Quarterly report pursuant to Section 13 or 15(d)

Shareholders' Equity (Details Textual)

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Shareholders' Equity (Details Textual) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Feb. 21, 2012
May 03, 2010
Shareholders' Equity (Textual) [Abstract]        
Cash dividends per common share $ 0.3      
Aggregate amount of cash dividend paid     $ 35,200,000  
Dividends paid (35,172,000) (14,819,000)    
Share repurchase program capacity authorization       1,000,000,000
Share repurchase program, remaining authorized capacity 427,900,000      
Repurchase of common shares through open market purchases, Share 0.7      
Share repurchased through open market purchases, Aggregate cost $ 50,000,000      
Average cost per share of share repurchased $ 67.24