Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share, Basic, Two Class Method [Abstract]
Net income	$ 6,529	$ 4,924
Less: Preferred stock dividends	182	157
Net income applicable to common equity	6,347	4,767
Less: Dividends and undistributed earnings allocated to participating securities	216	190
Net income applicable to common stockholders	6,131	4,577
Total weighted-average basic shares outstanding	3,818.2	3,818.8
Net income per share (Basic)	$ 1.61	$ 1.20
Earnings Per Share, Diluted, Two Class Method [Abstract]
Net income applicable to common stockholders	$ 6,131	$ 4,577
Total weighted-average basic shares outstanding	3,818.2	3,818.8
Add: Employee stock options, SARs and warrants	28.8	14.6
Total weighted-average diluted shares outstanding	3,847.0	3,833.4
Net income per share (Diluted)	$ 1.59	$ 1.19
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Aggregate antidilutive number of shares issuable	13	169