Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Operating Lease, Right-of-Use Asset	$ 95		$ 95
Operating Lease, Liability	93		93
Operating Lease, Cost	6		13
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	11		11
Lessee, Operating Lease, Liability, Payments, Due Year Two	20		20
Lessee, Operating Lease, Liability, Payments, Due Year Three	15		15
Lessee, Operating Lease, Liability, Payments, Due Year Four	12		12
Finance Lease, Liability, Payments, Due Year Five	9		9
Lessee, Operating Lease, Liability, Payments, Due after Year Five	39		39
Lessee, Operating Lease, Liability, Payments, Due	106		106
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ 13		$ 13
Operating Leases, Rent Expense		$ 11		$ 21
Operating Leases, Future Minimum Payments Due, Next Twelve Months					$ 24
Operating Leases, Future Minimum Payments, Due in Two Years					21
Operating Leases, Future Minimum Payments, Due in Three Years					15
Operating Leases, Future Minimum Payments, Due in Four Years					13
Operating Leases, Future Minimum Payments, Due in Five Years					10
Operating Leases, Future Minimum Payments, Due Thereafter					38
Operating Leases, Future Minimum Payments Due					$ 121
Operating Lease, Weighted Average Remaining Lease Term	8 years		8 years
Finance Lease, Weighted Average Remaining Lease Term	3 years		3 years
Operating Lease, Weighted Average Discount Rate, Percent	2.80%		2.80%
Finance Lease, Weighted Average Discount Rate, Percent	3.30%		3.30%
Operating Lease, Payments			$ 12
Minimum [Member]
Lessee, Operating Lease, Renewal Term	1 year		1 year
Maximum [Member]
Lessee, Operating Lease, Renewal Term	5 years		5 years
Finance Lease, Right-of-Use Asset, Amortization			$ 1
Finance Lease, Interest Expense			1
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	$ 95		95
Accounts Payable and Accrued Liabilities [Member]
Operating Lease, Liability, Current	22		22
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	$ 71		$ 71