Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Summary of Stock Option Activity (Detail)

v3.8.0.1
Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]      
Number of shares, Outstanding, Beginning Balance 3,883,432    
Number of shares, Granted 79,875 0  
Number of shares, Exercised (196,801)    
Number of shares, Canceled (147,000)    
Number of shares, Outstanding, Ending Balance 3,619,506   3,883,432
Number of shares, Exercisable at March 31 , 2018 1,125,083    
Weighted average exercise price per share, Granted $ 10.39    
Weighted average exercise price per share, Exercised 3.77    
Weighted average exercise price per share, Canceled 13.29    
Weighted average exercise price per share outstanding 9.60   $ 9.16
Weighted average exercise price per share Exercisable $ 5.41    
Aggregate intrinsic value, Exercised $ 3,260 $ 0  
Aggregate intrinsic value, Outstanding 14,617 $ 49,965  
Aggregate intrinsic value, Exercisable $ 9,386    
Weighted average remaining contractual life, Outstanding 8 years 7 months 6 days   8 years 9 months 18 days
Weighted average remaining contractual life, Exercisable 7 years 10 months 25 days