Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Apr. 01, 2019	Mar. 31, 2019
Leases [Abstract]
Lessee, Operating Lease, Remaining Lease Term	10 years
Operating Lease, Expense	$ 15
Operating Leases, Future Minimum Payments Due, Next Twelve Months			$ 52
Operating Lease, Right-of-Use Asset	206	$ 215
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 46
Operating Lease, Weighted Average Remaining Lease Term	5 years 4 months 24 days
Operating Lease, Payments	$ 13
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 4
Operating Lease, Weighted Average Discount Rate, Percent	3.60%
Lessee, Operating Lease, Liability, Payments, Due Year Two	$ 56
Lessee, Operating Lease, Liability, Payments, Due Year Three	46
Lessee, Operating Lease, Liability, Payments, Due Year Four	37
Lessee, Operating Lease, Liability, Payments, Due Year Five	29
Lessee, Operating Lease, Liability, Payments, Due Year Six	23
Lessee, Operating Lease, Liability, Payments, Due After Year Six	28
Operating Leases, Future Minimum Payments Due	265
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(25)
Operating Lease, Liability	240	247
Operating Lease, Liability, Current	55	50
Operating Lease, Liability, Noncurrent	185	$ 197
Prepaid Rent			6
Deferred Rent Credit			38
Operating Leases, Future Minimum Payments, Due in Two Years			54
Operating Leases, Future Minimum Payments, Due in Three Years			44
Operating Leases, Future Minimum Payments, Due in Four Years			36
Operating Leases, Future Minimum Payments, Due in Five Years			28
Operating Leases, Future Minimum Payments, Due Thereafter			50
Operating Leases, Future Minimum Payments Due			$ 264
Variable Lease, Cost	9
Short-term Lease, Cost	7
Operating Lease, Cost	$ 31