Shareholders' Equity (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended	3 Months Ended					9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 March 2014 Repurchase Program	Sep. 30, 2014 March 2014 Repurchase Program	Mar. 31, 2014 March 2014 Repurchase Program	Sep. 30, 2014 March 2014 Repurchase Program	Mar. 31, 2014 March 2013 Repurchase Program	Mar. 31, 2014 Depositary Shares	Sep. 30, 2014 Series C Preferred Stock	Mar. 31, 2014 Series C Preferred Stock	Sep. 30, 2013 Series C Preferred Stock	Sep. 30, 2014 Series C Preferred Stock	Sep. 30, 2013 Series C Preferred Stock	Sep. 30, 2014 Series C Preferred Stock, Depository Share	Sep. 30, 2013 Series C Preferred Stock, Depository Share	Sep. 30, 2014 Series C Preferred Stock, Depository Share	Sep. 30, 2013 Series C Preferred Stock, Depository Share	Sep. 30, 2014 Retained Earnings	Sep. 30, 2013 Retained Earnings	Sep. 30, 2014 Retained Earnings	Sep. 30, 2013 Retained Earnings	Sep. 30, 2014 Series D Preferred Stock	Mar. 31, 2014 Series D Preferred Stock	Sep. 30, 2014 Series D Preferred Stock	Sep. 30, 2014 Series D Preferred Stock, Depository Share	Sep. 30, 2014 Series D Preferred Stock, Depository Share
Equity, Class of Treasury Stock [Line Items]
Stock issued during period												30,000,000
Depositary shares, ownership interest																0.025%												0.025%
Liquidation preference (in dollars per share)												$ 25		$ 100,000
Proceeds from issuance of preferred stock			$ 742,000,000	$ 0								$ 742,000,000
Preferred stock dividends (in dollars per share)													$ 1,313		$ 1,313	$ 3,939	$ 3,939	$ 0.33	$ 0.33	$ 0.99	$ 0.98					$ 1,475		$ 3,130	$ 0.37	$ 0.78
Preferred stock cash dividend			(43,000,000)	(20,000,000)									(7,000,000)		(7,000,000)	(20,000,000)	(20,000,000)									(11,000,000)		(23,000,000)
Dividend rate														5.25%													5.90%
Redemption price (in dollars per share)												$ 25		$ 100,000
Amount of common stock authorized for repurchase							1,700,000,000
Cash dividends declared (in dollars per share)	$ 0.3	$ 0.26	$ 0.86	$ 0.78
Common stock dividends			366,000,000	350,000,000																		126,000,000	115,000,000	366,000,000	350,000,000
Net gains (losses) from sales of available-for-sale securities			(15,000,000)	(11,000,000)
Net after tax realized gains (losses) on AFS securities	(9,000,000)	7,000,000	(9,000,000)	7,000,000
Unrealized pretax gains (losses) on securities included in AOCI					(43,000,000)	25,000,000
Deferred taxes on unrealized pretax gains (losses) on securities included in AOCI					(17,000,000)	10,000,000
Common stock acquired (shares)			18,200,000					5,800,000	0	12,100,000	6,100,000
Treasury Stock Acquired, Average Cost Per Share			$ 68.18					$ 70.61		$ 67.70	$ 69.14
Stock Repurchased During Period, Value			$ 1,240,000,000					$ 410,000,000		$ 820,000,000	$ 420,000,000
Shares available for purchase											0