Earnings per Share (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 Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 1,123	$ 546	$ 2,127	$ 1,357
Net income (loss) attributable to noncontrolling interests	1	(5)	(8)	1
Preferred stock dividends and discount accretion	53	25	128	64
Dividends and undistributed earnings allocated to nonvested restricted shares	5	1	9	5
Net income attributable to basic common shares	1,064	525	1,998	1,287
Basic weighted-average common shares outstanding	528	527	527	526
Basic earnings per common share (a)	$ 2.02	$ 1.00	$ 3.79	$ 2.44
Less: Impact of BlackRock earnings per share dilution	4	4	9	7
Net income attributable to diluted common shares	$ 1,060	$ 521	$ 1,989	$ 1,280
Dilutive potential common shares (b) (c)	3	3	3	3
Diluted weighted-average common shares outstanding	531	530	530	529
Diluted earnings per common share (a)	$ 1.99	$ 0.98	$ 3.76	$ 2.42
Stock Options [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	1	5	1	5
Warrant [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	0	17	17	17