Lessee - Components of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease expense	$ 113	$ 125
Short-term lease expense	20	21
Variable lease expense	47	48
Sublease income	(2)	(1)
Total Lease expense	$ 178	$ 193