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, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 560		$ 540		$ 1,545		$ 1,583
Less: Preferred stock dividends	(18)		(7)		(43)		(20)
Less: Dividends and undistributed earnings allocated to participating securities	0	[1]	(2)	[1]	(2)	[1]	(6)	[1]
Net income available to common shareholders	$ 542		$ 531		$ 1,500		$ 1,557
Basic average common shares	421,974		442,860		426,775		449,742
Effect of dilutive securities: common stock options and common stock awards (in shares)	7,762		9,294		7,735		8,650
Diluted average shares	429,736		452,154		434,510		458,392
Anti-dilutive securities (in shares)	876	[2]	1,788	[2]	1,502	[2]	2,384	[2]
Earnings per Common Share:
Basic (in dollars per share)	$ 1.28		$ 1.20		$ 3.52		$ 3.46
Diluted (in dollars per share)	$ 1.26	[3]	$ 1.17	[3]	$ 3.45	[3]	$ 3.40	[3]

[1] Represented the portion of net income available to common equity allocated to participating securities, composed of fully vested deferred director stock and unvested restricted stock that 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 common shares, because their effect was anti-dilutive.

[3] Calculations reflect allocation of earnings to participating securities using the two-class method, as this computation is more dilutive than the treasury stock method.