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Stock-Based Compensation - Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2017
Dec. 31, 2016
Options Outstanding    
Beginning balance (in shares) 1,098,823  
Granted (in shares) 64,507  
Exercised (in shares) (120,577)  
Canceled (in shares) (471)  
Ending balance (in shares) 1,042,282 1,098,823
Exercisable at period end (in shares) 851,494  
Weighted-Average Exercise Price per Share    
Beginning balance (in dollars per share) $ 35.39  
Granted (in dollars per share) 87.05  
Exercised (in dollars per share) 22.21  
Canceled (in dollars per share) 83.14  
Ending balance (in dollars per share) 40.09 $ 35.39
Exercisable (in dollars per share) $ 31.93  
Weighted-Average Remaining Contractual Life    
Outstanding, weighted average remaining contractual life (in years) 4 years 3 months 20 days 4 years 3 months 20 days
Exercisable weighted average remaining contractual life (in years) 3 years 7 months 6 days  
Aggregate Intrinsic Value    
Beginning balance $ 52,332  
Granted 287  
Exercised 7,388  
Canceled 4  
Ending balance 53,581 $ 52,332
Exercisable $ 50,722