Leases - Undiscounted Cash Flows under ASC 840 (Details) $ in Millions	Dec. 31, 2018 USD ($)
Operating Leases
2019	$ 24
2021	20
2022	12
2023	11
2024	6
Thereafter	2
Total minimum lease payments	75
Finance Leases
2019	19
2020	31
2021	0
2022	0
2023	0
Thereafter	0
Total	$ 50