Commitments and Contingencies Commitments and Contingencies - Lease Maturity Schedule (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2019	$ 4
2020	9
2021	8
2022	8
2023	9
Thereafter	72
Total lease payments	110
Less: imputed interest	19
Total operating lease liabilities	$ 91	$ 95
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019			$ 9
2020			9
2021			8
2022			8
2023			9
Thereafter			$ 72