Leases - Supplemental Cash Flow and Other Information Related to Leases (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases	$ 102	$ 95
Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases	3	4
Cash paid for amounts included in the measurement of lease liabilities: Financing cash flows from finance leases	3	4
Right-of-use assets obtained in exchange for new finance lease liabilities	15	21
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 36	$ 73