Shareholders' Equity (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Jan. 26, 2012
Shareholders' Equity (Textual) [Abstract]
Shares remaining under the share repurchase authorization	909,407
Authorized repurchase of the Corporation's common stock		$ 1,200,000,000
Dividends paid by domestic property and casualty insurance subsidiaries to parent	2,700,000,000
Maximum dividend distribution that may be made by the property and casualty insurance subsidiaries to parent company during 2012 without prior regulatory approval	$ 1,800,000,000