Lessee - Supplemental Information Related to Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities - Operating cash flows	$ 119	$ 126
Right-of-use assets obtained in exchange for new lease liabilities	$ 76	$ 75
Weighted-average remaining lease term (years)	5 years	4 years
Weighted-average discount rate (percentage)	5.03%	5.47%