Leases - Schedule of Maturities of Lease Obligations (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating Leases
2021	$ 83
2022	83
2023	72
2024	71
2025	67
Remaining years	287
Total lease payments	663
Less: Imputed interest	(122)
Total lease obligations	541	$ 535
Finance Leases
2021	36
2022	36
2023	36
2024	36
2025	36
Remaining years	176
Total lease payments	356
Less: Imputed interest	(118)
Total lease obligations	$ 238	$ 255