Leases - Weighted Average Lease Term and Discount Rate (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating Lease, Cost	$ 13	$ 39
Operating Lease, Weighted Average Remaining Lease Term	10 years	10 years
Finance Lease, Weighted Average Remaining Lease Term	10 years	10 years
Operating Lease, Weighted Average Discount Rate, Percent	4.60%	4.60%
Finance Lease, Weighted Average Discount Rate, Percent	3.50%	3.50%
Short-term Lease, Cost	$ 2	$ 5
Variable Lease, Cost	1	2
Finance Lease, Right-of-Use Asset, Amortization	1	2
Finance Lease, Interest Expense	$ 0	$ 1