Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Common Share (Detail) (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
Basic earnings
Income from continuing operations, net of tax	$ 1,125	$ 1,118	$ 3,453	$ 3,479
Loss from discontinued operations, net of tax	(44)	(13)	(24)	(210)
Net income	1,081	1,105	3,429	3,269
Dividends and undistributed earnings allocated to participating securities	(5)	(5)	(14)	(14)
Preferred stock dividends	(20)	(13)	(46)	(39)
Net income available to common stockholders	$ 1,056	$ 1,087	$ 3,369	$ 3,216
Net income from continuing operations (in dollars per share)	$ 1.97	$ 1.89	$ 5.99	$ 5.89
Income (loss) from discontinued operations (in dollars per share)	$ (0.08)	$ (0.02)	$ (0.04)	$ (0.36)
Net income per basic common share (in dollars per share)	$ 1.89	$ 1.87	$ 5.95	$ 5.53
Total weighted-average basic shares outstanding	559.9	582.3	566.1	581.4
Diluted earnings
Net income from continuing operations (in dollars per share)	$ 1.94	$ 1.86	$ 5.90	$ 5.82
Income (loss) from discontinued operations (in dollars per share)	$ (0.08)	$ (0.02)	$ (0.04)	$ (0.36)
Net income per diluted common share (in dollars per share)	$ 1.86	$ 1.84	$ 5.86	$ 5.46
Effect of dilutive securities:
Stock options	2.8	2.4	2.7	2.1
Other contingently issuable shares	1.6	1.7	1.5	1.6
Warrants	3.6	4.7	4.9	3.9
Total effect of dilutive securities	8.0	8.8	9.1	7.6
Total weighted-average diluted shares outstanding	567.9	591.1	575.2	589.0