Leases - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases		$ 144	$ 107
Financing cash flows from finance leases		1	1
Right-of-use assets obtained in exchange for new lease liabilities
Operating leases	[1]	$ 78	$ 32

[1] As the rate implicit in the lease cannot be readily determined, we use our incremental borrowing rate based on the information available at the lease commencement date in determining the imputed interest and present value of lease payments. We used the incremental borrowing rate on January 1, 2019 for operating leases that commenced prior to that date.