Stock-Based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Issuable Under Options, Beginning balance	3,079,175	1,657,225
Shares Issuable Under Options, Granted	1,448,000
Shares Issuable Under Options, Exercised	(308,011)	(30,195)	(109,441)
Shares Issuable Under Options, Cancelled	(419,000)
Shares Issuable Under Options, Ending balance	3,799,965	3,079,175	1,657,225
Shares Issuable Under Options, Options vested and expected to vest at December 31, 2017	3,800,000
Shares Issuable Under Options, Options exercisable at December 31, 2017	1,688,652	1,173,671	728,621
Weighted Average Exercise Price, Beginning balance	$ 14.84	$ 14.28
Weighted Average Exercise Price, Granted	22.29
Weighted Average Exercise Price, Exercised	12.25
Weighted Average Exercise Price, Cancelled	22.78
Weighted Average Exercise Price, Ending balance	17.75	$ 14.84	$ 14.28
Weighted Average Exercise Price, Options vested and expected to vest	17.75
Weighted Average Exercise Price, Options exercisable	$ 14.99