Leases - Maturity of Lease Liabilities (Details) $ in Millions	Jun. 30, 2019 USD ($)
Operating Leases
The remainder of 2020	$ 319
2021	401
2022	344
2023	286
2024	232
Thereafter	900
Total lease payments	2,482
Less imputed interest	(304)
Present value of lease liabilities	2,178
Finance Leases
The remainder of 2020	8
2021	10
2022	10
2023	10
2024	10
Thereafter	69
Total lease payments	117
Less imputed interest	(24)
Present value of lease liabilities	93
Total
The remainder of 2020	327
2021	411
2022	354
2023	296
2024	242
Thereafter	969
Total lease payments	2,599
Less imputed interest	328
Present value of lease liabilities	2,271
Minimum sublease income under future noncancelable leases	$ 191