Consolidated Statement of Changes in Shareholders' Equity (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Convertible preferred stock - savings plan
Convertible preferred stock - savings plan, balance, beginning of year			$ 68	$ 79	$ 89
Convertible preferred stock - savings plan, redemptions			(5)	(11)	(10)
Convertible preferred stock - savings plan, conversion to common stock			(63)
Convertible preferred stock - savings plan, balance, end of year		68		68	79
Common stock
Common stock, balance, beginning of year			20,162	19,593	19,242
Common stock, employee share-based compensation			328	420	210
Common stock, common shares issued - conversion of preferred stock			93
Common stock, compensation amortization under share-based plans and other changes			149	149	141
Common stock, balance, end of year	20,732	20,162	20,732	20,162	19,593
Retained earnings
Retained earnings, balance, beginning of year			18,847	16,315	13,314
Retained earnings, cumulative effect of adoption of updated accounting guidance at April 1, 2009					71
Net income	618	894	1,426	3,216	3,622
Dividends			(669)	(677)	(696)
Premium on preferred stock converted to common stock			(30)
Retained earnings, other			5	(7)	4
Retained earnings, balance, end of year	19,579	18,847	19,579	18,847	16,315
Accumulated other changes in equity from nonowner sources, net of tax
Accumulated other changes in equity from nonowner sources, net of tax, balance, beginning of year			1,255	1,219	(900)
Accumulated other changes in equity from nonowner sources, net of tax, cumulative effect of adoption of updated accounting guidance at April 1, 2009					(71)
Change in net unrealized gain (loss) on investment securities having no credit losses recognized in the consolidated statement of income			1,010	(77)	1,942
Change in net unrealized gain (loss) on investment securities having credit losses recognized in the consolidated statement of income			2	80	131
Net change in benefit plan assets and obligations recognized in equity, net of tax			(201)	27	(88)
Net change in unrealized foreign currency translation and other changes			(61)	6	205
Accumulated other changes in equity from nonowner sources, net of tax, balance, end of year	2,005	1,255	2,005	1,255	1,219
Treasury stock (at cost)
Treasury stock (at cost), balance, beginning of year			(14,857)	(9,791)	(6,426)
Treasury stock (at cost), treasury shares acquired - share repurchase authorization			(2,900)	(5,000)	(3,300)
Treasury stock (at cost), net shares acquired related to employee share-based compensation plans			(82)	(66)	(65)
Treasury stock (at cost), balance, end of year	(17,839)	(14,857)	(17,839)	(14,857)	(9,791)
Total common shareholders' equity	24,477	25,407	24,477	25,407	27,336
Total shareholders' equity	24,477	25,475	24,477	25,475	27,415
Common shares outstanding
Common shares outstanding, balance, beginning of year			434.6	520.3	585.1
Common shares outstanding, treasury shares acquired - share repurchase authorization			(51.0)	(95.7)	(69.4)
Common shares outstanding, net shares issued under employee share-based compensation plans			7.7	10.0	4.6
Common shares outstanding, common shares issued - conversion of preferred stock			1.5
Common shares outstanding, balance, end of year	392.8	434.6	392.8	434.6	520.3
Summary of changes in equity from nonowner sources
Net income	618	894	1,426	3,216	3,622
Other changes in equity from nonowner sources, net of tax			750	36	2,190
Total changes in equity from nonowner sources			$ 2,176	$ 3,252	$ 5,812