Equity Award Plans - Summary of Stock Option Activity under the 2006 Plan and 2013 Plan (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Equity [Abstract]
Number of Shares, Options Outstanding, Balance	4,855
Number of Shares, Options granted	2,843
Number of Shares, Options exercised	(662)
Number of Shares, Options forfeited and cancelled	(832)
Number of Shares, Options Outstanding, Balance	6,204	4,855
Number of Shares, Options exercisable, Balance	3,112
Number of Shares, Options vested, Balance	2,304
Number of Shares, Options vested and expected to vest, Balance	5,812
Weighted Average Exercise Price Per Share, Options Outstanding, Balance	$ 6.56
Weighted Average Exercise Price Per Share, Options granted	$ 9.61
Weighted Average Exercise Price Per Share, Options exercised	$ 2.98
Weighted Average Exercise Price Per Share, Options forfeited and cancelled	$ 9.34
Weighted Average Exercise Price Per Share, Options Outstanding, Balance	$ 7.96	$ 6.56
Weighted Average Exercise Price Per Share, Options exercisable, Balance	$ 6.12
Weighted Average Exercise Price Per Share, Options vested, Balance	$ 5.09
Weighted Average Exercise Price Per Share, Options vested and expected to vest, Balance	$ 7.84
Weighted Average Remaining Contractual Term, Options granted (in Years)	9 years 7 months 21 days
Weighted Average Remaining Contractual Term, Options Outstanding (in Years)	8 years 1 month 2 days	7 years 10 months 6 days
Weighted Average Remaining Contractual Term, Options exercisable (in Years)	6 years 8 months 9 days
Weighted Average Remaining Contractual Term, Options vested (in Years)	6 years 3 months 7 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in Years)	8 years 4 days
Aggregate Intrinsic Value, Options Outstanding, Balance	$ 20,593
Aggregate Intrinsic Value, Options Outstanding, Balance	10,730	20,593
Aggregate Intrinsic Value, Options exercisable, Balance	10,509
Aggregate Intrinsic Value, Outstanding, Options vested, Balance	9,564
Aggregate Intrinsic Value, Outstanding, Options vested and expected to vest, Balance	$ 10,671