximum Borrowing Capacity",
        "label": "Commercial Paper, Maximum Borrowing Capacity",
        "terseLabel": "Commercial paper, maximum borrowing capacity"
       }
      }
     },
     "localname": "CommercialPaperMaximumBorrowingCapacity",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_CreditFacilityandShortTermDebtCovenantsTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of significant debt covenants related to Credit Facility and other short-term debt [Table Text Block]",
        "label": "Credit Facility and Short Term Debt Covenants [Table Text Block]",
        "terseLabel": "Schedule of Credit Facility Covenants"
       }
      }
     },
     "localname": "CreditFacilityandShortTermDebtCovenantsTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_CustomerDepositsandPrepayments": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accrued Liabilities - Customer Deposits and Prepayments",
        "label": "Customer Deposits and Prepayments",
        "terseLabel": "Customer deposits and prepayments"
       }
      }
     },
     "localname": "CustomerDepositsandPrepayments",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_DebtInstrumentConsolidatedIndebtednessToCapitalizationRatioRequirementForTheNextFiscalYear": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Debt Instrument, Consolidated Indebtedness To Capitalization Ratio Requirement For The Next Fiscal Year",
        "label": "Debt Instrument, Consolidated Indebtedness To Capitalization Ratio Requirement For The Next Fiscal Year",
        "terseLabel": "Consolidated Indebtedness to Capitalization Ratio"
       }
      }
     },
     "localname": "DebtInstrumentConsolidatedIndebtednessToCapitalizationRatioRequirementForTheNextFiscalYear",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "pureItemType"
    },
    "bkh_DebtInstrumentCovenantRecourseLeverageRatio": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The maximum allowed recourse leverage ratio under debt covenants.",
        "label": "Debt Instrument, Covenant, Recourse Leverage Ratio",
        "terseLabel": "Debt instrument, covenant, Leverage Recourse Ratio"
       }
      }
     },
     "localname": "DebtInstrumentCovenantRecourseLeverageRatio",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "pureItemType"
    },
    "bkh_DeferredIncomeTaxChargesaMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate Action of a regulator resulting in capitalization or accrual of income taxes",
        "label": "Deferred Income Tax Charges a [Member]",
        "terseLabel": "Excess deferred income taxes"
       }
      }
     },
     "localname": "DeferredIncomeTaxChargesaMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_DerivativeAssetsCurrentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line item in the statement of financial position in a classified presentation in which the fair value amounts of the derivative instruments are included.",
        "label": "Derivative Assets, Current [Member]",
        "terseLabel": "Derivative assets \u2014 current"
       }
      }
     },
     "localname": "DerivativeAssetsCurrentMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_DerivativeAssetsNoncurrentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line item in the statement of financial position in a classified presentation in which the fair value amounts of the derivative instruments are included.",
        "label": "Derivative Assets, Noncurrent [Member]",
        "terseLabel": "Other assets, non-current"
       }
      }
     },
     "localname": "DerivativeAssetsNoncurrentMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_DerivativeLiabilitiesCurrentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line item in the statement of financial position in a classified presentation in which the fair value amounts of the derivative instruments are included.",
        "label": "Derivative Liabilities, Current [Member]",
        "terseLabel": "Derivative liabilities \u2014 current"
       }
      }
     },
     "localname": "DerivativeLiabilitiesCurrentMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_DerivativeLiabilitiesNoncurrentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line item in the statement of financial position in a classified presentation in which the fair value amounts of the derivative instruments are included.",
        "label": "Derivative Liabilities, Noncurrent [Member]",
        "terseLabel": "Other deferred credits and other liabilities"
       }
      }
     },
     "localname": "DerivativeLiabilitiesNoncurrentMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disposal Groups, Including Discontinued Operations, Balance Sheet Accounts [Table Text Block]",
        "label": "Disposal Groups, Including Discontinued Operations, Balance Sheet Accounts [Table Text Block]",
        "terseLabel": "Disposal Groups, Including Discontinued Operations, Balance Sheet Accounts"
       }
      }
     },
     "localname": "DisposalGroupsIncludingDiscontinuedOperationsBalanceSheetAccountsTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_DocumentAndEntityInformationAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Abstract model section heading for document and entity information",
        "label": "Document and Entity Information [Abstract]"
       }
      }
     },
     "localname": "DocumentAndEntityInformationAbstract",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "xbrltype": "stringItemType"
    },
    "bkh_ElectricUtilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Electric Utilities Segment [Member]",
        "label": "Electric Utilities [Member]",
        "terseLabel": "Electric Utilities"
       }
      }
     },
     "localname": "ElectricUtilitiesMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_EnvironmentalMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Environmental costs associated with utility property [Member]",
        "label": "Environmental [Member]",
        "terseLabel": "Environmental"
       }
      }
     },
     "localname": "EnvironmentalMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_ExternalCustomersMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "External Customers",
        "label": "External Customers [Member]",
        "terseLabel": "External Operating Revenue"
       }
      }
     },
     "localname": "ExternalCustomersMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_FixedforFloatSwapsPurchasedMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fixed for Float Swaps Purchased [Member]",
        "label": "Fixed for Float Swaps Purchased [Member]",
        "terseLabel": "Natural gas over-the-counter swaps, net"
       }
      }
     },
     "localname": "FixedforFloatSwapsPurchasedMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_FlowThroughAccountingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The income tax effects of certain tax items are reflected in cost of service for the customer in which the tax benefits are realized and result in lower utiity rates.  The regulatory treatment under flow-through accounting was applied for this tax benefit generated by utility costs that were previously capitalized for tax purposes in a rate case settlement and resulted in a lower rate increase. A regulatory asset was established to reflect the future increase in taxes payable recovered from sutomers as the temporarty difference reverses.[Member]",
        "label": "Flow Through Accounting [Member]",
        "terseLabel": "Deferred taxes on flow through accounting"
       }
      }
     },
     "localname": "FlowThroughAccountingMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_FuelPurchasedPowerAndCostOfGasSold": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fuel costs incurred that are directly related to goods produced and sold and services rendered during the reporting period, combined with the amount of purchased power charged against earnings for the period, and cost of gas sold to customers for the period.",
        "label": "Fuel, Purchased Power and Cost of Gas Sold",
        "terseLabel": "Fuel, purchased power and cost of natural gas sold"
       }
      }
     },
     "localname": "FuelPurchasedPowerAndCostOfGasSold",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_GasSupplyContractTerminationMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gas Supply Contract Termination [Member]",
        "label": "Gas Supply Contract Termination [Member]",
        "terseLabel": "Gas supply contract termination"
       }
      }
     },
     "localname": "GasSupplyContractTerminationMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_GasUtilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gas Utilities [Member]",
        "label": "Gas Utilities [Member]",
        "terseLabel": "Gas Utilities"
       }
      }
     },
     "localname": "GasUtilitiesMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_IntercompanyCustomersMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Intercompany Customers [Member]",
        "label": "Intercompany Customers [Member]",
        "terseLabel": "Inter-company Operating Revenue"
       }
      }
     },
     "localname": "IntercompanyCustomersMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_LeaseLiability": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "order": 2.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability",
        "label": "Lease Liability",
        "terseLabel": "Present value of lease liabilities"
       }
      }
     },
     "localname": "LeaseLiability",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsAfterYearFive": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 6.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments After Year Five",
        "label": "Lease Liability Payments After Year Five",
        "totalLabel": "Thereafter"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsAfterYearFive",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsDue": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Due",
        "label": "Lease Liability Payments Due",
        "totalLabel": "Total lease payments"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsDue",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsDueYearFive": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 5.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Due Year Five",
        "label": "Lease Liability Payments Due Year Five",
        "totalLabel": "2023"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsDueYearFive",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsDueYearFour": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 4.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Due Year Four",
        "label": "Lease Liability Payments Due Year Four",
        "totalLabel": "2022"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsDueYearFour",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsDueYearThree": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 3.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Due Year Three",
        "label": "Lease Liability Payments Due Year Three",
        "totalLabel": "2021"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsDueYearThree",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsDueYearTwo": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 2.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Due Year Two",
        "label": "Lease Liability Payments Due Year Two",
        "totalLabel": "2020"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsDueYearTwo",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityPaymentsRemainderofFiscalYear": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 1.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Payments Remainder of Fiscal Year",
        "label": "Lease Liability Payments Remainder of Fiscal Year",
        "totalLabel": "2019"
       }
      }
     },
     "localname": "LeaseLiabilityPaymentsRemainderofFiscalYear",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LeaseLiabilityUndiscountedExcessAmount": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "order": 1.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lease Liability Undiscounted Excess Amount",
        "label": "Lease Liability Undiscounted Excess Amount",
        "terseLabel": "Less imputed interest"
       }
      }
     },
     "localname": "LeaseLiabilityUndiscountedExcessAmount",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_LesseeLeaseTerm": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lessee - Lease Term",
        "label": "Lessee - Lease Term",
        "terseLabel": "Lessee - Lease Term"
       }
      }
     },
     "localname": "LesseeLeaseTerm",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "bkh_LesseeSupplementalBalanceSheetInformationRelatedtoLeasesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lessee Supplemental Balance Sheet Information Related to Leases [Table Text Block]",
        "label": "Lessee Supplemental Balance Sheet Information Related to Leases [Table Text Block]",
        "terseLabel": "Lessee - Supplemental Balance Sheet Information"
       }
      }
     },
     "localname": "LesseeSupplementalBalanceSheetInformationRelatedtoLeasesTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_LesseeSupplementalCashFlowInformationRelatedtoLeasesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lessee Supplemental Cash Flow Information Related to Leases [Table Text Block]",
        "label": "Lessee Supplemental Cash Flow Information Related to Leases [Table Text Block]",
        "terseLabel": "Lessee - Supplemental Cash Flow Information"
       }
      }
     },
     "localname": "LesseeSupplementalCashFlowInformationRelatedtoLeasesTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_LesseeSupplementalWeightedAverageScheduleRelatedtoLeasesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Lessee Supplemental Weighted Average Schedule Related to Leases [Table Text Block]",
        "label": "Lessee Supplemental Weighted Average Schedule Related to Leases [Table Text Block]",
        "terseLabel": "Lessee - Supplemental Weighted Average Schedule"
       }
      }
     },
     "localname": "LesseeSupplementalWeightedAverageScheduleRelatedtoLeasesTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_MarketOffSystemSalesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Market Off-System Sales [Member]",
        "label": "Market Off-System Sales [Member]",
        "terseLabel": "Market - off-system sales"
       }
      }
     },
     "localname": "MarketOffSystemSalesMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_MiningMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Mining",
        "label": "Mining [Member]",
        "terseLabel": "Mining"
       }
      }
     },
     "localname": "MiningMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_NaturalGasDistributionMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Natural Gas for distribution [Member]",
        "label": "Natural Gas, Distribution [Member]",
        "terseLabel": "Natural Gas, Distribution"
       }
      }
     },
     "localname": "NaturalGasDistributionMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_NaturalGasPhysicalPurchasesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Natural Gas Physical Purchases [Member]",
        "label": "Natural Gas Physical Purchases [Member]",
        "terseLabel": "Natural gas physical contracts, net"
       }
      }
     },
     "localname": "NaturalGasPhysicalPurchasesMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_NebraskaPublicServiceCommissionNPSCMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Nebraska Public Service Commission (NPSC) [Member]",
        "label": "Nebraska Public Service Commission (NPSC) [Member]",
        "terseLabel": "Nebraska Public Service Commission (NPSC)"
       }
      }
     },
     "localname": "NebraskaPublicServiceCommissionNPSCMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_NumberOfOneYearExtensionOptions": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number Of One-Year Extension Options",
        "label": "Number Of One-Year Extension Options",
        "terseLabel": "Number of one-year extension options"
       }
      }
     },
     "localname": "NumberOfOneYearExtensionOptions",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "bkh_OperatingExpenseMaintenanceOperationsandOtherCostsandExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of operating expenses for the period including selling, general, and administrative expenses, costs include routine repairs and maintenance and operations.",
        "label": "Operating Expense, Maintenance, Operations, and Other Costs and Expense",
        "terseLabel": "Operations and maintenance"
       }
      }
     },
     "localname": "OperatingExpenseMaintenanceOperationsandOtherCostsandExpense",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_OperatingandFinanceLeaseAssets": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Operating and Finance Lease Assets",
        "label": "Operating and Finance Lease Assets",
        "totalLabel": "Total lease assets"
       }
      }
     },
     "localname": "OperatingandFinanceLeaseAssets",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_OperatingandFinanceLeaseLiabilities": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Operating and Finance Lease Liabilities",
        "label": "Operating and Finance Lease Liabilities",
        "totalLabel": "Total lease liabilities"
       }
      }
     },
     "localname": "OperatingandFinanceLeaseLiabilities",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_OperatingandFinanceLeaseTotalAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Operating and Finance Lease Total [Abstract]",
        "label": "Operating and Finance Lease Total [Abstract]",
        "terseLabel": "Operating and Finance Lease Total"
       }
      }
     },
     "localname": "OperatingandFinanceLeaseTotalAbstract",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_OtherMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other [Member]",
        "label": "Other [Member]",
        "terseLabel": "Other revenues",
        "verboseLabel": "Other Revenues"
       }
      }
     },
     "localname": "OtherMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_OtherRegulatoryAssetsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other regulatory assets [Member]",
        "label": "Other Regulatory Assets [Member]",
        "terseLabel": "Other regulatory assets"
       }
      }
     },
     "localname": "OtherRegulatoryAssetsMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_OtherRegulatoryLiabilitiesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Other regulatory liabilities [Member]",
        "label": "Other Regulatory Liabilities [Member]",
        "terseLabel": "Other regulatory liabilities"
       }
      }
     },
     "localname": "OtherRegulatoryLiabilitiesMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_PowerGenerationMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Power Generation",
        "label": "Power Generation [Member]",
        "terseLabel": "Power Generation"
       }
      }
     },
     "localname": "PowerGenerationMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_PriorYearEndOperatingLeaseFutureMinimumPaymentsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Prior Year End Operating Lease Future Minimum Payments [Abstract]",
        "label": "Prior Year End Operating Lease Future Minimum Payments [Abstract]",
        "terseLabel": "Prior Year End Operating Lease Future Minimum Payments"
       }
      }
     },
     "localname": "PriorYearEndOperatingLeaseFutureMinimumPaymentsAbstract",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_PublicUtilitiesAllowanceForFundsUsedDuringConstructionBorrowedInterestCostsCapitalized": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_NonoperatingIncomeExpense",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The component of the allowance for funds used during construction during the period which represents the approximate composite costs of borrowed funds and is netted against interest expense.",
        "label": "Public Utilities Allowance For Funds Used During Construction Borrowed Interest Costs Capitalized",
        "terseLabel": "Allowance for funds used during construction - borrowed"
       }
      }
     },
     "localname": "PublicUtilitiesAllowanceForFundsUsedDuringConstructionBorrowedInterestCostsCapitalized",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_PublicUtilitiesNumberofCompaniesBeingMerged": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Public Utilities, Number of Companies Being Merged",
        "label": "Public Utilities, Number of Companies Being Merged",
        "terseLabel": "Public Utilities, Number of Companies Being Merged"
       }
      }
     },
     "localname": "PublicUtilitiesNumberofCompaniesBeingMerged",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "integerItemType"
    },
    "bkh_RateReviewFiledwiththeRegulatoryAgencyMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate Review Filed with the Regulatory Agency [Member]",
        "label": "Rate Review Filed with the Regulatory Agency [Member]",
        "terseLabel": "Rate Review Filed with the Regulatory Agency"
       }
      }
     },
     "localname": "RateReviewFiledwiththeRegulatoryAgencyMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_RecourseLeverageRatio": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Recourse Leverage Ratio",
        "label": "Recourse Leverage Ratio",
        "terseLabel": "Recourse Leverage Ratio"
       }
      }
     },
     "localname": "RecourseLeverageRatio",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "bkh_RestrictedCashFairValueDisclosure": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This element represents the portion of the balance sheet assertion valued at fair value by the entity 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. This element represents the fair value of assets categorized as restricted cash",
        "label": "Restricted Cash Fair Value Disclosure",
        "terseLabel": "Restricted Cash Fair Value Disclosure"
       }
      }
     },
     "localname": "RestrictedCashFairValueDisclosure",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_RestrictedNetAssetsForSubsidiaries": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of Restricted Net Assets (Equity) for Subsidiaries as of the end of the reporting period.",
        "label": "Restricted Net Assets for Subsidiaries",
        "terseLabel": "Restricted Net Assets for Subsidiaries"
       }
      }
     },
     "localname": "RestrictedNetAssetsForSubsidiaries",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "bkh_RetailElectricNaturalGasandCoalMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Retail - Electric , Natural Gas and Coal",
        "label": "Retail - Electric , Natural Gas and Coal [Member]",
        "terseLabel": "Retail - Electric , Natural Gas and Coal"
       }
      }
     },
     "localname": "RetailElectricNaturalGasandCoalMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_ScheduleOfDefinedBenefitPlansContributionsTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of Defined Benefit Plans Contributions for the current year and specific future years.[Text Block]",
        "label": "Schedule of Defined Benefit Plans Contributions [Table Text Block]",
        "terseLabel": "Schedule of Defined Benefit Plans Contributions"
       }
      }
     },
     "localname": "ScheduleOfDefinedBenefitPlansContributionsTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_ScheduleOfMaturitiesofOperatingAndFinanceLeaseReceivableTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule Of Maturities of Operating And Finance Lease Receivable [Table Text Block]",
        "label": "Schedule Of Maturities of Operating And Finance Lease Receivable [Table Text Block]",
        "terseLabel": "Lessor - Operating and Finance Lease, Liability, Maturity"
       }
      }
     },
     "localname": "ScheduleOfMaturitiesofOperatingAndFinanceLeaseReceivableTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_ScheduleOfRegulatoryAssetsAndLiabilitiesLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of regulatory asset and liabilities line items",
        "label": "Schedule Of Regulatory Assets And Liabilities [Line Items]",
        "terseLabel": "Schedule Of Regulatory Assets And Liabilities [Line Items]"
       }
      }
     },
     "localname": "ScheduleOfRegulatoryAssetsAndLiabilitiesLineItems",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_ScheduleOfRegulatoryAssetsAndLiabilitiesTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A table of assets and liabilities that are created when regulatory agencies permit public utilities to defer recognitiion of certain revenues or costs included in rate setting.",
        "label": "Schedule Of Regulatory Assets And Liabilities [Table]",
        "terseLabel": "Schedule Of Regulatory Assets And Liabilities [Table]"
       }
      }
     },
     "localname": "ScheduleOfRegulatoryAssetsAndLiabilitiesTable",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for detailed information about regulatory assets and liabilities, including current and noncurrent assets created when regulatory agencies permit the deferral of costs to the balance sheet that would otherwise be required to appear on the company's income statement and would be charged against current expenses or revenues, as well as current and noncurrent liabilities created when regulatory agencies permit. [Table Text Block]",
        "label": "Schedule of Regulatory Assets and Liabilities [Table Text Block]",
        "terseLabel": "Schedule of Regulatory Assets and Liabilities"
       }
      }
     },
     "localname": "ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "bkh_TransmissionOtherMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Transmission/Other [Member]",
        "label": "Transmission/Other [Member]",
        "terseLabel": "Transmission/Other"
       }
      }
     },
     "localname": "TransmissionOtherMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_TransportationMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Transportation [Member]",
        "label": "Transportation [Member]",
        "terseLabel": "Transportation"
       }
      }
     },
     "localname": "TransportationMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_UtilitiesGroupMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Utilities Group - consists of our Electric Utilities and our Gas Utilities segments",
        "label": "Utilities Group [Member]",
        "terseLabel": "Utilities Group"
       }
      }
     },
     "localname": "UtilitiesGroupMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_WeightedAverageNumberOfSharesOutstandingBasicAndDilutedAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average number of shares of common stock, basic and diluted[Abstract]",
        "label": "Weighted Average Number of Shares Outstanding, Basic and Diluted [Abstract]",
        "terseLabel": "Weighted Average Number of Shares Outstanding, Basic and Diluted [Abstract]"
       }
      }
     },
     "localname": "WeightedAverageNumberOfSharesOutstandingBasicAndDilutedAbstract",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "bkh_WholesaleMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Wholesale [Member]",
        "label": "Wholesale [Member]",
        "terseLabel": "Wholesale"
       }
      }
     },
     "localname": "WholesaleMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "bkh_WyomingPublicServiceCommissionWPSCMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Wyoming Public Service Commission (WPSC) [Member]",
        "label": "Wyoming Public Service Commission (WPSC) [Member]",
        "terseLabel": "Wyoming Public Service Commission (WPSC)"
       }
      }
     },
     "localname": "WyomingPublicServiceCommissionWPSCMember",
     "nsuri": "http://www.blackhillscorp.com/20190331",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "dei_AmendmentFlag": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "If the value is true, then the document is an amendment to previously-filed/accepted document.",
        "label": "Amendment Flag",
        "terseLabel": "Amendment Flag"
       }
      }
     },
     "localname": "AmendmentFlag",
     "nsuri": "http://xbrl.sec.gov/dei/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "booleanItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "gMonthDayItemType"
    },
    "dei_DocumentFiscalPeriodFocus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This is focus fiscal period of the document report. For a first quarter 2006 quarterly report, which may also provide financial information from prior periods, the first fiscal quarter should be given as the fiscal period focus. Values: FY, Q1, Q2, Q3, Q4, H1, H2, M9, T1, T2, T3, M8, CY.",
        "label": "Document Fiscal Period Focus",
        "terseLabel": "Document Fiscal Period Focus"
       }
      }
     },
     "localname": "DocumentFiscalPeriodFocus",
     "nsuri": "http://xbrl.sec.gov/dei/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "gYearItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "dateItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "submissionTypeItemType"
    },
    "dei_EntityCentralIndexKey": {
     "auth_ref": [
      "r413"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "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"
       }
      }
     },
     "localname": "EntityCommonStockSharesOutstanding",
     "nsuri": "http://xbrl.sec.gov/dei/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "dei_EntityEmergingGrowthCompany": {
     "auth_ref": [
      "r413"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntityFilerCategory": {
     "auth_ref": [
      "r413"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate whether the registrant is one of the following: (1) Large Accelerated Filer, (2) Accelerated Filer, (3) Non-accelerated Filer, (4) Smaller Reporting Company (Non-accelerated), (5) Smaller Reporting Accelerated Filer or (6) Smaller Reporting Company and Large 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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "filerCategoryItemType"
    },
    "dei_EntityRegistrantName": {
     "auth_ref": [
      "r413"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntitySmallBusiness": {
     "auth_ref": [
      "r413"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicates that the company is a smaller reporting company with both a public float and revenues of less than $75 million.",
        "label": "Entity Small Business",
        "terseLabel": "Entity Small Business"
       }
      }
     },
     "localname": "EntitySmallBusiness",
     "nsuri": "http://xbrl.sec.gov/dei/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "booleanItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DocumentAndEntityInformationDocument"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "invest_DerivativeNonmonetaryNotionalAmount": {
     "auth_ref": [
      "r414"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.",
        "label": "Derivative, Nonmonetary Notional Amount",
        "terseLabel": "Derivative, Nonmonetary Notional Amount"
       }
      }
     },
     "localname": "DerivativeNonmonetaryNotionalAmount",
     "nsuri": "http://xbrl.sec.gov/invest/2013-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "decimalItemType"
    },
    "srt_ConsolidationEliminationsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Consolidation, Eliminations [Member]",
        "terseLabel": "Consolidation, Eliminations"
       }
      }
     },
     "localname": "ConsolidationEliminationsMember",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ConsolidationItemsAxis": {
     "auth_ref": [
      "r169",
      "r179"
     ],
     "lang": {
      "en-US": {
       "role": {
        "label": "Consolidation Items [Axis]",
        "terseLabel": "Consolidation Items [Axis]"
       }
      }
     },
     "localname": "ConsolidationItemsAxis",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ConsolidationItemsDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Consolidation Items [Domain]",
        "terseLabel": "Consolidation Items [Domain]"
       }
      }
     },
     "localname": "ConsolidationItemsDomain",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_MajorCustomersAxis": {
     "auth_ref": [
      "r183",
      "r220",
      "r223"
     ],
     "lang": {
      "en-US": {
       "role": {
        "label": "Customer [Axis]",
        "terseLabel": "Customer [Axis]"
       }
      }
     },
     "localname": "MajorCustomersAxis",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_MaximumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Maximum [Member]",
        "terseLabel": "Maximum"
       }
      }
     },
     "localname": "MaximumMember",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails",
      "http://www.blackhillscorp.com/role/LeasesLessorDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_MinimumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Minimum [Member]",
        "terseLabel": "Minimum"
       }
      }
     },
     "localname": "MinimumMember",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails",
      "http://www.blackhillscorp.com/role/LeasesLessorDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_NameOfMajorCustomerDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Customer [Domain]",
        "terseLabel": "Customer [Domain]"
       }
      }
     },
     "localname": "NameOfMajorCustomerDomain",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_ProductOrServiceAxis": {
     "auth_ref": [
      "r182",
      "r220",
      "r222",
      "r401"
     ],
     "lang": {
      "en-US": {
       "role": {
        "label": "Product and Service [Axis]",
        "terseLabel": "Product and Service [Axis]"
       }
      }
     },
     "localname": "ProductOrServiceAxis",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_ProductsAndServicesDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Product and Service [Domain]",
        "terseLabel": "Product and Service [Domain]"
       }
      }
     },
     "localname": "ProductsAndServicesDomain",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_RangeAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Range [Axis]",
        "terseLabel": "Range [Axis]"
       }
      }
     },
     "localname": "RangeAxis",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails",
      "http://www.blackhillscorp.com/role/LeasesLessorDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_RangeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Range [Domain]",
        "terseLabel": "Range [Domain]"
       }
      }
     },
     "localname": "RangeMember",
     "nsuri": "http://fasb.org/srt/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails",
      "http://www.blackhillscorp.com/role/LeasesLessorDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccountingStandardsUpdate201602Member": {
     "auth_ref": [
      "r344"
     ],
     "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 [Member]"
       }
      }
     },
     "localname": "AccountingStandardsUpdate201602Member",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "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 Receivable [Line Items]"
       }
      }
     },
     "localname": "AccountsNotesAndLoansReceivableLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock": {
     "auth_ref": [
      "r51"
     ],
     "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]",
        "terseLabel": "Accrued Liabilities"
       }
      }
     },
     "localname": "AccountsPayableAndAccruedLiabilitiesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilities"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_AccountsPayableCurrent": {
     "auth_ref": [
      "r50"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccountsReceivableGrossCurrent": {
     "auth_ref": [
      "r35",
      "r389"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AccountsReceivableNetCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "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 (including trade receivables) that have been delivered or sold in the normal course of business.",
        "label": "Accounts Receivable, Gross, Current",
        "terseLabel": "Accounts Receivable, Trade"
       }
      }
     },
     "localname": "AccountsReceivableGrossCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccountsReceivableNetCurrent": {
     "auth_ref": [
      "r35",
      "r221"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount 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 (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.",
        "label": "Accounts Receivable, Net, Current",
        "terseLabel": "Accounts receivable, net",
        "totalLabel": "Accounts receivable, net"
       }
      }
     },
     "localname": "AccountsReceivableNetCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent": {
     "auth_ref": [
      "r21",
      "r56",
      "r262"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "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 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": "Accrued property taxes"
       }
      }
     },
     "localname": "AccrualForTaxesOtherThanIncomeTaxesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccruedLiabilitiesCurrent": {
     "auth_ref": [
      "r56"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "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 liabilities",
        "totalLabel": "Total accrued liabilities"
       }
      }
     },
     "localname": "AccruedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember": {
     "auth_ref": [
      "r79",
      "r85",
      "r88",
      "r245",
      "r282"
     ],
     "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": "Accumulated Defined Benefit Plans Adjustment"
       }
      }
     },
     "localname": "AccumulatedDefinedBenefitPlansAdjustmentMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember": {
     "auth_ref": [
      "r80",
      "r85",
      "r88",
      "r244",
      "r282"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive (income) loss related to prior service cost (credit) component of defined benefit plans attributable to the parent.",
        "label": "Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]",
        "terseLabel": "Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit)"
       }
      }
     },
     "localname": "AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember": {
     "auth_ref": [
      "r78",
      "r85",
      "r88",
      "r244",
      "r282"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated other comprehensive income (loss) related to gain (loss) component of defined benefit plans attributable to the parent.",
        "label": "Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]",
        "terseLabel": "Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)"
       }
      }
     },
     "localname": "AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment": {
     "auth_ref": [
      "r48",
      "r199"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "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",
        "negatedTerseLabel": "Less: accumulated depreciation and depletion"
       }
      }
     },
     "localname": "AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember": {
     "auth_ref": [
      "r77",
      "r85",
      "r88",
      "r281"
     ],
     "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": "Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent",
        "verboseLabel": "Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges"
       }
      }
     },
     "localname": "AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax": {
     "auth_ref": [
      "r82",
      "r84",
      "r85"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 5.0,
       "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",
        "periodEndLabel": "Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End",
        "periodStartLabel": "Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start",
        "verboseLabel": "Accumulated other comprehensive income (loss)"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeMember": {
     "auth_ref": [
      "r81",
      "r85",
      "r88",
      "r282"
     ],
     "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": "AOCI Attributable to Parent"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdditionalPaidInCapital": {
     "auth_ref": [
      "r36"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "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. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.",
        "label": "Additional Paid in Capital",
        "terseLabel": "Additional paid-in capital"
       }
      }
     },
     "localname": "AdditionalPaidInCapital",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdjustmentsForNewAccountingPronouncementsAxis": {
     "auth_ref": [
      "r139"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts": {
     "auth_ref": [
      "r213",
      "r214"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of decrease in additional paid in capital (APIC) resulting from direct costs associated with issuing stock. Includes, but is not limited to, legal and accounting fees and direct costs associated with stock issues under a shelf registration.",
        "label": "Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs",
        "negatedTerseLabel": "Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs"
       }
      }
     },
     "localname": "AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "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]",
        "terseLabel": "Adjustments to reconcile net income to net cash provided by operating activities:"
       }
      }
     },
     "localname": "AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent": {
     "auth_ref": [
      "r65",
      "r187"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_AccountsReceivableNetCurrent",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.",
        "label": "Allowance for Doubtful Accounts Receivable, Current",
        "negatedTerseLabel": "Allowance for Doubtful Accounts"
       }
      }
     },
     "localname": "AllowanceForDoubtfulAccountsReceivableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AmortizationOfFinancingCostsAndDiscounts": {
     "auth_ref": [
      "r120",
      "r336"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.",
        "label": "Amortization of Debt Issuance Costs and Discounts",
        "terseLabel": "Deferred financing cost amortization"
       }
      }
     },
     "localname": "AmortizationOfFinancingCostsAndDiscounts",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount": {
     "auth_ref": [
      "r154"
     ],
     "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"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis": {
     "auth_ref": [
      "r154"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems": {
     "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": "Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]",
        "terseLabel": "Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AntidilutiveSecuritiesNameDomain": {
     "auth_ref": [
      "r154"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AssetRecoverableGasCostsMember": {
     "auth_ref": [
      "r403"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of gas costs.",
        "label": "Asset Recoverable Gas Costs [Member]",
        "terseLabel": "Deferred gas cost adjustments"
       }
      }
     },
     "localname": "AssetRecoverableGasCostsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Assets": {
     "auth_ref": [
      "r173",
      "r378",
      "r390"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "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": "Assets",
        "totalLabel": "TOTAL ASSETS"
       }
      }
     },
     "localname": "Assets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets [Abstract]",
        "terseLabel": "ASSETS"
       }
      }
     },
     "localname": "AssetsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsCurrent": {
     "auth_ref": [
      "r18",
      "r19",
      "r69"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsFairValueDisclosure": {
     "auth_ref": [
      "r322"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.",
        "label": "Assets, Fair Value Disclosure",
        "terseLabel": "Derivative Assets, Total"
       }
      }
     },
     "localname": "AssetsFairValueDisclosure",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts as of the balance sheet date of all assets, excluding property, plant, and equipment and other property and investments, that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Alternate captions include Total Deferred Charges and Other Assets.",
        "label": "Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment",
        "totalLabel": "Total other assets, non-current"
       }
      }
     },
     "localname": "AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r13",
      "r197",
      "r202"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 9.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as assets attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.",
        "label": "Disposal Group, Including Discontinued Operation, Assets, Current",
        "terseLabel": "Current assets held for sale"
       }
      }
     },
     "localname": "AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BalanceSheetLocationDomain": {
     "auth_ref": [
      "r297",
      "r302"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BaseRateMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Minimum rate investor will accept.",
        "label": "Base Rate [Member]",
        "terseLabel": "Base Rate"
       }
      }
     },
     "localname": "BaseRateMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_BasisSwapMember": {
     "auth_ref": [
      "r310"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest-rate swap contract where both rates are variable but are tied to different index rates. For example, but not limited to, one party's rate indexed to three-month London Interbank Offered Rate (LIBOR) while the other party's rate is indexed to six-month LIBOR.",
        "label": "Basis Swap [Member]",
        "terseLabel": "Natural gas basis swaps purchased"
       }
      }
     },
     "localname": "BasisSwapMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CapitalExpendituresIncurredButNotYetPaid": {
     "auth_ref": [
      "r124",
      "r125",
      "r126"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Future cash outflow to pay for purchases of fixed assets that have occurred.",
        "label": "Capital Expenditures Incurred but Not yet Paid",
        "terseLabel": "Property, plant and equipment acquired with accrued liabilities"
       }
      }
     },
     "localname": "CapitalExpendituresIncurredButNotYetPaid",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CarryingReportedAmountFairValueDisclosureMember": {
     "auth_ref": [
      "r332",
      "r333"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measured as reported on the statement of financial position (balance sheet).",
        "label": "Reported Value Measurement [Member]",
        "terseLabel": "Carrying Amount"
       }
      }
     },
     "localname": "CarryingReportedAmountFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CashAndCashEquivalentsAtCarryingValue": {
     "auth_ref": [
      "r16",
      "r45",
      "r122"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashAndCashEquivalentsFairValueDisclosure": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value portion 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.",
        "label": "Cash and Cash Equivalents, Fair Value Disclosure",
        "verboseLabel": "Cash and cash equivalents, Fair Value"
       }
      }
     },
     "localname": "CashAndCashEquivalentsFairValueDisclosure",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents": {
     "auth_ref": [
      "r116",
      "r122",
      "r127"
     ],
     "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, cash equivalents and restricted cash at end of period",
        "periodStartLabel": "Cash, cash equivalents and restricted cash at beginning of period"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect": {
     "auth_ref": [
      "r116",
      "r334"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; excluding 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), Excluding Exchange Rate Effect",
        "totalLabel": "Net change in cash, cash equivalents and restricted cash"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths": {
     "auth_ref": [
      "r319"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.",
        "label": "Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months",
        "terseLabel": "Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months"
       }
      }
     },
     "localname": "CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashFlowHedgingMember": {
     "auth_ref": [
      "r293"
     ],
     "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 Hedging"
       }
      }
     },
     "localname": "CashFlowHedgingMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CashFlowSupplementalDisclosuresTextBlock": {
     "auth_ref": [
      "r128"
     ],
     "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 Disclosure of Cash Flow Information"
       }
      }
     },
     "localname": "CashFlowSupplementalDisclosuresTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations": {
     "auth_ref": [
      "r11",
      "r116"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) of investing activities of 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": "Cash Provided by (Used in) Investing Activities, Discontinued Operations",
        "terseLabel": "Net cash provided by (used in) investing activities of discontinued operations"
       }
      }
     },
     "localname": "CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations": {
     "auth_ref": [
      "r11",
      "r116"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) of operating activities of discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.",
        "label": "Cash Provided by (Used in) Operating Activities, Discontinued Operations",
        "terseLabel": "Net cash provided by (used in) operating activities of discontinued operations"
       }
      }
     },
     "localname": "CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CollateralAlreadyPostedAggregateFairValue": {
     "auth_ref": [
      "r312"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.",
        "label": "Collateral Already Posted, Aggregate Fair Value",
        "terseLabel": "Credit Risk Derivative Liabilities, at Fair Value"
       }
      }
     },
     "localname": "CollateralAlreadyPostedAggregateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CommercialPaperMember": {
     "auth_ref": [
      "r210"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Unsecured promissory note (generally negotiable) that provides institutions with short-term funds.",
        "label": "Commercial Paper [Member]",
        "terseLabel": "Commercial Paper"
       }
      }
     },
     "localname": "CommercialPaperMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommitmentsAndContingencies": {
     "auth_ref": [
      "r60",
      "r208",
      "r384",
      "r397"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "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 Notes 8, 10, 15, 16)"
       }
      }
     },
     "localname": "CommitmentsAndContingencies",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CommitmentsAndContingenciesDisclosureTextBlock": {
     "auth_ref": [
      "r207",
      "r209"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingencies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CommodityContractMember": {
     "auth_ref": [
      "r234",
      "r308"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Derivative instrument whose primary underlying risk is tied to commodity prices.",
        "label": "Commodity Contract [Member]",
        "terseLabel": "Commodity Contract"
       }
      }
     },
     "localname": "CommodityContractMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommodityOptionMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Option contract in which the underlying asset is a commodity.",
        "label": "Commodity Option [Member]",
        "terseLabel": "Natural gas options purchased, net"
       }
      }
     },
     "localname": "CommodityOptionMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonStockDividendsPerShareCashPaid": {
     "auth_ref": [
      "r214"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate dividends paid during the period for each share of common stock outstanding.",
        "label": "Common Stock, Dividends, Per Share, Cash Paid",
        "terseLabel": "Dividends per share of common stock (usd per share)"
       }
      }
     },
     "localname": "CommonStockDividendsPerShareCashPaid",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityDividendsOnCommonStockDetails"
     ],
     "xbrltype": "perShareItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonStockParOrStatedValuePerShare": {
     "auth_ref": [
      "r34"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_CommonStockSharesAuthorized": {
     "auth_ref": [
      "r34"
     ],
     "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"
       }
      }
     },
     "localname": "CommonStockSharesAuthorized",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesIssued": {
     "auth_ref": [
      "r34"
     ],
     "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",
        "terseLabel": "Common Stock, Shares Issued"
       }
      }
     },
     "localname": "CommonStockSharesIssued",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesOutstanding": {
     "auth_ref": [
      "r34",
      "r213"
     ],
     "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"
       }
      }
     },
     "localname": "CommonStockSharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockValue": {
     "auth_ref": [
      "r34"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "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 $1 par value; 100,000,000 shares authorized; issued 60,378,020; 60,048,567; and 53,648,817 shares, respectively"
       }
      }
     },
     "localname": "CommonStockValue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ComprehensiveIncomeNetOfTax": {
     "auth_ref": [
      "r91",
      "r93",
      "r94"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "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",
        "totalLabel": "Comprehensive income available for common stock"
       }
      }
     },
     "localname": "ComprehensiveIncomeNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r91",
      "r93",
      "r277",
      "r285"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ComprehensiveIncomeNoteTextBlock": {
     "auth_ref": [
      "r105"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.",
        "label": "Comprehensive Income (Loss) Note [Text Block]",
        "terseLabel": "Other Comprehensive Income (Loss)"
       }
      }
     },
     "localname": "ComprehensiveIncomeNoteTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLoss"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ContributionsInAidOfConstruction": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Developers, builders, governmental agencies and municipalities will provide the entity with cash, or in some cases property, to extend its services to their properties. Nonrefundable contributions are recorded as contributions in aid of construction (\"CIAC\").",
        "label": "Contributions in Aid of Construction",
        "terseLabel": "CIAC current portion"
       }
      }
     },
     "localname": "ContributionsInAidOfConstruction",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CorporateNonSegmentMember": {
     "auth_ref": [
      "r181"
     ],
     "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]",
        "verboseLabel": "Corporate"
       }
      }
     },
     "localname": "CorporateNonSegmentMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CostOfSalesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing cost of sales.",
        "label": "Cost of Sales [Member]",
        "terseLabel": "Cost of Sales"
       }
      }
     },
     "localname": "CostOfSalesMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CreditFacilityAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of credit facility. Credit facilities provide capital to borrowers without the need to structure a loan for each borrowing.",
        "label": "Credit Facility [Axis]",
        "terseLabel": "Credit Facility [Axis]"
       }
      }
     },
     "localname": "CreditFacilityAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_CreditFacilityDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Type of credit facility. Credit facilities provide capital to borrowers without the need to structure a loan for each borrowing.",
        "label": "Credit Facility [Domain]",
        "terseLabel": "Credit Facility [Domain]"
       }
      }
     },
     "localname": "CreditFacilityDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.",
        "label": "Cumulative Effect of New Accounting Principle in Period of Adoption",
        "terseLabel": "Cumulative Effect of New Accounting Principle in Period of Adoption"
       }
      }
     },
     "localname": "CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DebtDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Debt Disclosure [Abstract]"
       }
      }
     },
     "localname": "DebtDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DebtDisclosureTextBlock": {
     "auth_ref": [
      "r212"
     ],
     "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": "Notes Payable, Current Maturities and Debt"
       }
      }
     },
     "localname": "DebtDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebt"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DebtInstrumentTerm": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Debt Instrument, Term",
        "terseLabel": "Debt instrument, term"
       }
      }
     },
     "localname": "DebtInstrumentTerm",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_DeferredDerivativeGainLossMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of gain (loss) on derivative contracts.",
        "label": "Deferred Derivative Gain (Loss) [Member]",
        "terseLabel": "Deferred Derivative Gain (Loss)"
       }
      }
     },
     "localname": "DeferredDerivativeGainLossMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DeferredFuelCostsMember": {
     "auth_ref": [
      "r403"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of fuel costs incurred.",
        "label": "Deferred Fuel Costs [Member]",
        "terseLabel": "Deferred energy and gas costs",
        "verboseLabel": "Deferred energy and fuel cost adjustments"
       }
      }
     },
     "localname": "DeferredFuelCostsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DeferredIncomeTaxExpenseBenefit": {
     "auth_ref": [
      "r120",
      "r132",
      "r269",
      "r270"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 5.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "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 income taxes"
       }
      }
     },
     "localname": "DeferredIncomeTaxExpenseBenefit",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredRentReceivablesNet": {
     "auth_ref": [
      "r68",
      "r340",
      "r341",
      "r342"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property, by the lessor or lessee, respectively. Such receivable is reduced by allowances attributable to, for instance, credit risk associated with a lessee.",
        "label": "Deferred Rent Receivables, Net",
        "terseLabel": "Accrued Rent Receivable"
       }
      }
     },
     "localname": "DeferredRentReceivablesNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxAssetsGoodwillAndIntangibleAssets": {
     "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 intangible assets including goodwill.",
        "label": "Deferred Tax Assets, Goodwill and Intangible Assets",
        "terseLabel": "Deferred Tax Assets, Goodwill and Intangible Assets"
       }
      }
     },
     "localname": "DeferredTaxAssetsGoodwillAndIntangibleAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredTaxLiabilitiesNoncurrent": {
     "auth_ref": [
      "r264",
      "r265",
      "r266"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_LiabilitiesNoncurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences, with jurisdictional netting and classified as noncurrent.",
        "label": "Deferred Tax Liabilities, Net, Noncurrent",
        "terseLabel": "Deferred income tax liabilities, net"
       }
      }
     },
     "localname": "DeferredTaxLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPensionPlansAndDefinedBenefitPostretirementPlansDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Defined Benefit Plan [Abstract]"
       }
      }
     },
     "localname": "DefinedBenefitPensionPlansAndDefinedBenefitPostretirementPlansDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses": {
     "auth_ref": [
      "r241",
      "r254",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "order": 4.0,
       "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": "Net loss (gain)"
       }
      }
     },
     "localname": "DefinedBenefitPlanAmortizationOfGainsLosses",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit": {
     "auth_ref": [
      "r242",
      "r255",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "order": 3.0,
       "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": "Prior service cost (benefit)"
       }
      }
     },
     "localname": "DefinedBenefitPlanAmortizationOfPriorServiceCostCredit",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanContributionsByEmployer": {
     "auth_ref": [
      "r232",
      "r234",
      "r235",
      "r256",
      "r257"
     ],
     "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": "Contributions by Employer"
       }
      }
     },
     "localname": "DefinedBenefitPlanContributionsByEmployer",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear": {
     "auth_ref": [
      "r236"
     ],
     "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": "Estimated Future Employer Contributions in Next Fiscal Year"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsRemainderOfFiscalYear": {
     "auth_ref": [
      "r256"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.",
        "label": "Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year",
        "terseLabel": "Estimated Future Employer Contributions in Current Fiscal Year"
       }
      }
     },
     "localname": "DefinedBenefitPlanExpectedFutureEmployerContributionsRemainderOfFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets": {
     "auth_ref": [
      "r240",
      "r253",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "order": 5.0,
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanInterestCost": {
     "auth_ref": [
      "r231",
      "r239",
      "r252",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost": {
     "auth_ref": [
      "r237",
      "r250",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "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 benefit cost"
       }
      }
     },
     "localname": "DefinedBenefitPlanNetPeriodicBenefitCost",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]",
        "terseLabel": "Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]"
       }
      }
     },
     "localname": "DefinedBenefitPlanNetPeriodicBenefitCostAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DefinedBenefitPlanServiceCost": {
     "auth_ref": [
      "r230",
      "r238",
      "r251",
      "r257"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DepreciationDepletionAndAmortization": {
     "auth_ref": [
      "r120",
      "r171"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset": {
     "auth_ref": [
      "r71",
      "r75",
      "r288"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value of liability associated with financial asset or other 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, and obligation to return cash collateral under master netting arrangements.",
        "label": "Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset",
        "negatedTerseLabel": "Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset"
       }
      }
     },
     "localname": "DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeAssets": {
     "auth_ref": [
      "r72",
      "r73",
      "r331"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, after the effects of master netting arrangements, of a financial asset or other 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. Includes assets not subject to a master netting arrangement and not elected to be offset.",
        "label": "Derivative Asset",
        "terseLabel": "Derivative Assets, Commodity Derivatives"
       }
      }
     },
     "localname": "DerivativeAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeAssetsCurrent": {
     "auth_ref": [
      "r72"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 5.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, after the effects of master netting arrangements, of a financial asset or other 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 Asset, Current",
        "terseLabel": "Derivative assets, current"
       }
      }
     },
     "localname": "DerivativeAssetsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DerivativeFairValueOfDerivativeAsset": {
     "auth_ref": [
      "r70",
      "r74",
      "r300",
      "r377"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, before effects of master netting arrangements, of a financial asset or other 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.",
        "label": "Derivative Asset, Fair Value, Gross Asset",
        "terseLabel": "Derivative Asset, Fair Value, Gross Asset"
       }
      }
     },
     "localname": "DerivativeFairValueOfDerivativeAsset",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral": {
     "auth_ref": [
      "r72",
      "r73",
      "r76",
      "r314"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, after offset of derivative liability, of financial asset or other 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.",
        "label": "Derivative Asset, Fair Value, Amount Not Offset Against Collateral",
        "terseLabel": "Derivative Asset, Fair Value, Net"
       }
      }
     },
     "localname": "DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeFairValueOfDerivativeLiability": {
     "auth_ref": [
      "r70",
      "r74",
      "r300",
      "r377"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value, before 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. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.",
        "label": "Derivative Liability, Fair Value, Gross Liability",
        "terseLabel": "Derivative Liability, Fair Value, Gross Liability"
       }
      }
     },
     "localname": "DerivativeFairValueOfDerivativeLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeGainLossOnDerivativeNet": {
     "auth_ref": [
      "r299"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.",
        "label": "Derivative, Gain (Loss) on Derivative, Net",
        "terseLabel": "Derivative, Gain (Loss) on Derivative, Net"
       }
      }
     },
     "localname": "DerivativeGainLossOnDerivativeNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeInstrumentRiskAxis": {
     "auth_ref": [
      "r298",
      "r301",
      "r305",
      "r310"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Derivative Instruments and Hedging Activities Disclosure [Abstract]"
       }
      }
     },
     "localname": "DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock": {
     "auth_ref": [
      "r320"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.",
        "label": "Derivative Instruments and Hedging Activities Disclosure [Text Block]",
        "terseLabel": "Risk Management Activities"
       }
      }
     },
     "localname": "DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivities"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis": {
     "auth_ref": [
      "r294",
      "r298",
      "r305"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet": {
     "auth_ref": [
      "r304",
      "r309"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.",
        "label": "Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net",
        "terseLabel": "Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net"
       }
      }
     },
     "localname": "DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeLiabilities": {
     "auth_ref": [
      "r72",
      "r73",
      "r331"
     ],
     "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. Includes liabilities not subject to a master netting arrangement and not elected to be offset.",
        "label": "Derivative Liability",
        "terseLabel": "Derivative Liabilities, Fair Value Disclosure"
       }
      }
     },
     "localname": "DerivativeLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeLiabilitiesCurrent": {
     "auth_ref": [
      "r72"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "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": "Derivative liabilities, current"
       }
      }
     },
     "localname": "DerivativeLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset": {
     "auth_ref": [
      "r71",
      "r75",
      "r288"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value of asset associated with 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, and right to receive cash collateral under master netting arrangements.",
        "label": "Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset",
        "negatedTerseLabel": "Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset"
       }
      }
     },
     "localname": "DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DerivativeLineItems": {
     "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": "Derivative [Line Items]",
        "terseLabel": "Derivative [Line Items]"
       }
      }
     },
     "localname": "DerivativeLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Nominal energy measure used to calculate payments on a derivative instrument.",
        "label": "Derivative, Nonmonetary Notional Amount, Energy Measure",
        "terseLabel": "Derivative, Nonmonetary Notional Amount, Energy Measure"
       }
      }
     },
     "localname": "DerivativeNonmonetaryNotionalAmountEnergyMeasure",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "energyItemType"
    },
    "us-gaap_DerivativeRemainingMaturity1": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Derivative, Remaining Maturity",
        "terseLabel": "Derivative, Remaining Maturity"
       }
      }
     },
     "localname": "DerivativeRemainingMaturity1",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_DerivativeTable": {
     "auth_ref": [
      "r136",
      "r289",
      "r291",
      "r292",
      "r294",
      "r296",
      "r303",
      "r305",
      "r313",
      "r315",
      "r317"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule that describes and identifies a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.",
        "label": "Derivative [Table]",
        "terseLabel": "Derivative [Table]"
       }
      }
     },
     "localname": "DerivativeTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DerivativesAndFairValueTextBlock": {
     "auth_ref": [
      "r320",
      "r329"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for derivatives and fair value of assets and liabilities.",
        "label": "Derivatives and Fair Value [Text Block]",
        "terseLabel": "Fair Value Measurements"
       }
      }
     },
     "localname": "DerivativesAndFairValueTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurements"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DerivativesFairValueLineItems": {
     "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": "Derivatives, Fair Value [Line Items]",
        "terseLabel": "Derivatives, Carrying Amount and Fair Value [Line Items]"
       }
      }
     },
     "localname": "DerivativesFairValueLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DesignatedAsHedgingInstrumentMember": {
     "auth_ref": [
      "r294"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Derivative instrument designated as hedging instrument under Generally Accepted Accounting Principles (GAAP).",
        "label": "Designated as Hedging Instrument [Member]",
        "terseLabel": "Designated as Hedging Instrument"
       }
      }
     },
     "localname": "DesignatedAsHedgingInstrumentMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DilutiveSecuritiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]",
        "terseLabel": "Dilutive effect of:"
       }
      }
     },
     "localname": "DilutiveSecuritiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisaggregationOfRevenueLineItems": {
     "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": "Disaggregation of Revenue [Line Items]",
        "terseLabel": "Disaggregation of Revenue [Line Items]"
       }
      }
     },
     "localname": "DisaggregationOfRevenueLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisaggregationOfRevenueTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about 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]",
        "terseLabel": "Disaggregation of Revenue [Table]"
       }
      }
     },
     "localname": "DisaggregationOfRevenueTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisaggregationOfRevenueTableTextBlock": {
     "auth_ref": [
      "r220"
     ],
     "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": "Disaggregation of Revenue"
       }
      }
     },
     "localname": "DisaggregationOfRevenueTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerBasicShare": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_EarningsPerShareBasic",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation.",
        "label": "Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share",
        "terseLabel": "(Loss) from discontinued operations, Basic (usd per share)"
       }
      }
     },
     "localname": "DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerBasicShare",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_DiscontinuedOperationsAndDisposalGroupsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Discontinued Operations and Disposal Groups [Abstract]"
       }
      }
     },
     "localname": "DiscontinuedOperationsAndDisposalGroupsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_DiscontinuedOperationsHeldforsaleMember": {
     "auth_ref": [
      "r2",
      "r3",
      "r13"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Component or group of components classified as held-for-sale and representing a strategic shift that has or will have a major effect on operations and financial results. Includes a business or nonprofit activity on acquisition classified as held-for-sale.",
        "label": "Discontinued Operations, Held-for-sale [Member]",
        "terseLabel": "Discontinued Operations, Held-for-sale"
       }
      }
     },
     "localname": "DiscontinuedOperationsHeldforsaleMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DisposalGroupClassificationAxis": {
     "auth_ref": [
      "r13"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by disposal group classification.",
        "label": "Disposal Group Classification [Axis]",
        "terseLabel": "Disposal Group Classification [Axis]"
       }
      }
     },
     "localname": "DisposalGroupClassificationAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisposalGroupClassificationDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Component or group of components disposed of, including but not limited to, disposal group held-for-sale or disposed of by sale, disposed of by means other than sale, and discontinued operations.",
        "label": "Disposal Group Classification [Domain]",
        "terseLabel": "Disposal Group Classification [Domain]"
       }
      }
     },
     "localname": "DisposalGroupClassificationDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationBalanceSheetDisclosuresAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationBalanceSheetDisclosuresAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationDeferredTaxAssetsNoncurrent": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r196",
      "r202"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as deferred tax assets attributable to disposal group held for sale or disposed of, expected to be disposed of after one year or the normal operating cycle, if longer.",
        "label": "Disposal Group, Including Discontinued Operation, Deferred Tax Assets, Noncurrent",
        "terseLabel": "Deferred income tax assets, noncurrent, net"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationDeferredTaxAssetsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r197",
      "r202"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as other assets attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.",
        "label": "Disposal Group, Including Discontinued Operation, Other Assets, Current",
        "terseLabel": "Other current assets"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherLiabilities": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r202"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as other liabilities attributable to disposal group held for sale or disposed of.",
        "label": "Disposal Group, Including Discontinued Operation, Other Liabilities",
        "negatedLabel": "Other current liabilities"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationOtherLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r196",
      "r202"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as other liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of beyond one year or the normal operating cycle, if longer.",
        "label": "Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent",
        "negatedLabel": "Other noncurrent liabilities"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r202"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as property, plant and equipment attributable to disposal group held for sale or disposed of.",
        "label": "Disposal Group, Including Discontinued Operation, Property, Plant and Equipment",
        "terseLabel": "Property, plant and equipment, net"
       }
      }
     },
     "localname": "DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisposalGroupsIncludingDiscontinuedOperationsDisclosureTextBlock": {
     "auth_ref": [
      "r15",
      "r204"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.",
        "label": "Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]",
        "terseLabel": "Discontinued Operations"
       }
      }
     },
     "localname": "DisposalGroupsIncludingDiscontinuedOperationsDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperations"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_DividendsCommonStockCash": {
     "auth_ref": [
      "r214"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.",
        "label": "Dividends, Common Stock, Cash",
        "negatedTerseLabel": "Dividends on common stock"
       }
      }
     },
     "localname": "DividendsCommonStockCash",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EarningsPerShareAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Earnings Per Share [Abstract]",
        "terseLabel": "Earnings per share of common stock:"
       }
      }
     },
     "localname": "EarningsPerShareAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareBasic": {
     "auth_ref": [
      "r97",
      "r140",
      "r147",
      "r151",
      "r152",
      "r153",
      "r156",
      "r387",
      "r400"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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",
        "totalLabel": "Earnings (loss) per share, Basic (usd per share)"
       }
      }
     },
     "localname": "EarningsPerShareBasic",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_EarningsPerShareBasicAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Earnings Per Share, Basic [Abstract]",
        "terseLabel": "Earnings Per Share, Basic [Abstract]"
       }
      }
     },
     "localname": "EarningsPerShareBasicAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareDiluted": {
     "auth_ref": [
      "r97",
      "r140",
      "r147",
      "r151",
      "r152",
      "r153",
      "r156",
      "r387",
      "r400"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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",
        "totalLabel": "Earnings (loss) per share, Diluted (usd per share)"
       }
      }
     },
     "localname": "EarningsPerShareDiluted",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_EarningsPerShareDilutedAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Earnings Per Share, Diluted [Abstract]",
        "terseLabel": "Earnings Per Share, Diluted [Abstract]"
       }
      }
     },
     "localname": "EarningsPerShareDilutedAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareTextBlock": {
     "auth_ref": [
      "r157"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for earnings per share.",
        "label": "Earnings Per Share [Text Block]",
        "terseLabel": "Earnings Per Share"
       }
      }
     },
     "localname": "EarningsPerShareTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShare"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_EmployeeRelatedLiabilitiesCurrent": {
     "auth_ref": [
      "r56"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_AccruedLiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Employee-related Liabilities, Current",
        "terseLabel": "Accrued employee compensation, benefits and withholdings"
       }
      }
     },
     "localname": "EmployeeRelatedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EnergyAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of energy source.",
        "label": "Energy [Axis]",
        "terseLabel": "Energy [Axis]"
       }
      }
     },
     "localname": "EnergyAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EnergyDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Combustible material used to power engines, power plants or reactors. Examples include, but are not limited to, fuel and oil.",
        "label": "Energy [Domain]",
        "terseLabel": "Energy [Domain]"
       }
      }
     },
     "localname": "EnergyDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EnergyRelatedInventoryNaturalGasInStorage": {
     "auth_ref": [
      "r67"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount as of the balance sheet date of natural gas in storage, which is a mixture of gases (liquefied or otherwise), used for fuel and manufacturing purposes, which is ready for sale.",
        "label": "Energy Related Inventory, Natural Gas in Storage",
        "terseLabel": "Natural gas in storage held for distribution"
       }
      }
     },
     "localname": "EnergyRelatedInventoryNaturalGasInStorage",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EnergyRelatedInventoryOtherFossilFuel": {
     "auth_ref": [
      "r67"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of fossil fuel included in inventory classified as other.",
        "label": "Energy Related Inventory, Other Fossil Fuel",
        "terseLabel": "Fuel - Electric Utilities"
       }
      }
     },
     "localname": "EnergyRelatedInventoryOtherFossilFuel",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EnvironmentalRestorationCostsMember": {
     "auth_ref": [
      "r407"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of costs associated with site remediation or other environmental exit costs that may occur on the sale, disposal, abandonment or decommissioning of a property.",
        "label": "Environmental Restoration Costs [Member]",
        "terseLabel": "Decommissioning costs"
       }
      }
     },
     "localname": "EnvironmentalRestorationCostsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EquityComponentDomain": {
     "auth_ref": [
      "r213"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EstimateOfFairValueFairValueDisclosureMember": {
     "auth_ref": [
      "r331"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measured as an estimate of fair value.",
        "label": "Estimate of Fair Value Measurement [Member]",
        "terseLabel": "Estimate of Fair Value Measurement",
        "verboseLabel": "Fair Value"
       }
      }
     },
     "localname": "EstimateOfFairValueFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EurodollarMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Interest rate based on U.S. dollar denominated deposits at foreign banks or foreign branches of U.S. banks.",
        "label": "Eurodollar [Member]",
        "terseLabel": "Eurodollar"
       }
      }
     },
     "localname": "EurodollarMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable": {
     "auth_ref": [
      "r321",
      "r322",
      "r323",
      "r324",
      "r326",
      "r327"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are 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. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.",
        "label": "Fair Value Measurements, Recurring and Nonrecurring [Table]",
        "terseLabel": "Fair Value Measurements, Recurring and Nonrecurring [Table]"
       }
      }
     },
     "localname": "FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "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": "Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]"
       }
      }
     },
     "localname": "FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByBalanceSheetGroupingTable": {
     "auth_ref": [
      "r322",
      "r332",
      "r333"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByBalanceSheetGroupingTextBlock": {
     "auth_ref": [
      "r322",
      "r332"
     ],
     "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": "Fair Value of Financial Instruments"
       }
      }
     },
     "localname": "FairValueByBalanceSheetGroupingTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FairValueByFairValueHierarchyLevelAxis": {
     "auth_ref": [
      "r234",
      "r235",
      "r257",
      "r323",
      "r373"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByMeasurementBasisAxis": {
     "auth_ref": [
      "r322",
      "r328"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByMeasurementFrequencyAxis": {
     "auth_ref": [
      "r321"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by measurement frequency.",
        "label": "Measurement Frequency [Axis]",
        "terseLabel": "Measurement Frequency [Axis]"
       }
      }
     },
     "localname": "FairValueByMeasurementFrequencyAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueDisclosuresAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Fair Value Disclosures [Abstract]"
       }
      }
     },
     "localname": "FairValueDisclosuresAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueDisclosuresTextBlock": {
     "auth_ref": [
      "r329"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstruments"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FairValueInputsLevel1Member": {
     "auth_ref": [
      "r234",
      "r235",
      "r257",
      "r323",
      "r374"
     ],
     "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": "Fair Value, Inputs, Level 1"
       }
      }
     },
     "localname": "FairValueInputsLevel1Member",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueInputsLevel2Member": {
     "auth_ref": [
      "r234",
      "r235",
      "r257",
      "r323",
      "r375"
     ],
     "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": "Fair Value, Inputs, Level 2"
       }
      }
     },
     "localname": "FairValueInputsLevel2Member",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueInputsLevel3Member": {
     "auth_ref": [
      "r234",
      "r235",
      "r257",
      "r323",
      "r376"
     ],
     "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": "Fair Value, Inputs, Level 3"
       }
      }
     },
     "localname": "FairValueInputsLevel3Member",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueMeasurementFrequencyDomain": {
     "auth_ref": [
      "r321",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Provides the general categories used to describe the frequency with which financial assets and liabilities (as defined) are measured at fair value (on a recurring or nonrecurring basis).",
        "label": "Fair Value, Measurement Frequency [Domain]",
        "terseLabel": "Fair Value, Measurement Frequency [Domain]"
       }
      }
     },
     "localname": "FairValueMeasurementFrequencyDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueMeasurementsRecurringMember": {
     "auth_ref": [
      "r321",
      "r325"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This item represents a description of the frequency with which certain items are measured at fair value. Items measured at fair value on a recurring basis generally include those items for which measurement inputs are readily available and which are measured at fair value at successive reporting periods.",
        "label": "Fair Value, Measurements, Recurring [Member]",
        "terseLabel": "Fair Value, Measurements, Recurring"
       }
      }
     },
     "localname": "FairValueMeasurementsRecurringMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable": {
     "auth_ref": [
      "r297",
      "r303",
      "r316"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule that discloses the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position.",
        "label": "Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]",
        "terseLabel": "Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]"
       }
      }
     },
     "localname": "FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FinanceLeaseInterestExpense": {
     "auth_ref": [
      "r347",
      "r352",
      "r360"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails": {
       "order": 3.0,
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseInterestPaymentOnLiability": {
     "auth_ref": [
      "r349",
      "r354"
     ],
     "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 flows from finance lease"
       }
      }
     },
     "localname": "FinanceLeaseInterestPaymentOnLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Finance Lease Liabilities, Payments, Due [Abstract]",
        "terseLabel": "Finance Leases"
       }
      }
     },
     "localname": "FinanceLeaseLiabilitiesPaymentsDueAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FinanceLeaseLiability": {
     "auth_ref": [
      "r346",
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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",
        "terseLabel": "Present value of lease liabilities - Finance Leases"
       }
      }
     },
     "localname": "FinanceLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityCurrent": {
     "auth_ref": [
      "r346"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 2.0,
       "parentTag": "bkh_OperatingandFinanceLeaseLiabilities",
       "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": "Finance lease liability, current"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock": {
     "auth_ref": [
      "r359"
     ],
     "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": "Lessee - Finance Lease, Liability, Maturity"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityMaturityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FinanceLeaseLiabilityNoncurrent": {
     "auth_ref": [
      "r346"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 4.0,
       "parentTag": "bkh_OperatingandFinanceLeaseLiabilities",
       "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": "Finance lease liability, non-current"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDue": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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, Payments, Due",
        "totalLabel": "Total lease payments"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2023"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearFive",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2022"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearFour",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2021"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearThree",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2020"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsDueYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 2.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsRemainderofFiscalYear",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for finance lease, due in remainder of fiscal year following latest fiscal year ended.",
        "label": "Finance Lease, Liability, Payments, Remainder of Fiscal Year",
        "terseLabel": "2019"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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",
        "terseLabel": "Less imputed interest"
       }
      }
     },
     "localname": "FinanceLeaseLiabilityUndiscountedExcessAmount",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeasePrincipalPayments": {
     "auth_ref": [
      "r348",
      "r354"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow for principal payment on finance lease.",
        "label": "Finance Lease, Principal Payments",
        "terseLabel": "Financing cash flows from finance lease"
       }
      }
     },
     "localname": "FinanceLeasePrincipalPayments",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseRightOfUseAsset": {
     "auth_ref": [
      "r345"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 2.0,
       "parentTag": "bkh_OperatingandFinanceLeaseAssets",
       "weight": 1.0
      }
     },
     "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",
        "terseLabel": "Finance lease assets"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAsset",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseRightOfUseAssetAmortization": {
     "auth_ref": [
      "r347",
      "r352",
      "r360"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails": {
       "order": 2.0,
       "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 asset"
       }
      }
     },
     "localname": "FinanceLeaseRightOfUseAssetAmortization",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent": {
     "auth_ref": [
      "r357",
      "r360"
     ],
     "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 leases"
       }
      }
     },
     "localname": "FinanceLeaseWeightedAverageDiscountRatePercent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeWeightedAverageInformationDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_FinanceLeaseWeightedAverageRemainingLeaseTerm1": {
     "auth_ref": [
      "r356",
      "r360"
     ],
     "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 leases"
       }
      }
     },
     "localname": "FinanceLeaseWeightedAverageRemainingLeaseTerm1",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeWeightedAverageInformationDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_FutureMember": {
     "auth_ref": [
      "r306"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Futures contracts are forward-based contracts to make or take delivery of a specified financial instrument, foreign currency, or commodity at a specified future date or during a specified period at as specified price or yield. Futures are standardized contracts traded on an organized exchange.",
        "label": "Future [Member]",
        "terseLabel": "Natural gas futures purchased"
       }
      }
     },
     "localname": "FutureMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Goodwill": {
     "auth_ref": [
      "r191",
      "r192"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment",
       "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",
        "terseLabel": "Goodwill"
       }
      }
     },
     "localname": "Goodwill",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_HedgingDesignationAxis": {
     "auth_ref": [
      "r294",
      "r311"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by designation of purpose of derivative instrument.",
        "label": "Hedging Designation [Axis]",
        "terseLabel": "Hedging Designation [Axis]"
       }
      }
     },
     "localname": "HedgingDesignationAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_HedgingDesignationDomain": {
     "auth_ref": [
      "r294"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Designation of purpose of derivative instrument.",
        "label": "Hedging Designation [Domain]",
        "terseLabel": "Hedging Designation [Domain]"
       }
      }
     },
     "localname": "HedgingDesignationDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_HedgingRelationshipDomain": {
     "auth_ref": [
      "r294"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesUtilitiesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperations": {
     "auth_ref": [
      "r99",
      "r121",
      "r153",
      "r276"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnauditedCalc2": {
       "order": 1.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of income (loss) from continuing operations attributable to the parent.",
        "label": "Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent",
        "terseLabel": "Net income from continuing operations"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperations",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments": {
     "auth_ref": [
      "r135"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.",
        "label": "Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest",
        "terseLabel": "Income before income taxes",
        "totalLabel": "Income before income taxes"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r277"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_ProfitLoss",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest.",
        "label": "Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest",
        "terseLabel": "Income from continuing operations",
        "totalLabel": "Income from continuing operations"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperationsPerBasicShare": {
     "auth_ref": [
      "r96",
      "r97",
      "r147",
      "r151",
      "r152",
      "r385",
      "r386",
      "r387",
      "r399"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_EarningsPerShareBasic",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.",
        "label": "Income (Loss) from Continuing Operations, Per Basic Share",
        "terseLabel": "Income from continuing operations, Basic (usd per share)"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperationsPerBasicShare",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare": {
     "auth_ref": [
      "r96",
      "r97",
      "r147",
      "r151",
      "r152",
      "r153",
      "r387",
      "r399",
      "r400"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_EarningsPerShareDiluted",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of net income (loss) derived from continuing operations during 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": "Income (Loss) from Continuing Operations, Per Diluted Share",
        "terseLabel": "Income from continuing operations, Diluted (usd per share)"
       }
      }
     },
     "localname": "IncomeLossFromContinuingOperationsPerDilutedShare",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity": {
     "auth_ref": [
      "r4",
      "r5",
      "r6",
      "r7",
      "r8",
      "r10",
      "r14",
      "r277"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_ProfitLoss",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnauditedCalc2": {
       "order": 2.0,
       "parentTag": "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of income (loss) from a discontinued operation attributable to the parent. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.",
        "label": "Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent",
        "negatedTerseLabel": "Loss from discontinued operations, net of tax",
        "terseLabel": "Net (loss) from discontinued operations"
       }
      }
     },
     "localname": "IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare": {
     "auth_ref": [
      "r150",
      "r151",
      "r152",
      "r286"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_EarningsPerShareDiluted",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Per diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.",
        "label": "Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share",
        "terseLabel": "(Loss) from discontinued operations, Diluted (usd per share)"
       }
      }
     },
     "localname": "IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_IncomeStatementAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Income Statement [Abstract]"
       }
      }
     },
     "localname": "IncomeStatementAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeStatementLocationAxis": {
     "auth_ref": [
      "r201"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeTaxDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Income Tax Disclosure [Abstract]"
       }
      }
     },
     "localname": "IncomeTaxDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeTaxDisclosureTextBlock": {
     "auth_ref": [
      "r273"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/IncomeTaxes"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_IncomeTaxExpenseBenefit": {
     "auth_ref": [
      "r132",
      "r172",
      "r272"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": -1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "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)",
        "negatedTerseLabel": "Income tax benefit (expense)",
        "terseLabel": "Income Tax Expense (Benefit)"
       }
      }
     },
     "localname": "IncomeTaxExpenseBenefit",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/IncomeTaxesDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate": {
     "auth_ref": [
      "r263",
      "r267",
      "r268"
     ],
     "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": "Income tax benefit for deferred tax amortization related to tax reform",
        "verboseLabel": "Income tax expense (benefit) associated with changes in the prior estimated impact of tax reform on deferred income taxes"
       }
      }
     },
     "localname": "IncomeTaxReconciliationChangeInEnactedTaxRate",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/IncomeTaxesDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTcjaDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxReconciliationTaxCreditsOther": {
     "auth_ref": [
      "r267",
      "r268"
     ],
     "crdr": "credit",
     "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 other tax credits.",
        "label": "Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount",
        "terseLabel": "Increase in income tax benefit from forecasted federal production tax credits and state investment tax credits"
       }
      }
     },
     "localname": "IncomeTaxReconciliationTaxCreditsOther",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/IncomeTaxesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxesPaidNet": {
     "auth_ref": [
      "r123"
     ],
     "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",
        "negatedTerseLabel": "Income taxes"
       }
      }
     },
     "localname": "IncomeTaxesPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncomeTaxesReceivable": {
     "auth_ref": [
      "r63",
      "r383",
      "r398"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 6.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.",
        "label": "Income Taxes Receivable, Current",
        "terseLabel": "Income tax receivable, net"
       }
      }
     },
     "localname": "IncomeTaxesReceivable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 9.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in receivables, and operating assets classified as other.",
        "label": "Increase (Decrease) in Accounts Receivable and Other Operating Assets",
        "negatedLabel": "Accounts receivable, unbilled revenues and other operating assets"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccountsReceivableAndOtherOperatingAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInInventories": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 8.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "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": "Materials, supplies and fuel"
       }
      }
     },
     "localname": "IncreaseDecreaseInInventories",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOperatingCapitalAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Increase (Decrease) in Operating Capital [Abstract]",
        "terseLabel": "Changes in certain operating assets and liabilities:"
       }
      }
     },
     "localname": "IncreaseDecreaseInOperatingCapitalAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in other obligations or expenses incurred but not yet paid.",
        "label": "Increase (Decrease) in Other Accounts Payable and Accrued Liabilities",
        "terseLabel": "Accounts payable and other operating liabilities"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 13.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in operating assets after deduction of operating liabilities classified as other.",
        "label": "Increase (Decrease) in Other Operating Assets and Liabilities, Net",
        "negatedLabel": "Other operating activities, net"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherOperatingCapitalNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherRegulatoryAssets": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 11.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the value of other assets that are created when regulatory agencies permits public utilities to defer costs to the balance sheet.",
        "label": "Increase (Decrease) in Other Regulatory Assets",
        "negatedTerseLabel": "Regulatory assets - current"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherRegulatoryAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInRegulatoryLiabilities": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 12.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in regulated liabilities. Regulated liabilities are created when regulatory agency permits an entity to defer revenues to the balance sheet.",
        "label": "Increase (Decrease) in Regulatory Liabilities",
        "terseLabel": "Regulatory liabilities - current"
       }
      }
     },
     "localname": "IncreaseDecreaseInRegulatoryLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "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 [Roll Forward]"
       }
      }
     },
     "localname": "IncreaseDecreaseInStockholdersEquityRollForward",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncrementalCommonSharesAttributableToEquityUnitPurchaseAgreements": {
     "auth_ref": [
      "r148",
      "r153"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails": {
       "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 equity unit purchase agreements using the treasury stock method.",
        "label": "Incremental Common Shares Attributable to Dilutive Effect of Equity Unit Purchase Agreements",
        "terseLabel": "Equity Units (in shares)"
       }
      }
     },
     "localname": "IncrementalCommonSharesAttributableToEquityUnitPurchaseAgreements",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements": {
     "auth_ref": [
      "r149",
      "r155"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails": {
       "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 share based payment arrangements using the treasury stock method.",
        "label": "Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements",
        "terseLabel": "Equity compensation (in shares)"
       }
      }
     },
     "localname": "IncrementalCommonSharesAttributableToShareBasedPaymentArrangements",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_IntangibleAssetsNetExcludingGoodwill": {
     "auth_ref": [
      "r194",
      "r195"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment",
       "weight": 1.0
      }
     },
     "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)",
        "terseLabel": "Intangible assets, net"
       }
      }
     },
     "localname": "IntangibleAssetsNetExcludingGoodwill",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestAndDebtExpenseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Interest and Debt Expense [Abstract]",
        "terseLabel": "Interest charges -"
       }
      }
     },
     "localname": "InterestAndDebtExpenseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_InterestCostsIncurred": {
     "auth_ref": [
      "r335"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NonoperatingIncomeExpense",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total interest costs incurred during the period and either capitalized or charged against earnings.",
        "label": "Interest Costs Incurred",
        "negatedTerseLabel": "Interest expense incurred net of amounts capitalized (including amortization of debt issuance costs, premiums and discounts)",
        "terseLabel": "Interest expense"
       }
      }
     },
     "localname": "InterestCostsIncurred",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestExpenseMember": {
     "auth_ref": [
      "r309"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing interest expense.",
        "label": "Interest Expense [Member]",
        "terseLabel": "Interest expense incurred net of amounts capitalized (including amortization of debt issuance costs, premiums and discounts)"
       }
      }
     },
     "localname": "InterestExpenseMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_InterestIncomeExpenseNet": {
     "auth_ref": [
      "r388"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The net amount of operating interest income (expense).",
        "label": "Interest Income (Expense), Net",
        "terseLabel": "Interest expense, net"
       }
      }
     },
     "localname": "InterestIncomeExpenseNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestPaidNet": {
     "auth_ref": [
      "r114",
      "r117",
      "r123"
     ],
     "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",
        "negatedTerseLabel": "Interest (net of amounts capitalized)"
       }
      }
     },
     "localname": "InterestPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestPayableCurrent": {
     "auth_ref": [
      "r21",
      "r22",
      "r56"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "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 [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": "Accrued interest and contract adjustment payments"
       }
      }
     },
     "localname": "InterestPayableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestRateSwapMember": {
     "auth_ref": [
      "r307"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Forward based contracts in which two parties agree to swap periodic payments that are fixed at the outset of the swap contract with variable payments based on a market interest rate (index rate) over a specified period.",
        "label": "Interest Rate Swap [Member]",
        "terseLabel": "Interest rate swaps",
        "verboseLabel": "Interest Rate Swaps"
       }
      }
     },
     "localname": "InterestRateSwapMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IntersegmentEliminationMember": {
     "auth_ref": [
      "r176"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Eliminating entries used in operating segment consolidation.",
        "label": "Intersegment Eliminations [Member]",
        "terseLabel": "Inter-company Revenues"
       }
      }
     },
     "localname": "IntersegmentEliminationMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_InventoryDisclosureTextBlock": {
     "auth_ref": [
      "r190"
     ],
     "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": "Materials, Supplies and Fuel"
       }
      }
     },
     "localname": "InventoryDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuel"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_InventoryNet": {
     "auth_ref": [
      "r17",
      "r67",
      "r189"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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": "Materials, supplies and fuel",
        "totalLabel": "Total materials, supplies and fuel"
       }
      }
     },
     "localname": "InventoryNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InventoryNetAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Inventory, Net [Abstract]"
       }
      }
     },
     "localname": "InventoryNetAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_InventoryRawMaterialsAndSupplies": {
     "auth_ref": [
      "r66"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_InventoryNet",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.",
        "label": "Inventory, Raw Materials and Supplies, Gross",
        "terseLabel": "Materials and supplies"
       }
      }
     },
     "localname": "InventoryRawMaterialsAndSupplies",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InvestmentIncomeInterest": {
     "auth_ref": [
      "r102",
      "r170"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_NonoperatingIncomeExpense",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.",
        "label": "Investment Income, Interest",
        "terseLabel": "Interest income"
       }
      }
     },
     "localname": "InvestmentIncomeInterest",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LeaseCost": {
     "auth_ref": [
      "r358",
      "r360"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LeaseCostTableTextBlock": {
     "auth_ref": [
      "r358"
     ],
     "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": "Lease, Cost"
       }
      }
     },
     "localname": "LeaseCostTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.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/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Lessee Disclosure [Abstract]"
       }
      }
     },
     "localname": "LesseeDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeFinanceLeasesTextBlock": {
     "auth_ref": [
      "r361"
     ],
     "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": "Lessee, Finance Leases"
       }
      }
     },
     "localname": "LesseeFinanceLeasesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeLeaseDescriptionTable": {
     "auth_ref": [
      "r351"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock": {
     "auth_ref": [
      "r359"
     ],
     "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": "Lessee, Operating Lease, Liability, Maturity"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityMaturityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2023"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearFive",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2022"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearFour",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2021"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearThree",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "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": "2020"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsDueYearTwo",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 1.0,
       "parentTag": "bkh_LeaseLiabilityPaymentsRemainderofFiscalYear",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's undiscounted obligation for lease payments for operating lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year.",
        "label": "Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year",
        "terseLabel": "2019"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount": {
     "auth_ref": [
      "r359"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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",
        "terseLabel": "Less imputed interest"
       }
      }
     },
     "localname": "LesseeOperatingLeaseLiabilityUndiscountedExcessAmount",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LesseeOperatingLeasesTextBlock": {
     "auth_ref": [
      "r361"
     ],
     "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": "Lessee, Operating Leases"
       }
      }
     },
     "localname": "LesseeOperatingLeasesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/Leases"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LessorDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Lessor Disclosure [Abstract]"
       }
      }
     },
     "localname": "LessorDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LessorLeaseDescriptionLineItems": {
     "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": "Lessor, Lease, Description [Line Items]",
        "terseLabel": "Lessor, Lease, Description [Line Items]"
       }
      }
     },
     "localname": "LessorLeaseDescriptionLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LessorLeaseDescriptionTable": {
     "auth_ref": [
      "r365"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about lessor's leases.",
        "label": "Lessor, Lease, Description [Table]",
        "terseLabel": "Lessor, Lease, Description [Table]"
       }
      }
     },
     "localname": "LessorLeaseDescriptionTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsFiscalYearMaturityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]",
        "terseLabel": "Operating Leases"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsFiscalYearMaturityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceived": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor for operating lease.",
        "label": "Lessor, Operating Lease, Payments to be Received",
        "totalLabel": "Total lease receivables"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceived",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedFiveYears": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor in fifth fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Five Years",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedFiveYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedFourYears": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor in fourth year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Four Years",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedFourYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor in remainder of fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year",
        "terseLabel": "2019"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedRemainderOfFiscalYear",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedThereafter": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor after fifth fiscal year following latest statement of financial position date for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Thereafter",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedThereafter",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedThreeYears": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor in third fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Three Years",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedThreeYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeasePaymentsToBeReceivedTwoYears": {
     "auth_ref": [
      "r363"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_LessorOperatingLeasePaymentsToBeReceived",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lease payments to be received by lessor in second fiscal year following latest fiscal year for operating lease. Excludes interim and annual periods when interim periods are reported on rolling approach, from latest statement of financial position date.",
        "label": "Lessor, Operating Lease, Payments to be Received, Two Years",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "LessorOperatingLeasePaymentsToBeReceivedTwoYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LessorOperatingLeaseTermOfContract": {
     "auth_ref": [
      "r364"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Lessor, Operating Lease, Term of Contract",
        "terseLabel": "Lessor - Lease Term"
       }
      }
     },
     "localname": "LessorOperatingLeaseTermOfContract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_LetterOfCreditMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A document typically issued by a financial institution which acts as a guarantee of payment to a beneficiary, or as the source of payment for a specific transaction (for example, wiring funds to a foreign exporter if and when specified merchandise is accepted pursuant to the terms of the letter of credit).",
        "label": "Letter of Credit [Member]",
        "terseLabel": "Letter of Credit"
       }
      }
     },
     "localname": "LetterOfCreditMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_LettersOfCreditOutstandingAmount": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.",
        "label": "Letters of Credit Outstanding, Amount",
        "terseLabel": "Letters of Credit"
       }
      }
     },
     "localname": "LettersOfCreditOutstandingAmount",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquity": {
     "auth_ref": [
      "r40",
      "r381",
      "r394"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "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 TOTAL EQUITY"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities and Equity [Abstract]",
        "terseLabel": "LIABILITIES AND TOTAL EQUITY"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesCurrent": {
     "auth_ref": [
      "r57"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesFairValueDisclosure": {
     "auth_ref": [
      "r322"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value of financial and nonfinancial obligations.",
        "label": "Financial and Nonfinancial Liabilities, Fair Value Disclosure",
        "terseLabel": "Derivative Liabilities, Total"
       }
      }
     },
     "localname": "LiabilitiesFairValueDisclosure",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesNoncurrent": {
     "auth_ref": [
      "r24",
      "r25",
      "r26",
      "r30",
      "r31"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of obligation due after one year or beyond the normal operating cycle, if longer.",
        "label": "Liabilities, Noncurrent",
        "totalLabel": "Total deferred credits and other liabilities"
       }
      }
     },
     "localname": "LiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesNoncurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities, Noncurrent [Abstract]",
        "terseLabel": "Deferred credits and other liabilities:"
       }
      }
     },
     "localname": "LiabilitiesNoncurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r13",
      "r202"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as liabilities attributable to disposal group held for sale or disposed of.",
        "label": "Disposal Group, Including Discontinued Operation, Liabilities",
        "negatedTerseLabel": "Net (liabilities)"
       }
      }
     },
     "localname": "LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/DiscontinuedOperationsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent": {
     "auth_ref": [
      "r0",
      "r1",
      "r12",
      "r13",
      "r197",
      "r202"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 7.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount classified as liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.",
        "label": "Disposal Group, Including Discontinued Operation, Liabilities, Current",
        "terseLabel": "Current liabilities held for sale"
       }
      }
     },
     "localname": "LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity": {
     "auth_ref": [
      "r53"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.",
        "label": "Line of Credit Facility, Current Borrowing Capacity",
        "terseLabel": "Current borrowing capacity"
       }
      }
     },
     "localname": "LineOfCreditFacilityCurrentBorrowingCapacity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd": {
     "auth_ref": [
      "r53"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The effective interest rate at the end of the reporting period.",
        "label": "Line of Credit Facility, Interest Rate at Period End",
        "terseLabel": "Interest rate"
       }
      }
     },
     "localname": "LineOfCreditFacilityInterestRateAtPeriodEnd",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_LineOfCreditFacilityLineItems": {
     "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": "Line of Credit Facility [Line Items]",
        "terseLabel": "Line of Credit Facility [Line Items]"
       }
      }
     },
     "localname": "LineOfCreditFacilityLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity": {
     "auth_ref": [
      "r53"
     ],
     "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": "Maximum borrowing capacity"
       }
      }
     },
     "localname": "LineOfCreditFacilityMaximumBorrowingCapacity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LineOfCreditFacilityTable": {
     "auth_ref": [
      "r53",
      "r134"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A table or schedule providing information pertaining to short-term or long-term contractual arrangements with lenders, including letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to 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.",
        "label": "Line of Credit Facility [Table]",
        "terseLabel": "Line of Credit Facility [Table]"
       }
      }
     },
     "localname": "LineOfCreditFacilityTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.",
        "label": "Line of Credit Facility, Unused Capacity, Commitment Fee Percentage",
        "terseLabel": "Commitment fee"
       }
      }
     },
     "localname": "LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_LoansNotesTradeAndOtherReceivablesDisclosureTextBlock": {
     "auth_ref": [
      "r35",
      "r41",
      "r185",
      "r186",
      "r187",
      "r382",
      "r395",
      "r402"
     ],
     "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]",
        "terseLabel": "Accounts Receivable"
       }
      }
     },
     "localname": "LoansNotesTradeAndOtherReceivablesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivable"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LongTermDebt": {
     "auth_ref": [
      "r30",
      "r211",
      "r380",
      "r392"
     ],
     "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, including current maturities"
       }
      }
     },
     "localname": "LongTermDebt",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtCurrent": {
     "auth_ref": [
      "r55"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 6.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "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 maturities of long-term debt"
       }
      }
     },
     "localname": "LongTermDebtCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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",
        "terseLabel": "Long-term debt, including current maturities, Fair Value"
       }
      }
     },
     "localname": "LongTermDebtFairValue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermDebtNoncurrent": {
     "auth_ref": [
      "r58"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LongTermInvestments": {
     "auth_ref": [
      "r46"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).",
        "label": "Long-term Investments",
        "terseLabel": "Investments"
       }
      }
     },
     "localname": "LongTermInvestments",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LossOnReacquiredDebtMember": {
     "auth_ref": [
      "r403",
      "r408"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of loss incurred on reacquisition or refinancing of debt.",
        "label": "Loss on Reacquired Debt [Member]",
        "terseLabel": "Loss on reacquired debt"
       }
      }
     },
     "localname": "LossOnReacquiredDebtMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MaterialReconcilingItemsMember": {
     "auth_ref": [
      "r176",
      "r177"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Items used in reconciling reportable segments' amounts to consolidated amount. Excludes corporate-level activity.",
        "label": "Segment Reconciling Items [Member]",
        "terseLabel": "Segment Reconciling Items [Member]"
       }
      }
     },
     "localname": "MaterialReconcilingItemsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders": {
     "auth_ref": [
      "r214"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.",
        "label": "Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders",
        "negatedTerseLabel": "Distribution to noncontrolling interest"
       }
      }
     },
     "localname": "MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInFinancingActivities": {
     "auth_ref": [
      "r116"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect",
       "weight": 1.0
      }
     },
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Financing Activities [Abstract]",
        "terseLabel": "Financing activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInFinancingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivities": {
     "auth_ref": [
      "r116"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect",
       "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",
        "totalLabel": "Net cash provided by (used in) investing activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Investing Activities [Abstract]",
        "terseLabel": "Investing activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations": {
     "auth_ref": [
      "r116"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) of investing activities, excluding 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, Continuing Operations",
        "totalLabel": "Net cash provided by (used in) investing activities of continuing operations"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivitiesContinuingOperations",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivities": {
     "auth_ref": [
      "r116",
      "r118",
      "r121"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect",
       "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",
        "totalLabel": "Net cash provided by operating activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Cash Provided by (Used in) Operating Activities [Abstract]",
        "terseLabel": "Operating activities:"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations": {
     "auth_ref": [
      "r116",
      "r118",
      "r121"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash inflow (outflow) from operating activities, excluding 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, Continuing Operations",
        "totalLabel": "Net cash provided by operating activities of continuing operations"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetIncomeLossAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r89",
      "r92",
      "r279",
      "r284"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "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",
        "negatedLabel": "Net income attributable to noncontrolling interest"
       }
      }
     },
     "localname": "NetIncomeLossAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest": {
     "auth_ref": [
      "r100"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.",
        "label": "Net Income (Loss) Attributable to Redeemable Noncontrolling Interest",
        "negatedTerseLabel": "Less: comprehensive income attributable to noncontrolling interest"
       }
      }
     },
     "localname": "NetIncomeLossAttributableToRedeemableNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic": {
     "auth_ref": [
      "r140",
      "r145"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnauditedCalc2": {
       "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 available for common stock",
        "totalLabel": "Net income available for common stock"
       }
      }
     },
     "localname": "NetIncomeLossAvailableToCommonStockholdersBasic",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NetRegulatoryAssetsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Net Regulatory Assets [Abstract]",
        "terseLabel": "Regulatory assets"
       }
      }
     },
     "localname": "NetRegulatoryAssetsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems": {
     "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 Pronouncements or Change in Accounting Principle [Line Items]",
        "terseLabel": "New Accounting Pronouncements or Change in Accounting Principle [Line Items]"
       }
      }
     },
     "localname": "NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable": {
     "auth_ref": [
      "r139",
      "r141",
      "r142"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summarization of the changes in an accounting principle or a new accounting pronouncement, including the line items affected by the change and the financial effects of the change on those particular line items.",
        "label": "New Accounting Pronouncements or Change in Accounting Principle [Table]",
        "terseLabel": "New Accounting Pronouncements or Change in Accounting Principle [Table]"
       }
      }
     },
     "localname": "NewAccountingPronouncementsOrChangeInAccountingPrincipleTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "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": "Recently Issued and Adopted Accounting Standards"
       }
      }
     },
     "localname": "NewAccountingPronouncementsPolicyPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_NoncashInvestingAndFinancingItemsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Noncash Investing and Financing Items [Abstract]",
        "terseLabel": "Non-cash Investing and Financing Activities from Continuing Operations [Abstract]"
       }
      }
     },
     "localname": "NoncashInvestingAndFinancingItemsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NoncontrollingInterestInVariableInterestEntity": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 6.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Portion of equity (net assets) in a variable interest entity (VIE) not attributable, directly or indirectly, to the parent entity. That is, this is the portion of equity in a VIE that is attributable to the noncontrolling interest (previously referred to as minority interest).",
        "label": "Noncontrolling Interest in Variable Interest Entity",
        "terseLabel": "Noncontrolling interest"
       }
      }
     },
     "localname": "NoncontrollingInterestInVariableInterestEntity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NoncontrollingInterestMember": {
     "auth_ref": [
      "r274"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This element represents that portion of equity (net assets) in a subsidiary not attributable, directly or indirectly, to the parent. A noncontrolling interest is sometimes called a minority interest.",
        "label": "Noncontrolling Interest [Member]",
        "terseLabel": "Noncontrolling Interest"
       }
      }
     },
     "localname": "NoncontrollingInterestMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_NondesignatedMember": {
     "auth_ref": [
      "r294"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Derivative instrument not designated as hedging instrument under Generally Accepted Accounting Principles (GAAP).",
        "label": "Not Designated as Hedging Instrument [Member]",
        "terseLabel": "Not Designated as Hedging Instrument"
       }
      }
     },
     "localname": "NondesignatedMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsBalanceSheetLocationDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_NonoperatingIncomeExpense": {
     "auth_ref": [
      "r103"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).",
        "label": "Nonoperating Income (Expense)",
        "totalLabel": "Total other income (expense)"
       }
      }
     },
     "localname": "NonoperatingIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_NonoperatingIncomeExpenseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Nonoperating Income (Expense) [Abstract]",
        "terseLabel": "Other income (expense):"
       }
      }
     },
     "localname": "NonoperatingIncomeExpenseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingExpenses": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.",
        "label": "Operating Expenses",
        "totalLabel": "Total operating expenses"
       }
      }
     },
     "localname": "OperatingExpenses",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingExpensesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Operating Expenses [Abstract]",
        "terseLabel": "Operating expenses:"
       }
      }
     },
     "localname": "OperatingExpensesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingIncomeLoss": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments",
       "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",
        "totalLabel": "Operating income"
       }
      }
     },
     "localname": "OperatingIncomeLoss",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseCost": {
     "auth_ref": [
      "r353",
      "r360"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeLeaseCostsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLeaseIncome": {
     "auth_ref": [
      "r158",
      "r362",
      "r366"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.",
        "label": "Operating Lease, Lease Income",
        "terseLabel": "Operating lease income"
       }
      }
     },
     "localname": "OperatingLeaseLeaseIncome",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLessorDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLeaseIncomeTableTextBlock": {
     "auth_ref": [
      "r158",
      "r366"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of components of income from operating lease.",
        "label": "Operating Lease, Lease Income [Table Text Block]",
        "terseLabel": "Operating Lease, Lease Income"
       }
      }
     },
     "localname": "OperatingLeaseLeaseIncomeTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Operating Lease Liabilities, Payments Due [Abstract]",
        "terseLabel": "Operating Leases"
       }
      }
     },
     "localname": "OperatingLeaseLiabilitiesPaymentsDueAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingLeaseLiability": {
     "auth_ref": [
      "r346"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetailsCalc2": {
       "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 liabilities",
        "verboseLabel": "Present Value of Lease Liabilities - Operating leases"
       }
      }
     },
     "localname": "OperatingLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails",
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilityCurrent": {
     "auth_ref": [
      "r346"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 1.0,
       "parentTag": "bkh_OperatingandFinanceLeaseLiabilities",
       "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": "Operating lease liability, current"
       }
      }
     },
     "localname": "OperatingLeaseLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilityNoncurrent": {
     "auth_ref": [
      "r346"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 3.0,
       "parentTag": "bkh_OperatingandFinanceLeaseLiabilities",
       "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": "Operating lease liability, non-current"
       }
      }
     },
     "localname": "OperatingLeaseLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasePayments": {
     "auth_ref": [
      "r350",
      "r354"
     ],
     "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 flows from operating leases"
       }
      }
     },
     "localname": "OperatingLeasePayments",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseRightOfUseAsset": {
     "auth_ref": [
      "r345"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails": {
       "order": 1.0,
       "parentTag": "bkh_OperatingandFinanceLeaseAssets",
       "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 assets",
        "verboseLabel": "Operating lease - right of use assets"
       }
      }
     },
     "localname": "OperatingLeaseRightOfUseAsset",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalBalanceSheetInformationDetails",
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent": {
     "auth_ref": [
      "r357",
      "r360"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeWeightedAverageInformationDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1": {
     "auth_ref": [
      "r356",
      "r360"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeWeightedAverageInformationDetails"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDue": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.",
        "label": "Operating Leases, Future Minimum Payments Due",
        "totalLabel": "Total lease payments"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 7.0,
       "parentTag": "us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments Due, Next Twelve Months",
        "terseLabel": "2019"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 5.0,
       "parentTag": "us-gaap_OperatingLeasesFutureMinimumPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments, Due in Five Years",
        "terseLabel": "2023"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueInFiveYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 4.0,
       "parentTag": "us-gaap_OperatingLeasesFutureMinimumPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments, Due in Four Years",
        "terseLabel": "2022"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueInFourYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_OperatingLeasesFutureMinimumPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments, Due in Three Years",
        "terseLabel": "2021"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueInThreeYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_OperatingLeasesFutureMinimumPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments, Due in Two Years",
        "terseLabel": "2020"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueInTwoYears",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter": {
     "auth_ref": [
      "r337",
      "r343"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails": {
       "order": 6.0,
       "parentTag": "us-gaap_OperatingLeasesFutureMinimumPaymentsDue",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year 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": "Operating Leases, Future Minimum Payments, Due Thereafter",
        "terseLabel": "Thereafter"
       }
      }
     },
     "localname": "OperatingLeasesFutureMinimumPaymentsDueThereafter",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeFutureMinimumPaymentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeasesOfLessorDisclosureTextBlock": {
     "auth_ref": [
      "r338",
      "r339",
      "r367"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for lessor's operating leases.",
        "label": "Lessor, Operating Leases [Text Block]",
        "verboseLabel": "Lessor, Operating Leases"
       }
      }
     },
     "localname": "OperatingLeasesOfLessorDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/Leases"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Organization, Consolidation and Presentation of Financial Statements [Abstract]"
       }
      }
     },
     "localname": "OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock": {
     "auth_ref": [
      "r138",
      "r143",
      "r166",
      "r287"
     ],
     "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": "Management's Statement"
       }
      }
     },
     "localname": "OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatement"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_OtherAccruedLiabilitiesCurrent": {
     "auth_ref": [
      "r20",
      "r21",
      "r22",
      "r56"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails": {
       "order": 6.0,
       "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 (none of which is individually significant)"
       }
      }
     },
     "localname": "OtherAccruedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherAssetsCurrent": {
     "auth_ref": [
      "r68"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 8.0,
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherAssetsNoncurrent": {
     "auth_ref": [
      "r49"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of noncurrent assets classified as other.",
        "label": "Other Assets, Noncurrent",
        "terseLabel": "Other assets, non-current"
       }
      }
     },
     "localname": "OtherAssetsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherAssetsNoncurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Other Assets, Noncurrent [Abstract]",
        "terseLabel": "Other assets:"
       }
      }
     },
     "localname": "OtherAssetsNoncurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax": {
     "auth_ref": [
      "r82",
      "r86",
      "r87",
      "r243"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "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",
        "terseLabel": "Reclassification adjustments of benefit plan liability - prior service cost"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax": {
     "auth_ref": [
      "r83"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax (expense) benefit 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, Tax",
        "negatedLabel": "Reclassification adjustment of benefit plan - prior service cost, (tax) benefit"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax": {
     "auth_ref": [
      "r85",
      "r95"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax, before reclassification adjustments of other comprehensive income (loss).",
        "label": "Other Comprehensive Income (Loss), before Reclassifications, Net of Tax",
        "terseLabel": "Other Comprehensive Income (Loss), before Reclassifications, Net of Tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax": {
     "auth_ref": [
      "r77"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount before tax, after 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).",
        "label": "Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax",
        "terseLabel": "Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossNetOfTax": {
     "auth_ref": [
      "r90",
      "r93",
      "r95",
      "r213"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "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",
        "totalLabel": "Other comprehensive income, net of tax",
        "verboseLabel": "Other comprehensive income"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "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), net of tax:"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax": {
     "auth_ref": [
      "r82",
      "r86",
      "r87",
      "r295"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).",
        "label": "Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax",
        "negatedLabel": "Reclassification of net realized (gains) losses"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax": {
     "auth_ref": [
      "r83"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).",
        "label": "Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax",
        "terseLabel": "Reclassification of net realized gains/losses, (tax) benefit"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax": {
     "auth_ref": [
      "r82",
      "r86",
      "r87",
      "r243"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.",
        "label": "Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax",
        "negatedLabel": "Reclassification adjustments of benefit plan liability - net gain (loss)"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax": {
     "auth_ref": [
      "r83",
      "r277"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan.",
        "label": "Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax",
        "negatedTerseLabel": "Reclassification adjustment of benefit plan liabilities, (tax) benefit"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax": {
     "auth_ref": [
      "r77",
      "r82",
      "r318"
     ],
     "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": "Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesCashFlowHedgesDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax": {
     "auth_ref": [
      "r77",
      "r82",
      "r318"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_OtherComprehensiveIncomeLossNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after 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, Net of Tax",
        "terseLabel": "Net unrealized gains (losses)"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax": {
     "auth_ref": [
      "r77",
      "r83"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax expense (benefit), before reclassification adjustments, related to 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, Tax",
        "negatedTerseLabel": "Net unrealized gains/losses, (tax) benefit"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherCostAndExpenseOperating": {
     "auth_ref": [
      "r101"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 5.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The total amount of other operating cost and expense items that are associated with the entity's normal revenue producing operation.",
        "label": "Other Cost and Expense, Operating",
        "terseLabel": "Other operating expenses"
       }
      }
     },
     "localname": "OtherCostAndExpenseOperating",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherLiabilitiesNoncurrent": {
     "auth_ref": [
      "r59"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_LiabilitiesNoncurrent",
       "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 deferred credits and other liabilities"
       }
      }
     },
     "localname": "OtherLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNoncashIncomeExpense": {
     "auth_ref": [
      "r121"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 7.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "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 adjustments, net"
       }
      }
     },
     "localname": "OtherNoncashIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNonoperatingExpense": {
     "auth_ref": [
      "r104"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails": {
       "order": 3.0,
       "parentTag": "us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expense related to nonoperating activities, classified as other.",
        "label": "Other Nonoperating Expense",
        "negatedTerseLabel": "Other income (expense), net"
       }
      }
     },
     "localname": "OtherNonoperatingExpense",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNonoperatingIncomeExpense": {
     "auth_ref": [
      "r104"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 5.0,
       "parentTag": "us-gaap_NonoperatingIncomeExpense",
       "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)",
        "terseLabel": "Other income (expense), net"
       }
      }
     },
     "localname": "OtherNonoperatingIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember": {
     "auth_ref": [
      "r227",
      "r246",
      "r247",
      "r258"
     ],
     "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": "Defined Benefit Postretirement Healthcare Plans"
       }
      }
     },
     "localname": "OtherPostretirementBenefitPlansDefinedBenefitMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_OtherRestructuringMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Restructuring and related activities classified as other.",
        "label": "Other Restructuring [Member]",
        "terseLabel": "Other Restructuring"
       }
      }
     },
     "localname": "OtherRestructuringMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PayablesAndAccrualsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Payables and Accruals [Abstract]"
       }
      }
     },
     "localname": "PayablesAndAccrualsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PaymentsForProceedsFromOtherInvestingActivities": {
     "auth_ref": [
      "r106",
      "r108",
      "r137"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations",
       "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 investing activities"
       }
      }
     },
     "localname": "PaymentsForProceedsFromOtherInvestingActivities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfDividends": {
     "auth_ref": [
      "r111"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.",
        "label": "Payments of Dividends",
        "negatedLabel": "Dividends paid on common stock"
       }
      }
     },
     "localname": "PaymentsOfDividends",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsOfStockIssuanceCosts": {
     "auth_ref": [
      "r113"
     ],
     "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",
        "terseLabel": "Payments of Stock Issuance Costs"
       }
      }
     },
     "localname": "PaymentsOfStockIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquireOtherInvestments": {
     "auth_ref": [
      "r108"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow to acquire investments classified as other.",
        "label": "Payments to Acquire Other Investments",
        "negatedTerseLabel": "Purchase of investment"
       }
      }
     },
     "localname": "PaymentsToAcquireOtherInvestments",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquirePropertyPlantAndEquipment": {
     "auth_ref": [
      "r107"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations",
       "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": "Property, plant and equipment additions"
       }
      }
     },
     "localname": "PaymentsToAcquirePropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToMinorityShareholders": {
     "auth_ref": [
      "r113"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 5.0,
       "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",
        "negatedTerseLabel": "Distributions to noncontrolling interest"
       }
      }
     },
     "localname": "PaymentsToMinorityShareholders",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementBenefitContributionsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Payment for Pension and Other Postretirement Benefits [Abstract]",
        "terseLabel": "Payment for Pension and Other Postretirement Benefits [Abstract]"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementBenefitContributionsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PensionAndOtherPostretirementBenefitExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 6.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost (reversal of cost) for pension and other postretirement benefits.",
        "label": "Pension and Other Postretirement Benefits Cost (Reversal of Cost)",
        "terseLabel": "Employee benefit plans"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementBenefitExpense",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock": {
     "auth_ref": [
      "r259"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for pension and other postretirement benefits.",
        "label": "Pension and Other Postretirement Benefits Disclosure [Text Block]",
        "terseLabel": "Employee Benefit Plans"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementBenefitsDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlans"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent": {
     "auth_ref": [
      "r32",
      "r228",
      "r229",
      "r233"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_LiabilitiesNoncurrent",
       "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",
        "terseLabel": "Benefit plan liabilities"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PensionAndOtherPostretirementPlansCostsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of pension and other postretirement costs.",
        "label": "Pension and Other Postretirement Plans Costs [Member]",
        "verboseLabel": "Employee benefit plans"
       }
      }
     },
     "localname": "PensionAndOtherPostretirementPlansCostsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PensionPlansDefinedBenefitMember": {
     "auth_ref": [
      "r226",
      "r246",
      "r247",
      "r258"
     ],
     "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]",
        "verboseLabel": "Defined Benefit Pension Plans"
       }
      }
     },
     "localname": "PensionPlansDefinedBenefitMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PortionAtFairValueFairValueDisclosureMember": {
     "auth_ref": [
      "r330"
     ],
     "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"
       }
      }
     },
     "localname": "PortionAtFairValueFairValueDisclosureMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsScheduleOfFairValuesDetails",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PriceRiskDerivativeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Derivative instrument whose primary underlying is tied to price risk.",
        "label": "Price Risk Derivative [Member]",
        "terseLabel": "Gas price derivatives"
       }
      }
     },
     "localname": "PriceRiskDerivativeMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ProceedsFromIssuanceOfCommonStock": {
     "auth_ref": [
      "r109"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 2.0,
       "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": "Common stock issued"
       }
      }
     },
     "localname": "ProceedsFromIssuanceOfCommonStock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromPaymentsForOtherFinancingActivities": {
     "auth_ref": [
      "r110",
      "r113",
      "r137"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 6.0,
       "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 financing activities"
       }
      }
     },
     "localname": "ProceedsFromPaymentsForOtherFinancingActivities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromRepaymentsOfShortTermDebt": {
     "auth_ref": [
      "r137"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.",
        "label": "Proceeds from (Repayments of) Short-term Debt",
        "terseLabel": "Net (payments) borrowings of short-term debt"
       }
      }
     },
     "localname": "ProceedsFromRepaymentsOfShortTermDebt",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProfitLoss": {
     "auth_ref": [
      "r89",
      "r92",
      "r115",
      "r173",
      "r180",
      "r277",
      "r278",
      "r280",
      "r284",
      "r285"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "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"
       }
      }
     },
     "localname": "ProfitLoss",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentGross": {
     "auth_ref": [
      "r47",
      "r198"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentNet": {
     "auth_ref": [
      "r27",
      "r28",
      "r200",
      "r396"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "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",
        "totalLabel": "Total property, plant and equipment, net"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentNet",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity": {
     "auth_ref": [
      "r411",
      "r412"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_NonoperatingIncomeExpense",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.",
        "label": "Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity",
        "terseLabel": "Allowance for funds used during construction - equity"
       }
      }
     },
     "localname": "PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PublicUtilitiesGeneralDisclosuresLineItems": {
     "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": "Public Utilities, General Disclosures [Line Items]",
        "terseLabel": "Public Utilities, General Disclosures [Line Items]"
       }
      }
     },
     "localname": "PublicUtilitiesGeneralDisclosuresLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PublicUtilitiesGeneralDisclosuresTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about regulation for public utility entities, including, but not limited to, rate requests, decommissioning costs and the amount of allowance for earnings on equity capitalized for rate making purposes.",
        "label": "Public Utilities General Disclosures [Table]",
        "terseLabel": "Public Utilities General Disclosures [Table]"
       }
      }
     },
     "localname": "PublicUtilitiesGeneralDisclosuresTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PublicUtilitiesRegulatoryProceedingAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by name of regulatory proceeding.",
        "label": "Public Utilities, Regulatory Proceeding [Axis]",
        "terseLabel": "Public Utilities, Regulatory Proceeding [Axis]"
       }
      }
     },
     "localname": "PublicUtilitiesRegulatoryProceedingAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PublicUtilitiesRegulatoryProceedingDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Proceeding with public utility's regulatory body.",
        "label": "Public Utilities, Regulatory Proceeding [Domain]",
        "terseLabel": "Public Utilities, Regulatory Proceeding [Domain]"
       }
      }
     },
     "localname": "PublicUtilitiesRegulatoryProceedingDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of public utility's requested rate increase (decrease) with regulatory agency.",
        "label": "Public Utilities, Requested Rate Increase (Decrease), Amount",
        "terseLabel": "Public Utilities, Requested Rate Increase, Amount"
       }
      }
     },
     "localname": "PublicUtilitiesRequestedRateIncreaseDecreaseAmount",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ReceivablesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Receivables [Abstract]"
       }
      }
     },
     "localname": "ReceivablesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems": {
     "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": "Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]",
        "terseLabel": "Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]"
       }
      }
     },
     "localname": "ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax": {
     "auth_ref": [
      "r85",
      "r88",
      "r95"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax of reclassification adjustments of other comprehensive income (loss).",
        "label": "Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax",
        "terseLabel": "Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax"
       }
      }
     },
     "localname": "ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ReclassificationFromAociCurrentPeriodTax": {
     "auth_ref": [
      "r83",
      "r87",
      "r271"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss).",
        "label": "Reclassification from AOCI, Current Period, Tax",
        "terseLabel": "Reclassification from AOCI, Current Period, Tax"
       }
      }
     },
     "localname": "ReclassificationFromAociCurrentPeriodTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by item reclassified out of accumulated other comprehensive income (loss).",
        "label": "Reclassification out of Accumulated Other Comprehensive Income [Axis]",
        "terseLabel": "Reclassification Out Of Accumulated Other Comprehensive Income [Axis]"
       }
      }
     },
     "localname": "ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Item reclassified out of accumulated other comprehensive income (loss).",
        "label": "Reclassification out of Accumulated Other Comprehensive Income [Domain]",
        "terseLabel": "Reclassification Out Of Accumulated Other Comprehensive Income [Domain]"
       }
      }
     },
     "localname": "ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Identifies item reclassified out of accumulated other comprehensive income (loss).",
        "label": "Reclassification out of Accumulated Other Comprehensive Income [Member]",
        "terseLabel": "Reclassification Out Of Accumulated Other Comprehensive Income"
       }
      }
     },
     "localname": "ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss).",
        "label": "Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]",
        "terseLabel": "Reclassification Out of Accumulated Other Comprehensive Income (Loss)"
       }
      }
     },
     "localname": "ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable": {
     "auth_ref": [
      "r175",
      "r177"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Identification, description, and amounts of all significant reconciling items in the reconciliation of total assets from reportable segments to the entity's consolidated assets.",
        "label": "Reconciliation of Assets from Segment to Consolidated [Table]",
        "terseLabel": "Reconciliation of Assets from Segment to Consolidated [Table]"
       }
      }
     },
     "localname": "ReconciliationOfAssetsFromSegmentToConsolidatedTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTextBlock": {
     "auth_ref": [
      "r175",
      "r177"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of all significant reconciling items in the reconciliation of total assets from reportable segments to the entity's consolidated assets.",
        "label": "Reconciliation of Assets from Segment to Consolidated [Table Text Block]",
        "terseLabel": "Reconciliation of Assets from Segment to Consolidated"
       }
      }
     },
     "localname": "ReconciliationOfAssetsFromSegmentToConsolidatedTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_RegulatoryAgencyAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by name of regulatory agency.",
        "label": "Regulatory Agency [Axis]",
        "terseLabel": "Regulatory Agency [Axis]"
       }
      }
     },
     "localname": "RegulatoryAgencyAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RegulatoryAgencyDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Organization that establishes and ensures compliance with rules or regulations.",
        "label": "Regulatory Agency [Domain]",
        "terseLabel": "Regulatory Agency [Domain]"
       }
      }
     },
     "localname": "RegulatoryAgencyDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingRateReviewDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RegulatoryAssetAxis": {
     "auth_ref": [
      "r404",
      "r405",
      "r410"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of regulatory asset.",
        "label": "Regulatory Asset [Axis]",
        "terseLabel": "Regulatory Asset [Axis]"
       }
      }
     },
     "localname": "RegulatoryAssetAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RegulatoryAssetDomain": {
     "auth_ref": [
      "r404"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization of costs incurred.",
        "label": "Regulatory Asset [Domain]",
        "terseLabel": "Regulatory Asset [Domain]"
       }
      }
     },
     "localname": "RegulatoryAssetDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RegulatoryAssets": {
     "auth_ref": [
      "r404"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.",
        "label": "Regulatory Assets",
        "terseLabel": "Regulatory assets",
        "totalLabel": "Regulatory assets"
       }
      }
     },
     "localname": "RegulatoryAssets",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails",
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesDerivativesNotDesignatedAsHedgeInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RegulatoryAssetsAndLiabilitiesDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Regulatory Assets and Liabilities Disclosure [Abstract]"
       }
      }
     },
     "localname": "RegulatoryAssetsAndLiabilitiesDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_RegulatoryAssetsAndLiabilitiesOtherDisclosuresAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Regulatory Assets and Liabilities, Other Disclosures [Abstract]",
        "terseLabel": "Regulatory liabilities"
       }
      }
     },
     "localname": "RegulatoryAssetsAndLiabilitiesOtherDisclosuresAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RegulatoryAssetsCurrent": {
     "auth_ref": [
      "r404"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 7.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_RegulatoryAssets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.",
        "label": "Regulatory Assets, Current",
        "negatedTerseLabel": "Less current regulatory assets",
        "terseLabel": "Regulatory assets, current"
       }
      }
     },
     "localname": "RegulatoryAssetsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RegulatoryAssetsNoncurrent": {
     "auth_ref": [
      "r404"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_RegulatoryAssets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.",
        "label": "Regulatory Assets, Noncurrent",
        "terseLabel": "Regulatory assets, non-current"
       }
      }
     },
     "localname": "RegulatoryAssetsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RegulatoryLiabilities": {
     "auth_ref": [
      "r406"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.",
        "label": "Regulatory Liabilities",
        "totalLabel": "Regulatory liabilities"
       }
      }
     },
     "localname": "RegulatoryLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RegulatoryLiabilityAxis": {
     "auth_ref": [
      "r406"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of regulatory liability.",
        "label": "Regulatory Liability [Axis]",
        "terseLabel": "Regulatory Liability [Axis]"
       }
      }
     },
     "localname": "RegulatoryLiabilityAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RegulatoryLiabilityCurrent": {
     "auth_ref": [
      "r406"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": 1.0,
       "parentTag": "us-gaap_RegulatoryLiabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.",
        "label": "Regulatory Liability, Current",
        "negatedTerseLabel": "Less current regulatory liabilities",
        "terseLabel": "Regulatory liabilities, current"
       }
      }
     },
     "localname": "RegulatoryLiabilityCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RegulatoryLiabilityDomain": {
     "auth_ref": [
      "r406"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in accrual of costs or expenses.",
        "label": "Regulatory Liability [Domain]",
        "terseLabel": "Regulatory Liability [Domain]"
       }
      }
     },
     "localname": "RegulatoryLiabilityDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RegulatoryLiabilityNoncurrent": {
     "auth_ref": [
      "r59"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_LiabilitiesNoncurrent",
       "weight": 1.0
      },
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_RegulatoryLiabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.",
        "label": "Regulatory Liability, Noncurrent",
        "terseLabel": "Regulatory liabilities, non-current"
       }
      }
     },
     "localname": "RegulatoryLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RelatedPartyTransactionLineItems": {
     "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": "Related Party Transaction [Line Items]",
        "terseLabel": "Related Party Transaction [Line Items]"
       }
      }
     },
     "localname": "RelatedPartyTransactionLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RemovalCostsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of removal costs.",
        "label": "Removal Costs [Member]",
        "terseLabel": "Cost of removal"
       }
      }
     },
     "localname": "RemovalCostsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RenewableEnergyProgramMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of costs related to implementation of renewable energy program.",
        "label": "Renewable Energy Program [Member]",
        "terseLabel": "Renewable energy standard adjustment"
       }
      }
     },
     "localname": "RenewableEnergyProgramMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RepaymentsOfLongTermDebt": {
     "auth_ref": [
      "r112"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.",
        "label": "Repayments of Long-term Debt",
        "negatedTerseLabel": "Long-term debt - repayments"
       }
      }
     },
     "localname": "RepaymentsOfLongTermDebt",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestrictedCashAndInvestmentsCurrent": {
     "auth_ref": [
      "r45"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 2.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The current cash, cash equivalents and investments that are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes current cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.",
        "label": "Restricted Cash and Investments, Current",
        "terseLabel": "Restricted cash"
       }
      }
     },
     "localname": "RestrictedCashAndInvestmentsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestructuringCostAndReserveAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of restructuring cost.",
        "label": "Restructuring Type [Axis]",
        "terseLabel": "Restructuring Type [Axis]"
       }
      }
     },
     "localname": "RestructuringCostAndReserveAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RetainedEarningsAccumulatedDeficit": {
     "auth_ref": [
      "r37",
      "r214",
      "r393"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 3.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "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": "Retained earnings"
       }
      }
     },
     "localname": "RetainedEarningsAccumulatedDeficit",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "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": "Retained Earnings"
       }
      }
     },
     "localname": "RetainedEarningsMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RetirementPlanTypeAxis": {
     "auth_ref": [
      "r226",
      "r227",
      "r246",
      "r247",
      "r258"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_RetirementPlanTypeDomain": {
     "auth_ref": [
      "r226",
      "r227",
      "r246",
      "r247",
      "r258"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "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/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax": {
     "auth_ref": [
      "r218",
      "r219",
      "r220"
     ],
     "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 from contracts with customers"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerExcludingAssessedTax",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RevenueFromContractWithCustomerTextBlock": {
     "auth_ref": [
      "r138",
      "r225"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.",
        "label": "Revenue from Contract with Customer [Text Block]",
        "terseLabel": "Revenue"
       }
      }
     },
     "localname": "RevenueFromContractWithCustomerTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/Revenue"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_RevenueRecognitionPolicyTextBlock": {
     "auth_ref": [
      "r129",
      "r130",
      "r131"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.",
        "label": "Revenue Recognition, Policy [Policy Text Block]",
        "terseLabel": "Revenue Recognition"
       }
      }
     },
     "localname": "RevenueRecognitionPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_RevenueSubjectToRefundMember": {
     "auth_ref": [
      "r409"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Rate action of a regulator resulting in capitalization or accrual of revenue subject to refund.",
        "label": "Revenue Subject to Refund [Member]",
        "terseLabel": "TCJA revenue reduction"
       }
      }
     },
     "localname": "RevenueSubjectToRefundMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccountingDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Revenues": {
     "auth_ref": [
      "r98",
      "r168",
      "r169",
      "r178"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 1.0,
       "parentTag": "us-gaap_OperatingIncomeLoss",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).",
        "label": "Revenues",
        "terseLabel": "Total revenues",
        "verboseLabel": "Revenues"
       }
      }
     },
     "localname": "Revenues",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RevolvingCreditFacilityMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Arrangement in which loan proceeds can continuously be obtained following repayments, but the total amount borrowed cannot exceed a specified maximum amount.",
        "label": "Revolving Credit Facility [Member]",
        "terseLabel": "Revolving Credit Facility"
       }
      }
     },
     "localname": "RevolvingCreditFacilityMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtDebtCovenantsDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability": {
     "auth_ref": [
      "r355",
      "r360"
     ],
     "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": "Finance leases"
       }
      }
     },
     "localname": "RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability": {
     "auth_ref": [
      "r355",
      "r360"
     ],
     "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": "Operating leases"
       }
      }
     },
     "localname": "RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/LeasesLesseeSupplementalCashFlowInformationDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ScenarioAdjustmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Domain member used to indicate figures that are adjustments during a period or as of a point in time. This domain member would never be expected to appear in a relationship group without the \"Scenario, Previously Reported\" Member with the same parent.",
        "label": "Scenario, Adjustment [Member]",
        "verboseLabel": "Recasting of Intercompany Capital Lease"
       }
      }
     },
     "localname": "ScenarioAdjustmentMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ScenarioUnspecifiedDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Any scenario, that is, the particular reporting scenario is left unspecified. Scenarios distinguish among different kinds of business reporting facts, as for example actual versus budgeted figures.",
        "label": "Scenario, Unspecified [Domain]",
        "terseLabel": "Scenario, Unspecified [Domain]"
       }
      }
     },
     "localname": "ScenarioUnspecifiedDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable": {
     "auth_ref": [
      "r64"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock": {
     "auth_ref": [
      "r64"
     ],
     "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": "Accounts Receivable and Allowance for Doubtful Accounts"
       }
      }
     },
     "localname": "ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableTables"
     ],
     "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": "Schedule of Accrued Liabilities"
       }
      }
     },
     "localname": "ScheduleOfAccruedLiabilitiesTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccruedLiabilitiesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock": {
     "auth_ref": [
      "r85"
     ],
     "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 Accumulated Other Comprehensive Income (Loss)"
       }
      }
     },
     "localname": "ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable": {
     "auth_ref": [
      "r154"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule for 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]",
        "terseLabel": "Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table]"
       }
      }
     },
     "localname": "ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock": {
     "auth_ref": [
      "r154"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "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": "Supplemental Disclosure of Cash Flow Information"
       }
      }
     },
     "localname": "ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable": {
     "auth_ref": [
      "r246",
      "r247",
      "r248",
      "r249",
      "r257"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock": {
     "auth_ref": [
      "r298",
      "r305",
      "r311"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the location and amount of derivative instruments and nonderivative instruments designated as hedging instruments reported before netting adjustments, and the amount of gain (loss) on derivative instruments and nonderivative instruments designated and qualified as hedging instruments.",
        "label": "Derivative Instruments, Gain (Loss) [Table Text Block]",
        "terseLabel": "Derivative Instruments, Gain (Loss)"
       }
      }
     },
     "localname": "ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock": {
     "auth_ref": [
      "r303"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position.",
        "label": "Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]",
        "verboseLabel": "Schedule of Derivative Instruments Balance Sheet Location"
       }
      }
     },
     "localname": "ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock": {
     "auth_ref": [
      "r155"
     ],
     "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 Earnings Per Share Reconciliation"
       }
      }
     },
     "localname": "ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock": {
     "auth_ref": [
      "r321"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date 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 (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).",
        "label": "Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]",
        "terseLabel": "Schedule of Fair Value Hierarchy, Measured on Recurring Basis"
       }
      }
     },
     "localname": "ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueMeasurementsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfInventoryCurrentTableTextBlock": {
     "auth_ref": [
      "r23",
      "r42",
      "r43",
      "r44"
     ],
     "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": "Materials, Supplies and Fuel"
       }
      }
     },
     "localname": "ScheduleOfInventoryCurrentTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/MaterialsSuppliesAndFuelTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfNetBenefitCostsTableTextBlock": {
     "auth_ref": [
      "r237"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfNotionalAmountsOfOutstandingDerivativePositionsTableTextBlock": {
     "auth_ref": [
      "r290"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of the notional amounts of outstanding derivative positions.",
        "label": "Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]",
        "terseLabel": "Contract or notional amounts and terms of marketing activities and derivative commodity instruments"
       }
      }
     },
     "localname": "ScheduleOfNotionalAmountsOfOutstandingDerivativePositionsTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RiskManagementActivitiesTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfRegulatoryAssetsAndLiabilitiesTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for detailed information about regulatory assets and liabilities, including current and noncurrent assets created when regulatory agencies permit the deferral of costs to the balance sheet that would otherwise be required to appear on the company's income statement and would be charged against current expenses or revenues, as well as current and noncurrent liabilities created when regulatory agencies permit.",
        "label": "Schedule of Regulatory Assets and Liabilities [Text Block]",
        "terseLabel": "Regulatory Accounting"
       }
      }
     },
     "localname": "ScheduleOfRegulatoryAssetsAndLiabilitiesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RegulatoryAccounting"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable": {
     "auth_ref": [
      "r133",
      "r368",
      "r369",
      "r370",
      "r371",
      "r372"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of quantitative and qualitative information pertaining to related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.",
        "label": "Schedule of Related Party Transactions, by Related Party [Table]",
        "terseLabel": "Schedule of Related Party Transactions, by Related Party [Table]"
       }
      }
     },
     "localname": "ScheduleOfRelatedPartyTransactionsByRelatedPartyTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CommitmentsAndContingenciesDividendRestrictionsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable": {
     "auth_ref": [
      "r167",
      "r173",
      "r174",
      "r176",
      "r193"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock": {
     "auth_ref": [
      "r167",
      "r173",
      "r174",
      "r176",
      "r193"
     ],
     "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]",
        "verboseLabel": "Segment Reporting"
       }
      }
     },
     "localname": "ScheduleOfSegmentReportingInformationBySegmentTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfShortTermDebtTable": {
     "auth_ref": [
      "r54"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A table or schedule providing information pertaining to borrowings under which repayment was required in less than twelve months (or normal operating cycle, if longer) after its issuance. It may include: (1) description of the short-term debt arrangement; (2) identification of the lender or type of lender; (3) repayment terms; (4) weighted average interest rate; (5) carrying amount of funds borrowed under the specified short-term debt arrangement as of the balance sheet date and measures of the maximum and average amount outstanding during the period; (6) description of the refinancing of a short-term obligation when that obligation is excluded from current liabilities in the balance sheet; and (7) amount of a short-term obligation that has been excluded from current liabilities in the balance sheet because of a refinancing of the obligation.",
        "label": "Schedule of Short-term Debt [Table]",
        "terseLabel": "Schedule of Short-term Debt [Table]"
       }
      }
     },
     "localname": "ScheduleOfShortTermDebtTable",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfShortTermDebtTextBlock": {
     "auth_ref": [
      "r54"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of short-term debt arrangements (having initial terms of repayment within one year or the normal operating cycle, if longer) including: (1) description of the short-term debt arrangement; (2) identification of the lender or type of lender; (3) repayment terms; (4) weighted average interest rate; (5) carrying amount of funds borrowed under the specified short-term debt arrangement as of the balance sheet date; (6) description of the refinancing of a short-term obligation when that obligation is excluded from current liabilities in the balance sheet; and (7) amount of a short-term obligation that has been excluded from current liabilities in the balance sheet because of a refinancing of the obligation.",
        "label": "Schedule of Short-term Debt [Table Text Block]",
        "terseLabel": "Schedule of Short-term Debt"
       }
      }
     },
     "localname": "ScheduleOfShortTermDebtTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfStockholdersEquityTableTextBlock": {
     "auth_ref": [
      "r213"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of changes in the separate accounts comprising stockholders' equity (in addition to retained earnings) and of the changes in the number of shares of equity securities during at least the most recent annual fiscal period and any subsequent interim period presented is required to make the financial statements sufficiently informative if both financial position and results of operations are presented.",
        "label": "Schedule of Stockholders Equity [Table Text Block]",
        "terseLabel": "Schedule of Stockholders Equity"
       }
      }
     },
     "localname": "ScheduleOfStockholdersEquityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityTables"
     ],
     "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": "Segment [Domain]"
       }
      }
     },
     "localname": "SegmentDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_SegmentReportingAssetReconcilingItemLineItems": {
     "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, Asset Reconciling Item [Line Items]",
        "terseLabel": "Segment Reporting, Asset Reconciling Item [Line Items]"
       }
      }
     },
     "localname": "SegmentReportingAssetReconcilingItemLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SegmentReportingDisclosureTextBlock": {
     "auth_ref": [
      "r184"
     ],
     "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": "Business Segment Information"
       }
      }
     },
     "localname": "SegmentReportingDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformation"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SegmentReportingInformationAdditionalInformationAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Segment Reporting Information, Additional Information [Abstract]"
       }
      }
     },
     "localname": "SegmentReportingInformationAdditionalInformationAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "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"
       }
      }
     },
     "localname": "SegmentReportingInformationLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SegmentReportingPolicyPolicyTextBlock": {
     "auth_ref": [
      "r130"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for segment reporting.",
        "label": "Segment Reporting, Policy [Policy Text Block]",
        "terseLabel": "Segment Reporting"
       }
      }
     },
     "localname": "SegmentReportingPolicyPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ShareBasedCompensation": {
     "auth_ref": [
      "r119"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.",
        "label": "Share-based Compensation",
        "terseLabel": "Stock compensation"
       }
      }
     },
     "localname": "ShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShortTermBorrowings": {
     "auth_ref": [
      "r29",
      "r379",
      "r391"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 5.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.",
        "label": "Short-term Debt",
        "terseLabel": "Notes payable"
       }
      }
     },
     "localname": "ShortTermBorrowings",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails",
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShortTermDebtLineItems": {
     "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": "Short-term Debt [Line Items]",
        "terseLabel": "Short-term Debt [Line Items]"
       }
      }
     },
     "localname": "ShortTermDebtLineItems",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShortTermDebtTypeAxis": {
     "auth_ref": [
      "r54"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of short-term debt arrangement.",
        "label": "Short-term Debt, Type [Axis]",
        "terseLabel": "Short-term Debt, Type [Axis]"
       }
      }
     },
     "localname": "ShortTermDebtTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShortTermDebtTypeDomain": {
     "auth_ref": [
      "r50"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Type of short-term debt arrangement, such as notes, line of credit, commercial paper, asset-based financing, project financing, letter of credit financing.",
        "label": "Short-term Debt, Type [Domain]",
        "terseLabel": "Short-term Debt, Type [Domain]"
       }
      }
     },
     "localname": "ShortTermDebtTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ShortTermDebtWeightedAverageInterestRate": {
     "auth_ref": [
      "r52"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average interest rate of short-term debt outstanding calculated at point in time.",
        "label": "Short-term Debt, Weighted Average Interest Rate, at Point in Time",
        "terseLabel": "Short-term interest rate"
       }
      }
     },
     "localname": "ShortTermDebtWeightedAverageInterestRate",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_ShorttermDebtFairValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This element represents the portion of the balance sheet assertion valued at fair value by the entity 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. This item represents the amount of short-term debt existing as of the balance sheet date.",
        "label": "Short-term Debt, Fair Value",
        "terseLabel": "Notes payable, Fair Value"
       }
      }
     },
     "localname": "ShorttermDebtFairValue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/FairValueOfFinancialInstrumentsDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StatementBusinessSegmentsAxis": {
     "auth_ref": [
      "r9",
      "r173",
      "r193",
      "r203",
      "r205",
      "r206",
      "r401"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by business segments.",
        "label": "Segments [Axis]",
        "terseLabel": "Segments [Axis]"
       }
      }
     },
     "localname": "StatementBusinessSegmentsAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementEquityComponentsAxis": {
     "auth_ref": [
      "r62",
      "r213"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossAccumulatedOtherComprehensiveIncomeDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "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/2018-01-31",
     "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/2018-01-31",
     "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/2018-01-31",
     "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/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementScenarioAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by scenario to be reported. Scenarios distinguish among different kinds of business reporting facts, as for example actual versus budgeted figures.",
        "label": "Scenario [Axis]",
        "terseLabel": "Scenario [Axis]"
       }
      }
     },
     "localname": "StatementScenarioAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationSegmentAndCorporateAssetsDetails",
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited",
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/EquityAtTheMarketEquityOfferingProgramDetails",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails",
      "http://www.blackhillscorp.com/role/OtherComprehensiveIncomeLossReclassificationOutOfAccumulatedOtherComprehensiveIncomeLossDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockCompensationPlanMember": {
     "auth_ref": [
      "r154"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Equity-based payment arrangement where one or more employees receive shares of stock (units), stock (unit) options, or other equity instruments, or the employer incurs a liability to the employee in amounts based on the price of the employer's stock (unit).",
        "label": "Stock Compensation Plan [Member]",
        "terseLabel": "Equity compensation"
       }
      }
     },
     "localname": "StockCompensationPlanMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EarningsPerShareAntiDilutiveSharesDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan": {
     "auth_ref": [
      "r213"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares issued during the period from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the shareholders to reinvest dividends paid to them by the entity on new issues of stock by the entity.",
        "label": "Stock Issued During Period, Shares, Dividend Reinvestment Plan",
        "terseLabel": "Stock Issued During Period, Shares, Dividend Reinvestment Plan"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesDividendReinvestmentPlan",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesNewIssues": {
     "auth_ref": [
      "r33",
      "r34",
      "r213",
      "r214"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of new stock issued during the period.",
        "label": "Stock Issued During Period, Shares, New Issues",
        "terseLabel": "Stock Issued During Period, Shares, New Issues"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesNewIssues",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation": {
     "auth_ref": [
      "r33",
      "r34",
      "r213",
      "r214"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.",
        "label": "Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures",
        "terseLabel": "Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan": {
     "auth_ref": [
      "r213"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of stock issued during the period from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the holder of the stock to reinvest dividends paid to them by the entity on new issues of stock by the entity.",
        "label": "Stock Issued During Period, Value, Dividend Reinvestment Plan",
        "terseLabel": "Dividend reinvestment and stock purchase plan"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueDividendReinvestmentPlan",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueNewIssues": {
     "auth_ref": [
      "r33",
      "r34",
      "r213",
      "r214"
     ],
     "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": "Stock Issued During Period, Value, New Issues"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueNewIssues",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation": {
     "auth_ref": [
      "r33",
      "r34",
      "r214",
      "r260",
      "r261"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.",
        "label": "Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures",
        "terseLabel": "Share-based compensation"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquity": {
     "auth_ref": [
      "r34",
      "r38",
      "r39",
      "r188"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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": "Total stockholders\u2019 equity"
       }
      }
     },
     "localname": "StockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Stockholders' Equity Attributable to Parent [Abstract]",
        "terseLabel": "Equity:"
       }
      }
     },
     "localname": "StockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest": {
     "auth_ref": [
      "r274",
      "r275",
      "r283"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 5.0,
       "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": "Total Equity, ending balance",
        "periodStartLabel": "Total Equity, beginning balance",
        "totalLabel": "Total equity"
       }
      }
     },
     "localname": "StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityNoteDisclosureTextBlock": {
     "auth_ref": [
      "r217"
     ],
     "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": "Equity"
       }
      }
     },
     "localname": "StockholdersEquityNoteDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/Equity"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_StockholdersEquityOther": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.",
        "label": "Stockholders' Equity, Other",
        "negatedTerseLabel": "Other stock transactions"
       }
      }
     },
     "localname": "StockholdersEquityOther",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_SupplementalCashFlowElementsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Supplemental Cash Flow Elements [Abstract]",
        "terseLabel": "Supplemental Cash Flow Elements [Abstract]"
       }
      }
     },
     "localname": "SupplementalCashFlowElementsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/SupplementalDisclosureOfCashFlowInformationDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SupplementalCashFlowInformationAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Supplemental Cash Flow Information [Abstract]"
       }
      }
     },
     "localname": "SupplementalCashFlowInformationAbstract",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Plan designed to provide limited group of employees with supplemental retirement benefits, in addition to other pension benefits. Includes, but is not limited to, defined benefit and defined contribution plans.",
        "label": "Supplemental Employee Retirement Plan [Member]",
        "terseLabel": "Supplemental Non-qualified Defined Benefit and Defined Contribution Plans"
       }
      }
     },
     "localname": "SupplementalEmployeeRetirementPlanDefinedBenefitMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EmployeeBenefitPlansDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TaxesExcludingIncomeAndExciseTaxes": {
     "auth_ref": [
      "r104"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "All taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.",
        "label": "Taxes, Miscellaneous",
        "terseLabel": "Taxes - property and production"
       }
      }
     },
     "localname": "TaxesExcludingIncomeAndExciseTaxes",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_TimingOfTransferOfGoodOrServiceAxis": {
     "auth_ref": [
      "r220",
      "r224"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by timing of transfer of good or service to customer.",
        "label": "Timing of Transfer of Good or Service [Axis]",
        "terseLabel": "Timing of Transfer of Good or Service [Axis]"
       }
      }
     },
     "localname": "TimingOfTransferOfGoodOrServiceAxis",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_TimingOfTransferOfGoodOrServiceDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Timing of transfer of good or service to customer. Includes, but is not limited to, at point in time or over time.",
        "label": "Timing of Transfer of Good or Service [Domain]",
        "terseLabel": "Timing of Transfer of Good or Service [Domain]"
       }
      }
     },
     "localname": "TimingOfTransferOfGoodOrServiceDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TransferredAtPointInTimeMember": {
     "auth_ref": [
      "r220",
      "r224"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Contract with customer in which good or service is transferred at point in time.",
        "label": "Transferred at Point in Time [Member]",
        "terseLabel": "Services transferred at a point in time"
       }
      }
     },
     "localname": "TransferredAtPointInTimeMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TransferredOverTimeMember": {
     "auth_ref": [
      "r220",
      "r224"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Contract with customer in which good or service is transferred over time.",
        "label": "Transferred over Time [Member]",
        "terseLabel": "Services transferred over time"
       }
      }
     },
     "localname": "TransferredOverTimeMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/RevenueDisaggregationOfRevenueDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TreasuryStockMember": {
     "auth_ref": [
      "r61",
      "r215"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Shares of an entity that have been repurchased by the entity. This stock has no voting rights and receives no dividends. Note that treasury stock may be recorded at its total cost or separately as par (or stated) value and additional paid in capital. Classified within stockholders' equity if nonredeemable or redeemable solely at the option of the issuer. Classified within temporary equity if redemption is outside the control of the issuer.",
        "label": "Treasury Stock [Member]",
        "terseLabel": "Treasury Stock"
       }
      }
     },
     "localname": "TreasuryStockMember",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TreasuryStockShares": {
     "auth_ref": [
      "r61",
      "r215"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.",
        "label": "Treasury Stock, Shares",
        "terseLabel": "Treasury Stock, Shares"
       }
      }
     },
     "localname": "TreasuryStockShares",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical",
      "http://www.blackhillscorp.com/role/EquityStockholdersEquityRecapDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_TreasuryStockValue": {
     "auth_ref": [
      "r61",
      "r215",
      "r216"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 4.0,
       "parentTag": "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest",
       "weight": -1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount allocated to treasury stock. Treasury stock is common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury.",
        "label": "Treasury Stock, Value",
        "negatedTerseLabel": "Treasury stock, at cost \u2013 23,756; 44,253; and 53,959 shares, respectively"
       }
      }
     },
     "localname": "TreasuryStockValue",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_TypeOfRestructuringDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Identification of the types of restructuring costs.",
        "label": "Type of Restructuring [Domain]",
        "terseLabel": "Type of Restructuring [Domain]"
       }
      }
     },
     "localname": "TypeOfRestructuringDomain",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/BusinessSegmentInformationInformationRelatingToSegmentStatementOfIncomeDetails",
      "http://www.blackhillscorp.com/role/IncomeTaxesTaxBenefitRelatedToLegalRestructuringDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_UnbilledReceivablesCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails": {
       "order": 2.0,
       "parentTag": "us-gaap_AccountsReceivableNetCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.",
        "label": "Unbilled Receivables, Current",
        "terseLabel": "Unbilled Receivables, Current"
       }
      }
     },
     "localname": "UnbilledReceivablesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/AccountsReceivableDetails"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_UseOfEstimates": {
     "auth_ref": [
      "r159",
      "r160",
      "r161",
      "r162",
      "r163",
      "r164",
      "r165"
     ],
     "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 and Basis of Presentation"
       }
      }
     },
     "localname": "UseOfEstimates",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/ManagementsStatementPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "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/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/NotesPayableCurrentMaturitiesAndDebtScheduleOfShortTermDebtAndNarrativeDetails"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding": {
     "auth_ref": [
      "r146",
      "r153"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails": {
       "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 shares - diluted (in shares)"
       }
      }
     },
     "localname": "WeightedAverageNumberOfDilutedSharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_WeightedAverageNumberOfSharesOutstandingBasic": {
     "auth_ref": [
      "r144",
      "r153"
     ],
     "calculation": {
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails": {
       "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 - basic (in shares)"
       }
      }
     },
     "localname": "WeightedAverageNumberOfSharesOutstandingBasic",
     "nsuri": "http://fasb.org/us-gaap/2018-01-31",
     "presentation": [
      "http://www.blackhillscorp.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited",
      "http://www.blackhillscorp.com/role/EarningsPerShareEarningsPerShareReconciliationDetails"
     ],
     "xbrltype": "sharesItemType"
    }
   },
   "unitCount": 7
  }
 },
 "std_ref": {
  "r0": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=d3e1107-107759"
  },
  "r1": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=SL51721533-107759"
  },
  "r10": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760"
  },
  "r100": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.19)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227"
  },
  "r101": {
   "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=115205541&loc=SL114868664-224227"
  },
  "r102": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.7(b))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227"
  },
  "r103": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.7)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227"
  },
  "r104": {
   "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=115205541&loc=SL114868664-224227"
  },
  "r105": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "220",
   "URI": "http://asc.fasb.org/topic&trid=2134417"
  },
  "r106": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585"
  },
  "r107": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585"
  },
  "r108": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585"
  },
  "r109": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585"
  },
  "r11": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)(1)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760"
  },
  "r110": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585"
  },
  "r111": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585"
  },
  "r112": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585"
  },
  "r113": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585"
  },
  "r114": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585"
  },
  "r115": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3000-108585"
  },
  "r116": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "24",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3521-108585"
  },
  "r117": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585"
  },
  "r118": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585"
  },
  "r119": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585"
  },
  "r12": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(e)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760"
  },
  "r120": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585"
  },
  "r121": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585"
  },
  "r122": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=109223946&loc=d3e3044-108585"
  },
  "r123": {
   "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"
  },
  "r124": {
   "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"
  },
  "r125": {
   "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"
  },
  "r126": {
   "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"
  },
  "r127": {
   "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"
  },
  "r128": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "230",
   "URI": "http://asc.fasb.org/topic&trid=2134446"
  },
  "r129": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=84158767&loc=d3e18726-107790"
  },
  "r13": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5C",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(2)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=SL51721675-107760"
  },
  "r130": {
   "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"
  },
  "r131": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=84158767&loc=d3e18823-107790"
  },
  "r132": {
   "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"
  },
  "r133": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(k))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r134": {
   "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"
  },
  "r135": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(h)(1)(i))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r136": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(n)(2))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r137": {
   "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"
  },
  "r138": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "235",
   "URI": "http://asc.fasb.org/topic&trid=2122369"
  },
  "r139": {
   "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"
  },
  "r14": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5C",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(2)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=SL51721675-107760"
  },
  "r140": {
   "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"
  },
  "r141": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "250",
   "URI": "http://asc.fasb.org/extlink&oid=109234566&loc=d3e22580-107794"
  },
  "r142": {
   "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"
  },
  "r143": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "250",
   "URI": "http://asc.fasb.org/topic&trid=2122394"
  },
  "r144": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1448-109256"
  },
  "r145": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1377-109256"
  },
  "r146": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "16",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1505-109256"
  },
  "r147": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256"
  },
  "r148": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1707-109256"
  },
  "r149": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1500-109256"
  },
  "r15": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/subtopic&trid=2122178"
  },
  "r150": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1278-109256"
  },
  "r151": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "60B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256"
  },
  "r152": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256"
  },
  "r153": {
   "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"
  },
  "r154": {
   "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"
  },
  "r155": {
   "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"
  },
  "r156": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "52",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258"
  },
  "r157": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "260",
   "URI": "http://asc.fasb.org/topic&trid=2144383"
  },
  "r158": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "270",
   "URI": "http://asc.fasb.org/extlink&oid=109225645&loc=SL77927221-108306"
  },
  "r159": {
   "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"
  },
  "r16": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765"
  },
  "r160": {
   "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"
  },
  "r161": {
   "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"
  },
  "r162": {
   "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"
  },
  "r163": {
   "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"
  },
  "r164": {
   "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"
  },
  "r165": {
   "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"
  },
  "r166": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "275",
   "URI": "http://asc.fasb.org/topic&trid=2134479"
  },
  "r167": {
   "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"
  },
  "r168": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "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": "(b)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r17": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765"
  },
  "r170": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "22",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "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",
   "Subparagraph": "(e)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599"
  },
  "r172": {
   "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"
  },
  "r173": {
   "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"
  },
  "r174": {
   "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"
  },
  "r175": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "30",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8906-108599"
  },
  "r176": {
   "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"
  },
  "r177": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "31",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8924-108599"
  },
  "r178": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "32",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599"
  },
  "r179": {
   "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"
  },
  "r18": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765"
  },
  "r180": {
   "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"
  },
  "r181": {
   "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"
  },
  "r182": {
   "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"
  },
  "r183": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "42",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "280",
   "URI": "http://asc.fasb.org/extlink&oid=115929826&loc=d3e9054-108599"
  },
  "r184": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "280",
   "URI": "http://asc.fasb.org/topic&trid=2134510"
  },
  "r185": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84173941&loc=d3e5162-111524"
  },
  "r186": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84173941&loc=d3e5066-111524"
  },
  "r187": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524"
  },
  "r188": {
   "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"
  },
  "r189": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "10",
   "Topic": "330",
   "URI": "http://asc.fasb.org/extlink&oid=68049868&loc=d3e3927-108312"
  },
  "r19": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6801-107765"
  },
  "r190": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "330",
   "URI": "http://asc.fasb.org/topic&trid=2126998"
  },
  "r191": {
   "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"
  },
  "r192": {
   "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"
  },
  "r193": {
   "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"
  },
  "r194": {
   "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"
  },
  "r195": {
   "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"
  },
  "r196": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=109226348&loc=d3e2510-110228"
  },
  "r197": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=109226348&loc=d3e2473-110228"
  },
  "r198": {
   "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"
  },
  "r199": {
   "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"
  },
  "r2": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=SL51721494-107759"
  },
  "r20": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6911-107765"
  },
  "r200": {
   "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"
  },
  "r201": {
   "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"
  },
  "r202": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230"
  },
  "r203": {
   "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"
  },
  "r204": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "360",
   "URI": "http://asc.fasb.org/topic&trid=2155823"
  },
  "r205": {
   "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"
  },
  "r206": {
   "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"
  },
  "r207": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "440",
   "URI": "http://asc.fasb.org/topic&trid=2144648"
  },
  "r208": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349"
  },
  "r209": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "450",
   "URI": "http://asc.fasb.org/topic&trid=2127136"
  },
  "r21": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e6935-107765"
  },
  "r210": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "470",
   "URI": "http://asc.fasb.org/extlink&oid=99376301&loc=SL5988623-112600"
  },
  "r211": {
   "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"
  },
  "r212": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "470",
   "URI": "http://asc.fasb.org/topic&trid=2208564"
  },
  "r213": {
   "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"
  },
  "r214": {
   "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"
  },
  "r215": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655"
  },
  "r216": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=6405834&loc=d3e23315-112656"
  },
  "r217": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "505",
   "URI": "http://asc.fasb.org/topic&trid=2208762"
  },
  "r218": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045"
  },
  "r219": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045"
  },
  "r22": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=82887183&loc=d3e7018-107765"
  },
  "r220": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045"
  },
  "r221": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045"
  },
  "r222": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "91",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=108792157&loc=SL49130690-203046-203046"
  },
  "r223": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "91",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=108792157&loc=SL49130690-203046-203046"
  },
  "r224": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "91",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "(f)",
   "Topic": "606",
   "URI": "http://asc.fasb.org/extlink&oid=108792157&loc=SL49130690-203046-203046"
  },
  "r225": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "606",
   "URI": "http://asc.fasb.org/topic&trid=49130388"
  },
  "r226": {
   "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"
  },
  "r227": {
   "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"
  },
  "r228": {
   "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"
  },
  "r229": {
   "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"
  },
  "r23": {
   "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"
  },
  "r230": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r231": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r232": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r233": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r234": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(ii)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r235": {
   "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=108410482&loc=d3e1928-114920"
  },
  "r236": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(g)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r237": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r238": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r239": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r24": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 201.5-02(24))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r240": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r241": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(4)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r242": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(h)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r243": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(i)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r244": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(i),(j)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r245": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(j)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r246": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920"
  },
  "r247": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2410-114920"
  },
  "r248": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2417-114920"
  },
  "r249": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2439-114920"
  },
  "r25": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 201.5-02(25))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r250": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r251": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(1)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r252": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(2)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r253": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(3)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r254": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(4)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r255": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)(5)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r256": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920"
  },
  "r257": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921"
  },
  "r258": {
   "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"
  },
  "r259": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "715",
   "URI": "http://asc.fasb.org/topic&trid=2235017"
  },
  "r26": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 201.5-02(26))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r260": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901"
  },
  "r261": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901"
  },
  "r262": {
   "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"
  },
  "r263": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84176650&loc=d3e32059-109318"
  },
  "r264": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84176650&loc=d3e31917-109318"
  },
  "r265": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84176650&loc=d3e31931-109318"
  },
  "r266": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=84176650&loc=d3e31958-109318"
  },
  "r267": {
   "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"
  },
  "r268": {
   "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"
  },
  "r269": {
   "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"
  },
  "r27": {
   "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"
  },
  "r270": {
   "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=34349781&loc=d3e330036-122817"
  },
  "r271": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "740",
   "URI": "http://asc.fasb.org/extlink&oid=109238882&loc=d3e39076-109324"
  },
  "r272": {
   "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"
  },
  "r273": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "740",
   "URI": "http://asc.fasb.org/topic&trid=2144680"
  },
  "r274": {
   "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"
  },
  "r275": {
   "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"
  },
  "r276": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "18",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=108774443&loc=SL4613673-111683"
  },
  "r277": {
   "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"
  },
  "r278": {
   "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"
  },
  "r279": {
   "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"
  },
  "r28": {
   "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"
  },
  "r280": {
   "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"
  },
  "r281": {
   "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"
  },
  "r282": {
   "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"
  },
  "r283": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4I",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686"
  },
  "r284": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4J",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=84234705&loc=SL4591551-111686"
  },
  "r285": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4K",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=84234705&loc=SL4591552-111686"
  },
  "r286": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 5.E)",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=27015204&loc=d3e355146-122828"
  },
  "r287": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "810",
   "URI": "http://asc.fasb.org/topic&trid=2197479"
  },
  "r288": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958"
  },
  "r289": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5579240-113959"
  },
  "r29": {
   "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"
  },
  "r290": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959"
  },
  "r291": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959"
  },
  "r292": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959"
  },
  "r293": {
   "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"
  },
  "r294": {
   "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"
  },
  "r295": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "c",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41638-113959"
  },
  "r296": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41638-113959"
  },
  "r297": {
   "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"
  },
  "r298": {
   "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"
  },
  "r299": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)(1)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959"
  },
  "r3": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1D",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=SL51721503-107759"
  },
  "r30": {
   "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"
  },
  "r300": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a),(c)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959"
  },
  "r301": {
   "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"
  },
  "r302": {
   "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"
  },
  "r303": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4B",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959"
  },
  "r304": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4C",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959"
  },
  "r305": {
   "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"
  },
  "r306": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959"
  },
  "r307": {
   "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"
  },
  "r308": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(4)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959"
  },
  "r309": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959"
  },
  "r31": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(23))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r310": {
   "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"
  },
  "r311": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4E",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624181-113959"
  },
  "r312": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4H",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959"
  },
  "r313": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41641-113959"
  },
  "r314": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959"
  },
  "r315": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959"
  },
  "r316": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "182",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109975725&loc=SL5629052-113961"
  },
  "r317": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "25",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=109977999&loc=d3e76258-113986"
  },
  "r318": {
   "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"
  },
  "r319": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(c)",
   "Topic": "815",
   "URI": "http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994"
  },
  "r32": {
   "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"
  },
  "r320": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "815",
   "URI": "http://asc.fasb.org/topic&trid=2229140"
  },
  "r321": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19190-110258"
  },
  "r322": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258"
  },
  "r323": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258"
  },
  "r324": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bb)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258"
  },
  "r325": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258"
  },
  "r326": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2C",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=SL7498348-110258"
  },
  "r327": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=d3e19279-110258"
  },
  "r328": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258"
  },
  "r329": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "820",
   "URI": "http://asc.fasb.org/topic&trid=2155941"
  },
  "r33": {
   "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"
  },
  "r330": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=75026489&loc=d3e13220-108610"
  },
  "r331": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611"
  },
  "r332": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=109250915&loc=d3e13467-108611"
  },
  "r333": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "825",
   "URI": "http://asc.fasb.org/extlink&oid=109250915&loc=d3e13476-108611"
  },
  "r334": {
   "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"
  },
  "r335": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "835",
   "URI": "http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391"
  },
  "r336": {
   "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"
  },
  "r337": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "40",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "(Note 3)",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697"
  },
  "r338": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "40",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "Note 1",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697"
  },
  "r339": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "40",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Subparagraph": "Note 3",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697"
  },
  "r34": {
   "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"
  },
  "r340": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "20",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=77902458&loc=d3e39896-112707"
  },
  "r341": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "20",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=77902458&loc=d3e39927-112707"
  },
  "r342": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "20",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=77913719&loc=d3e40879-112712"
  },
  "r343": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "840",
   "URI": "http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717"
  },
  "r344": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "65",
   "SubTopic": "10",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=113997351&loc=SL77916155-209984"
  },
  "r345": {
   "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"
  },
  "r346": {
   "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"
  },
  "r347": {
   "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"
  },
  "r348": {
   "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"
  },
  "r349": {
   "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"
  },
  "r35": {
   "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"
  },
  "r350": {
   "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"
  },
  "r351": {
   "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"
  },
  "r352": {
   "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"
  },
  "r353": {
   "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"
  },
  "r354": {
   "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"
  },
  "r355": {
   "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"
  },
  "r356": {
   "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"
  },
  "r357": {
   "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"
  },
  "r358": {
   "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"
  },
  "r359": {
   "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"
  },
  "r36": {
   "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"
  },
  "r360": {
   "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"
  },
  "r361": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "20",
   "Topic": "842",
   "URI": "http://asc.fasb.org/subtopic&trid=77888251"
  },
  "r362": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888421&loc=SL77919311-209978"
  },
  "r363": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888428&loc=SL77919396-209981"
  },
  "r364": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Subparagraph": "(a)(3)",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981"
  },
  "r365": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981"
  },
  "r366": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "842",
   "URI": "http://asc.fasb.org/extlink&oid=77888428&loc=SL77919372-209981"
  },
  "r367": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "SubTopic": "30",
   "Topic": "842",
   "URI": "http://asc.fasb.org/subtopic&trid=77888252"
  },
  "r368": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864"
  },
  "r369": {
   "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"
  },
  "r37": {
   "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"
  },
  "r370": {
   "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"
  },
  "r371": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864"
  },
  "r372": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39691-107864"
  },
  "r373": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719"
  },
  "r374": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(1)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719"
  },
  "r375": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(2)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719"
  },
  "r376": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(3)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=109247956&loc=d3e107207-111719"
  },
  "r377": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4D",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(c)(2)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719"
  },
  "r378": {
   "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"
  },
  "r379": {
   "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"
  },
  "r38": {
   "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"
  },
  "r380": {
   "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"
  },
  "r381": {
   "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"
  },
  "r382": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(7))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r383": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03.10)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r384": {
   "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"
  },
  "r385": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.7-04(19))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260"
  },
  "r386": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04(20))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260"
  },
  "r387": {
   "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=114873765&loc=SL114874048-224260"
  },
  "r388": {
   "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=114873765&loc=SL114874048-224260"
  },
  "r389": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(5))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910"
  },
  "r39": {
   "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"
  },
  "r390": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r391": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(16)(a)(1))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910"
  },
  "r392": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r393": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r394": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r395": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(5))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910"
  },
  "r396": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r397": {
   "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=6879938&loc=d3e572229-122910"
  },
  "r398": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03.5(c))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910"
  },
  "r399": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.7-04(11))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263"
  },
  "r4": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=d3e957-107759"
  },
  "r40": {
   "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"
  },
  "r400": {
   "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=114873790&loc=SL114874131-224263"
  },
  "r401": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4H",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "40",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=99384497&loc=SL65671331-158438"
  },
  "r402": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.6-04(6))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996"
  },
  "r403": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "340",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=77907324&loc=d3e43603-110378"
  },
  "r404": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "340",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382"
  },
  "r405": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "340",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382"
  },
  "r406": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "405",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394"
  },
  "r407": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "410",
   "Subparagraph": "(SAB Topic 10.F)",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6228715&loc=d3e660557-123036"
  },
  "r408": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "40",
   "SubTopic": "470",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6500971&loc=d3e49673-110406"
  },
  "r409": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "605",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=109242873&loc=d3e50972-110412"
  },
  "r41": {
   "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"
  },
  "r410": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "715",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6501251&loc=d3e52485-110419"
  },
  "r411": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "25",
   "SubTopic": "835",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430"
  },
  "r412": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "835",
   "Topic": "980",
   "URI": "http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433"
  },
  "r413": {
   "Name": "Regulation 12B",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b-2"
  },
  "r414": {
   "Article": "12",
   "Name": "Regulation S-X (SX)",
   "Number": "210",
   "Publisher": "SEC",
   "Section": "13",
   "Sentence": "Column B"
  },
  "r42": {
   "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"
  },
  "r43": {
   "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"
  },
  "r44": {
   "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"
  },
  "r45": {
   "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"
  },
  "r46": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.12)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r47": {
   "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"
  },
  "r48": {
   "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"
  },
  "r49": {
   "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"
  },
  "r5": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=SL51721523-107759"
  },
  "r50": {
   "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"
  },
  "r51": {
   "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"
  },
  "r52": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19(b))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r53": {
   "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"
  },
  "r54": {
   "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"
  },
  "r55": {
   "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"
  },
  "r56": {
   "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"
  },
  "r57": {
   "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"
  },
  "r58": {
   "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"
  },
  "r59": {
   "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"
  },
  "r6": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=SL51721525-107759"
  },
  "r60": {
   "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"
  },
  "r61": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.29,30)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r62": {
   "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"
  },
  "r63": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.3(a)(4))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r64": {
   "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"
  },
  "r65": {
   "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"
  },
  "r66": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.6(a)(4),(5))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r67": {
   "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"
  },
  "r68": {
   "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"
  },
  "r69": {
   "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"
  },
  "r7": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222160&loc=d3e1012-107759"
  },
  "r70": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(a)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312"
  },
  "r71": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312"
  },
  "r72": {
   "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"
  },
  "r73": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313"
  },
  "r74": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313"
  },
  "r75": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=99393222&loc=SL20226003-175313"
  },
  "r76": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=99393222&loc=SL20226006-175313"
  },
  "r77": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580"
  },
  "r78": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(i)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580"
  },
  "r79": {
   "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=114867106&loc=SL7669646-108580"
  },
  "r8": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(b)",
   "Topic": "205",
   "URI": "http://asc.fasb.org/extlink&oid=109222650&loc=d3e1361-107760"
  },
  "r80": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(j)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580"
  },
  "r81": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580"
  },
  "r82": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580"
  },
  "r83": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580"
  },
  "r84": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=d3e681-108580"
  },
  "r85": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580"
  },
  "r86": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=d3e689-108580"
  },
  "r87": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL34724391-108580"
  },
  "r88": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL34724394-108580"
  },
  "r89": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580"
  },
  "r9": {
   "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"
  },
  "r90": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580"
  },
  "r91": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580"
  },
  "r92": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580"
  },
  "r93": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580"
  },
  "r94": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=114867106&loc=d3e557-108580"
  },
  "r95": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581"
  },
  "r96": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(13))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868656-224227"
  },
  "r97": {
   "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=115205541&loc=SL114868664-224227"
  },
  "r98": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.1)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227"
  },
  "r99": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.13)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227"
  }
 },
 "version": "2.1"
}
