Earnings Per Common Share (EPS under Basic and Diluted Computations) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Earnings Per Common Share [Abstract]
Net income	$ 256		$ 275		$ 462		$ 470
Preferred stock dividends	(23)		(14)		(31)		(14)
Net income available to common stockholders	$ 233		$ 261		$ 431		$ 456
Weighted-average common shares outstanding - basic	1,282		1,273		1,280		1,272
Common stock equivalent shares related to stock incentive plans	6		1		5		1
Weighted-average common shares outstanding - diluted	1,288	[1]	1,274	[1]	1,285	[1]	1,273	[1]
Basic EPS	$ 0.18		$ 0.20		$ 0.33		$ 0.36
Diluted EPS	$ 0.18		$ 0.20		$ 0.33		$ 0.36
Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS	28		59		32		61

[1] Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS totaled 28 million and 59 million shares for the second quarters of 2013 and 2012, respectively, and 32 million and 61 million shares for the first halves of 2013 and 2012, respectively.