Derivative Financial Instruments - Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges - GM Financial - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | $ 23,315 | $ 20,397 |
| Cumulative Amount of Fair Value Hedging Adjustments | (739) | (77) |
| Short-term Debt | ||
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | 4,858 | 996 |
| Cumulative Amount of Fair Value Hedging Adjustments | (69) | 4 |
| Long-term Debt | ||
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | 18,457 | 19,401 |
| Cumulative Amount of Fair Value Hedging Adjustments | (670) | $ (81) |
| Cumulative fair value adjustment on discontinued hedging relationships | $ 200 |