Derivative Financial Instruments Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges [Member] - Long-term Debt [Member] - GM Financial [Member] $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Items	$ 15,452
Cumulative Amount of Fair Value Hedging Adjustments on Hedging Relationships	685
Cumulative fair value adjustment on discontinued hedging relationships	$ 167

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.

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