Other Assets - Intangible Assets Disclosure (Detail) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | $ 2,188 | $ 2,217 |
| Accumulated amortization | (1,558) | (1,576) |
| Net carrying value | 630 | 641 |
| Customer Lists [Member] | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | 1,478 | 1,427 |
| Accumulated amortization | (1,089) | (1,044) |
| Net carrying value | 389 | 383 |
| Acquired leases and other [Member] | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross carrying value | 710 | 790 |
| Accumulated amortization | (469) | (532) |
| Net carrying value | $ 241 | $ 258 |