Leases - Future Maturities of Lease Liabilities (Details) $ in Millions	Jun. 30, 2019 USD ($)
Operating Leases
2019 (excluding the six months ended June 30, 2019)	$ 28
2020	53
2021	45
2022	36
2023	25
Thereafter	127
Total lease payments	314
Less: imputed interest	(62)
Total	252
Finance Leases
2019 (excluding the six months ended June 30, 2019)	7
2020	3
2021	3
2022	3
2023	4
Thereafter	23
Total lease payments	43
Less: imputed interest	(7)
Total	$ 36