Other Assets - Intangible Assets Disclosure (Detail) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | $ 2,048 | $ 2,188 |
| Accumulated amortization | (1,551) | (1,558) |
| Net carrying value | 497 | 630 |
| Customer Lists [Member] | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | 1,472 | 1,478 |
| Accumulated amortization | (1,123) | (1,089) |
| Net carrying value | 349 | 389 |
| Acquired leases and other [Member] | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | 576 | 710 |
| Accumulated amortization | (428) | (469) |
| Net carrying value | $ 148 | $ 241 |