Shareholders' Equity (details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Jun. 07, 2011	Dec. 31, 2010
Shareholders' Equity disclosure
Share repurchase authorization, number of shares repurchased (in shares)	7,300,000		30,100,000
Share repurchase authorization, cost of shares repurchased	$ 375,000,000		$ 1,710,000,000
Share repurchase authorization, average cost per share repurchased	$ 51.77		$ 56.94
Share repurchase authorization, remaining capacity under share repurchase authorization			4,800,000,000
Number of common shares issued upon conversion of preferred shares, per preferred share					8
Preferred shares outstanding	0		0		190,083	200,000
Number of common shares issued upon conversion of preferred shares, total					1,520,000
Net income	333,000,000	1,005,000,000	808,000,000	2,322,000,000
Change in net unrealized gain on investment securities having no credit losses recognized in the consolidated statement of income	389,000,000	585,000,000	758,000,000	1,061,000,000
Change in net unrealized gain on investment securities having credit losses recognized in the consolidated statement of income	(6,000,000)	24,000,000	6,000,000	68,000,000
Other changes	(62,000,000)	73,000,000	13,000,000	24,000,000
Total changes in equity from nonowner sources	$ 654,000,000	$ 1,687,000,000	$ 1,585,000,000	$ 3,475,000,000