Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Operating Lease, Right-of-Use Asset	$ 98
Operating Lease, Liability	97
Operating Lease, Cost	7
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	18
Lessee, Operating Lease, Liability, Payments, Due Year Two	20
Lessee, Operating Lease, Liability, Payments, Due Year Three	15
Lessee, Operating Lease, Liability, Payments, Due Year Four	12
Finance Lease, Liability, Payments, Due Year Five	8
Lessee, Operating Lease, Liability, Payments, Due after Year Five	37
Lessee, Operating Lease, Liability, Payments, Due	110
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ 13
Operating Leases, Rent Expense		$ 10
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
Finance Lease, Weighted Average Remaining Lease Term	2 years
Operating Lease, Weighted Average Discount Rate, Percent	2.70%
Finance Lease, Weighted Average Discount Rate, Percent	3.10%
Operating Lease, Payments	$ 6
Minimum [Member]
Lessee, Operating Lease, Renewal Term	1 year
Maximum [Member]
Lessee, Operating Lease, Renewal Term	5 years
Short-term Lease, Cost	$ 1
Short-term Lease Commitment, Amount	1
Finance Lease, Right-of-Use Asset	1
Finance Lease, Liability	1
Finance Lease, Right-of-Use Asset, Amortization	1
Finance Lease, Interest Expense	1
Finance Lease, Liability, Payments, Due Year Five	1
Finance Lease, Liability, Payments, Due Next Twelve Months	1
Finance Lease, Liability, Payments, Due Year Two	1
Finance Lease, Liability, Payments, Due Year Three	1
Finance Lease, Liability, Payments, Due Year Four	1
Finance Lease, Liability, Payments, Due after Year Five	1
Finance Lease, Principal Payments	1
Finance Lease, Interest Payment on Liability	1
Other Noncurrent Assets [Member]
Operating Lease, Right-of-Use Asset	98
Accounts Payable and Accrued Liabilities [Member]
Operating Lease, Liability, Current	23
Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Noncurrent	$ 74