Stock Compensation Plans - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Number of Options (shares)
Options, Outstanding, Beginning balance | shares		3,210,693
Options, Granted | shares		942,277
Options, Exercised | shares		(217,570)
Options, Forfeited | shares		(218,880)
Options, Outstanding, Ending balance | shares	3,716,520	3,716,520
Options vested and expected to vest, Ending balance (shares) | shares	3,621,869	3,621,869
Options exercisable, Ending balance (shares) | shares	2,723,091	2,723,091
Weighted-Average Exercise Price (usd per share)
Outstanding, Weighted-Average Exercise Price, Beginning balance | $ / shares		$ 7.54
Granted, Weighted-Average Exercise Price | $ / shares		8.32
Exercised, Weighted-Average Exercise Price | $ / shares		2.36
Forfeited, Weighted-Average Exercise Price | $ / shares		12.28
Outstanding, Weighted-Average Exercise Price, Ending balance | $ / shares	$ 7.76	7.76
Options vested and expected to vest, Weighted-Average Exercise Price, Ending balance | $ / shares	7.72	7.72
Options exercisable, Weighted-Average Exercise Price, Ending balance | $ / shares	$ 7.29	$ 7.29
Weighted- Average Remaining Contractual Term (Years)
Outstanding, Weighted-Average Remaining Contractual Term (Years), Ending balance	7 years 8 months 1 day
Options vested and expected to vest , Weighted-Average Remaining Contractual Term (Years), Ending balance	7 years 7 months 13 days
Options exercisable, Weighted-Average Remaining Contractual Term (Years), Ending balance	6 years 11 months 19 days
Outstanding, Aggregate Intrinsic Value, Ending balance | $	$ 17,282	$ 17,282
Options vested and expected to vest , Aggregate Intrinsic Value, Ending balance | $	16,852	16,852
Options exercisable, Aggregate Intrinsic Value, Ending balance | $	$ 12,290	$ 12,290