Shareholders' Equity (Details Textuals) (USD $)	3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2011	Mar. 31, 2011	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Stockholders' Equity Note [Abstract]
Stock Repurchase Program, Authorized Amount	$ 300,000,000	$ 300,000,000	$ 300,000,000				$ 100,000,000
Stock Repurchase Program Authorized Amount Cancelled		265,300,000	700,000
Treasury Stock Shares Acquired				12,645,000	1,660,000	3,013,000
Treasury Stock Shares Acquired Current Plan				2,800,000
Treasury Stock Acquired, Average Cost Per Share				$ 29.55	$ 26.99
Treasury Stock Value Acquired Cost Method				(373,600,000)	(35,124,000)	(35,464,000)
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments				255,100,000
Treasury Stock Value Acquired Cost Method Current Plan				$ 73,600,000