Derivative Financial Instruments - Balance Sheet Location of GM Financial Unsecured Debt (Details) - Fair Value Hedges - GM Financial - USD ($) $ in Millions |
Mar. 31, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | $ 23,631 | $ 23,315 |
| Cumulative Amount of Fair Value Hedging Adjustments on Hedging Relationships | (311) | (739) |
| Long-term unsecured debt | ||
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | 19,266 | 18,457 |
| Cumulative Amount of Fair Value Hedging Adjustments on Hedging Relationships | (257) | (670) |
| Cumulative fair value adjustment on discontinued hedging relationships | 201 | 200 |
| Short-term unsecured debt | ||
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | 4,365 | 4,858 |
| Cumulative Amount of Fair Value Hedging Adjustments on Hedging Relationships | $ (54) | $ (69) |