Contingencies and Commitments - Operating leases minimum payments (Detail) $ in Millions |
Dec. 31, 2018
USD ($)
|
|---|---|
| Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] | |
| Future minimum rental payments, 2019 | $ 1,360 |
| Future minimum rental payments, 2020 | 1,317 |
| Future minimum rental payments, 2021 | 1,098 |
| Future minimum rental payments, 2022 | 872 |
| Future minimum rental payments, 2023 | 708 |
| Future minimum rental payments, after 2023 | 3,658 |
| Future minimum rental payments, total | $ 9,013 |