Summary of Significant Accounting Policies - Schedule of Deferred Revenue Activity (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Accounting Policies [Abstract] | ||
| Deferred revenue on automotive sales with and without resale value guarantee— beginning of period | $ 883 | $ 476 |
| Additions | 880 | 532 |
| Net changes in liability for pre-existing contracts | 9 | (13) |
| Revenue recognized | (300) | (112) |
| Deferred revenue on automotive sales with and without resale value guarantee— end of period | $ 1,472 | $ 883 |