Net Loss per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	2,113,995	2,153,180
Restricted stock units for common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	1,694,129	787,713
Restricted shares of common stock subject to repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	286,125	481,849
Restricted stock issued in connection with Skyfence acquisition [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	354,678
Common stock warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share		8,333