Quarterly report pursuant to Section 13 or 15(d)

Shareholders' Equity (Details)

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Shareholders' Equity (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Sep. 30, 2016
Sep. 30, 2015
Jul. 21, 2016
Feb. 07, 2014
Shareholders' Equity [Line Items]                      
Stock Repurchase Program, Number of Shares Authorized to be Repurchased                   3,000,000 2,000,000
Stock Repurchase Program Number Of Shares Repurchased 222,388       204,590     676,773 204,590    
Stock Repurchased and Retired During Period, In Total Dollars $ 9,996,000       $ 9,996,000     $ 29,986,000 $ 9,996,000    
Stock repurchased, common stock acquired, average cost per share $ 44.95       $ 48.86     $ 44.31 $ 48.86    
Common Stock [Member]                      
Shareholders' Equity [Line Items]                      
Dividends per share (in dollars per share) $ 0.12 $ 0.12 $ 0.12 $ 0.12 $ 0.12 $ 0.12 $ 0.12 $ 0.36 $ 0.36