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