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
	Mar. 31, 2014		Mar. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 363		$ 464
Less: Preferred stock dividends	(6)		(7)
Less: Dividends and undistributed earnings allocated to participating securities	(1)	[1]	(2)	[1]
Net income available to common shareholders	$ 356		$ 455
Basic average common shares	430,621		454,315
Effect of dilutive securities: common stock options and common stock awards (in shares)	8,194		8,436
Diluted average shares	438,815		462,751
Anti-dilutive securities (in shares)	1,504	[2]	2,488	[2]
Earnings per Common Share:
Basic (in dollars per share)	$ 0.83		$ 1.00
Diluted (in dollars per share)	$ 0.81	[3]	$ 0.98	[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 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.