Leases Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset			$ 191
Operating Lease, Liability			201
Operating Leases, Rent Expense	$ 56	$ 57
Operating Leases, Income Statement, Sublease Revenue	$ 4	$ 3
Forecast [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset			$ 54