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Stock-Based Compensation - Options Granted and Options Exercised Under Stock Option Plan (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract]        
Weighted average grant-date fair value per share of options granted $ 11.63 $ 7.00 $ 11.21 $ 5.96
Total intrinsic value of options exercised $ 1,493 $ 5,063 $ 7,138 $ 6,733
Cash received from options exercised 856 3,859 4,113 5,735
Tax benefit realized from options exercised $ 578 $ 1,958 $ 2,761 $ 2,604