{
 "instance": {
  "atra-10q_20200331.htm": {
   "axisCustom": 0,
   "axisStandard": 15,
   "contextCount": 110,
   "dts": {
    "calculationLink": {
     "local": [
      "atra-20200331_cal.xml"
     ]
    },
    "definitionLink": {
     "local": [
      "atra-20200331_def.xml"
     ],
     "remote": [
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-eedm-def-2019-01-31.xml",
      "http://xbrl.fasb.org/srt/2019/elts/srt-eedm1-def-2019-01-31.xml"
     ]
    },
    "inline": {
     "local": [
      "atra-10q_20200331.htm"
     ]
    },
    "labelLink": {
     "local": [
      "atra-20200331_lab.xml"
     ],
     "remote": [
      "https://xbrl.sec.gov/dei/2019/dei-doc-2019-01-31.xml",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-doc-2019-01-31.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "atra-20200331_pre.xml"
     ]
    },
    "referenceLink": {
     "remote": [
      "https://xbrl.sec.gov/dei/2019/dei-ref-2019-01-31.xml",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-ref-2019-01-31.xml"
     ]
    },
    "schema": {
     "local": [
      "atra-20200331.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",
      "https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd",
      "http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd",
      "https://xbrl.sec.gov/currency/2019/currency-2019-01-31.xsd",
      "https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd",
      "http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd",
      "https://xbrl.sec.gov/exch/2019/exch-2019-01-31.xsd",
      "http://www.xbrl.org/lrr/arcrole/factExplanatory-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",
      "https://xbrl.sec.gov/naics/2017/naics-2017-01-31.xsd",
      "https://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd",
      "http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd",
      "http://www.xbrl.org/2006/ref-2006-02-27.xsd",
      "http://xbrl.fasb.org/srt/2019/elts/srt-types-2019-01-31.xsd",
      "http://xbrl.fasb.org/srt/2019/elts/srt-roles-2019-01-31.xsd",
      "https://xbrl.sec.gov/stpr/2018/stpr-2018-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-roles-2019-01-31.xsd",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-types-2019-01-31.xsd",
      "http://www.xbrl.org/lrr/role/reference-2009-12-16.xsd",
      "http://xbrl.fasb.org/us-gaap/2019/elts/us-parts-codification-2019-01-31.xsd",
      "http://www.xbrl.org/lrr/role/deprecated-2009-12-16.xsd"
     ]
    }
   },
   "elementCount": 330,
   "entityCount": 1,
   "hidden": {
    "http://fasb.org/us-gaap/2019-01-31": 3,
    "http://xbrl.sec.gov/dei/2019-01-31": 6,
    "total": 9
   },
   "keyCustom": 36,
   "keyStandard": 235,
   "memberCustom": 16,
   "memberStandard": 28,
   "nsprefix": "atra",
   "nsuri": "http://www.atarabio.com/20200331",
   "report": {
    "R1": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:DocumentType",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "document",
     "isDefault": "true",
     "longName": "100000 - Document - Document and Entity Information",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation",
     "shortName": "Document and Entity Information",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:DocumentType",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R10": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100100 - Disclosure - Net Loss per Common Share",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShare",
     "shortName": "Net Loss per Common Share",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:EarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R11": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FinancialInstrumentsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100110 - Disclosure - Financial Instruments",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstruments",
     "shortName": "Financial Instruments",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:FinancialInstrumentsDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R12": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100120 - Disclosure - Property and Equipment",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipment",
     "shortName": "Property and Equipment",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R13": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CollaborativeArrangementDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100130 - Disclosure - License and Collaboration Agreements",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreements",
     "shortName": "License and Collaboration Agreements",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CollaborativeArrangementDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R14": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100140 - Disclosure - Commitments and Contingencies",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCommitmentsAndContingencies",
     "shortName": "Commitments and Contingencies",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R15": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100150 - Disclosure - Stockholders' Equity",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquity",
     "shortName": "Stockholders' Equity",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R16": {
     "firstAnchor": {
      "ancestors": [
       "us-gaap:SignificantAccountingPoliciesTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:BasisOfAccountingPolicyPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100160 - Disclosure - Summary of Significant Accounting Policies (Policies)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies",
     "shortName": "Summary of Significant Accounting Policies (Policies)",
     "subGroupType": "policies",
     "uniqueAnchor": {
      "ancestors": [
       "us-gaap:SignificantAccountingPoliciesTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:BasisOfAccountingPolicyPolicyTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R17": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100170 - Disclosure - Net Loss per Common Share (Tables)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareTables",
     "shortName": "Net Loss per Common Share (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R18": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "atra:SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100180 - Disclosure - Financial Instruments (Tables)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsTables",
     "shortName": "Financial Instruments (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "atra:SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R19": {
     "firstAnchor": {
      "ancestors": [
       "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100190 - Disclosure - Property and Equipment (Tables)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentTables",
     "shortName": "Property and Equipment (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:PropertyPlantAndEquipmentTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R2": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100010 - Statement - Condensed Consolidated Balance Sheets (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited",
     "shortName": "Condensed Consolidated Balance Sheets (Unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:ShortTermInvestments",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R20": {
     "firstAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100200 - Disclosure - Stockholders' Equity (Tables)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityTables",
     "shortName": "Stockholders' Equity (Tables)",
     "subGroupType": "tables",
     "uniqueAnchor": {
      "ancestors": [
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R21": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "dei:EntityIncorporationStateCountryCode",
      "reportCount": 1,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100210 - Disclosure - Description of Business (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureDescriptionOfBusinessDetail",
     "shortName": "Description of Business (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R22": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:RetainedEarningsAccumulatedDeficit",
      "reportCount": 1,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100220 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail",
     "shortName": "Summary of Significant Accounting Policies - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R23": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100230 - Disclosure - Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail",
     "shortName": "Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R24": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:InvestmentsClassifiedByContractualMaturityDateTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AvailableForSaleSecuritiesDebtSecurities",
      "reportCount": 1,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100240 - Disclosure - Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail",
     "shortName": "Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "atra:SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapFairValueByMeasurementFrequencyAxis_us-gaapFairValueMeasurementsRecurringMember_20200331",
      "decimals": "-3",
      "lang": null,
      "name": "us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R25": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:InvestmentsClassifiedByContractualMaturityDateTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100250 - Disclosure - Financial Instruments - Amortized Cost and Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail",
     "shortName": "Financial Instruments - Amortized Cost and Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:InvestmentsClassifiedByContractualMaturityDateTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R26": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestReceivable",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100260 - Disclosure - Financial Instruments - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail",
     "shortName": "Financial Instruments - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-5",
      "first": true,
      "lang": null,
      "name": "us-gaap:InterestReceivable",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R27": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:CashAndCashEquivalentsAtCarryingValue",
      "reportCount": 1,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100270 - Disclosure - Financial Instruments - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail",
     "shortName": "Financial Instruments - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R28": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:PropertyPlantAndEquipmentTextBlock",
       "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:PropertyPlantAndEquipmentGross",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100280 - Disclosure - Property and Equipment - Schedule of Property and Equipment (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail",
     "shortName": "Property and Equipment - Schedule of Property and Equipment (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:PropertyPlantAndEquipmentTextBlock",
       "us-gaap:PropertyPlantAndEquipmentDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:PropertyPlantAndEquipmentGross",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R29": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:DepreciationAndAmortization",
      "reportCount": 1,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100290 - Disclosure - Property and Equipment - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformationDetail",
     "shortName": "Property and Equipment - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": null
    },
    "R3": {
     "firstAnchor": {
      "ancestors": [
       "span",
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CommonStockParOrStatedValuePerShare",
      "reportCount": 1,
      "unitRef": "U_iso4217USD_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited",
     "shortName": "Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:CommonStockSharesIssued",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R30": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "0",
      "first": true,
      "lang": null,
      "name": "atra:DueToLicensorsCurrentAndNoncurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100300 - Disclosure - License and Collaboration Agreements - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail",
     "shortName": "License and Collaboration Agreements - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "0",
      "first": true,
      "lang": null,
      "name": "atra:DueToLicensorsCurrentAndNoncurrent",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R31": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "atra:AccruedTerminationCharges",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100310 - Disclosure - Commitments and Contingencies - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail",
     "shortName": "Commitments and Contingencies - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "us-gaap:CommitmentsAndContingenciesDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "atra:AccruedTerminationCharges",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R32": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CapitalUnitsAuthorized",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100320 - Disclosure - Stockholders' Equity - Additional Information (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
     "shortName": "Stockholders' Equity - Additional Information (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "us-gaap:StockholdersEquityNoteDisclosureTextBlock",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CapitalUnitsAuthorized",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R33": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapAwardTypeAxis_us-gaapRestrictedStockUnitsRSUMember_20191231",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100330 - Disclosure - Stockholders' Equity - Summary of RSU Activity (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail",
     "shortName": "Stockholders' Equity - Summary of RSU Activity (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "ix:continuation",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapAwardTypeAxis_us-gaapRestrictedStockUnitsRSUMember_20191231",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R34": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapPlanNameAxis_atraTwoThousandFourteenEquityIncentivePlanAndInducementPlanMember_20191231",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100340 - Disclosure - Stockholders' Equity - Summary of Stock Option Activity (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail",
     "shortName": "Stockholders' Equity - Summary of Stock Option Activity (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapPlanNameAxis_atraTwoThousandFourteenEquityIncentivePlanAndInducementPlanMember_20191231",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R35": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "atra:CommonStockReservedForFutureIssuanceTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200331",
      "decimals": "INF",
      "first": true,
      "lang": null,
      "name": "us-gaap:CommonStockCapitalSharesReservedForFutureIssuance",
      "reportCount": 1,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100350 - Disclosure - Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail",
     "shortName": "Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "atra:CommonStockReservedForFutureIssuanceTableTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapPlanNameAxis_atraTwoThousandEighteenInducementPlanMember_20200331",
      "decimals": "INF",
      "lang": null,
      "name": "us-gaap:CommonStockCapitalSharesReservedForFutureIssuance",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_xbrlishares",
      "xsiNil": "false"
     }
    },
    "R36": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AllocatedShareBasedCompensationExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100360 - Disclosure - Stockholders' Equity - Schedule of Stock-based Compensation Related to All Employee And Non-employee Stock Awards (Detail)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail",
     "shortName": "Stockholders' Equity - Schedule of Stock-based Compensation Related to All Employee And Non-employee Stock Awards (Detail)",
     "subGroupType": "details",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "us-gaap:ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock",
       "ix:continuation",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AllocatedShareBasedCompensationExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R4": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ResearchAndDevelopmentExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100030 - Statement - Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited",
     "shortName": "Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ResearchAndDevelopmentExpense",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R5": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20181231",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquity",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100040 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited",
     "shortName": "Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20181231",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:StockholdersEquity",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R6": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapStatementEquityComponentsAxis_us-gaapCommonStockMember_us-gaapSubsidiarySaleOfStockAxis_atraAtTheMarketOfferingMember_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100050 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
     "shortName": "Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (Unaudited)",
     "subGroupType": "parenthetical",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_us-gaapStatementEquityComponentsAxis_us-gaapCommonStockMember_us-gaapSubsidiarySaleOfStockAxis_atraAtTheMarketOfferingMember_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R7": {
     "firstAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     },
     "groupType": "statement",
     "isDefault": "false",
     "longName": "100060 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited",
     "shortName": "Condensed Consolidated Statements of Cash Flows (Unaudited)",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "p",
       "td",
       "tr",
       "table",
       "div",
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": "-3",
      "first": true,
      "lang": null,
      "name": "us-gaap:ProfitLoss",
      "reportCount": 1,
      "unique": true,
      "unitRef": "U_iso4217USD",
      "xsiNil": "false"
     }
    },
    "R8": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "atra:BusinessDescriptionTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100080 - Disclosure - Description of Business",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureDescriptionOfBusiness",
     "shortName": "Description of Business",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "atra:BusinessDescriptionTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    },
    "R9": {
     "firstAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SignificantAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     },
     "groupType": "disclosure",
     "isDefault": "false",
     "longName": "100090 - Disclosure - Summary of Significant Accounting Policies",
     "role": "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies",
     "shortName": "Summary of Significant Accounting Policies",
     "subGroupType": "",
     "uniqueAnchor": {
      "ancestors": [
       "body",
       "html"
      ],
      "baseRef": "atra-10q_20200331.htm",
      "contextRef": "C_0001604464_20200101_20200331",
      "decimals": null,
      "first": true,
      "lang": "en-US",
      "name": "us-gaap:SignificantAccountingPoliciesTextBlock",
      "reportCount": 1,
      "unique": true,
      "unitRef": null,
      "xsiNil": "false"
     }
    }
   },
   "segmentCount": 46,
   "tag": {
    "atra_AccruedCostsOfFinancingActivitiesChargedToStockholdersEquity": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accrued costs charged to stockholders' equity.",
        "label": "Accrued Costs Of Financing Activities Charged To Stockholders Equity",
        "terseLabel": "Accrued costs related to ATM facilities"
       }
      }
     },
     "localname": "AccruedCostsOfFinancingActivitiesChargedToStockholdersEquity",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_AccruedResearchAndDevelopmentExpensesCurrent": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10130.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accrued research and development expenses current.",
        "label": "Accrued Research And Development Expenses Current",
        "terseLabel": "Accrued research and development expenses"
       }
      }
     },
     "localname": "AccruedResearchAndDevelopmentExpensesCurrent",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_AccruedTerminationCharges": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accrued termination charges.",
        "label": "Accrued Termination Charges",
        "terseLabel": "Accrued termination charges"
       }
      }
     },
     "localname": "AccruedTerminationCharges",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_AggregateOfferingPriceOfCommonStock": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate Offering Price of common stock.",
        "label": "Aggregate Offering Price Of Common Stock",
        "terseLabel": "Common stock aggregate offering price"
       }
      }
     },
     "localname": "AggregateOfferingPriceOfCommonStock",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_AtTheMarketOfferingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "At the market offering.",
        "label": "At The Market Offering [Member]",
        "terseLabel": "At The Market Offering"
       }
      }
     },
     "localname": "AtTheMarketOfferingMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_BusinessDescriptionTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for the business description concept. Business description describes the nature and type of organization including but not limited to organizational structure as may be applicable to holding companies, parent and subsidiary relationships, business divisions, business units, business segments, affiliates and information about significant ownership of the reporting entity.",
        "label": "Business Description [Text Block]",
        "terseLabel": "Description of Business"
       }
      }
     },
     "localname": "BusinessDescriptionTextBlock",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureDescriptionOfBusiness"
     ],
     "xbrltype": "textBlockItemType"
    },
    "atra_CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10010.0,
       "parentTag": "atra_CashEquivalentsAmortizedCost",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash equivalents, accumulated gross unrealized gain, before tax.",
        "label": "Cash Equivalents Accumulated Gross Unrealized Gain Before Tax",
        "negatedLabel": "Total Unrealized Gain"
       }
      }
     },
     "localname": "CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10020.0,
       "parentTag": "atra_CashEquivalentsAmortizedCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash equivalents, accumulated gross unrealized loss, before tax.",
        "label": "Cash Equivalents Accumulated Gross Unrealized Loss Before Tax",
        "terseLabel": "Total Unrealized Loss"
       }
      }
     },
     "localname": "CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_CashEquivalentsAmortizedCost": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash equivalents, amortized cost.",
        "label": "Cash Equivalents Amortized Cost",
        "negatedTotalLabel": "Total Amortized Cost"
       }
      }
     },
     "localname": "CashEquivalentsAmortizedCost",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_CashEquivalentsFairValue": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10030.0,
       "parentTag": "atra_CashEquivalentsAmortizedCost",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cash equivalents, fair value.",
        "label": "Cash Equivalents Fair Value",
        "negatedLabel": "Total Fair Value"
       }
      }
     },
     "localname": "CashEquivalentsFairValue",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_ClassOfWarrantOrRightTerm": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Class of warrant or right, term.",
        "label": "Class Of Warrant Or Right Term",
        "terseLabel": "Warrants, term"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightTerm",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "atra_CommonStockAveragePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Common stock average price.",
        "label": "Common Stock Average Price",
        "terseLabel": "Common stock average price"
       }
      }
     },
     "localname": "CommonStockAveragePrice",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "atra_CommonStockReservedForFutureIssuanceTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Common stock reserved for future issuance.",
        "label": "Common Stock Reserved For Future Issuance Table [Text Block]",
        "terseLabel": "Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans"
       }
      }
     },
     "localname": "CommonStockReservedForFutureIssuanceTableTextBlock",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "atra_CommonStockValueRemainedAvailableToBeSold": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Common stock value remained available to be sold.",
        "label": "Common Stock Value Remained Available To Be Sold",
        "terseLabel": "Common stock value remaining to be sold"
       }
      }
     },
     "localname": "CommonStockValueRemainedAvailableToBeSold",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_ComputerEquipmentAndSoftwareMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Computer equipment and software.",
        "label": "Computer Equipment And Software [Member]",
        "terseLabel": "Computer Equipment and Software"
       }
      }
     },
     "localname": "ComputerEquipmentAndSoftwareMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_CowenAndCompanyLimitedLiabilityCompanyMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cowen and Company Limited Liability Company.",
        "label": "Cowen And Company Limited Liability Company [Member]",
        "terseLabel": "Cowen"
       }
      }
     },
     "localname": "CowenAndCompanyLimitedLiabilityCompanyMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_DueToLicensorsCurrentAndNoncurrent": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount as of the balance sheet date of obligations due all licensors.",
        "label": "Due To Licensors Current And Noncurrent",
        "terseLabel": "Contractual obligations due to MSK and QIMR"
       }
      }
     },
     "localname": "DueToLicensorsCurrentAndNoncurrent",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_EmployeeStockPurchasePlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Employee stock purchase plan.",
        "label": "Employee Stock Purchase Plan [Member]",
        "terseLabel": "ESPP Share Purchase Rights"
       }
      }
     },
     "localname": "EmployeeStockPurchasePlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_EmployeesAndNonEmployeesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Employees and non-employees.",
        "label": "Employees And Non Employees [Member]",
        "terseLabel": "Employees And Non Employees"
       }
      }
     },
     "localname": "EmployeesAndNonEmployeesMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_FinanceLeaseAssetsObtainedInExchangeForLeaseObligations": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Finance lease assets obtained in exchange for lease obligations.",
        "label": "Finance Lease Assets Obtained In Exchange For Lease Obligations",
        "terseLabel": "Finance lease assets obtained in exchange for lease obligations"
       }
      }
     },
     "localname": "FinanceLeaseAssetsObtainedInExchangeForLeaseObligations",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_FinancialInstrumentsDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "financial instruments disclosure.",
        "label": "Financial Instruments Disclosure [Abstract]"
       }
      }
     },
     "localname": "FinancialInstrumentsDisclosureAbstract",
     "nsuri": "http://www.atarabio.com/20200331",
     "xbrltype": "stringItemType"
    },
    "atra_FromDateOfGrantMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Expire from date of grant.",
        "label": "From Date Of Grant [Member]",
        "terseLabel": "From Date Of Grant"
       }
      }
     },
     "localname": "FromDateOfGrantMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_IncreaseDecreaseInAccruedResearchAndDevelopment": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10220.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Increase (decrease) in accrued research and development.",
        "label": "Increase Decrease In Accrued Research And Development",
        "terseLabel": "Accrued research and development expenses"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccruedResearchAndDevelopment",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_IncreaseDecreaseInOperatingLeaseLiabilities": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10240.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Increase (decrease) in operating lease liabilities.",
        "label": "Increase Decrease In Operating Lease Liabilities",
        "terseLabel": "Operating lease liabilities"
       }
      }
     },
     "localname": "IncreaseDecreaseInOperatingLeaseLiabilities",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_InducementPlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Inducement plan.",
        "label": "Inducement Plan [Member]",
        "terseLabel": "Inducement Plan"
       }
      }
     },
     "localname": "InducementPlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Issuance of Common Stock, Net of Commissions and Offering Costs, Shares.",
        "label": "Issuance Of Common Stock Net Of Commissions And Offering Costs Shares",
        "terseLabel": "Issuance of common stock, net of commissions and offering costs, shares"
       }
      }
     },
     "localname": "IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Issuance of common stock, net of commissions and offering costs, value.",
        "label": "Issuance Of Common Stock Net Of Commissions And Offering Costs Value",
        "terseLabel": "Issuance of common stock, net of commissions and offering costs, value"
       }
      }
     },
     "localname": "IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Issuance of common stock pursuant to employee stock awards shares.",
        "label": "Issuance Of Common Stock Pursuant To Employee Stock Awards Shares",
        "terseLabel": "Issuance of common stock pursuant to employee stock awards, shares"
       }
      }
     },
     "localname": "IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Issuance of common stock pursuant to employee stock awards value.",
        "label": "Issuance Of Common Stock Pursuant To Employee Stock Awards Value",
        "terseLabel": "Issuance of common stock pursuant to employee stock awards"
       }
      }
     },
     "localname": "IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_LiabilitiesRelatedToIndemnificationAgreements": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Liabilities related to indemnification agreements.",
        "label": "Liabilities Related To Indemnification Agreements",
        "terseLabel": "Liabilities related to indemnification agreements"
       }
      }
     },
     "localname": "LiabilitiesRelatedToIndemnificationAgreements",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_LicenseCollaborationAndManufacturingAgreementsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "License, collaboration and manufacturing agreements.",
        "label": "License Collaboration And Manufacturing Agreements [Abstract]"
       }
      }
     },
     "localname": "LicenseCollaborationAndManufacturingAgreementsAbstract",
     "nsuri": "http://www.atarabio.com/20200331",
     "xbrltype": "stringItemType"
    },
    "atra_LicenseCollaborationAndManufacturingAgreementsLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "License, collaboration and manufacturing agreements.",
        "label": "License Collaboration And Manufacturing Agreements [Line Items]",
        "terseLabel": "License Collaboration And Manufacturing Agreements [Line Items]"
       }
      }
     },
     "localname": "LicenseCollaborationAndManufacturingAgreementsLineItems",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "atra_LiquidityAndGoingConcernPolicyTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Liquidity and Going Concern.",
        "label": "Liquidity And Going Concern Policy [Text Block]",
        "terseLabel": "Liquidity and Going Concern"
       }
      }
     },
     "localname": "LiquidityAndGoingConcernPolicyTextBlock",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "atra_MaximumOwnershipPercentage": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Maximum ownership percentage.",
        "label": "Maximum Ownership Percentage",
        "terseLabel": "Maximum ownership Percentage"
       }
      }
     },
     "localname": "MaximumOwnershipPercentage",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "atra_MemorialSloanKetteringCancerCenterAgreementMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "MSK agreement.",
        "label": "Memorial Sloan Kettering Cancer Center Agreement [Member]",
        "terseLabel": "MSK Agreements"
       }
      }
     },
     "localname": "MemorialSloanKetteringCancerCenterAgreementMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_NonCashOperatingLeaseExpense": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10160.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Non cash operating lease expense.",
        "label": "Non Cash Operating Lease Expense",
        "terseLabel": "Non-cash operating lease expense"
       }
      }
     },
     "localname": "NonCashOperatingLeaseExpense",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_PaymentsForResearchAndDevelopment": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Payments for research and development.",
        "label": "Payments For Research And Development",
        "verboseLabel": "Payments for research and development"
       }
      }
     },
     "localname": "PaymentsForResearchAndDevelopment",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Percentage of commission to be paid on gross sales proceeds of common stock sold.",
        "label": "Percentage Of Commission To Be Paid On Gross Sales Proceeds Of Common Stock Sold",
        "terseLabel": "Percentage of commission to be paid on gross sales proceeds of common stock sold"
       }
      }
     },
     "localname": "PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "atra_PotentialMilestonePaymentsPayable": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Potential milestone payments payable.",
        "label": "Potential Milestone Payments Payable",
        "terseLabel": "Potential milestone payments payable"
       }
      }
     },
     "localname": "PotentialMilestonePaymentsPayable",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Prior notice period to increase or decrease maximum ownership percentage.",
        "label": "Prior Notice Period To Increase Or Decrease Maximum Ownership Percentage",
        "terseLabel": "Prior notice period"
       }
      }
     },
     "localname": "PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "atra_ProceedsFromIssuanceOfCommonStockGross": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Proceeds from issuance of common stock gross.",
        "label": "Proceeds From Issuance Of Common Stock Gross",
        "verboseLabel": "Proceeds from sale of common stock, gross"
       }
      }
     },
     "localname": "ProceedsFromIssuanceOfCommonStockGross",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_ReceivableForOptionsExercised": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Receivable for options exercised.",
        "label": "Receivable For Options Exercised",
        "terseLabel": "Receivable for options exercised"
       }
      }
     },
     "localname": "ReceivableForOptionsExercised",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of license, collaboration and manufacturing agreements.",
        "label": "Schedule Of License Collaboration And Manufacturing Agreements [Table]",
        "terseLabel": "Schedule Of License Collaboration And Manufacturing Agreements [Table]"
       }
      }
     },
     "localname": "ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "atra_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share based compensation arrangement by share based payment award equity instruments options and restricted stock units outstanding.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Options And Restricted Stock Units Outstanding",
        "terseLabel": "Outstanding options and RSUs"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "atra_ShareholderOwnershipPercent": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Shareholders ownership percent.",
        "label": "Shareholder Ownership Percent",
        "terseLabel": "Ownership percent"
       }
      }
     },
     "localname": "ShareholderOwnershipPercent",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "atra_StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Stock issued during period shares stock options exercised of pre-funded warrants.",
        "label": "Stock Issued During Period Shares Stock Options Exercised Of Pre Funded Warrants",
        "terseLabel": "Exercise of pre-funded warrants, shares"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "atra_StockIssuedDuringPeriodValueStockOptionsExercisedOfPreFundedWarrants": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Stock issued during period value stock options exercised of pre funded warrants.",
        "label": "Stock Issued During Period Value Stock Options Exercised Of Pre Funded Warrants",
        "terseLabel": "Exercise of pre-funded warrants"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodValueStockOptionsExercisedOfPreFundedWarrants",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "atra_SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summary of estimated fair value and related valuation input hierarchy of available-for-sale securities.",
        "label": "Summary Of Estimated Fair Value And Related Valuation Input Hierarchy Of Available For Sale Securities Table [Text Block]",
        "terseLabel": "Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities"
       }
      }
     },
     "localname": "SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "atra_TenPercentShareHolderMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Ten percent share holder.",
        "label": "Ten Percent Share Holder [Member]",
        "terseLabel": "10% Shareholder"
       }
      }
     },
     "localname": "TenPercentShareHolderMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandAndFourteenEquityIncentivePlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two thousand and fourteen equity incentive plan.",
        "label": "Two Thousand And Fourteen Equity Incentive Plan [Member]",
        "terseLabel": "2014 Equity Incentive Plan"
       }
      }
     },
     "localname": "TwoThousandAndFourteenEquityIncentivePlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandEighteenInducementPlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two thousand eighteen inducement plan.",
        "label": "Two Thousand Eighteen Inducement Plan [Member]",
        "terseLabel": "2018 Inducement Plan"
       }
      }
     },
     "localname": "TwoThousandEighteenInducementPlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandFourteenEmployeeStockPurchasePlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two thousand fourteen employee stock purchase plan.",
        "label": "Two Thousand Fourteen Employee Stock Purchase Plan [Member]",
        "terseLabel": "2014 Employee Stock Purchase Plan"
       }
      }
     },
     "localname": "TwoThousandFourteenEmployeeStockPurchasePlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "2014 EIP and Inducement Plan.",
        "label": "Two Thousand Fourteen Equity Incentive Plan And Inducement Plan [Member]",
        "terseLabel": "2014 EIP and Inducement Plan"
       }
      }
     },
     "localname": "TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandNineteenAtTheMarketOfferingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two thousand nineteen at the market offering.",
        "label": "Two Thousand Nineteen At The Market Offering [Member]",
        "terseLabel": "2019 ATM Facility"
       }
      }
     },
     "localname": "TwoThousandNineteenAtTheMarketOfferingMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_TwoThousandTwentyAtTheMarketOfferingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two thousand twenty at the market offering.",
        "label": "Two Thousand Twenty At The Market Offering [Member]",
        "terseLabel": "2020 ATM Facility"
       }
      }
     },
     "localname": "TwoThousandTwentyAtTheMarketOfferingMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_UnderwrittenPublicOfferingMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Underwritten public offering.",
        "label": "Underwritten Public Offering [Member]",
        "terseLabel": "Underwritten Public Offering"
       }
      }
     },
     "localname": "UnderwrittenPublicOfferingMember",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "atra_WriteOffOfAccruedInterestReceivable": {
     "auth_ref": [],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Write off of accrued interest receivable.",
        "label": "Write Off Of Accrued Interest Receivable",
        "terseLabel": "Write off, of accrued interest receivable"
       }
      }
     },
     "localname": "WriteOffOfAccruedInterestReceivable",
     "nsuri": "http://www.atarabio.com/20200331",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "dei_AmendmentFlag": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.",
        "label": "Amendment Flag",
        "terseLabel": "Amendment Flag"
       }
      }
     },
     "localname": "AmendmentFlag",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_CityAreaCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Area code of city",
        "label": "City Area Code",
        "terseLabel": "City Area Code"
       }
      }
     },
     "localname": "CityAreaCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_CoverAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Cover page.",
        "label": "Cover [Abstract]"
       }
      }
     },
     "localname": "CoverAbstract",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "dei_CurrentFiscalYearEndDate": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "End date of current fiscal year in the format --MM-DD.",
        "label": "Current Fiscal Year End Date",
        "terseLabel": "Current Fiscal Year End Date"
       }
      }
     },
     "localname": "CurrentFiscalYearEndDate",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "gMonthDayItemType"
    },
    "dei_DocumentFiscalPeriodFocus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fiscal period values are FY, Q1, Q2, and Q3.  1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY.",
        "label": "Document Fiscal Period Focus",
        "terseLabel": "Document Fiscal Period Focus"
       }
      }
     },
     "localname": "DocumentFiscalPeriodFocus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "fiscalPeriodItemType"
    },
    "dei_DocumentFiscalYearFocus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.",
        "label": "Document Fiscal Year Focus",
        "terseLabel": "Document Fiscal Year Focus"
       }
      }
     },
     "localname": "DocumentFiscalYearFocus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "dateItemType"
    },
    "dei_DocumentQuarterlyReport": {
     "auth_ref": [
      "r231"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true only for a form used as an quarterly report.",
        "label": "Document Quarterly Report",
        "terseLabel": "Document Quarterly Report"
       }
      }
     },
     "localname": "DocumentQuarterlyReport",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_DocumentTransitionReport": {
     "auth_ref": [
      "r232"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true only for a form used as a transition report.",
        "label": "Document Transition Report",
        "terseLabel": "Document Transition Report"
       }
      }
     },
     "localname": "DocumentTransitionReport",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_DocumentType": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.",
        "label": "Document Type",
        "verboseLabel": "Document Type"
       }
      }
     },
     "localname": "DocumentType",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "submissionTypeItemType"
    },
    "dei_EntityAddressAddressLine1": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Address Line 1 such as Attn, Building Name, Street Name",
        "label": "Entity Address Address Line1",
        "terseLabel": "Entity Address, Address Line One"
       }
      }
     },
     "localname": "EntityAddressAddressLine1",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressAddressLine2": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Address Line 2 such as Street or Suite number",
        "label": "Entity Address Address Line2",
        "terseLabel": "Entity Address, Address Line Two"
       }
      }
     },
     "localname": "EntityAddressAddressLine2",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressCityOrTown": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the City or Town",
        "label": "Entity Address City Or Town",
        "terseLabel": "Entity Address, City or Town"
       }
      }
     },
     "localname": "EntityAddressCityOrTown",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressPostalZipCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Code for the postal or zip code",
        "label": "Entity Address Postal Zip Code",
        "terseLabel": "Entity Address, Postal Zip Code"
       }
      }
     },
     "localname": "EntityAddressPostalZipCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityAddressStateOrProvince": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the state or province.",
        "label": "Entity Address State Or Province",
        "terseLabel": "Entity Address, State or Province"
       }
      }
     },
     "localname": "EntityAddressStateOrProvince",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "stateOrProvinceItemType"
    },
    "dei_EntityCentralIndexKey": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.",
        "label": "Entity Central Index Key",
        "terseLabel": "Entity Central Index Key"
       }
      }
     },
     "localname": "EntityCentralIndexKey",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "sharesItemType"
    },
    "dei_EntityCurrentReportingStatus": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure.",
        "label": "Entity Current Reporting Status",
        "terseLabel": "Entity Current Reporting Status"
       }
      }
     },
     "localname": "EntityCurrentReportingStatus",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_EntityEmergingGrowthCompany": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate if registrant meets the emerging growth company criteria.",
        "label": "Entity Emerging Growth Company",
        "terseLabel": "Entity Emerging Growth Company"
       }
      }
     },
     "localname": "EntityEmergingGrowthCompany",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntityFileNumber": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.",
        "label": "Entity File Number",
        "terseLabel": "Entity File Number"
       }
      }
     },
     "localname": "EntityFileNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "fileNumberItemType"
    },
    "dei_EntityFilerCategory": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.",
        "label": "Entity Filer Category",
        "terseLabel": "Entity Filer Category"
       }
      }
     },
     "localname": "EntityFilerCategory",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "filerCategoryItemType"
    },
    "dei_EntityIncorporationDateOfIncorporation": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Date when an entity was incorporated",
        "label": "Entity Incorporation Date Of Incorporation",
        "terseLabel": "Entity incorporation date"
       }
      }
     },
     "localname": "EntityIncorporationDateOfIncorporation",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureDescriptionOfBusinessDetail"
     ],
     "xbrltype": "dateItemType"
    },
    "dei_EntityIncorporationStateCountryCode": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Two-character EDGAR code representing the state or country of incorporation.",
        "label": "Entity Incorporation State Country Code",
        "terseLabel": "Entity Incorporation, State or Country Code",
        "verboseLabel": "Entity incorporation state"
       }
      }
     },
     "localname": "EntityIncorporationStateCountryCode",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureDescriptionOfBusinessDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "edgarStateCountryItemType"
    },
    "dei_EntityInteractiveDataCurrent": {
     "auth_ref": [
      "r234"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).",
        "label": "Entity Interactive Data Current",
        "terseLabel": "Entity Interactive Data Current"
       }
      }
     },
     "localname": "EntityInteractiveDataCurrent",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "yesNoItemType"
    },
    "dei_EntityRegistrantName": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.",
        "label": "Entity Registrant Name",
        "terseLabel": "Entity Registrant Name"
       }
      }
     },
     "localname": "EntityRegistrantName",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_EntityShellCompany": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.",
        "label": "Entity Shell Company",
        "terseLabel": "Entity Shell Company"
       }
      }
     },
     "localname": "EntityShellCompany",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntitySmallBusiness": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Indicates that the company is a Smaller Reporting Company (SRC).",
        "label": "Entity Small Business",
        "terseLabel": "Entity Small Business"
       }
      }
     },
     "localname": "EntitySmallBusiness",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "booleanItemType"
    },
    "dei_EntityTaxIdentificationNumber": {
     "auth_ref": [
      "r233"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.",
        "label": "Entity Tax Identification Number",
        "terseLabel": "Entity Tax Identification Number"
       }
      }
     },
     "localname": "EntityTaxIdentificationNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "employerIdItemType"
    },
    "dei_LocalPhoneNumber": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Local phone number for entity.",
        "label": "Local Phone Number",
        "terseLabel": "Local Phone Number"
       }
      }
     },
     "localname": "LocalPhoneNumber",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "normalizedStringItemType"
    },
    "dei_Security12bTitle": {
     "auth_ref": [
      "r229"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Title of a 12(b) registered security.",
        "label": "Security12b Title",
        "terseLabel": "Title of 12(b) Security"
       }
      }
     },
     "localname": "Security12bTitle",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "securityTitleItemType"
    },
    "dei_SecurityExchangeName": {
     "auth_ref": [
      "r230"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Name of the Exchange on which a security is registered.",
        "label": "Security Exchange Name",
        "terseLabel": "Security Exchange Name"
       }
      }
     },
     "localname": "SecurityExchangeName",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "edgarExchangeCodeItemType"
    },
    "dei_TradingSymbol": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Trading symbol of an instrument as listed on an exchange.",
        "label": "Trading Symbol",
        "terseLabel": "Trading Symbol"
       }
      }
     },
     "localname": "TradingSymbol",
     "nsuri": "http://xbrl.sec.gov/dei/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DocumentDocumentAndEntityInformation"
     ],
     "xbrltype": "tradingSymbolItemType"
    },
    "srt_CounterpartyNameAxis": {
     "auth_ref": [
      "r35",
      "r73"
     ],
     "lang": {
      "en-US": {
       "role": {
        "label": "Counterparty Name [Axis]",
        "terseLabel": "Counterparty Name"
       }
      }
     },
     "localname": "CounterpartyNameAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_MaximumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Maximum [Member]",
        "terseLabel": "Maximum"
       }
      }
     },
     "localname": "MaximumMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_MinimumMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Minimum [Member]",
        "terseLabel": "Minimum"
       }
      }
     },
     "localname": "MinimumMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_RangeAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Range [Axis]",
        "terseLabel": "Statistical Measurement"
       }
      }
     },
     "localname": "RangeAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_RangeMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Range [Member]",
        "terseLabel": "Statistical Measurement"
       }
      }
     },
     "localname": "RangeMember",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_RepurchaseAgreementCounterpartyNameDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Repurchase Agreement Counterparty Name [Domain]",
        "terseLabel": "Counterparty Name"
       }
      }
     },
     "localname": "RepurchaseAgreementCounterpartyNameDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "srt_TitleOfIndividualAxis": {
     "auth_ref": [
      "r92",
      "r194"
     ],
     "lang": {
      "en-US": {
       "role": {
        "label": "Title Of Individual [Axis]",
        "terseLabel": "Title of Individual"
       }
      }
     },
     "localname": "TitleOfIndividualAxis",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "srt_TitleOfIndividualWithRelationshipToEntityDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Title Of Individual With Relationship To Entity [Domain]",
        "terseLabel": "Title of Individual"
       }
      }
     },
     "localname": "TitleOfIndividualWithRelationshipToEntityDomain",
     "nsuri": "http://fasb.org/srt/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AccountingPoliciesAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Accounting Policies [Abstract]"
       }
      }
     },
     "localname": "AccountingPoliciesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_AccountsPayableCurrent": {
     "auth_ref": [
      "r24"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10110.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).",
        "label": "Accounts Payable Current",
        "terseLabel": "Accounts payable"
       }
      }
     },
     "localname": "AccountsPayableCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccretionExpense": {
     "auth_ref": [
      "r123",
      "r124"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10170.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.",
        "label": "Accretion Expense",
        "terseLabel": "Asset retirement obligation accretion expense"
       }
      }
     },
     "localname": "AccretionExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment": {
     "auth_ref": [
      "r22",
      "r119"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail": {
       "order": 10020.0,
       "parentTag": "us-gaap_PropertyPlantAndEquipmentNet",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.",
        "label": "Accumulated Depreciation Depletion And Amortization Property Plant And Equipment",
        "negatedLabel": "Less: accumulated depreciation and amortization"
       }
      }
     },
     "localname": "AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax": {
     "auth_ref": [
      "r38",
      "r39",
      "r40"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10060.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.",
        "label": "Accumulated Other Comprehensive Income Loss Net Of Tax",
        "terseLabel": "Accumulated other comprehensive income"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeLossNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AccumulatedOtherComprehensiveIncomeMember": {
     "auth_ref": [
      "r37",
      "r40",
      "r41",
      "r180"
     ],
     "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": "Accumulated Other Comprehensive Income [Member]",
        "terseLabel": "Accumulated Other Comprehensive (Loss) Income"
       }
      }
     },
     "localname": "AccumulatedOtherComprehensiveIncomeMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdditionalPaidInCapitalCommonStock": {
     "auth_ref": [
      "r13"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10050.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value received from shareholders in common stock-related transactions that are in excess of par value or stated value and amounts received from other stock-related transactions. Includes only common stock transactions (excludes preferred stock transactions). May be called contributed capital, capital in excess of par, capital surplus, or paid-in capital.",
        "label": "Additional Paid In Capital Common Stock",
        "terseLabel": "Additional paid-in capital"
       }
      }
     },
     "localname": "AdditionalPaidInCapitalCommonStock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AdditionalPaidInCapitalMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders.",
        "label": "Additional Paid In Capital [Member]",
        "terseLabel": "Additional Paid-in Capital"
       }
      }
     },
     "localname": "AdditionalPaidInCapitalMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue": {
     "auth_ref": [
      "r144",
      "r146",
      "r170",
      "r171"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase to additional paid-in capital (APIC) for recognition of cost for award under share-based payment arrangement.",
        "label": "Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value",
        "terseLabel": "Stock-based compensation expense"
       }
      }
     },
     "localname": "AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts": {
     "auth_ref": [
      "r132",
      "r139"
     ],
     "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",
        "terseLabel": "Stock issuance, discounts, commissions and offering costs"
       }
      }
     },
     "localname": "AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited"
     ],
     "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 loss to net cash used in operating activities:"
       }
      }
     },
     "localname": "AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AllocatedShareBasedCompensationExpense": {
     "auth_ref": [
      "r146",
      "r166",
      "r169"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.",
        "label": "Allocated Share Based Compensation Expense",
        "verboseLabel": "Total stock-based compensation expense"
       }
      }
     },
     "localname": "AllocatedShareBasedCompensationExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount": {
     "auth_ref": [
      "r80"
     ],
     "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": "Antidilutive securities excluded from computation of earnings per share"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis": {
     "auth_ref": [
      "r80"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of antidilutive security.",
        "label": "Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis]",
        "terseLabel": "Antidilutive Securities"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AntidilutiveSecuritiesNameDomain": {
     "auth_ref": [
      "r80"
     ],
     "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"
       }
      }
     },
     "localname": "AntidilutiveSecuritiesNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ArrangementsAndNonarrangementTransactionsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations.",
        "label": "Arrangements And Nonarrangement Transactions [Member]",
        "terseLabel": "Collaborative Arrangement and Arrangement Other than Collaborative"
       }
      }
     },
     "localname": "ArrangementsAndNonarrangementTransactionsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_AssetBackedSecuritiesMember": {
     "auth_ref": [
      "r104",
      "r141"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Securities that are primarily serviced by the cash flows of a discrete pool of receivables or other financial assets for example, but not limited to, credit card receivables, car loans, recreational vehicle loans, and mobile home loans.",
        "label": "Asset Backed Securities [Member]",
        "terseLabel": "Asset-Backed Securities"
       }
      }
     },
     "localname": "AssetBackedSecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Assets": {
     "auth_ref": [
      "r90",
      "r199",
      "r214"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "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",
        "totalLabel": "Total assets"
       }
      }
     },
     "localname": "Assets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets [Abstract]",
        "terseLabel": "Assets"
       }
      }
     },
     "localname": "AssetsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AssetsCurrent": {
     "auth_ref": [
      "r1",
      "r2",
      "r34"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10150.0,
       "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AssetsCurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Assets Current [Abstract]",
        "terseLabel": "Current assets:"
       }
      }
     },
     "localname": "AssetsCurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax": {
     "auth_ref": [
      "r97"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10040.0,
       "parentTag": "us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).",
        "label": "Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax",
        "terseLabel": "Total Unrealized Gain"
       }
      }
     },
     "localname": "AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax": {
     "auth_ref": [
      "r98"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10050.0,
       "parentTag": "us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).",
        "label": "Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax",
        "negatedLabel": "Total Unrealized Loss"
       }
      }
     },
     "localname": "AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis": {
     "auth_ref": [
      "r95",
      "r114"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).",
        "label": "Available For Sale Debt Securities Amortized Cost Basis",
        "totalLabel": "Total Amortized Cost"
       }
      }
     },
     "localname": "AvailableForSaleDebtSecuritiesAmortizedCostBasis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost": {
     "auth_ref": [
      "r102"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": 10040.0,
       "parentTag": "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.",
        "label": "Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost",
        "terseLabel": "Maturing in one to five years, Amortized cost"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue": {
     "auth_ref": [
      "r99",
      "r102",
      "r210"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": 10020.0,
       "parentTag": "us-gaap_AvailableForSaleSecuritiesDebtSecurities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.",
        "label": "Available For Sale Securities Debt Maturities After One Through Five Years Fair Value",
        "terseLabel": "Maturing in one to five years, Estimated fair value"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Available For Sale Securities Debt Maturities Fair Value [Abstract]",
        "terseLabel": "Estimated Fair value"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis": {
     "auth_ref": [
      "r99",
      "r103",
      "r211"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date.",
        "label": "Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis",
        "totalLabel": "Total available-for-sale securities, Amortized cost"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis [Abstract]",
        "terseLabel": "Amortized cost"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost": {
     "auth_ref": [
      "r101"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": 10030.0,
       "parentTag": "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amortized cost of investment in debt security measured at fair value with change recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.",
        "label": "Available For Sale Securities Debt Maturities Within One Year Amortized Cost",
        "terseLabel": "Maturing within one year, Amortized cost"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue": {
     "auth_ref": [
      "r99",
      "r101",
      "r209"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": 10010.0,
       "parentTag": "us-gaap_AvailableForSaleSecuritiesDebtSecurities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.",
        "label": "Available For Sale Securities Debt Maturities Within One Year Fair Value",
        "terseLabel": "Maturing within one year, Estimated fair value"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AvailableForSaleSecuritiesDebtSecurities": {
     "auth_ref": [
      "r94",
      "r96",
      "r114"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail": {
       "order": 10060.0,
       "parentTag": "us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).",
        "label": "Available For Sale Securities Debt Securities",
        "terseLabel": "Total Fair Value",
        "totalLabel": "Total available-for-sale securities, Estimated fair value"
       }
      }
     },
     "localname": "AvailableForSaleSecuritiesDebtSecurities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAmortizedCostAndFairValueOfAvailableForSaleSecuritiesByContractualMaturityDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_AwardTypeAxis": {
     "auth_ref": [
      "r147",
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of award under share-based payment arrangement.",
        "label": "Award Type [Axis]",
        "terseLabel": "Award Type"
       }
      }
     },
     "localname": "AwardTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_BasisOfAccountingPolicyPolicyTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of accounting policy for basis of accounting, or basis of presentation, used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).",
        "label": "Basis Of Accounting Policy Policy [Text Block]",
        "terseLabel": "Basis of Presentation"
       }
      }
     },
     "localname": "BasisOfAccountingPolicyPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CapitalExpendituresIncurredButNotYetPaid": {
     "auth_ref": [
      "r69",
      "r70",
      "r71"
     ],
     "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 and equipment purchases included in accounts payable and other accrued liabilities"
       }
      }
     },
     "localname": "CapitalExpendituresIncurredButNotYetPaid",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CapitalUnitsAuthorized": {
     "auth_ref": [
      "r222"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of authorized capital units or capital shares. This element is relevant to issuers of face-amount certificates and registered investment companies.",
        "label": "Capital Units Authorized",
        "terseLabel": "Authorized capital stock"
       }
      }
     },
     "localname": "CapitalUnitsAuthorized",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CashAndCashEquivalentsAtCarryingValue": {
     "auth_ref": [
      "r0",
      "r20",
      "r67"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail": {
       "order": 10010.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
       "weight": 1.0
      },
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10200.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.",
        "label": "Cash And Cash Equivalents At Carrying Value",
        "terseLabel": "Cash and cash equivalents"
       }
      }
     },
     "localname": "CashAndCashEquivalentsAtCarryingValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents": {
     "auth_ref": [
      "r61",
      "r67",
      "r72"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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",
        "totalLabel": "Total cash, cash equivalents and restricted cash"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect": {
     "auth_ref": [
      "r61",
      "r189"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "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": "Decrease in cash, cash equivalents and restricted cash"
       }
      }
     },
     "localname": "CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CashEquivalentsMember": {
     "auth_ref": [
      "r6"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "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 Equivalents [Member]",
        "terseLabel": "Amounts Classified As Cash Equivalents"
       }
      }
     },
     "localname": "CashEquivalentsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]",
        "terseLabel": "Non-cash investing and financing activities"
       }
      }
     },
     "localname": "CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_CertificatesOfDepositMember": {
     "auth_ref": [
      "r212"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Short to medium-term investment available at banks and savings and loan institutions where a customer agrees to lend money to the institution for a certain amount of time and is paid a predetermined rate of interest. Certificates of deposit (CD) are typically Federal Deposit Insurance Corporation (FDIC) insured.",
        "label": "Certificates Of Deposit [Member]",
        "terseLabel": "Certificates of Deposit"
       }
      }
     },
     "localname": "CertificatesOfDepositMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ClassOfStockLineItems": {
     "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": "Class Of Stock [Line Items]",
        "terseLabel": "Class Of Stock [Line Items]"
       }
      }
     },
     "localname": "ClassOfStockLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1": {
     "auth_ref": [
      "r75"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Exercise price per share or per unit of warrants or rights outstanding.",
        "label": "Class Of Warrant Or Right Exercise Price Of Warrants Or Rights1",
        "terseLabel": "Warrants, exercise price"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.",
        "label": "Class Of Warrant Or Right Number Of Securities Called By Each Warrant Or Right",
        "terseLabel": "Number of securities called by each warrant"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ClassOfWarrantOrRightOutstanding": {
     "auth_ref": [
      "r76"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of warrants or rights outstanding.",
        "label": "Class Of Warrant Or Right Outstanding",
        "terseLabel": "Warrants outstanding"
       }
      }
     },
     "localname": "ClassOfWarrantOrRightOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CollaborativeArrangementDisclosureTextBlock": {
     "auth_ref": [
      "r173",
      "r174",
      "r176"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for collaborative arrangements in which the entity is a participant, including a) information about the nature and purpose of such arrangements; b) its rights and obligations thereunder; c) the accounting policy for collaborative arrangements; and d) the income statement classification and amounts attributable to transactions arising from the collaborative arrangement between participants.",
        "label": "Collaborative Arrangement Disclosure [Text Block]",
        "terseLabel": "License and Collaboration Agreements"
       }
      }
     },
     "localname": "CollaborativeArrangementDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreements"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CommercialPaperMember": {
     "auth_ref": [
      "r128"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommitmentsAndContingencies": {
     "auth_ref": [
      "r29",
      "r126",
      "r205",
      "r219"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10020.0,
       "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 (Note 7)"
       }
      }
     },
     "localname": "CommitmentsAndContingencies",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_CommitmentsAndContingenciesDisclosureAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Commitments And Contingencies Disclosure [Abstract]"
       }
      }
     },
     "localname": "CommitmentsAndContingenciesDisclosureAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CommitmentsAndContingenciesDisclosureTextBlock": {
     "auth_ref": [
      "r125",
      "r127"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for commitments and contingencies.",
        "label": "Commitments And Contingencies Disclosure [Text Block]",
        "terseLabel": "Commitments and Contingencies"
       }
      }
     },
     "localname": "CommitmentsAndContingenciesDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCommitmentsAndContingencies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_CommonStockCapitalSharesReservedForFutureIssuance": {
     "auth_ref": [
      "r31"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate number of common shares reserved for future issuance.",
        "label": "Common Stock Capital Shares Reserved For Future Issuance",
        "terseLabel": "Total reserved shares of common stock",
        "verboseLabel": "Shares of common stock, reserved for issuance"
       }
      }
     },
     "localname": "CommonStockCapitalSharesReservedForFutureIssuance",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockIncludingAdditionalPaidInCapitalNetOfDiscountAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Common Stock Including Additional Paid In Capital Net Of Discount [Abstract]"
       }
      }
     },
     "localname": "CommonStockIncludingAdditionalPaidInCapitalNetOfDiscountAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CommonStockMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Stock that is subordinate to all other stock of the issuer.",
        "label": "Common Stock [Member]",
        "terseLabel": "Common Stock"
       }
      }
     },
     "localname": "CommonStockMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CommonStockParOrStatedValuePerShare": {
     "auth_ref": [
      "r12"
     ],
     "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"
       }
      }
     },
     "localname": "CommonStockParOrStatedValuePerShare",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_CommonStockSharesAuthorized": {
     "auth_ref": [
      "r12"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesIssued": {
     "auth_ref": [
      "r12"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockSharesOutstanding": {
     "auth_ref": [
      "r12",
      "r132"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParentheticalUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_CommonStockValue": {
     "auth_ref": [
      "r12"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10040.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity.",
        "label": "Common Stock Value",
        "terseLabel": "Common stock\u2014$0.0001 par value, 500,000 shares authorized as of March 31, 2020 and December 31, 2019; 58,940 and 56,806 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively"
       }
      }
     },
     "localname": "CommonStockValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ComprehensiveIncomeNetOfTax": {
     "auth_ref": [
      "r43",
      "r45",
      "r46"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "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 Net Of Tax",
        "totalLabel": "Comprehensive loss"
       }
      }
     },
     "localname": "ComprehensiveIncomeNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ConstructionInProgressMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.",
        "label": "Construction In Progress [Member]",
        "terseLabel": "Construction in Progress"
       }
      }
     },
     "localname": "ConstructionInProgressMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CorporateDebtSecuritiesMember": {
     "auth_ref": [
      "r141",
      "r143",
      "r221"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Debt securities issued by domestic or foreign corporate business, banks and other entities with a promise of repayment.",
        "label": "Corporate Debt Securities [Member]",
        "terseLabel": "Corporate Debt Obligations"
       }
      }
     },
     "localname": "CorporateDebtSecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_CreditLossAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Credit Loss [Abstract]"
       }
      }
     },
     "localname": "CreditLossAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_CreditLossFinancialInstrumentTextBlock": {
     "auth_ref": [
      "r109",
      "r110",
      "r111",
      "r112",
      "r113",
      "r115",
      "r116"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for credit loss on financial instrument measured at amortized cost basis, net investment in lease, off-balance sheet credit exposure, and available-for-sale debt security.",
        "label": "Credit Loss Financial Instrument [Text Block]",
        "terseLabel": "Credit Losses"
       }
      }
     },
     "localname": "CreditLossFinancialInstrumentTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureCreditLosses"
     ],
     "xbrltype": "textBlockItemType"
    },
    "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",
        "periodStartLabel": "Effect of the adoption of ASC topic 842 (Leases)"
       }
      }
     },
     "localname": "CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis": {
     "auth_ref": [
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of deferred compensation related to equity-based payment arrangements. Includes, but is not limited to, employment contracts with one or more selected officers or key employees. Excludes broad group equity-based compensation plans, defined benefit pension plans, defined benefit other postretirement benefit plans and other deferred compensation that is not equivalent to a defined benefit pension plan or a defined benefit other postretirement benefit plan.",
        "label": "Deferred Compensation Arrangement With Individual Share Based Payments By Type Of Deferred Compensation [Axis]",
        "terseLabel": "Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation"
       }
      }
     },
     "localname": "DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_DepreciationAndAmortization": {
     "auth_ref": [
      "r65",
      "r117"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10140.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.",
        "label": "Depreciation And Amortization",
        "terseLabel": "Depreciation and amortization expense"
       }
      }
     },
     "localname": "DepreciationAndAmortization",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]"
       }
      }
     },
     "localname": "DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Earnings Per Share [Abstract]",
        "terseLabel": "Net loss per common share:"
       }
      }
     },
     "localname": "EarningsPerShareAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EarningsPerShareBasicAndDiluted": {
     "auth_ref": [
      "r79"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements.  Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period.  Diluted earnings per share includes the amount of net income or 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 Basic And Diluted",
        "terseLabel": "Basic and diluted net loss per common share"
       }
      }
     },
     "localname": "EarningsPerShareBasicAndDiluted",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_EarningsPerShareTextBlock": {
     "auth_ref": [
      "r82"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for earnings per share.",
        "label": "Earnings Per Share [Text Block]",
        "terseLabel": "Net Loss per Common Share"
       }
      }
     },
     "localname": "EarningsPerShareTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShare"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_EmployeeRelatedLiabilitiesCurrent": {
     "auth_ref": [
      "r26"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10120.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "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 compensation"
       }
      }
     },
     "localname": "EmployeeRelatedLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems": {
     "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": "Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]",
        "terseLabel": "Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]"
       }
      }
     },
     "localname": "EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1": {
     "auth_ref": [
      "r167"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.",
        "label": "Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1",
        "terseLabel": "Unrecognized stock-based compensation weighted average recognition period"
       }
      }
     },
     "localname": "EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions": {
     "auth_ref": [
      "r167"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.",
        "label": "Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Share Based Awards Other Than Options",
        "terseLabel": "Unrecognized stock-based compensation expense"
       }
      }
     },
     "localname": "EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions": {
     "auth_ref": [
      "r167"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cost to be recognized for option under share-based payment arrangement.",
        "label": "Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options",
        "terseLabel": "Unrecognized stock-based compensation"
       }
      }
     },
     "localname": "EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_EmployeeStockOptionMember": {
     "auth_ref": [
      "r164"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share-based payment arrangement granting right, subject to vesting and other restrictions, to purchase or sell certain number of shares at predetermined price for specified period of time.",
        "label": "Employee Stock Option [Member]",
        "terseLabel": "Vested and Unvested Options"
       }
      }
     },
     "localname": "EmployeeStockOptionMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tangible personal property used to produce goods and services.",
        "label": "Equipment [Member]",
        "terseLabel": "Lab Equipment"
       }
      }
     },
     "localname": "EquipmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EquityBasedArrangementsIndividualContractsTypeOfDeferredCompensationDomain": {
     "auth_ref": [
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Deferred compensation related to equity-based payment arrangements. Includes, but is not limited to, employment contracts with one or more selected officers or key employees. Excludes broad group equity-based compensation plans, defined benefit pension plans, defined benefit other postretirement benefit plans and other deferred compensation that is not equivalent to a defined benefit pension plan or a defined benefit other postretirement benefit plan.",
        "label": "Equity Based Arrangements Individual Contracts Type Of Deferred Compensation [Domain]",
        "terseLabel": "Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation"
       }
      }
     },
     "localname": "EquityBasedArrangementsIndividualContractsTypeOfDeferredCompensationDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_EquityComponentDomain": {
     "auth_ref": [
      "r132"
     ],
     "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"
       }
      }
     },
     "localname": "EquityComponentDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueByFairValueHierarchyLevelAxis": {
     "auth_ref": [
      "r141",
      "r142",
      "r143",
      "r184",
      "r195"
     ],
     "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 By Fair Value Hierarchy Level [Axis]",
        "terseLabel": "Fair Value Hierarchy and NAV"
       }
      }
     },
     "localname": "FairValueByFairValueHierarchyLevelAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueByMeasurementFrequencyAxis": {
     "auth_ref": [
      "r183",
      "r184",
      "r185",
      "r186",
      "r188"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by measurement frequency.",
        "label": "Fair Value By Measurement Frequency [Axis]",
        "terseLabel": "Measurement Frequency"
       }
      }
     },
     "localname": "FairValueByMeasurementFrequencyAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_FairValueInputsLevel1Member": {
     "auth_ref": [
      "r141",
      "r142",
      "r143",
      "r184",
      "r196"
     ],
     "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 Level1 [Member]",
        "terseLabel": "Level 1"
       }
      }
     },
     "localname": "FairValueInputsLevel1Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueInputsLevel2Member": {
     "auth_ref": [
      "r141",
      "r142",
      "r143",
      "r184",
      "r197"
     ],
     "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 Level2 [Member]",
        "terseLabel": "Level 2"
       }
      }
     },
     "localname": "FairValueInputsLevel2Member",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueMeasurementFrequencyDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Measurement frequency.",
        "label": "Fair Value Measurement Frequency [Domain]",
        "terseLabel": "Measurement Frequency"
       }
      }
     },
     "localname": "FairValueMeasurementFrequencyDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "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 Measurements Fair Value Hierarchy [Domain]",
        "terseLabel": "Fair Value Hierarchy and NAV"
       }
      }
     },
     "localname": "FairValueMeasurementsFairValueHierarchyDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FairValueMeasurementsRecurringMember": {
     "auth_ref": [
      "r187",
      "r188"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Frequent fair value measurement. Includes, but is not limited to, fair value adjustment for impairment of asset, liability or equity, frequently measured at fair value.",
        "label": "Fair Value Measurements Recurring [Member]",
        "terseLabel": "Fair Value, Measurements, Recurring"
       }
      }
     },
     "localname": "FairValueMeasurementsRecurringMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_FinanceLeasePrincipalPayments": {
     "auth_ref": [
      "r192",
      "r193"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10070.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow for principal payment on finance lease.",
        "label": "Finance Lease Principal Payments",
        "negatedLabel": "Principal payments on finance lease obligations"
       }
      }
     },
     "localname": "FinanceLeasePrincipalPayments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_FinancialInstrumentsDisclosureTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for financial instruments. This disclosure includes, but is not limited to, fair value measurements of short and long term marketable securities, international currencies forward contracts, and auction rate securities. Financial instruments may include hedging and non-hedging currency exchange instruments, derivatives, securitizations and securities available for sale at fair value. Also included are investment results, realized and unrealized gains and losses as well as impairments and risk management disclosures.",
        "label": "Financial Instruments Disclosure [Text Block]",
        "terseLabel": "Financial Instruments"
       }
      }
     },
     "localname": "FinancialInstrumentsDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstruments"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_FurnitureAndFixturesMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.",
        "label": "Furniture And Fixtures [Member]",
        "terseLabel": "Furniture and Fixtures"
       }
      }
     },
     "localname": "FurnitureAndFixturesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_GeneralAndAdministrativeExpense": {
     "auth_ref": [
      "r49"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10060.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.",
        "label": "General And Administrative Expense",
        "terseLabel": "General and administrative"
       }
      }
     },
     "localname": "GeneralAndAdministrativeExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_GeneralAndAdministrativeExpenseMember": {
     "auth_ref": [
      "r48"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption encompassing general and administrative expense.",
        "label": "General And Administrative Expense [Member]",
        "terseLabel": "General and administrative"
       }
      }
     },
     "localname": "GeneralAndAdministrativeExpenseMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeStatementAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Income Statement [Abstract]"
       }
      }
     },
     "localname": "IncomeStatementAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncomeStatementLocationAxis": {
     "auth_ref": [
      "r121"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by location in the income statement.",
        "label": "Income Statement Location [Axis]",
        "terseLabel": "Income Statement Location"
       }
      }
     },
     "localname": "IncomeStatementLocationAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "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"
       }
      }
     },
     "localname": "IncomeStatementLocationDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_IncomeTaxesPaidNet": {
     "auth_ref": [
      "r68"
     ],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.",
        "label": "Income Taxes Paid Net",
        "terseLabel": "Cash paid for income taxes"
       }
      }
     },
     "localname": "IncomeTaxesPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInAccountsPayable": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10200.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.",
        "label": "Increase Decrease In Accounts Payable",
        "terseLabel": "Accounts payable"
       }
      }
     },
     "localname": "IncreaseDecreaseInAccountsPayable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10210.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The increase (decrease) during the reporting period in the aggregate amount of obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits.",
        "label": "Increase Decrease In Employee Related Liabilities",
        "terseLabel": "Accrued compensation"
       }
      }
     },
     "localname": "IncreaseDecreaseInEmployeeRelatedLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherCurrentLiabilities": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10230.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in current liabilities classified as other.",
        "label": "Increase Decrease In Other Current Liabilities",
        "terseLabel": "Other current liabilities"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherCurrentLiabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherOperatingAssets": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10190.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in operating assets classified as other.",
        "label": "Increase Decrease In Other Operating Assets",
        "negatedLabel": "Other assets"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherOperatingAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Increase Decrease In Other Operating Assets And Liabilities Net [Abstract]",
        "terseLabel": "Changes in operating assets and liabilities:"
       }
      }
     },
     "localname": "IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10180.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of increase (decrease) in prepaid expenses, and assets classified as other.",
        "label": "Increase Decrease In Prepaid Deferred Expense And Other Assets",
        "negatedLabel": "Prepaid expenses and other current assets"
       }
      }
     },
     "localname": "IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestPaidNet": {
     "auth_ref": [
      "r59",
      "r62",
      "r68"
     ],
     "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 Net",
        "terseLabel": "Cash paid for interest"
       }
      }
     },
     "localname": "InterestPaidNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InterestReceivable": {
     "auth_ref": [
      "r33"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.",
        "label": "Interest Receivable",
        "terseLabel": "Accrued interest receivable"
       }
      }
     },
     "localname": "InterestReceivable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium": {
     "auth_ref": [
      "r50"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10150.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities.",
        "label": "Investment Income Net Amortization Of Discount And Premium",
        "negatedLabel": "Amortization (accretion) of investment premiums (discounts)"
       }
      }
     },
     "localname": "InvestmentIncomeNetAmortizationOfDiscountAndPremium",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_InvestmentTypeAxis": {
     "auth_ref": [
      "r223",
      "r224",
      "r225",
      "r226"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of investments.",
        "label": "Investment Type [Axis]",
        "terseLabel": "Investment Type"
       }
      }
     },
     "localname": "InvestmentTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_InvestmentTypeCategorizationMember": {
     "auth_ref": [
      "r223",
      "r224",
      "r225",
      "r226"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Asset obtained to generate income or appreciate in value.",
        "label": "Investment Type Categorization [Member]",
        "terseLabel": "Investments"
       }
      }
     },
     "localname": "InvestmentTypeCategorizationMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments.",
        "label": "Investments Classified By Contractual Maturity Date Table [Text Block]",
        "terseLabel": "Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity"
       }
      }
     },
     "localname": "InvestmentsClassifiedByContractualMaturityDateTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_LeaseholdImprovementsMember": {
     "auth_ref": [
      "r118"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Additions or improvements to assets held under a lease arrangement.",
        "label": "Leasehold Improvements [Member]",
        "terseLabel": "Leasehold Improvements"
       }
      }
     },
     "localname": "LeaseholdImprovementsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_Liabilities": {
     "auth_ref": [
      "r25"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10010.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.",
        "label": "Liabilities",
        "totalLabel": "Total liabilities"
       }
      }
     },
     "localname": "Liabilities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquity": {
     "auth_ref": [
      "r17",
      "r200",
      "r217"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "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 Stockholders Equity",
        "totalLabel": "Total liabilities and stockholders\u2019 equity"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesAndStockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities And Stockholders Equity [Abstract]",
        "terseLabel": "Liabilities and stockholders\u2019 equity"
       }
      }
     },
     "localname": "LiabilitiesAndStockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_LiabilitiesCurrent": {
     "auth_ref": [
      "r27"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10080.0,
       "parentTag": "us-gaap_Liabilities",
       "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_LiabilitiesCurrentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Liabilities Current [Abstract]",
        "terseLabel": "Current liabilities:"
       }
      }
     },
     "localname": "LiabilitiesCurrentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_MachineryAndEquipmentMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.",
        "label": "Machinery And Equipment [Member]",
        "terseLabel": "Machinery and Equipment"
       }
      }
     },
     "localname": "MachineryAndEquipmentMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_MoneyMarketFundsMember": {
     "auth_ref": [
      "r141"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Fund that invests in short-term money-market instruments, for example, but not limited to, commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and other highly liquid securities.",
        "label": "Money Market Funds [Member]",
        "terseLabel": "Money Market Funds"
       }
      }
     },
     "localname": "MoneyMarketFundsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_NetCashProvidedByUsedInFinancingActivities": {
     "auth_ref": [
      "r61"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10030.0,
       "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInInvestingActivities": {
     "auth_ref": [
      "r61"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10020.0,
       "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 investing activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInInvestingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetCashProvidedByUsedInOperatingActivities": {
     "auth_ref": [
      "r61",
      "r63",
      "r66"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10010.0,
       "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 used in operating activities"
       }
      }
     },
     "localname": "NetCashProvidedByUsedInOperatingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_NetIncomeLoss": {
     "auth_ref": [
      "r42",
      "r44",
      "r47",
      "r66",
      "r81",
      "r207",
      "r220"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10010.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.",
        "label": "Net Income Loss",
        "terseLabel": "Net loss",
        "totalLabel": "Net loss"
       }
      }
     },
     "localname": "NetIncomeLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "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": "Recent Accounting Pronouncements"
       }
      }
     },
     "localname": "NewAccountingPronouncementsPolicyPolicyTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_OperatingExpenses": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      }
     },
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OperatingIncomeLoss": {
     "auth_ref": [],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10030.0,
       "parentTag": "us-gaap_NetIncomeLoss",
       "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": "Loss from operations"
       }
      }
     },
     "localname": "OperatingIncomeLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseLiabilityNoncurrent": {
     "auth_ref": [
      "r191"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10090.0,
       "parentTag": "us-gaap_Liabilities",
       "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 liabilities - long-term"
       }
      }
     },
     "localname": "OperatingLeaseLiabilityNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OperatingLeaseRightOfUseAsset": {
     "auth_ref": [
      "r190"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10170.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of lessee's right to use underlying asset under operating lease.",
        "label": "Operating Lease Right Of Use Asset",
        "terseLabel": "Operating lease assets"
       }
      }
     },
     "localname": "OperatingLeaseRightOfUseAsset",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "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/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherAssetsNoncurrent": {
     "auth_ref": [
      "r23"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10190.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of noncurrent assets classified as other.",
        "label": "Other Assets Noncurrent",
        "terseLabel": "Other assets"
       }
      }
     },
     "localname": "OtherAssetsNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract]",
        "terseLabel": "Other comprehensive (loss) gain:"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax": {
     "auth_ref": [
      "r36",
      "r38"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10020.0,
       "parentTag": "us-gaap_ComprehensiveIncomeNetOfTax",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.",
        "label": "Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax",
        "terseLabel": "Unrealized (loss) gain on available-for-sale securities",
        "verboseLabel": "Unrealized (loss) gain on available-for-sale securities"
       }
      }
     },
     "localname": "OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherLiabilitiesCurrent": {
     "auth_ref": [
      "r4",
      "r5",
      "r26"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10140.0,
       "parentTag": "us-gaap_LiabilitiesCurrent",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.",
        "label": "Other Liabilities Current",
        "terseLabel": "Other current liabilities"
       }
      }
     },
     "localname": "OtherLiabilitiesCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherLiabilitiesNoncurrent": {
     "auth_ref": [
      "r28"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10100.0,
       "parentTag": "us-gaap_Liabilities",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.",
        "label": "Other Liabilities Noncurrent",
        "terseLabel": "Other long-term liabilities"
       }
      }
     },
     "localname": "OtherLiabilitiesNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_OtherNonoperatingIncomeExpense": {
     "auth_ref": [
      "r51"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10040.0,
       "parentTag": "us-gaap_NetIncomeLoss",
       "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": "Interest and other income, net"
       }
      }
     },
     "localname": "OtherNonoperatingIncomeExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation": {
     "auth_ref": [
      "r57"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10060.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.",
        "label": "Payments Related To Tax Withholding For Share Based Compensation",
        "negatedLabel": "Taxes paid related to net share settlement of restricted stock units"
       }
      }
     },
     "localname": "PaymentsRelatedToTaxWithholdingForShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquirePropertyPlantAndEquipment": {
     "auth_ref": [
      "r53"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10110.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.",
        "label": "Payments To Acquire Property Plant And Equipment",
        "negatedLabel": "Purchases of property and equipment"
       }
      }
     },
     "localname": "PaymentsToAcquirePropertyPlantAndEquipment",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PaymentsToAcquireShortTermInvestments": {
     "auth_ref": [
      "r54"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10090.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": -1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash outflow for securities or other assets acquired, which qualify for treatment as an investing activity and are to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.",
        "label": "Payments To Acquire Short Term Investments",
        "negatedLabel": "Purchases of short-term investments"
       }
      }
     },
     "localname": "PaymentsToAcquireShortTermInvestments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PlanNameAxis": {
     "auth_ref": [
      "r147",
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by plan name for share-based payment arrangement.",
        "label": "Plan Name [Axis]",
        "terseLabel": "Plan Name"
       }
      }
     },
     "localname": "PlanNameAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PlanNameDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Plan name for share-based payment arrangement.",
        "label": "Plan Name [Domain]",
        "terseLabel": "Plan Name"
       }
      }
     },
     "localname": "PlanNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_PreferredStockParOrStatedValuePerShare": {
     "auth_ref": [
      "r11"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.",
        "label": "Preferred Stock Par Or Stated Value Per Share",
        "terseLabel": "Preferred stock, par value"
       }
      }
     },
     "localname": "PreferredStockParOrStatedValuePerShare",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_PreferredStockSharesAuthorized": {
     "auth_ref": [
      "r11"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.",
        "label": "Preferred Stock Shares Authorized",
        "terseLabel": "Preferred stock, shares authorized"
       }
      }
     },
     "localname": "PreferredStockSharesAuthorized",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_PreferredStockSharesOutstanding": {
     "auth_ref": [
      "r11"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.",
        "label": "Preferred Stock Shares Outstanding",
        "verboseLabel": "Preferred stock, shares outstanding"
       }
      }
     },
     "localname": "PreferredStockSharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_PrepaidExpenseAndOtherAssetsCurrent": {
     "auth_ref": [
      "r1",
      "r18",
      "r19"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10230.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.",
        "label": "Prepaid Expense And Other Assets Current",
        "terseLabel": "Prepaid expenses and other current assets"
       }
      }
     },
     "localname": "PrepaidExpenseAndOtherAssetsCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromIssuanceOfCommonStock": {
     "auth_ref": [
      "r55"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10040.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from the additional capital contribution to the entity.",
        "label": "Proceeds From Issuance Of Common Stock",
        "terseLabel": "Proceeds from issuance of common stock through ATM facilities, net",
        "verboseLabel": "Proceeds from sale of common stock, net"
       }
      }
     },
     "localname": "ProceedsFromIssuanceOfCommonStock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromPaymentsForOtherFinancingActivities": {
     "auth_ref": [
      "r56",
      "r58",
      "r77"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10080.0,
       "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, net"
       }
      }
     },
     "localname": "ProceedsFromPaymentsForOtherFinancingActivities",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments": {
     "auth_ref": [
      "r52"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10100.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInInvestingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow from sales, maturities, prepayments, calls and collections of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.",
        "label": "Proceeds From Sale Maturity And Collection Of Shortterm Investments",
        "terseLabel": "Proceeds from maturities and sales of short-term investments"
       }
      }
     },
     "localname": "ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProceedsFromStockPlans": {
     "auth_ref": [
      "r55"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10050.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInFinancingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cash inflow associated with the amount received from the stock plan during the period.",
        "label": "Proceeds From Stock Plans",
        "terseLabel": "Proceeds from employee stock awards"
       }
      }
     },
     "localname": "ProceedsFromStockPlans",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ProfitLoss": {
     "auth_ref": [
      "r42",
      "r44",
      "r60",
      "r90",
      "r91",
      "r177",
      "r178",
      "r179",
      "r181",
      "r182"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10120.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "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": "Profit Loss",
        "terseLabel": "Net loss"
       }
      }
     },
     "localname": "ProfitLoss",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Property Plant And Equipment [Abstract]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentByTypeAxis": {
     "auth_ref": [
      "r22",
      "r120"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of long-lived, physical assets used to produce goods and services and not intended for resale.",
        "label": "Property Plant And Equipment By Type [Axis]",
        "terseLabel": "Property, Plant and Equipment, Type"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentByTypeAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock": {
     "auth_ref": [
      "r122"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures.",
        "label": "Property Plant And Equipment Disclosure [Text Block]",
        "terseLabel": "Property and Equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipment"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentGross": {
     "auth_ref": [
      "r21",
      "r118"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail": {
       "order": 10010.0,
       "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 and equipment, gross"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentGross",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Property Plant And Equipment [Line Items]",
        "terseLabel": "Property Plant And Equipment [Line Items]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentNet": {
     "auth_ref": [
      "r7",
      "r8",
      "r120",
      "r218"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail": {
       "order": null,
       "parentTag": null,
       "root": true,
       "weight": null
      },
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10160.0,
       "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",
        "terseLabel": "Property and equipment, net",
        "totalLabel": "Property and equipment, net"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentNet",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Property Plant And Equipment Net By Type [Abstract]"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentNetByTypeAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentTextBlock": {
     "auth_ref": [
      "r7",
      "r120"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.",
        "label": "Property Plant And Equipment [Text Block]",
        "terseLabel": "Schedule of Property and Equipment"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_PropertyPlantAndEquipmentTypeDomain": {
     "auth_ref": [
      "r7",
      "r118"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Listing of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.",
        "label": "Property Plant And Equipment Type [Domain]",
        "terseLabel": "Property, Plant and Equipment, Type"
       }
      }
     },
     "localname": "PropertyPlantAndEquipmentTypeDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ResearchAndDevelopmentExpense": {
     "auth_ref": [
      "r172",
      "r228"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited": {
       "order": 10050.0,
       "parentTag": "us-gaap_OperatingExpenses",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.",
        "label": "Research And Development Expense",
        "terseLabel": "Research and development"
       }
      }
     },
     "localname": "ResearchAndDevelopmentExpense",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ResearchAndDevelopmentExpenseMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Primary financial statement caption in which the reported facts about research and development expense have been included.",
        "label": "Research And Development Expense [Member]",
        "verboseLabel": "Research and development"
       }
      }
     },
     "localname": "ResearchAndDevelopmentExpenseMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RestrictedCash": {
     "auth_ref": [
      "r72",
      "r198",
      "r215"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash restricted as to withdrawal or usage. 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.",
        "label": "Restricted Cash",
        "terseLabel": "Restricted Cash"
       }
      }
     },
     "localname": "RestrictedCash",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestrictedCashCurrent": {
     "auth_ref": [
      "r0",
      "r6",
      "r72"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail": {
       "order": 10020.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
       "weight": 1.0
      },
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10220.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash restricted as to withdrawal or usage, classified as current. 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.",
        "label": "Restricted Cash Current",
        "terseLabel": "Restricted cash - short-term"
       }
      }
     },
     "localname": "RestrictedCashCurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestrictedCashNoncurrent": {
     "auth_ref": [
      "r3",
      "r9",
      "r72",
      "r227"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail": {
       "order": 10030.0,
       "parentTag": "us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents",
       "weight": 1.0
      },
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10180.0,
       "parentTag": "us-gaap_Assets",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of cash restricted as to withdrawal or usage, classified as noncurrent. 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.",
        "label": "Restricted Cash Noncurrent",
        "terseLabel": "Restricted cash - long-term"
       }
      }
     },
     "localname": "RestrictedCashNoncurrent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsReconciliationOfCashCashEquivalentsAndRestrictedCashDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number, after shares used to satisfy grantee's tax withholding obligation for award under share-based payment arrangement, of restricted shares issued. Excludes cash used to satisfy grantee's tax withholding obligation.",
        "label": "Restricted Stock Shares Issued Net Of Shares For Tax Withholdings",
        "verboseLabel": "RSU settlements, net of shares withheld, shares"
       }
      }
     },
     "localname": "RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_RestrictedStockUnitsRSUMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Share instrument which is convertible to stock or an equivalent amount of cash, after a specified period of time or when specified performance conditions are met.",
        "label": "Restricted Stock Units R S U [Member]",
        "terseLabel": "Restricted Stock Units (RSUs)",
        "verboseLabel": "Unvested RSUs"
       }
      }
     },
     "localname": "RestrictedStockUnitsRSUMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Value, after value of shares used to satisfy grantee's tax withholding obligation for award under share-based payment arrangement, of restricted shares issued. Excludes cash used to satisfy grantee's tax withholding obligation.",
        "label": "Restricted Stock Value Shares Issued Net Of Tax Withholdings",
        "negatedLabel": "RSU settlements, net of shares withheld"
       }
      }
     },
     "localname": "RestrictedStockValueSharesIssuedNetOfTaxWithholdings",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RetainedEarningsAccumulatedDeficit": {
     "auth_ref": [
      "r14",
      "r139",
      "r216"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10070.0,
       "parentTag": "us-gaap_StockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cumulative amount of the reporting entity's undistributed earnings or deficit.",
        "label": "Retained Earnings Accumulated Deficit",
        "negatedLabel": "Accumulated Deficit",
        "terseLabel": "Accumulated deficit"
       }
      }
     },
     "localname": "RetainedEarningsAccumulatedDeficit",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_RetainedEarningsMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The cumulative amount of the reporting entity's undistributed earnings or deficit.",
        "label": "Retained Earnings [Member]",
        "terseLabel": "Accumulated Deficit"
       }
      }
     },
     "localname": "RetainedEarningsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_SaleOfStockNameOfTransactionDomain": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Sale of the entity's stock, including, but not limited to, initial public offering (IPO) and private placement.",
        "label": "Sale Of Stock Name Of Transaction [Domain]",
        "terseLabel": "Sale of Stock"
       }
      }
     },
     "localname": "SaleOfStockNameOfTransactionDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable": {
     "auth_ref": [
      "r80"
     ],
     "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/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetLossPerCommonShareDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock": {
     "auth_ref": [
      "r80"
     ],
     "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 [Text Block]",
        "terseLabel": "Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share"
       }
      }
     },
     "localname": "ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureNetLossPerCommonShareTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Schedule Of Available For Sale Securities [Line Items]",
        "terseLabel": "Schedule of Available-for-sale Securities [Line Items]"
       }
      }
     },
     "localname": "ScheduleOfAvailableForSaleSecuritiesLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfAvailableForSaleSecuritiesTable": {
     "auth_ref": [
      "r100",
      "r103",
      "r105",
      "r106",
      "r107",
      "r108",
      "r208",
      "r211"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.",
        "label": "Schedule Of Available For Sale Securities [Table]",
        "terseLabel": "Schedule Of Available For Sale Securities [Table]"
       }
      }
     },
     "localname": "ScheduleOfAvailableForSaleSecuritiesTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable": {
     "auth_ref": [
      "r146",
      "r165",
      "r169"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about amount recognized for award under share-based payment arrangement. Includes, but is not limited to, amount expensed in statement of income or comprehensive income, amount capitalized in statement of financial position, and corresponding reporting line item in financial statements.",
        "label": "Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]",
        "terseLabel": "Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]"
       }
      }
     },
     "localname": "ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfStockBasedCompensationRelatedToAllEmployeeAndNonEmployeeStockAwardsDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock": {
     "auth_ref": [
      "r146",
      "r165",
      "r169"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement.",
        "label": "Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block]",
        "terseLabel": "Schedule of Stock-based Compensation, Related to Employee and Nonemployee Stock Awards"
       }
      }
     },
     "localname": "ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfPropertyPlantAndEquipmentTable": {
     "auth_ref": [
      "r22",
      "r120"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation.",
        "label": "Schedule Of Property Plant And Equipment [Table]",
        "terseLabel": "Schedule Of Property Plant And Equipment [Table]"
       }
      }
     },
     "localname": "ScheduleOfPropertyPlantAndEquipmentTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock": {
     "auth_ref": [
      "r6",
      "r72",
      "r198",
      "r215"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure of cash and cash equivalents restricted as to withdrawal or usage.",
        "label": "Schedule Of Restricted Cash And Cash Equivalents [Text Block]",
        "terseLabel": "Reconciliation of Cash, Cash Equivalents and Restricted Cash"
       }
      }
     },
     "localname": "ScheduleOfRestrictedCashAndCashEquivalentsTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable": {
     "auth_ref": [
      "r147",
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of information about share-based payment arrangement.",
        "label": "Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]",
        "terseLabel": "Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]"
       }
      }
     },
     "localname": "ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock": {
     "auth_ref": [
      "r152",
      "r161",
      "r162"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value.",
        "label": "Schedule Of Share Based Compensation Stock Options Activity Table [Text Block]",
        "terseLabel": "Summary of Stock Option Activity"
       }
      }
     },
     "localname": "ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year.",
        "label": "Schedule Of Sharebased Compensation Restricted Stock And Restricted Stock Units Activity Table [Text Block]",
        "terseLabel": "Summary of RSU Activity"
       }
      }
     },
     "localname": "ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityTables"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_ScheduleOfStockByClassTable": {
     "auth_ref": [
      "r30",
      "r74",
      "r129",
      "r130",
      "r131",
      "r133",
      "r134",
      "r135",
      "r136",
      "r137",
      "r138",
      "r139"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule detailing information related to equity by class of stock. Class of stock includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. It also includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity.",
        "label": "Schedule Of Stock By Class [Table]",
        "terseLabel": "Schedule Of Stock By Class [Table]"
       }
      }
     },
     "localname": "ScheduleOfStockByClassTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityScheduleOfCommonStockReservedForFutureIssuanceUnderEquityIncentivePlansDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensation": {
     "auth_ref": [
      "r64"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited": {
       "order": 10130.0,
       "parentTag": "us-gaap_NetCashProvidedByUsedInOperatingActivities",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of noncash expense for share-based payment arrangement.",
        "label": "Share Based Compensation",
        "terseLabel": "Stock-based compensation expense"
       }
      }
     },
     "localname": "ShareBasedCompensation",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1": {
     "auth_ref": [
      "r149"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1",
        "terseLabel": "Share based compensation, vesting period"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod": {
     "auth_ref": [
      "r156"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period",
        "negatedLabel": "Shares, Forfeited"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r160"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value",
        "terseLabel": "Weighted Average Grant Date Fair Value, Forfeited"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod": {
     "auth_ref": [
      "r158"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period",
        "terseLabel": "Shares, Granted"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r158"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value",
        "verboseLabel": "Weighted Average Grant Date Fair Value, Granted"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber": {
     "auth_ref": [
      "r157"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number",
        "periodEndLabel": "Shares, Outstanding as of March 31, 2020",
        "periodStartLabel": "Shares, Unvested as of December 31, 2019"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r157"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value",
        "periodEndLabel": "Weighted Average Grant Date Fair Value, Outstanding as of March 31, 2020",
        "periodStartLabel": "Weighted Average Grant Date Fair Value, Unvested as of December 31, 2019"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod": {
     "auth_ref": [
      "r159"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period",
        "negatedLabel": "Shares, Vested"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue": {
     "auth_ref": [
      "r159"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value",
        "terseLabel": "Weighted Average Grant Date Fair Value, Vested"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award [Line Items]",
        "terseLabel": "Share Based Compensation Arrangement By Share Based Payment Award [Line Items]"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant": {
     "auth_ref": [
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant",
        "terseLabel": "Aggregate number of awards available for grant to be issued"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod": {
     "auth_ref": [
      "r156"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period",
        "negatedLabel": "Forfeited or expired, Shares"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Gross number of share options (or share units) granted during the period.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross",
        "terseLabel": "Granted, Shares"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue": {
     "auth_ref": [
      "r168"
     ],
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value",
        "terseLabel": "Aggregate intrinsic value"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber": {
     "auth_ref": [
      "r154",
      "r168"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of options outstanding, including both vested and non-vested options.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number",
        "periodEndLabel": "Outstanding, Shares, ending balance",
        "periodStartLabel": "Outstanding, Shares, beginning balance"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice": {
     "auth_ref": [
      "r153"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price",
        "periodEndLabel": "Outstanding, Weighted Average Exercise Price, ending balance",
        "periodStartLabel": "Outstanding, Weighted Average Exercise Price, beginning balance"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward": {
     "auth_ref": [
      "r148"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Description of terms of award under share-based payment arrangement.",
        "label": "Share Based Compensation Arrangement By Share Based Payment Award Terms Of Award",
        "terseLabel": "Stock option granted description terms"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain": {
     "auth_ref": [
      "r145",
      "r151"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Award under share-based payment arrangement.",
        "label": "Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain]",
        "terseLabel": "Award Type"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfRSUActivityDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which option holders acquired shares when converting their stock options into shares.",
        "label": "Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price",
        "terseLabel": "Exercised, Weighted Average Exercise Price"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.",
        "label": "Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price",
        "terseLabel": "Forfeited or expired, Weighted Average Exercise price"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.",
        "label": "Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price",
        "terseLabel": "Granted, Weighted Average Exercise Price"
       }
      }
     },
     "localname": "ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "perShareItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod": {
     "auth_ref": [
      "r150"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period",
        "terseLabel": "Share based compensation award expiration period"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2": {
     "auth_ref": [
      "r163"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.",
        "label": "Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2",
        "terseLabel": "Outstanding, Weighted Average Remaining Contractual Term"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "durationItemType"
    },
    "us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Purchase price of common stock expressed as a percentage of its fair value.",
        "label": "Sharebased Compensation Arrangement By Sharebased Payment Award Purchase Price Of Common Stock Percent",
        "terseLabel": "Percentage of employees purchase price of common stock"
       }
      }
     },
     "localname": "SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "percentItemType"
    },
    "us-gaap_SharesOutstanding": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of shares issued which are neither cancelled nor held in the treasury.",
        "label": "Shares Outstanding",
        "periodEndLabel": "Ending balance (in shares)",
        "periodStartLabel": "Beginning balance (in shares)"
       }
      }
     },
     "localname": "SharesOutstanding",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_ShortTermInvestments": {
     "auth_ref": [
      "r10",
      "r201",
      "r202",
      "r204",
      "r213"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10210.0,
       "parentTag": "us-gaap_AssetsCurrent",
       "weight": 1.0
      }
     },
     "crdr": "debit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.",
        "label": "Short Term Investments",
        "terseLabel": "Short-term investments"
       }
      }
     },
     "localname": "ShortTermInvestments",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_ShortTermInvestmentsMember": {
     "auth_ref": [
      "r226"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Investments which are not otherwise included in another category or item that the entity has the intent to sell or dispose of within one year from the date of the balance sheet.",
        "label": "Short Term Investments [Member]",
        "terseLabel": "Amounts Classified As Short-Term Investments"
       }
      }
     },
     "localname": "ShortTermInvestmentsMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_SignificantAccountingPoliciesTextBlock": {
     "auth_ref": [
      "r78"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "The entire disclosure for all significant accounting policies of the reporting entity.",
        "label": "Significant Accounting Policies [Text Block]",
        "terseLabel": "Summary of Significant Accounting Policies"
       }
      }
     },
     "localname": "SignificantAccountingPoliciesTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_StatementEquityComponentsAxis": {
     "auth_ref": [
      "r32",
      "r132"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by component of equity.",
        "label": "Statement Equity Components [Axis]",
        "terseLabel": "Equity Components"
       }
      }
     },
     "localname": "StatementEquityComponentsAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementLineItems": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.",
        "label": "Statement [Line Items]",
        "terseLabel": "Statement [Line Items]"
       }
      }
     },
     "localname": "StatementLineItems",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfCashFlowsAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement Of Cash Flows [Abstract]"
       }
      }
     },
     "localname": "StatementOfCashFlowsAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfFinancialPositionAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement Of Financial Position [Abstract]"
       }
      }
     },
     "localname": "StatementOfFinancialPositionAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementOfStockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Statement Of Stockholders Equity [Abstract]"
       }
      }
     },
     "localname": "StatementOfStockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "xbrltype": "stringItemType"
    },
    "us-gaap_StatementTable": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Schedule reflecting a Statement of Income, Statement of Cash Flows, Statement of Financial Position, Statement of Shareholders' Equity and Other Comprehensive Income, or other statement as needed.",
        "label": "Statement [Table]",
        "terseLabel": "Statement [Table]"
       }
      }
     },
     "localname": "StatementTable",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesNewIssues": {
     "auth_ref": [
      "r11",
      "r12",
      "r132",
      "r139"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of new stock issued during the period.",
        "label": "Stock Issued During Period Shares New Issues",
        "verboseLabel": "Common stock, shares issued"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesNewIssues",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number, before forfeiture, of shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).",
        "label": "Stock Issued During Period Shares Share Based Compensation Gross",
        "terseLabel": "Stock options, issued"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesShareBasedCompensationGross",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised": {
     "auth_ref": [
      "r11",
      "r12",
      "r132",
      "r139",
      "r155"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Number of share options (or share units) exercised during the current period.",
        "label": "Stock Issued During Period Shares Stock Options Exercised",
        "negatedLabel": "Exercised, Shares"
       }
      }
     },
     "localname": "StockIssuedDuringPeriodSharesStockOptionsExercised",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquitySummaryOfStockOptionActivityDetail"
     ],
     "xbrltype": "sharesItemType"
    },
    "us-gaap_StockholdersEquity": {
     "auth_ref": [
      "r12",
      "r15",
      "r16",
      "r93"
     ],
     "calculation": {
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited": {
       "order": 10030.0,
       "parentTag": "us-gaap_LiabilitiesAndStockholdersEquity",
       "weight": 1.0
      }
     },
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.",
        "label": "Stockholders Equity",
        "periodEndLabel": "Ending balance",
        "periodStartLabel": "Beginning balance",
        "totalLabel": "Total stockholders\u2019 equity"
       }
      }
     },
     "localname": "StockholdersEquity",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Stockholders Equity [Abstract]",
        "terseLabel": "Stockholders\u2019 equity:"
       }
      }
     },
     "localname": "StockholdersEquityAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1": {
     "auth_ref": [],
     "crdr": "credit",
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Amount of stockholders' equity including the portion attributable to noncontrolling interests, after the cumulative effect adjustment of a new accounting principle applied in the period of adoption.",
        "label": "Stockholders Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1",
        "periodStartLabel": "Beginning balance, as adjusted"
       }
      }
     },
     "localname": "StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "monetaryItemType"
    },
    "us-gaap_StockholdersEquityNoteDisclosureTextBlock": {
     "auth_ref": [
      "r140"
     ],
     "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": "Stockholders' Equity"
       }
      }
     },
     "localname": "StockholdersEquityNoteDisclosureTextBlock",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquity"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_SubsidiarySaleOfStockAxis": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by type of sale of the entity's stock.",
        "label": "Subsidiary Sale Of Stock [Axis]",
        "terseLabel": "Sale of Stock"
       }
      }
     },
     "localname": "SubsidiarySaleOfStockAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityParentheticalUnaudited",
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquityUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_SupplementalCashFlowInformationAbstract": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "label": "Supplemental Cash Flow Information [Abstract]",
        "terseLabel": "Supplemental cash flow disclosure"
       }
      }
     },
     "localname": "SupplementalCashFlowInformationAbstract",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_TypeOfArrangementAxis": {
     "auth_ref": [
      "r175"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Information by collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations.",
        "label": "Type Of Arrangement [Axis]",
        "terseLabel": "Collaborative Arrangement and Arrangement Other than Collaborative"
       }
      }
     },
     "localname": "TypeOfArrangementAxis",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail"
     ],
     "xbrltype": "stringItemType"
    },
    "us-gaap_USGovernmentAgenciesShorttermDebtSecuritiesMember": {
     "auth_ref": [
      "r206"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Debt securities issued by US government agencies, for example, but not limited to, Government National Mortgage Association (GNMA or Ginnie Mae) which have maturities of one year or less. Excludes US Treasury securities and debt issued by Government-sponsored Enterprises (GSEs), for example, but not limited to, Federal Home Loan Mortgage Corporation (FHLMC or Freddie Mac), Federal National Mortgage Association (FNMA or Fannie Mae).",
        "label": "U S Government Agencies Shortterm Debt Securities [Member]",
        "terseLabel": "Government Agency Obligations"
       }
      }
     },
     "localname": "USGovernmentAgenciesShorttermDebtSecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_USTreasurySecuritiesMember": {
     "auth_ref": [
      "r141",
      "r143",
      "r203"
     ],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "This category includes information about debt securities issued by the United States Department of the Treasury and backed by the United States government. Such securities primarily consist of treasury bills (short-term maturities - one year or less), treasury notes (intermediate term maturities - two to ten years), and treasury bonds (long-term maturities - ten to thirty years).",
        "label": "U S Treasury Securities [Member]",
        "terseLabel": "U.S. Treasury Obligations"
       }
      }
     },
     "localname": "USTreasurySecuritiesMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureFinancialInstrumentsSummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_UseOfEstimates": {
     "auth_ref": [
      "r83",
      "r84",
      "r85",
      "r86",
      "r87",
      "r88",
      "r89"
     ],
     "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",
        "terseLabel": "Use of Estimates"
       }
      }
     },
     "localname": "UseOfEstimates",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies"
     ],
     "xbrltype": "textBlockItemType"
    },
    "us-gaap_WarrantMember": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Security that gives the holder the right to purchase shares of stock in accordance with the terms of the instrument, usually upon payment of a specified amount.",
        "label": "Warrant [Member]",
        "terseLabel": "Warrant"
       }
      }
     },
     "localname": "WarrantMember",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetail"
     ],
     "xbrltype": "domainItemType"
    },
    "us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted": {
     "auth_ref": [],
     "lang": {
      "en-US": {
       "role": {
        "documentation": "Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).",
        "label": "Weighted Average Number Of Share Outstanding Basic And Diluted",
        "terseLabel": "Weighted-average shares outstanding used to calculate basic and diluted net loss per common share"
       }
      }
     },
     "localname": "WeightedAverageNumberOfShareOutstandingBasicAndDiluted",
     "nsuri": "http://fasb.org/us-gaap/2019-01-31",
     "presentation": [
      "http://www.atarabio.com/20200331/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossUnaudited"
     ],
     "xbrltype": "sharesItemType"
    }
   },
   "unitCount": 4
  }
 },
 "std_ref": {
  "r0": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r1": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6676-107765"
  },
  "r10": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(2))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r100": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  },
  "r101": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27198-111563"
  },
  "r102": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27198-111563"
  },
  "r103": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27198-111563"
  },
  "r104": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563"
  },
  "r105": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563"
  },
  "r106": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563"
  },
  "r107": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27340-111563"
  },
  "r108": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "9",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)-(d)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27357-111563"
  },
  "r109": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=119407570&loc=SL82919244-210447"
  },
  "r11": {
   "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"
  },
  "r110": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "20",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=119407570&loc=SL82919269-210447"
  },
  "r111": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "21",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=119407570&loc=SL82919272-210447"
  },
  "r112": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=119407570&loc=SL82919230-210447"
  },
  "r113": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=119407570&loc=SL82919236-210447"
  },
  "r114": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "30",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454"
  },
  "r115": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455"
  },
  "r116": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "30",
   "Topic": "326",
   "URI": "http://asc.fasb.org/extlink&oid=118955579&loc=SL82922895-210455"
  },
  "r117": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "360",
   "URI": "http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229"
  },
  "r118": {
   "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"
  },
  "r119": {
   "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"
  },
  "r12": {
   "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"
  },
  "r120": {
   "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"
  },
  "r121": {
   "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"
  },
  "r122": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "360",
   "URI": "http://asc.fasb.org/topic&trid=2155823"
  },
  "r123": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "20",
   "Topic": "410",
   "URI": "http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848"
  },
  "r124": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "10",
   "Topic": "420",
   "URI": "http://asc.fasb.org/extlink&oid=6394232&loc=d3e17558-110866"
  },
  "r125": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "440",
   "URI": "http://asc.fasb.org/topic&trid=2144648"
  },
  "r126": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "450",
   "URI": "http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349"
  },
  "r127": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "450",
   "URI": "http://asc.fasb.org/topic&trid=2127136"
  },
  "r128": {
   "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"
  },
  "r129": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(CFRR 211.02)",
   "Topic": "480",
   "URI": "http://asc.fasb.org/extlink&oid=65877616&loc=d3e177068-122764"
  },
  "r13": {
   "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"
  },
  "r130": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643"
  },
  "r131": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21553-112644"
  },
  "r132": {
   "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"
  },
  "r133": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644"
  },
  "r134": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21484-112644"
  },
  "r135": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21488-112644"
  },
  "r136": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644"
  },
  "r137": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644"
  },
  "r138": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "8",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "505",
   "URI": "http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644"
  },
  "r139": {
   "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"
  },
  "r14": {
   "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"
  },
  "r140": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "505",
   "URI": "http://asc.fasb.org/topic&trid=2208762"
  },
  "r141": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(ii)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r142": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(d)(iv)(01)",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920"
  },
  "r143": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "715",
   "URI": "http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921"
  },
  "r144": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "35",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116855982&loc=d3e4534-113899"
  },
  "r145": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r146": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r147": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901"
  },
  "r148": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r149": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r15": {
   "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"
  },
  "r150": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r151": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a),(g)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r152": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r153": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r154": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(i)-(ii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r155": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(iv)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r156": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(1)(iv)(3)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r157": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(i)-(ii)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r158": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r159": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(2)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r16": {
   "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"
  },
  "r160": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)(2)(iii)(3)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r161": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r162": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r163": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(e)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r164": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(g)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r165": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(h)(1)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r166": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(h)(1)(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r167": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(i)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r168": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901"
  },
  "r169": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SAB Topic 14.F)",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809"
  },
  "r17": {
   "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"
  },
  "r170": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=118258462&loc=d3e11149-113907"
  },
  "r171": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "718",
   "URI": "http://asc.fasb.org/extlink&oid=118258462&loc=d3e11178-113907"
  },
  "r172": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "730",
   "URI": "http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373"
  },
  "r173": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "808",
   "URI": "http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434"
  },
  "r174": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "808",
   "URI": "http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434"
  },
  "r175": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "808",
   "URI": "http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434"
  },
  "r176": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "808",
   "URI": "http://asc.fasb.org/topic&trid=5833765"
  },
  "r177": {
   "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"
  },
  "r178": {
   "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"
  },
  "r179": {
   "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"
  },
  "r18": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02(7))",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r180": {
   "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"
  },
  "r181": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4J",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4591551-111686"
  },
  "r182": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4K",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "10",
   "Topic": "810",
   "URI": "http://asc.fasb.org/extlink&oid=116874947&loc=SL4591552-111686"
  },
  "r183": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r184": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r185": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bbb)(1)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r186": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(bbb)(2)",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r187": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258"
  },
  "r188": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6A",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "820",
   "URI": "http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258"
  },
  "r189": {
   "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"
  },
  "r19": {
   "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"
  },
  "r190": {
   "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"
  },
  "r191": {
   "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"
  },
  "r192": {
   "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"
  },
  "r193": {
   "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"
  },
  "r194": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Topic": "850",
   "URI": "http://asc.fasb.org/extlink&oid=6457730&loc=d3e39599-107864"
  },
  "r195": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r196": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(1)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r197": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Subparagraph": "(bb)(2)",
   "Topic": "860",
   "URI": "http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719"
  },
  "r198": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(1)(a))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r199": {
   "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"
  },
  "r2": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6801-107765"
  },
  "r20": {
   "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"
  },
  "r200": {
   "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"
  },
  "r201": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(4))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r202": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(5))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r203": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(6)(a)(1))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r204": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03(6))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r205": {
   "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"
  },
  "r206": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.9-03.6(a)(1))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878"
  },
  "r207": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.9-04(22))",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260"
  },
  "r208": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "320",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=75019621&loc=d3e62557-112803"
  },
  "r209": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "320",
   "Subparagraph": "(a)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803"
  },
  "r21": {
   "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"
  },
  "r210": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "320",
   "Subparagraph": "(b)",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803"
  },
  "r211": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "3",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "320",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803"
  },
  "r212": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "405",
   "Topic": "942",
   "URI": "http://asc.fasb.org/extlink&oid=116652737&loc=d3e64164-112818"
  },
  "r213": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(1)(g))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r214": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(12))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r215": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(2))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r216": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(23)(a)(4))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r217": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(25))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r218": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03(a)(8))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r219": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.7-03.(a),19)",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910"
  },
  "r22": {
   "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"
  },
  "r220": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "220",
   "Subparagraph": "(SX 210.7-04(18))",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263"
  },
  "r221": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "80",
   "Subparagraph": "(e)",
   "Topic": "944",
   "URI": "http://asc.fasb.org/extlink&oid=117420044&loc=d3e19393-158473"
  },
  "r222": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "210",
   "Subparagraph": "(SX 210.6-04.16(a))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996"
  },
  "r223": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "320",
   "Subparagraph": "(SX 210.12-12(2)(i))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010"
  },
  "r224": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "320",
   "Subparagraph": "(SX 210.12-12C(1)(a))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010"
  },
  "r225": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "320",
   "Subparagraph": "(SX 210.12-13(1))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=50485924&loc=d3e611282-123010"
  },
  "r226": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "320",
   "Subparagraph": "(SX 210.12-15(Column A))",
   "Topic": "946",
   "URI": "http://asc.fasb.org/extlink&oid=50485924&loc=d3e611379-123010"
  },
  "r227": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "210",
   "Topic": "954",
   "URI": "http://asc.fasb.org/extlink&oid=116631420&loc=SL116631458-115580"
  },
  "r228": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "20",
   "Topic": "985",
   "URI": "http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756"
  },
  "r229": {
   "Name": "Exchange Act",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b"
  },
  "r23": {
   "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"
  },
  "r230": {
   "Name": "Exchange Act",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "d1-1"
  },
  "r231": {
   "Name": "Form 10-Q",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "13",
   "Subsection": "a-13"
  },
  "r232": {
   "Name": "Forms 10-K, 10-Q, 20-F",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "13",
   "Subsection": "a-1-"
  },
  "r233": {
   "Name": "Regulation 12B",
   "Number": "240",
   "Publisher": "SEC",
   "Section": "12",
   "Subsection": "b-2"
  },
  "r234": {
   "Name": "Regulation S-T",
   "Number": "232",
   "Publisher": "SEC",
   "Section": "405"
  },
  "r24": {
   "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"
  },
  "r25": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.19-26)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r26": {
   "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"
  },
  "r27": {
   "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"
  },
  "r28": {
   "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"
  },
  "r29": {
   "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"
  },
  "r3": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6812-107765"
  },
  "r30": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-02.28,29)",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682"
  },
  "r31": {
   "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"
  },
  "r32": {
   "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"
  },
  "r33": {
   "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"
  },
  "r34": {
   "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"
  },
  "r35": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "16",
   "Publisher": "FASB",
   "Section": "55",
   "SubTopic": "20",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=99393222&loc=SL20226024-175313"
  },
  "r36": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r37": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "10A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580"
  },
  "r38": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "11",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580"
  },
  "r39": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e681-108580"
  },
  "r4": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6904-107765"
  },
  "r40": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580"
  },
  "r41": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL34724394-108580"
  },
  "r42": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580"
  },
  "r43": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1A",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580"
  },
  "r44": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580"
  },
  "r45": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1B",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580"
  },
  "r46": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "5",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=118930883&loc=d3e557-108580"
  },
  "r47": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(20))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r48": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03(4))",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r49": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.4)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r5": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "6",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "210",
   "URI": "http://asc.fasb.org/extlink&oid=118951113&loc=d3e6911-107765"
  },
  "r50": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.8)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r51": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.5-03.9)",
   "Topic": "220",
   "URI": "http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227"
  },
  "r52": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "12",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585"
  },
  "r53": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585"
  },
  "r54": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585"
  },
  "r55": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585"
  },
  "r56": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "14",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585"
  },
  "r57": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  },
  "r58": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "15",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585"
  },
  "r59": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "17",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3367-108585"
  },
  "r6": {
   "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"
  },
  "r60": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3000-108585"
  },
  "r61": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "24",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3521-108585"
  },
  "r62": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(e)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585"
  },
  "r63": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "25",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585"
  },
  "r64": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r65": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r66": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "28",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585"
  },
  "r67": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "4",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "230",
   "URI": "http://asc.fasb.org/extlink&oid=118932676&loc=d3e3044-108585"
  },
  "r68": {
   "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"
  },
  "r69": {
   "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"
  },
  "r7": {
   "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"
  },
  "r70": {
   "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"
  },
  "r71": {
   "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"
  },
  "r72": {
   "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"
  },
  "r73": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08(m)(1)(iii))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r74": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(d),(e))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r75": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(i)(4))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r76": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "S99",
   "SubTopic": "10",
   "Subparagraph": "(SX 210.4-08.(i))",
   "Topic": "235",
   "URI": "http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690"
  },
  "r77": {
   "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"
  },
  "r78": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "235",
   "URI": "http://asc.fasb.org/topic&trid=2122369"
  },
  "r79": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "7",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "260",
   "URI": "http://asc.fasb.org/extlink&oid=117326831&loc=d3e1337-109256"
  },
  "r8": {
   "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"
  },
  "r80": {
   "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"
  },
  "r81": {
   "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"
  },
  "r82": {
   "Name": "Accounting Standards Codification",
   "Publisher": "FASB",
   "Topic": "260",
   "URI": "http://asc.fasb.org/topic&trid=2144383"
  },
  "r83": {
   "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"
  },
  "r84": {
   "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"
  },
  "r85": {
   "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"
  },
  "r86": {
   "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"
  },
  "r87": {
   "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"
  },
  "r88": {
   "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"
  },
  "r89": {
   "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"
  },
  "r9": {
   "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"
  },
  "r90": {
   "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"
  },
  "r91": {
   "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"
  },
  "r92": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "13",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Topic": "310",
   "URI": "http://asc.fasb.org/extlink&oid=118952595&loc=d3e4647-111522"
  },
  "r93": {
   "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"
  },
  "r94": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "1",
   "Publisher": "FASB",
   "Section": "45",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562"
  },
  "r95": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(a)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  },
  "r96": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(aa)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  },
  "r97": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(b)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  },
  "r98": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(c)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  },
  "r99": {
   "Name": "Accounting Standards Codification",
   "Paragraph": "2",
   "Publisher": "FASB",
   "Section": "50",
   "SubTopic": "10",
   "Subparagraph": "(d)",
   "Topic": "320",
   "URI": "http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563"
  }
 },
 "version": "2.1"
}
