Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Operating leases:
Operating lease right-of-use assets	$ 20,729	$ 20,860
Current portion of operating lease liabilities	1,638	1,596
Long-term operating lease liabilities	18,757	18,926
Total operating lease liabilities	20,395	20,522
Finance leases:
Property and equipment, gross	1,107	790
Accumulated depreciation	(106)	(38)
Property and equipment, net	1,001	752
Current portion of long-term debt	33	27
Long-term debt	1,050	781
Total finance lease liabilities	$ 1,083	$ 808
Weighted average remaining lease term (in years)
Operating leases	13 years 3 months 18 days	13 years 9 months 18 days
Finance leases	20 years 3 months 18 days	20 years 6 months
Weighted average discount rate
Operating leases	4.50%	4.60%
Finance leases	5.60%	6.70%