Equity Award Plans - Summary of Activity under the 2006 Plan and 2013 Plan (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Options Outstanding, Balance	5,960
Number of Shares, Options Granted	442
Number of Shares, Options Exercised	(67)
Number of Shares, Options Forfeited and Cancelled	(174)
Number of Shares, Options Outstanding, Balance	6,161	5,960
Number of Shares, Options Exercisable, Balance	2,825
Number of Shares, Options Vested, Balance	2,772
Number of Shares, Options Vested and Expected to Vest, Balance	5,870
Weighted Average Exercise Price, Options Outstanding, Balance	$ 7.58
Weighted Average Exercise Price, Options granted	3.29
Weighted Average Exercise Price, Options exercised	2.46
Weighted Average Exercise Price, Options forfeited and cancelled	8.94
Weighted Average Exercise Price, Options Outstanding, Balance	7.29	$ 7.58
Weighted Average Exercise Price, Options exercisable, Balance	7.96
Weighted Average Exercise Price, Options vested, Balance	7.91
Weighted Average Exercise Price, Options vested and expected to vest, Balance	$ 7.34
Weighted Average Remaining Contractual Term, Options Outstanding (in years)	7 years 9 months 22 days	7 years 10 months 6 days
Weighted Average Remaining Contractual Term, Options granted (in years)	9 years 11 months 5 days
Weighted Average Remaining Contractual Term, Options exercised (in years)	0 years
Weighted Average Remaining Contractual Term, Options forfeited and cancelled (in years)	0 years
Weighted Average Remaining Contractual Term, Options exercised (in years)	6 years 4 months 24 days
Weighted Average Remaining Contractual Term, Options vested (in years)	6 years 6 months 7 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in years)	7 years 9 months
Aggregate Intrinsic Value, Options Outstanding, Balance	$ 631	$ 957
Aggregate Intrinsic Value, Options exercisable, Balance	630
Aggregate Intrinsic Value, Options vested, Balance	630
Aggregate Intrinsic Value, Options vested and expected, Balance	$ 631