Equity Award Plans - Summary of Activity under the 2006 Plan and 2013 Plan (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Number of Shares, Options Outstanding, Balance	6,376
Number of Shares, Options Granted	1,265
Number of Shares, Options Exercised	(289)
Number of Shares, Options Forfeited and Cancelled	(281)
Number of Shares, Options Outstanding, Balance	7,071	6,376
Number of Shares, Options Exercisable, Balance	2,534
Number of Shares, Options Vested, Balance	2,148
Number of Shares, Options Vested and Expected to Vest, Balance	6,584
Weighted Average Exercise Price, Options Outstanding, Balance	$ 7.99
Weighted Average Exercise Price, Options granted	$ 6.53
Weighted Average Exercise Price, Options exercised	$ 1.21
Weighted Average Exercise Price, Options forfeited and cancelled	$ 9.84
Weighted Average Exercise Price, Options Outstanding, Balance	$ 7.93	$ 7.99
Weighted Average Exercise Price, Options exercisable, Balance	$ 6.56
Weighted Average Exercise Price, Options vested, Balance	$ 6.04
Weighted Average Exercise Price, Options vested and expected to vest, Balance	$ 7.90
Weighted Average Remaining Contractual Term, Options Outstanding (in years)	8 years 3 months	7 years 9 months 26 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 vested and expected to vest (in years)	0 years
Weighted Average Remaining Contractual Term, Options exercisable (in years)	6 years 2 months 23 days
Weighted Average Remaining Contractual Term, Options vested (in years)	6 years 4 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in years)	8 years 1 month 28 days
Aggregate Intrinsic Value, Options Outstanding, Balance	$ 4,113	$ 9,697
Aggregate Intrinsic Value, Options exercisable, Balance	4,107
Aggregate Intrinsic Value, Options vested, Balance	4,087
Aggregate Intrinsic Value, Options vested and expected, Balance	$ 4,112