Leases - Schedule Of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash Paid For Amounts Included In Measurement Of Lease Liabilities [Abstract]
Operating cash flows for operating leases	$ 445	$ 404
Operating cash flows for finance leases	31	32
Financing cash flows for finance leases	$ 86	$ 79