Leases - Maturities of Lease Liabilities (Details) $ in Millions	Jun. 30, 2019 USD ($)
Operating Leases Future Minimum Rental Payments
Remainder of 2019	$ 66
2020	147
2021	133
2022	117
2023	102
Thereafter	761
Total lease payments	1,326
Less: Imputed interest	367
Present value of lease liabilities	959
Finance Leases
Remainder of 2019	1
2020	1
2021	0
2022	0
2023	0
Thereafter	12
Total lease payments	14
Less: Imputed interest	10
Present value of lease liabilities	4
Legally binding lease payments for leases signed but not yet commenced	$ 3