Lessee - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease expense	$ 29	$ 31	$ 85	$ 97
Short-term lease expense	5	6	15	16
Variable lease expense	12	12	34	37
Sublease income	(1)	0	(2)	(1)
Total Lease expense	$ 45	$ 49	$ 132	$ 149