Leases - Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease expense	$ 4	$ 8
Financing lease expense:
Amortization of ROU	1	3
Interest expense on lease liability	1	3
Short-term lease expense	$ 2	$ 4