Leases - Components of Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finance lease cost
Amortization of right-of-use assets	$ 65	$ 51	$ 185	$ 140
Interest	4	4	11	9
Operating lease cost	352	298	1,036	818
Variable lease cost and other, net	$ 57	41	174	111
Total lease cost		$ 394	$ 1,406	$ 1,078
Weighted-average remaining lease term
Operating leases	12 years 4 months 24 days		12 years 4 months 24 days		13 years
Finance leases	15 years 1 month 6 days		15 years 1 month 6 days		15 years 3 months 18 days
Weighted-average discount rate
Operating leases	3.10%		3.10%		3.20%
Finance leases	2.90%		2.90%		3.10%