Lessee - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease expense	$ 27	$ 28	$ 54	$ 56
Short-term lease expense	6	5	11	10
Variable lease expense	11	10	23	22
Sublease income	(1)	(1)	(2)	(1)
Total Lease expense	$ 43	$ 42	$ 86	$ 87