Leases - Lease Cost (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 cost	$ 60	$ 64	$ 183	$ 141
Finance lease cost
Amortization of right-of-use assets	48	16	137	18
Interest on lease liabilities	7	3	16	3
Lease, cost	115	83	336	162
Variable lease cost included within operating lease cost	8	$ 14	27	$ 42
Accelerated amortization expense included within finance lease expense	$ 17		$ 62