Earnings Per Common Share (EPS under Basic and Diluted Computations) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Earnings Per Common Share [Abstract]
Net income	$ 319	$ 290	$ 256	$ 206	$ 211	$ 247	$ 275	$ 195	$ 1,071		$ 928		$ 864
Preferred stock dividends									61		45
Net income available to common stockholders	$ 297	$ 282	$ 233	$ 198	$ 189	$ 238	$ 261	$ 195	$ 1,010		$ 883		$ 864
Weighted-average common shares outstanding — basic									1,285		1,274		1,227
Common stock equivalent shares related to stock incentive plans									8		1		2
Weighted-average common shares outstanding — diluted	1,304	1,296	1,288	1,282	1,278	1,275	1,274	1,273	1,293	[1]	1,275	[1]	1,229	[1]
Basic EPS	$ 0.23	$ 0.22	$ 0.18	$ 0.15	$ 0.15	$ 0.19	$ 0.20	$ 0.15	$ 0.78		$ 0.69		$ 0.70
Diluted EPS	$ 0.23	$ 0.22	$ 0.18	$ 0.15	$ 0.15	$ 0.19	$ 0.20	$ 0.15	$ 0.78		$ 0.69		$ 0.70
Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS									34		74		63

[1] Antidilutive stock options and restricted stock awards excluded from the calculation of diluted EPS totaled 34 million, 74 million, and 63 million shares in 2013, 2012, and 2011, respectively.