Derivative Financial Instruments Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges [Member] - Long-term Debt [Member] - GM Financial [Member] $ in Millions |
12 Months Ended |
|---|---|
|
Dec. 31, 2018
USD ($)
| |
| Derivatives, Fair Value [Line Items] | |
| Carrying Amount of Hedged Items | $ 17,923 |
| Cumulative Amount of Fair Value Hedging Adjustments | 459 |
| Cumulative fair value adjustment on discontinued hedging relationships | $ 247 |