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Share-based Compensation - Summary of Additional Stock Option Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]        
Weighted-average grant date fair value per share $ 8.56   $ 7.13  
Intrinsic value of options exercised $ 630 $ 319 $ 1,524 $ 319
Fair value of stock options that vested $ 42 $ 698 $ 892 $ 698