Leases - Maturity of Lease Liabilities (Details) $ in Millions	Dec. 31, 2019 USD ($)
Operating Leases
The remainder of 2020	$ 99
2021	428
2022	372
2023	311
2024	255
Thereafter	969
Total lease payments	2,434
Less imputed interest	(289)
Present value of lease liabilities	2,145
Finance Leases
The remainder of 2020	2
2021	18
2022	18
2023	17
2024	16
Thereafter	125
Total lease payments	196
Less imputed interest	(33)
Present value of lease liabilities	163
Total
The remainder of 2020	101
2021	446
2022	390
2023	328
2024	271
Thereafter	1,094
Total lease payments	2,630
Less imputed interest	(322)
Present value of lease liabilities	2,308
Minimum sublease income under future noncancelable leases	$ 185