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Stockholders' Equity - Additional Information (Detail) - USD ($)
 3 Months Ended 6 Months Ended
Jul. 31, 2017
Jul. 25, 2011
Jun. 30, 2017
Mar. 31, 2017
Jun. 30, 2016
Mar. 31, 2016
Jun. 30, 2017
Jun. 30, 2016
Stockholders Equity [Line Items]                
Common stock, value of shares authorized to repurchase   $ 200,000,000            
Stock repurchase, shares   1,770,000         0 45,000
Value of shares repurchased   $ 52,000,000           $ 1,545,000
Average price of repurchased shares               $ 34.50
Cash dividends per common share     $ 0.175 $ 0.175 $ 0.170 $ 0.170 $ 0.350 $ 0.340
Dividend payment to common shareholders     $ 18,903,000 $ 18,903,000 $ 18,141,000 $ 18,141,000 $ 18,903,000 $ 18,141,000
Subsequent Event [Member]                
Stockholders Equity [Line Items]                
Dividend declared date Jul. 31, 2017              
Cash dividend to be paid $ 0.175              
Dividend to be paid date Sep. 08, 2017              
Dividend declared, shareholders of record date Aug. 28, 2017