Equity Level 4 (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended
	Jul. 25, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 975
Treasury stock acquired		6.6	6.7		13.3
Payments for Repurchase of Common Stock		$ 325	$ 325		$ 650	$ 700
Treasury Stock Acquired, Average Cost Per Share		$ 49,340,000	$ 48,470,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		650.0			650.0
Warrants outstanding		2.9			2.9		4.0
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 9.060			$ 9.060		$ 9.126
Stock Repurchase Program, Authorized Amount		$ 1,300			$ 1,300
Warrant [Member]
Class of Warrant or Right [Line Items]
Warrants Exercised		0.1		0.0	1.1	0.2
Treasury Stock [Member]
Class of Warrant or Right [Line Items]
Treasury Stock, Value, Acquired, Cost Method					$ 650	$ 700
Common Stock [Member]
Class of Warrant or Right [Line Items]
Treasury stock acquired					13,299.0	16,222.0
Subsequent Event [Member]
Class of Warrant or Right [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 85
Treasury stock acquired	1.6