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Stockholder's Equity - Additional Information (Detail) - USD ($)
 3 Months Ended 6 Months Ended
Jul. 25, 2016
Jun. 30, 2016
Mar. 31, 2016
Jun. 30, 2015
Mar. 31, 2015
Jun. 30, 2016
Jun. 30, 2015
Jul. 25, 2011
Stockholders Equity [Line Items]                
Common stock, value of shares authorized to repurchase               $ 200,000,000
Stock repurchase, shares           45,000 116,000  
Value of shares repurchased           $ 1,545,000 $ 4,341,000  
Average price of repurchased shares           $ 34.50 $ 37.55  
Cash dividends per common share   $ 0.170 $ 0.170 $ 0.170 $ 0.165 $ 0.340 $ 0.335  
Dividend payment to common shareholders   $ 18,141,000 $ 18,141,000 $ 17,868,000 $ 17,868,000 $ 18,141,000 $ 17,868,000  
Subsequent Event [Member]                
Stockholders Equity [Line Items]                
Dividend declared date Jul. 25, 2016              
Cash dividend to be paid $ 0.17              
Dividend to be paid date Sep. 09, 2016              
Dividend declared, shareholders of record date Aug. 29, 2016