Earnings Per Common Share (Computation of Basic and Diluted Earnings Per Share) (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 540		$ 674		$ 1,583		$ 1,591
Less: Preferred stock dividends	(7)		(15)		(20)		(29)
Less: Dividends and undistributed earnings allocated to participating securities	(2)	[1]	(5)	[1]	(6)	[1]	(11)	[1]
Net income available to common shareholders	$ 531		$ 654		$ 1,557		$ 1,551
Basic average common shares	442,860		472,355		449,742		479,536
Effect of dilutive securities: common stock options and common stock awards (in shares)	9,294		7,655		8,650		6,277
Diluted average shares	452,154		480,010		458,392		485,813
Anti-dilutive securities (in shares)	1,788	[2]	5,443	[2]	2,384	[2]	5,613	[2]
Earnings per Common Share:
Basic (per share)	$ 1.20		$ 1.39		$ 3.46		$ 3.23
Diluted (per share)	$ 1.17		$ 1.36		$ 3.40		$ 3.19

[1] Represented the portion of net income available to common equity allocated to participating securities; participating securities, composed of unvested restricted stock and director stock awards, contain non-forfeitable rights to dividends during the vesting period on a basis equivalent to dividends paid to common shareholders.

[2] Represented common stock options and other equity-based awards outstanding, but not included in the computation of diluted average shares because their effect was anti-dilutive.