Derivatives Balance Sheet Location (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	$ 1	$ (1)
Derivative Financial Instruments, Liabilities [Member] | Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	(2)
Derivative Financial Instruments, Assets [Member] | Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net		(6)
Derivative Financial Instruments, Assets [Member] | Net Investment Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	$ (23)	$ 6