Equity Level 4 (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 25, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Treasury stock acquired		6.7
Payments for Repurchase of Common Stock		$ 325	$ 350
Warrants outstanding		3.0		4.0
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 9.093		$ 9.126
Stock Repurchase Program, Authorized Amount		$ 1,300
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		$ 975
Warrant [Member]
Class of Warrant or Right [Line Items]
Warrants Exercised		1.0	0.2
Treasury Stock [Member]
Class of Warrant or Right [Line Items]
Treasury Stock, Value, Acquired, Cost Method		$ 325	$ 350
Common Stock [Member]
Class of Warrant or Right [Line Items]
Treasury stock acquired		6,709.0	8,394.0
Subsequent Event [Member]
Class of Warrant or Right [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 92
Treasury stock acquired	1.9