Leases - Components of Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 6	$ 11
Finance lease cost
Amortization of right-of-use assets	0	1
Interest on lease liabilities	1	1
Total finance lease cost	1	2
Short-term lease cost	0	0
Variable lease cost	0	0
Total lease cost	$ 7	$ 13