Leases (Future Minimum Maturities of Lease Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Operating Leases
2020	$ 1,226
2021	4,679
2022	4,372
2023	3,981
2024	3,449
Thereafter	13,543
Total lease payments	31,250
Less imputed interest	(5,711)
Total	25,539	$ 25,255
Finance Leases
2020	99
2021	316
2022	298
2023	278
2024	258
Thereafter	1,720
Total lease payments	2,969
Less imputed interest	(1,063)
Total	$ 1,906	$ 2,034