Leases - Summary of Lease Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Amortization of right-of-use assets	$ 1	$ 1
Interest on lease liabilities	0	0
Operating lease cost	53	105
Total lease cost	$ 54	$ 106