Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (17,624)	$ (6,195)
Available for sale investments:
Change in net unrealized gain on investments, net of tax	3	16
Net gains reclassified into earnings		(83)
Change in unrealized gain (loss) on investments	3	(67)
Cash flow hedging instruments:
Change in unrealized gain and losses, net of tax		360
Net gains reclassified into earnings		(223)
Change in unrealized gain (loss) on derivatives		137
Comprehensive loss	(17,621)	(6,125)
Comprehensive loss attributable to noncontrolling interest	213	136
Comprehensive loss attributable to Imperva, Inc. stockholders	$ (17,408)	$ (5,989)