Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Operating Leases
The remainder of 2020	$ 795
2021	1,281
2022	1,198
2023	1,137
2024	1,061
Thereafter	7,657
Total undiscounted cash flows	13,129
Less: Imputed interest	(2,785)
Present value of lease liabilities	10,344
Operating lease liabilities, current	835	$ 800
Operating lease liabilities, non-current	9,509	$ 9,524
Finance Leases
The remainder of 2020	45
2021	49
2022	38
2023	36
2024	36
Thereafter	386
Total undiscounted cash flows	590
Less: Imputed interest	(120)
Present value of lease liabilities	470
Lease liabilities, current	44
Lease liabilities, non-current	$ 426