Shareholders' Equity (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	May 31, 2011	Dec. 31, 2008	Jun. 30, 2010 Quarterly Amount Since June 2010 [Member]	Feb. 08, 2012 Dividend Declared [Member]
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments	$ 3,400,000,000
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	4,500,000,000	3,200,000,000
Extraordinary Dividends	1,100,000,000	686,000,000
Cash And Investment Held By Non Regulated Entities	1,600,000,000
Cash and cash equivalents	9,429,000,000	9,123,000,000	9,800,000,000		7,426,000,000
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	12,000,000,000
Shares of common stock authorized by Board of Directors for the Company to purchase				110
Common stock repurchases, shares	65
Common stock repurchases, average price per share	$ 46
Common stock repurchases	2,994,000,000	2,517,000,000	1,801,000,000
Remaining available shares authorized by Board of Directors	65
Annual Cash Dividend Rate Per Share				$ 0.65
Quarterly cash dividend rate per share						$ 0.125
Common Stock, Dividends, Per Share, Cash Paid	$ 0.6125	$ 0.4050	$ 0.0300
Total Amount Paid	651,000,000	449,000,000	36,000,000
Subsequent Event Dividend Declared Amount Per Share							$ 0.1625