Derivative Financial Instruments - Balance Sheet Location of Cumulative Basis Adjustments (Details) - Fair Value Hedges - Long-term Debt - GM Financial - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Derivatives, Fair Value [Line Items] | ||
| Carrying Amount of Hedged Items | $ 20,397 | $ 17,923 |
| Cumulative Amount of Fair Value Hedging Adjustments | (77) | 459 |
| Cumulative fair value adjustment on discontinued hedging relationships | $ 247 | |
| Interest Rate Swap | ||
| Derivatives, Fair Value [Line Items] | ||
| Loss on derivative instruments | $ 569 |