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				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 622		$ 579		$ 985		$ 1,043
Less: Preferred stock dividends	(19)		(6)		(25)		(13)
Less: Dividends and undistributed earnings allocated to participating securities	(1)	[1]	(2)	[1]	(2)	[1]	(4)	[1]
Net income available to common shareholders	$ 602		$ 571		$ 958		$ 1,026
Basic average common shares	427,824		452,176		429,215		453,240
Effect of dilutive securities: common stock options and common stock awards (in shares)	7,496		8,864		7,743		8,390
Diluted average shares	435,320		461,040		436,958		461,630
Anti-dilutive securities (in shares)	1,508	[2]	2,330	[2]	1,506	[2]	2,409	[2]
Earnings per Common Share:
Basic (in dollars per share)	$ 1.41		$ 1.26		$ 2.23		$ 2.26
Diluted (in dollars per share)	$ 1.38	[3]	$ 1.24	[3]	$ 2.19	[3]	$ 2.22	[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.