Stock-Based Compensation - Summary of Company's Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Shares Available for Grant
Shares Available for Grant, Beginning balance	3,166,968
Shares Available for Grant, Granted (unaudited)	(34,380)
Shares Available for Grant, Cancelled (unaudited)	21,020
Shares Available for Grant, Ending balance (unaudited)	3,153,608	3,166,968
Number of Stock Options Outstanding
Number of Stock Options Outstanding, Beginning balance	6,053,672
Number of Stock Options Outstanding, Granted (unaudited)	34,380
Number of Stock Options Outstanding, Exercised (unaudited)	(11,563)
Number of Stock Options Outstanding, Cancelled (unaudited)	(21,020)
Number of Stock Options Outstanding, Ending balance (unaudited)	6,055,469	6,053,672
Number of Stock Options Outstanding, Vested and exercisable	3,459,650
Number of Stock Options Outstanding, Vested and expected to vest	5,814,927
Weighted- Average Exercise Price
Weighted- Average Exercise Price, Beginning balance	$ 2.13
Weighted- Average Exercise Price, Granted (unaudited)	4.90
Weighted- Average Exercise Price, Exercised (unaudited)	0.74
Weighted- Average Exercise Price, Cancelled (unaudited)	3.38
Weighted- Average Exercise Price, Ending balance (unaudited)	2.15	$ 2.13
Weighted- Average Exercise Price, Vested and exercisable (unaudited)	1.09
Weighted- Average Exercise Price, Vested and expected to vest (unaudited)	$ 2.10
Weighted- Average Remaining Contractual Life (Years)
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 4 months 24 days	7 years 7 months 6 days
Weighted- Average Remaining Contractual Life (Years), Vested and exercisable (unaudited)	6 years 3 months 18 days
Weighted- Average Remaining Contractual Life (Years), Vested and expected to vest (unaudited)	7 years 3 months 18 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 14,637	$ 20,605
Aggregate Intrinsic Value, Vested and exercisable (unaudited)	11,302
Aggregate Intrinsic Value, Vested and expected to vest (unaudited)	$ 14,294