Stockholders' Equity - Summary of Stock Option Activity Under the 2010 Stock Plan and the 2013 Stock Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding, beginning balance	666,717
Number of Shares, Exercised	(272,917)
Number of Shares, Forfeited	(7,826)
Number of Shares, Outstanding, ending balance	385,974	666,717
Number of Shares, Exercisable as of June 30, 2018	360,495
Weighted-Average Exercise Price, Outstanding, beginning balance	$ 19.53
Weighted-Average Exercise Price, Exercised	19.48
Weighted-Average Exercise Price, Exercised, Forfeited	34.10
Weighted- Average Exercise Price, Outstanding, ending balance	19.27	$ 19.53
Weighted-Average Exercise Price, Exercisable as of June 30, 2018	$ 18.40
Weighted-Average Remaining Contractual Term, Outstanding	5 years 3 months 18 days	5 years 7 months 6 days
Weighted-Average Remaining Contractual Term, Exercisable as of June 30, 2018	5 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding	$ 45,325	$ 32,450
Aggregate Intrinsic Value, Exercisable as of June 30, 2018	$ 42,646