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Derivative Financial Instruments Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges [Member] - Long-term Debt [Member] - GM Financial [Member] $ in Millions | 9 Months Ended
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Sep. 30, 2018 USD ($)
Derivatives, Fair Value [Line Items] |
Carrying Amount of Hedged Items | $ 15,363
Cumulative Amount of Fair Value Hedging Adjustments on Hedging Relationships | 735
Cumulative fair value adjustment on discontinued hedging relationships | $ 178

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- Definition Derivative Liabilities, Fair Value Adjustment + References No definition available. + Details
Name: | gm_DerivativeLiabilitiesFairValueAdjustment
Namespace Prefix: | gm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Derivative Liabilities, Fair Value Adjustment on Discontinued Hedging Relationships + References No definition available. + Details
Name: | gm_DerivativeLiabilitiesFairValueAdjustmentonDiscontinuedHedgingRelationships
Namespace Prefix: | gm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Derivative Liability, Less Par Value + References No definition available. + Details
Name: | gm_DerivativeLiabilityLessParValue
Namespace Prefix: | gm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition 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. + References No definition available. + Details
Name: | us-gaap_DerivativesFairValueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_LongTermDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | gm_BusinessGroupAxis=gm_GmFinancialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |