Derivative Instruments (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 21, 2016
Derivative [Line Items]
Class of Warrant or Right, Unissued						1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	84,500,000			84,500,000
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 6.43			$ 6.43
Warrants and Rights Outstanding	$ 156		$ 70	$ 156
Fair Value Adjustment of Warrants			(86)	(16)	$ 0
Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Debt Instrument, Unamortized Premium	7		4	7
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge	(9)		$ (9)	(9)	$ (10)
Foreign currency forward contracts [Member]
Derivative [Line Items]
Notional amount	$ 1,600			$ 1,600
Additional Paid-in Capital [Member]
Derivative [Line Items]
Stock Issued During Period, Shares, New Issues	84,500,000	115,000,000