Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (48,882)	$ (59,176)	$ (26,331)
Other comprehensive loss (net of tax):
Net change in net unrealized loss on investments	(249)	(59)	(172)
Net change in unrealized gain (loss) on hedging instruments	407	(1,002)	(1,117)
Other comprehensive income (loss)	158	(1,061)	(1,289)
Comprehensive loss	(48,724)	(60,237)	(27,620)
Comprehensive loss attributable to non - controlling interest	0	213	1,153
Comprehensive loss attributable to Imperva, Inc. stockholders	$ (48,724)	$ (60,024)	$ (26,467)