Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Operating Leases
2019 (remaining three months)	$ 8
2020	32
2021	30
2022	27
2023	22
Thereafter	36
Total lease payments	155
Less: interest	(36)
Total	119
Less: current portion	(29)
Long-term portion	90	$ 0
Finance Leases
2019 (remaining three months)	2
2020	5
2021	1
2022	1
2023	1
Thereafter	4
Total lease payments	14
Less: interest	(2)
Total	12
Less: current portion	(7)
Long-term portion	$ 5