Leases - Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating and short-term lease cost	$ 8	$ 24
Finance lease cost:
Amortization of right-of-use assets	2	7
Interest on lease liability	1	1
Total finance lease cost	3	8
Total lease cost	$ 11	$ 32