Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net loss	$ (59,176)us-gaap_ProfitLoss	$ (26,331)us-gaap_ProfitLoss	$ (7,892)us-gaap_ProfitLoss
Other comprehensive loss (net of tax):
Net change in net unrealized gain (loss) on investments	(59)	(172)	227
Net change in unrealized gain (loss) on hedging instruments	(1,002)	(1,117)	1,250
Other comprehensive income (loss)	(1,061)	(1,289)	1,477
Comprehensive loss	(60,237)	(27,620)	(6,415)
Comprehensive loss attributable to noncontrolling interest	213	1,153	505
Comprehensive loss attributable to Imperva, Inc. stockholders	$ (60,024)us-gaap_ComprehensiveIncomeNetOfTax	$ (26,467)us-gaap_ComprehensiveIncomeNetOfTax	$ (5,910)us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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