Leases - Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease right-of-use assets	$ 5	$ 0
Finance lease assets	17
Total lease assets	22
Current finance lease liabilities	1
Noncurrent operating liabilities	4	0
Noncurrent finance lease liabilities	25	$ 25
Total lease liabilities	30
Finance lease, right-of-use asset, accumulated amortization	$ 6