Shareholders' Equity (details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 07, 2011	Dec. 31, 2010
Shareholders' Equity disclosure
Share repurchase authorization, number of shares repurchased (in shares)	3,900,000		22,800,000
Share repurchase authorization, cost of shares repurchased	$ 237,000,000		$ 1,340,000,000
Share repurchase authorization, average cost per share	$ 60.27		$ 58.58
Share repurchase authorization, remaining capacity under share repurchase authorization			5,170,000,000
Number of common shares issued upon conversion of preferred shares, per preferred share	8		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 (loss)	(364,000,000)	670,000,000	475,000,000	1,317,000,000
Change in net unrealized gain on investment securities having no credit losses recognized in the consolidated statement of income (loss)	429,000,000	422,000,000	369,000,000	476,000,000
Change in net unrealized gain on investment securities having credit losses recognized in the consolidated statement of income (loss)	(6,000,000)	21,000,000	12,000,000	44,000,000
Other changes	16,000,000	(24,000,000)	75,000,000	(49,000,000)
Total changes in equity from nonowner sources	$ 75,000,000	$ 1,089,000,000	$ 931,000,000	$ 1,788,000,000