Earnings Per Common Share (EPS under Basic and Diluted Computations) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Earnings Per Common Share [Abstract]
Net income	$ 321		$ 290		$ 971		$ 752
Preferred stock dividends	(9)		(8)		(39)		(39)
Net income available to common stockholders	$ 312		$ 282		$ 932		$ 713
Weighted-average common shares outstanding — basic	1,304		1,287		1,302		1,282
Common stock equivalent shares related to stock incentive plans	12		9		11		6
Weighted-average common shares outstanding — diluted	1,316	[1]	1,296	[1]	1,313	[1]	1,288	[1]
Basic EPS	$ 0.24		$ 0.22		$ 0.71		$ 0.55
Diluted EPS	$ 0.24		$ 0.22		$ 0.70		$ 0.55
Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS	12		19		18		31

[1] Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS totaled 12 million and 19 million shares for the third quarters of 2014 and 2013, respectively, and 18 million and 31 million shares for the first nine months of 2014 and 2013, respectively.