Leases - Schedule of Components of Leases (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current portion of lease liabilities:
Operating	$ 79	$ 82
Financing	23	28
Total	102	110
Long-term portion of lease liability:
Operating	371	376
Financing	222	236
Total	$ 593	$ 612