Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (13,618)	$ (3,920)	$ (46,680)	$ (16,160)
Other comprehensive loss (net of tax):
Net change in net unrealized gain (loss) on investments	(30)	25	(16)	(183)
Net change in unrealized gain (loss) on hedging instruments	(500)	(328)	(419)	(425)
Other comprehensive income (loss)	(530)	(303)	(435)	(608)
Comprehensive loss	(14,148)	(4,223)	(47,115)	(16,768)
Comprehensive loss attributable to noncontrolling interest		145	213	411
Comprehensive loss attributable to Imperva, Inc. stockholders	$ (14,148)	$ (4,078)	$ (46,902)	$ (16,357)