Lessee - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease expense	$ 25	$ 29	$ 79	$ 85
Short-term lease expense	5	5	16	15
Variable lease expense	12	12	35	34
Sublease income	(1)	(1)	(3)	(2)
Total Lease expense	$ 41	$ 45	$ 127	$ 132