Imperva 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	1-May-15
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	IMPV
Entity Registrant Name	IMPERVA INC
Entity Central Index Key	1364962
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		30,596,663

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
CURRENT ASSETS:
Cash and cash equivalents	$196,486,000	$68,096,000	[1]
Short-term investments	46,251,000	41,624,000	[1]
Restricted cash	73,000	62,000	[1]
Accounts receivable, net of allowance for doubtful accounts of $280 and $ 215 as of March 31, 2015 and December 31, 2014, respectively	33,365,000	47,446,000	[1]
Inventory	555,000	259,000	[1]
Deferred tax assets	404,000	408,000	[1]
Prepaid expenses and other current assets	4,446,000	3,927,000	[1]
Total current assets	281,580,000	161,822,000	[1]
Property and equipment, net	7,722,000	7,618,000	[1]
Goodwill	34,972,000	34,972,000	[1]
Acquired intangible assets, net	9,047,000	9,399,000	[1]
Severance pay fund	4,131,000	3,980,000	[1]
Restricted cash	1,665,000	1,665,000	[1]
Deferred tax assets	329,000	329,000	[1]
Other assets	856,000	860,000	[1]
TOTAL ASSETS	340,302,000	220,645,000	[1]
CURRENT LIABILITIES:
Accounts payable	3,733,000	5,376,000	[1]
Accrued compensation and benefits	14,481,000	15,749,000	[1]
Accrued and other current liabilities	6,482,000	6,376,000	[1]
Deferred revenue	58,996,000	56,077,000	[1]
Total current liabilities	83,692,000	83,578,000	[1]
Other liabilities	10,440,000	10,408,000	[1]
Deferred revenue	24,687,000	25,098,000	[1]
Accrued severance pay	4,405,000	4,318,000	[1]
TOTAL LIABILITIES	123,224,000	123,402,000	[1]
Commitments and Contingencies (Note 9)			[1]
STOCKHOLDERS' EQUITY:
Preferred stock, $0.0001 par value - 5,000,000 shares authorized, no shares issued and outstanding as of March 31, 2015 and December 31, 2014	0	0	[1]
Common stock, $0.0001 par value - 145,000,000 shares authorized, 30,593,720 and 26,895,480 shares issued and outstanding as of March 31, 2015 and December 31, 2014, respectively	3,000	2,000	[1]
Additional paid-in capital	396,338,000	256,388,000	[1]
Accumulated deficit	-177,688,000	-157,658,000	[1]
Accumulated other comprehensive loss	-1,575,000	-1,489,000	[1]
TOTAL IMPERVA, INC. STOCKHOLDERS' EQUITY	217,078,000	97,243,000	[1]
Noncontrolling interest	0	0	[1]
TOTAL STOCKHOLDERS' EQUITY	217,078,000	97,243,000	[1]
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$340,302,000	$220,645,000	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$280	$215	[1]
Preferred stock, par value	$0.00	$0.00	[1]
Preferred stock, shares authorized	5,000,000	5,000,000	[1]
Preferred stock, shares issued	0	0	[1]
Preferred stock, shares outstanding	0	0	[1]
Common stock, par value	$0.00	$0.00	[1]
Common stock, shares authorized	145,000,000	145,000,000	[1]
Common stock, shares issued	30,593,720	26,895,480	[1]
Common stock, shares outstanding	30,593,720	26,895,480	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net revenue:
Products and license	$17,104	$11,971
Services	27,653	19,545
Total net revenue	44,757	31,516
Cost of revenue:
Products and license	1,998	1,732
Services	8,332	6,020
Total cost of revenue	10,330	7,752
Gross profit	34,427	23,764
Operating expenses:
Research and development	12,678	9,961
Sales and marketing	31,253	23,035
General and administrative	9,743	8,405
Amortization of acquired intangible assets	352	204
Total operating expenses	54,026	41,605
Loss from operations	-19,599	-17,841
Other income (expense), net	-80	-154
Loss before provision (benefit) for income taxes	-19,679	-17,995
Provision (benefit) for income taxes	351	-371
Net loss	-20,030	-17,624
Loss attributable to noncontrolling interest	0	213
Net loss attributable to Imperva, Inc. stockholders	($20,030)	($17,411)
Net loss per share of common stock attributable to Imperva, Inc. stockholders, basic and diluted	($0.74)	($0.69)
Shares used in computing net loss per share of common stock, basic and diluted	26,973,317	25,255,161

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	($20,030)	($17,624)
Other comprehensive loss (net of tax):
Net change in net unrealized gain (loss) on investments	44	3
Net change in unrealized gain (loss) on hedging instruments	-130	0
Other comprehensive income (loss)	-86	3
Comprehensive loss	-20,116	-17,621
Comprehensive loss attributable to noncontrolling interest	0	213
Comprehensive loss attributable to Imperva, Inc. stockholders	($20,116)	($17,408)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (USD $)	Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
In Thousands, except Share data, unless otherwise specified
Beginning balance at Dec. 31, 2013	$86,222		$2	$187,957	($98,695)	($428)	($2,614)
Beginning balance, shares at Dec. 31, 2013			25,206,498
Issuance of common stock related to acquisitions	24,164			24,164
Issuance of common stock related to acquisitions, shares			737,523
Issuance of common stock under employee equity plans, net of repurchases	2,471			2,471
Issuance of common stock under employee equity plans, net of repurchases , shares			254,795
Vesting of restricted stock	200			200
Stock-based compensation	6,666			6,666
Shares withheld for tax withholding on vesting of restricted stock units	-1,182			-1,182
Shares withheld for tax withholding on vesting of restricted stock units, shares	0		0	0	0	0	0
Pre-combination service relating to acquired Skyfence option plan	354			354
Purchase of noncontrolling interest in Incapsula, Inc.				-2,827			2,827
Purchase of noncontrolling interest in Incapsula, Inc., Shares			89,603
Components of other comprehensive loss, net of tax:
Change in unrealized gain (loss) on investments	3					3
Change in unrealized gain (loss) on derivatives	0
Net loss	-17,624				-17,411		-213
Comprehensive loss	-17,621
Ending balance at Mar. 31, 2014	101,274		2	217,803	-116,106	-425
Ending balance, shares at Mar. 31, 2014			26,288,419
Beginning balance at Dec. 31, 2014	97,243	[1]	2	256,388	-157,658	-1,489
Beginning balance, shares at Dec. 31, 2014			26,895,480
Proceeds from follow-on public offering, net of offering costs	127,854		1	127,853
Proceeds from follow-on public offering, net of offering costs, shares			3,450,000
Issuance of common stock under employee equity plans, net of repurchases	1,618			1,618
Issuance of common stock under employee equity plans, net of repurchases, shares			248,240
Vesting of restricted stock	27			27
Stock-based compensation	12,546			12,546
Income tax benefit from employee stock option exercises	43			43
Shares withheld for tax withholding on vesting of restricted stock units	-2,137			-2,137
Shares withheld for tax withholding on vesting of restricted stock units, shares	0		0	0	0	0	0
Components of other comprehensive loss, net of tax:
Change in unrealized gain (loss) on investments	44					44
Change in unrealized gain (loss) on derivatives	-130					-130
Net loss	-20,030				-20,030
Comprehensive loss	-20,116
Ending balance at Mar. 31, 2015	$217,078		$3	$396,338	($177,688)	($1,575)
Ending balance, shares at Mar. 31, 2015			30,593,720
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	($20,030)		($17,624)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	1,056		800
Stock-based compensation	12,546		6,666
Amortization of acquired intangibles	352		204
Amortization of premiums/accretion of discounts on short-term investments	92		109
Excess tax benefits from share-based compensation	-43		0
Other	114		-1
Changes in operating assets and liabilities:
Accounts receivable, net	14,081		15,870
Inventory	-296		-181
Prepaid expenses and other assets	-515		110
Accounts payable	-1,812		-592
Accrued compensation and benefits	-1,268		-598
Accrued and other liabilities	79		269
Severance pay, net	-64		188
Deferred revenue	2,508		-2,025
Deferred tax assets	4		-19
Net cash provided by operating activities	6,804		3,176
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of short-term investments	-22,843		-10,206
Proceeds from sales/maturities of short-term investments	18,168		13,585
Acquisitions, net of cash acquired	0		-12,083
Purchase of property and equipment	-991		-1,718
Change in restricted cash	-11		0
Net cash used in investing activities	-5,677		-10,422
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from follow-on public offering, net of offering costs	127,854		0
Proceeds from issuance of common stock, net of repurchases	1,618		2,471
Excess tax benefits from share-based compensation	43		0
Shares withheld for tax withholding on vesting of restricted stock units	-2,137		-1,182
Net cash provided by financing activities	127,378		1,289
Effect of exchange rate changes on cash and cash equivalents	-115		0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	128,390		-5,957
CASH AND CASH EQUIVALENTS - Beginning of period	68,096	[1]	76,704
CASH AND CASH EQUIVALENTS - End of period	196,486		70,747
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment acquired but not yet paid	169		0
Vesting of restricted and early exercised stock options	27		200
Common stock issued in connection with acquisitions	$0		$24,163
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Basis_of_Presentation_and_Summ

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	1. Basis of Presentation and Summary of Significant Accounting Policies
	Business
	Imperva, Inc. (together with its subsidiaries, the “Company”) was incorporated in April 2002 in Delaware. The Company is headquartered in Redwood Shores, California and has subsidiaries located throughout the world including Israel, Asia and Europe. The Company is engaged in the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises.
	Basis of Presentation
	The Company has prepared the accompanying unaudited Condensed Consolidated Financial Statements in accordance with Article 10 of Regulation S-X and pursuant to the rules and regulations for Form 10-Q of the Securities and Exchange Commission (the “SEC”). Pursuant to those rules and regulations, the Company has condensed or omitted certain information and footnote disclosure it normally includes in its annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the Company has made all adjustments (consisting only of normal, recurring adjustments, except as otherwise indicated) necessary to fairly present its consolidated financial position, results of operations, and cash flows. The Company’s interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the consolidated financial statements and notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on March 2, 2015 (the “Annual Report”).
	The condensed consolidated financial statements include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
	Reclassifications
	From time to time the Company reclassifies certain period balances to conform to the current year presentation. These reclassifications have no material impact on previously reported total assets, total liabilities, stockholders’ equity, results of operations or cash flows.
	Concentration of Revenue and Accounts Receivable
	Significant customers are those which represent 10% or more of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the three months ended March 31, 2015 and 2014, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There were no customers who represented greater than 10% of gross accounts receivable as of March 31, 2015 and December 31, 2014.
	Significant Accounting Policies
	There have been no material changes to the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	Recent Accounting Pronouncements
	There have been no new accounting pronouncements during the three months ended March 31, 2015, as compared to the recent accounting pronouncements described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014 that are of significance, or potential significance, to the Company.

Incapsula

Incapsula	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
Incapsula	2. Incapsula
	On November 5, 2009, the Company entered into a license agreement for Incapsula to use certain developed technology of the Company. In lieu of any other fee or royalty under the license agreement, Incapsula issued to the Company 5,000,000 shares of its Series A Convertible Preferred Stock representing a 58% ownership interest at the date of issuance. The transaction was accounted for as a business combination. No value was assigned to the license on the acquisition date as the use of the license will stay within the control of the Company. Therefore, the Company’s historical carrying value of the developed technology immediately prior to the acquisition was used to determine the value of the purchase consideration exchanged in the transaction. As Incapsula was a newly-formed entity with no net assets on the acquisition date and the value of the license was determined to be zero, no goodwill was recorded by the Company on the acquisition.
	In March 2010, the Company entered into a Series A and Series A-1 Purchase Agreement whereby Incapsula issued 6,666,666 shares of its Series A Convertible Preferred Stock to the Company in exchange for cash consideration of $3.0 million. As a result of this transaction, the Company increased its ownership interest in Incapsula to 76% at the date of issuance. The purchase of the additional ownership interest in Incapsula was treated as an equity transaction. Under the terms of the Series A and Series A-1 Purchase Agreement, the Company entered into a forward contract with Incapsula to purchase 8,750,000 shares of Incapsula’s Series A-1 Convertible Preferred Stock in exchange for $7.0 million in cash consideration if certain milestones were achieved no later than September 2011. On the transaction date, no value was assigned to the forward contract as the option did not meet the definition of a derivative instrument as it did not contain a net settlement feature. Specifically, the forward contract could only be gross physically settled as Incapsula is a non-publicly traded company whose stock was not readily convertible to cash.
	In addition, during 2010, the board of directors of Incapsula adopted the Incapsula 2010 Share Incentive Plan pursuant to which Incapsula may grant to its employees options to purchase shares of Incapsula’s common stock or restricted shares.
	In July 2011, Incapsula achieved the required performance milestones. As a result, the Company purchased 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest to 82%. In January 2012, the Company purchased the remaining 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest in Incapsula to 85%.
	Under the terms of the agreements between the Company and Incapsula, the Company had the right, but not the obligation, to purchase the remaining ownership interest in Incapsula commencing on November 5, 2013 and ending on November 5, 2018 (the “Purchase Right”). Exercise of the Purchase Right was solely within the Company’s control and the price for the remaining ownership interest was to be based on an Incapsula enterprise valuation calculated as the greater of (i) eight times Incapsula’s prior 12 months trailing revenues or (ii) seven times the aggregate amount Incapsula had raised in connection with its Series A Convertible Preferred Stock financings. On the acquisition date, no value was assigned to this Purchase Right as the option did not meet the definition of a derivative instrument as it did not contain a net settlement feature. Specifically, the Purchase Right could only be gross physically settled as Incapsula was a non-publicly traded company whose stock was not readily convertible to cash.
	In March 2014, the Company acquired the remaining outstanding capital stock in exchange for approximately 124,088 shares of Company common stock with an aggregate fair value of $7.7 million, of which 34,485 shares are subject to a 15-month holdback pursuant to the acquisition agreement, and assumed outstanding options to acquire capital stock of Incapsula not already owned by Imperva (the “Incapsula Acquisition”) which are equivalent to 48,359 shares of Company common stock on an as-converted basis. The aggregate consideration for the Incapsula Acquisition is substantially on the same terms of the Purchase Right less the outstanding principal and interest under the Incapsula Loan. In addition, during 2013, the Company issued RSUs for approximately 264,878 shares of Imperva common stock with performance-based vesting tied to 2014 revenue for Incapsula and Incapsula-related products and services (effectively valuing such revenues similarly to the Purchase Right) less the outstanding principal and interest under the Incapsula Loan. At the same time, Incapsula issued similar RSUs for approximately 198,825 shares on an as-converted to Imperva common stock-basis, which the Company assumed in connection with the Incapsula Acquisition, in addition to the consideration for the Incapsula Purchase. These performance-based RSUs granted by Imperva and Incapsula were issued to continuing employees of Incapsula. Pursuant to the Purchase Right option discussed above, awards under the Incapsula 2010 Share Incentive Plan were assumed by the Company, substituted with Company stock options and all outstanding awards and the Incapsula 2010 Share Incentive Plan were terminated.
	As of the date of the acquisition, the remaining non-controlling interest on the Company’s balance sheet of $2.8 million was reclassified to additional paid-in capital given the Company’s complete ownership of Incapsula.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Acquisitions	3. Acquisitions
	Acquisitions during 2014 were accounted for in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations, and the results of operations of each acquisition have been included in the Company’s consolidated results of operations from the respective date of the acquisition. Each of the acquisitions was not material, either individually or in the aggregate to the Company’s results of operations in the period of acquisition.
	While management uses its best estimates and assumptions as part of the purchase price allocation process to value assets acquired and liabilities assumed at the business combination date, its estimates and assumptions are subject to refinement. As a result, during the preliminary purchase price allocation period, which may be up to one year from the business combination date, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. The Company records adjustments to assets acquired or liabilities assumed subsequent to the purchase price allocation period in its operating results in the period in which the adjustments were determined.
	The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The fair value assigned to identifiable intangible assets acquired is determined using the income approach which discounts expected future cash flows to present value using estimated assumptions determined by management. The Company believes that these identified intangible assets will have no residual value after their estimated economic useful lives. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets.
	The excess of the purchase price over the identified tangible and intangible assets, less liabilities assumed, is recorded as goodwill and primarily reflects the value of the synergies expected to be generated from combining the Company’s and the acquired entities’ technology and operations.
	Acquisition of Skyfence Networks Ltd.
	On February 7, 2014, the Company acquired Skyfence, a private company based and incorporated in Israel. Skyfence is a developer of a solution which allows real time visibility and control over corporate use of Software-as-a-Service (“SaaS”) applications, enforces security policies, protects sensitive data from external and inside threats, and ensures compliance with standards.
	Per the terms of the acquisition agreement (as amended) with Skyfence and its security holders, the Company purchased all of the outstanding shares of capital stock of Skyfence in exchange for (a) approximately $8.6 million in cash, in addition to a holdback payment commitment due 24 months from the date the acquisition closed valued at approximately $7.2 million, and (b) 884,422 shares of Company common stock, of which 532,262 shares are subject to forfeiture based upon time-based vesting and continuing employment, and were therefore excluded from purchase consideration as such amounts will be recorded as compensation expense over the term of the corresponding four-year service period. In addition, 29,871 of the shares are subject to a holdback period of up to 24 months from the date of acquisition. The Company also assumed stock options outstanding in accordance with the terms of the applicable Skyfence stock option plan and Skyfence stock option agreements relating to those Skyfence stock options. Based on Skyfence’s stock options outstanding at February 7, 2014, Imperva converted options to purchase 164,000 shares of Skyfence stock into options to purchase 24,248 shares of Imperva common stock.
	The fair value of Imperva’s shares issued is based on Imperva’s closing price per share of $59.08 as reported on the New York Stock Exchange at the closing of the acquisition on February 7, 2014.
	The fair values of the stock option awards assumed were estimated using a Black-Scholes option-pricing model. The estimated fair values of unvested equity awards of $1.1 million will be recorded as operating expense over the remaining requisite service periods as they relate to post-combination services, while the fair values of vested equity based awards of $0.3 million were included in the total purchase price as they relate to pre-combination services. The total purchase consideration is as follows (in thousands):
	Cash	$	8,558
	Cash holdback liability		7,157
	Fair value of common stock		20,855
	Estimated fair value of equity awards assumed and replaced		354
		$	36,924
	The acquisition of Skyfence was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. The Company expensed the related acquisition costs in the amount of $0.9 million in general and administrative expenses. In addition, stock-based compensation expense totaling $9.4 million was recognized from the date of acquisition through March 31, 2015.
	The excess of the consideration for Skyfence over the fair values assigned to the assets acquired and liabilities assumed represents the goodwill resulting from the acquisition. The Company’s management believes that the goodwill represents the synergies expected from combining the products and technologies of Imperva with those of Skyfence, which will enhance the Company’s overall product portfolio. The purchased technology will be amortized straight-line over a seven-year preliminary estimated useful life. Also as part of the acquisition, the Company assumed deferred tax liabilities related to the fair value of the developed technology the Company obtained in the acquisition. Goodwill recorded in connection with the acquisition is not deductible for income tax purposes. The total purchase price was allocated using the information available at the business combination date. The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands):
	Net tangible assets	$	1,014
	Existing technology		7,965
	Deferred tax liability assumed		(1,528	)
	Goodwill		29,473
	Total purchase price	$	36,924
	Acquisition of Certain Assets and Liabilities of Tomium Software, LLC.
	On January 30, 2014, the Company acquired certain assets and liabilities of Tomium, a private company based in Texas. Tomium is a provider of real-time mainframe security auditing agents. The purchase price of approximately $8.3 million includes approximately $4.6 million in cash and assumption of a liability to pay cash of $0.3 million, and also the issuance of 60,556 shares of Company common stock valued at approximately $3.4 million based upon the closing price of the Company’s stock on the acquisition date of $55.45 per share. Imperva acquired certain tangible assets and also assumed a facility lease of Tomium.
	The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands):
	Intangible assets	$	2,704
	Goodwill		5,499
	Total intangible assets acquired		8,203
	Other acquired tangible assets		60
	Fair value of assets acquired	$	8,263
	The total purchase price was allocated using the information available at the business combination date. Goodwill recorded in connection with the acquisition is deductible for U.S. income tax purposes.
	The acquisition of Tomium was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. The Company expensed the related acquisition costs, consisting primarily of legal costs in the amount of $0.3 million in general and administrative expenses. The Company’s management believes that the goodwill represents the synergies expected from combining the acquired technology and operations with those of Imperva. The intangible assets acquired by Imperva in conjunction with the acquisition of Tomium are being amortized straight-line over a ten-year estimated useful life.
	The results of operations related to the Tomium assets and liabilities have been included in the Company’s consolidated statements of operations from the acquisition date.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents, and Short-Term Investments	3 Months Ended
	Mar. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	4. Cash, Cash Equivalents, and Short-Term Investments
	The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand, highly liquid investments in commercial paper, money market funds and various deposit accounts.
	The Company considers all high quality investments purchased with original maturities at the date of purchase greater than three months to be short-term investments. Investments are available to be used for current operations and are, therefore, classified as current assets even though maturities may extend beyond one year. Cash equivalents and short-term investments are classified as available-for-sale and are, therefore, recorded at fair value on the condensed consolidated balance sheets, with any unrealized gains and losses reported in accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in its condensed consolidated balance sheets, until realized. The Company uses the specific-identification method to compute gains and losses on the investments. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included as a component of other income (expense), net in the condensed consolidated statements of operations.
	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		As of March 31, 2015
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	34,742	$	—	$	—	$	34,742
	Commercial paper		23,698		—		1		23,697
	Bank deposits		11,231		—		—		11,231
	Money market funds		126,816		—		—		126,816
	Total	$	196,487	$	—	$	1	$	196,486
	Short-term investments:
	Corporate debt obligations	$	35,956	$	14	$	21	$	35,949
	Bank deposits		10,302		—		—		10,302
	Total	$	46,258	$	14	$	21	$	46,251
		As of December 31, 2014
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	26,284	$	—	$	—	$	26,284
	Bank deposits		11,877				—		11,877
	Commercial paper		18,341		—		2		18,339
	Money market funds		11,596		—		—		11,596
	Total	$	68,098	$	—	$	2	$	68,096
	Short-term investments:
	Corporate debt obligations	$	31,404	$	3	$	53	$	31,354
	Bank deposits		10,270		—		—		10,270
	Total	$	41,674	$	3	$	53	$	41,624
	The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of March 31, 2015 (in thousands):
		As of March 31, 2015
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	27,361	$	27,365
	Due within two years		18,897		18,886
	Total	$	46,258	$	46,251
	The Company reviews its short-term investments on a regular basis to evaluate whether or not any security has experienced an other-than-temporary decline in fair value. The Company considers factors such as the length of time and extent to which the market value has been less than the cost, the financial condition and near-term prospects of the issuer and its intent to sell, or whether it is more likely than not the Company will be required to sell, the investment before recovery of the investment’s amortized cost basis. If the Company believes that an other-than-temporary decline exists in one of these securities, the Company writes down these investments to fair value. For debt securities, the portion of the write-down related to credit loss would be recorded to other income (expense), net, in the Company’s condensed consolidated statements of operations. Any portion not related to credit loss would be recorded to accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in the Company’s condensed consolidated balance sheets. During the three months ended March 31, 2015 and 2014, the Company did not consider any of its investments to be other-than-temporarily impaired.
	The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands):
		As of March 31, 2015
		Less than 12 Months				12 Months or Greater				Total
		Fair Value		Unrealized		Fair Value		Unrealized		Fair Value		Unrealized
				Losses				Losses				Losses
	Corporate debt obligations	$	15,559	$	20	$	2,003	$	1	$	17,562	$	21
		As of December 31, 2014
		Less than 12 Months				12 Months or Greater				Total
		Fair Value		Unrealized		Fair Value		Unrealized		Fair Value		Unrealized
				Losses				Losses				Losses
	Corporate debt obligations	$	12,735	$	47	$	12,088	$	6	$	24,823	$	53

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	5. Fair Value of Financial Instruments
	The Company evaluates assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level to classify them for each reporting period. There have been no transfers between fair value measurement levels during the three months ended March 31, 2015.
	The Company’s cash equivalents and short-term investment instruments are classified within Level 1 or Level 2 of the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The types of instruments valued based on quoted market prices in active markets include mutual funds and money market securities, and are generally classified within Level 1 of the fair value hierarchy. The types of instruments valued based on quoted prices in less active markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability include U.S. agency securities, investment-grade corporate bonds, bank deposits, and commercial paper. Such instruments are generally classified within Level 2 of the fair value hierarchy.
	The Company executes its foreign currency contracts primarily in the retail market in an over-the-counter environment with a relatively high level of price transparency. The market participants usually are large multi-national and regional banks. The Company’s foreign currency contracts valuation inputs are based on quoted prices and quoted pricing intervals from public data sources and do not involve management judgment. These contracts are typically classified within Level 2 of the fair value hierarchy.
	The following table sets forth the Company’s assets and liabilities that were measured at fair value as of March 31, 2015 and December 31, 2014, by level within the fair value hierarchy (in thousands):
		As of March 31, 2015
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	23,697	$	—	$	23,697
	Bank deposits		—		11,231		—		11,231
	Money market funds		126,816		—		—		126,816
	Short-term investments:
	Corporate debt obligations		—		35,949		—		35,949
	Bank deposits		—		10,302		—		10,302
	Total financial assets	$	126,816	$	81,179	$	—	$	207,995
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	1,132	$	—	$	1,132
		As of December 31, 2014
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash equivalents:
	Bank deposits	$	—	$	11,877	$	—	$	11,877
	Commercial paper		—		18,339		—		18,339
	Money market funds		11,596		—		—		11,596
	Short-term investments:
	Corporate debt obligations		—		31,354		—		31,354
	Bank deposits		—		10,270		—		10,270
	Total financial assets	$	11,596	$	71,840	$	—	$	83,436
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	1,002	$	—	$	1,002
	In addition to the amounts disclosed in the above table, the fair value of the Company’s Israeli severance pay assets, which were comprised of Level II assets, was $4.1 million and $4.0 million as of March 31, 2015 and December 31, 2014, respectively.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	6. Derivative Instruments
	The Company’s primary objective for holding derivative instruments is to reduce its exposure to foreign currency rate changes. The Company reduces its exposure by entering into forward foreign exchange contracts with respect to operating expenses that are forecast to be incurred in currencies other than U.S. dollars. Substantially all of the Company’s revenue and capital purchasing activities and a majority of its operating expenditures are transacted in U.S. dollars. However, certain operating expenditures are incurred in or exposed to other currencies, primarily the Israeli shekel and the Euro.
	The Company has established forecasted transaction currency risk management programs to protect against fluctuations in fair value and the volatility of future cash flows caused by changes in exchange rates. The Company’s currency risk management program includes forward foreign exchange contracts designated as cash flow hedges. These forward foreign exchange contracts generally mature within 12 months. The Company does not enter into derivative financial instruments for trading purposes.
	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands):
			As of March 31, 2015						As of December 31, 2014
			Notional			Fair Value			Notional		Fair Value
			Amount						Amount
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships - included in accrued and other current liabilities		$	19,497		$	(1,132	)	$	25,990	$	(1,002	)
	Gains (losses) on derivative instruments and their classification on the condensed consolidated statement of operations are presented in the following table (in thousands):
			Three months ended
			March 31,
			2015			2014
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Losses recognized in OCI (a)		$	(450	)	$	—
	Losses reclassified from accumulated OCI into net loss (b)		$	(320	)	$	—
	(a)	Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”).
	(b)	Effective portion of cash flow hedges reclassified from accumulated other comprehensive income (loss) into net loss, of which $32 and $288 losses were recognized within cost of sales and operating expenses, respectively, for the three months ended March 31, 2015. All amounts are reflected within the respective condensed consolidated statement of operations.

Acquired_Intangible_Assets

Acquired Intangible Assets	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Acquired Intangible Assets	7. Acquired Intangible Assets
	The Company amortizes intangible assets which consist of purchased technology over their estimated useful lives ranging from seven to 10 years using the straight-line method, as the consumption pattern of the asset is not apparent. The Company reviews them for impairment whenever an impairment indicator exists and continually monitors events and changes in circumstances that could indicate carrying amounts of the intangible assets may not be recoverable. When such events or changes in circumstances occur, the Company assesses recoverability by determining whether the carrying value of such assets exceed the estimates of future undiscounted future cash flows expected to be generated by such assets. Should impairment exist, the impairment loss would be measured based on the excess carrying value of the asset over the asset’s estimated fair value. There was no impairment of intangible assets recorded for the three months ended March 31, 2015. The weighted average remaining useful life of the Company’s acquired technology intangible assets is seven years as of March 31, 2015.
	Acquired technology intangible assets subject to amortization are presented as follows (in thousands):
		As of March 31, 2015							As of December 31, 2014
		Cost		Accumulated			Net		Cost		Accumulated			Net
				Amortization							Amortization
	Acquired Technology	$	10,668	$	(1,621	)	$	9,047	$	10,668	$	(1,269	)	$	9,399
	Acquired intangible assets are amortized over their estimated useful lives of 7 to 10 years. There were no acquired intangible assets prior to January 1, 2014. As of March 31, 2015, the amortization expense in future periods is expected to be as follows (in thousands):
	Fiscal Year	Acquired
		Technology
	2015 (remaining 9 months)	$	1,056
	2016		1,408
	2017		1,408
	2018		1,408
	2019		1,408
	Thereafter		2,359
	Total expected amortization expense	$	9,047

Revolving_Credit_Facility

Revolving Credit Facility	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Revolving Credit Facility	8. Revolving Credit Facility
	In September 2010, the Company entered into a revolving credit facility with a financial institution which expires on May 1, 2016. The agreement, as amended, provides for a maximum borrowing capacity of up to $4.5 million. As of March 31, 2015 and December 31, 2014, there was no balance outstanding on the credit facility.
	The credit facility is secured by the assets of the Company, and contains a restrictive covenant that requires the Company to maintain a minimum cash and cash equivalents balance of $3.0 million. The terms of this agreement requires payment of an unused line fee of 0.25% per quarter of the unused portion and bears interest at LIBOR plus 2.75%. As of March 31, 2015 and December 31, 2014, the Company was compliant with the amended covenant of the credit facility.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies
	(a) Operating Leases
	The Company rents its facilities under operating leases with lease periods expiring through 2019. Future minimum payments under these facility operating leases and minimum rentals to be received under non-cancellable subleases are as follows as of March 31, 2015 (in thousands):
	Fiscal Year	Operating		Estimated
		Leases		Sublease Income
	2015 (remaining 9 months)	$	3,680	$	354
	2016		5,730		105
	2017		5,367		—
	2018		3,411		—
	2019		513		—
	Thereafter		253		—
	Total	$	18,954	$	459
	Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Rent expense for the three months ended March 31, 2015 and 2014 was $1.0 million and $1.0 million, respectively.
	In connection with leases of office space, the Company received tenant improvement allowances of $336,000 and $639,000 during the years ended December 31, 2012 and 2010, respectively, from the lessor for certain improvements made to the leased properties. The Company has recorded the tenant improvement allowances as a leasehold improvement within property and equipment, net, and as deferred rent within other liabilities on the condensed consolidated balance sheets. The deferred rent liability is amortized to rent expense over the term of the lease on a straight-line basis. The leasehold improvements are being amortized to expense over the period from when the improvements were placed into service until the end of their useful life, which is the end of the lease term.
	In addition, certain of the Company’s operating lease agreements for office space also include rent holidays and scheduled rent escalations during the initial lease term. The Company has recorded the rent holidays as a deferred rent within other liabilities on the condensed consolidated balance sheets. The Company recognizes the deferred rent liability and scheduled rent increase on a straight-line basis into rent expense over the lease term commencing on the date the Company takes possession of the lease space.
	As of March 31, 2015 and December 31, 2014 the Company has $1.7 million and $1.7 million, respectively, in restricted deposits to secure bank guarantees provided to its lessors.
	(b) Cancelable Lease Agreement
	The Company leases motor vehicles under a cancelable operating lease agreements. The Company has an option to cancel the lease agreements, which may result in penalties in a maximum amount of $95,000 as of March 31, 2015. Motor vehicle lease expenses for the three months ended March 31, 2015 and 2014 were $0.6 million and $0.7 million, respectively.
	(c) Purchase Commitments
	As of March 31, 2015 and December 31, 2014, the Company had purchase commitments of $5.6 million and $4.8 million, respectively, to purchase inventory, trial units, and research and development equipment from its vendors. The purchase commitments result from the Company’s contractual obligation to order or build inventory in advance of anticipated sales. According to the Company’s agreements with its vendors, the Company committed to purchase inventory within nine months from the date the inventory arrived at the vendor’s warehouse.
	(d) Litigation
	From time to time, the Company may be subject to other legal proceedings and claims in the ordinary course of business.
	On April 11, 2014, a purported shareholder class action lawsuit was filed in the United States District Court for the Northern District of California against the Company and certain of its officers. On August 7, 2014, the Court entered an order appointing lead plaintiff and counsel for the purported class. The lead plaintiff filed an amended complaint on October 10, 2014. The lawsuit again names the Company and certain of its officers and purports to bring suit on behalf of those investors who purchased the Company’s publicly traded securities between May 2, 2013 and April 9, 2014. The plaintiff alleges that defendants made false and misleading statements about the Company’s operations and business and financial results and purports to assert claims for violations of the federal securities laws. The amended complaint seeks unspecified compensatory damages, interest thereon, costs incurred in the action and equitable/injunctive or other relief. On January 6, 2015, defendants filed a motion to dismiss the amended complaint. That motion is now fully briefed and pending before the court.
	On June 27, 2014, a purported shareholder derivative lawsuit was filed in the Court of Chancery for the State of Delaware against the Company (as a nominal defendant), and naming certain of the Company’s officers and directors as individual defendants. The lawsuit relates to the acquisition of Skyfence Networks, Ltd. and the complaint asserts claims for breach of fiduciary duty and unjust enrichment, and seeks to recover unspecified compensatory damages allegedly sustained by the Company, corporate reforms, the recovery of plaintiffs’ attorney’s fees and other relief. On September 23, 2014, the Company and the individual defendants moved to dismiss the action. Plaintiffs filed an amended complaint on November 6, 2014. Defendants filed a motion to dismiss the amended complaint on January 14, 2015. That motion is now fully briefed and pending before the court.
	In addition, the Company has received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of their intellectual property rights. Future litigation may be necessary to defend the Company, its channel partners and its customers by determining the scope, enforceability and validity of third-party proprietary rights or to establish its proprietary rights.
	In the opinion of management, liabilities associated with these claims, while possible, are not probable at this time, and therefore the Company has not recorded any accrual for them as of March 31, 2015 and December 31, 2014. Further, any possible range of loss cannot be reasonably estimated at this time. The ultimate outcome of any litigation is uncertain and, regardless of outcome, litigation can have an adverse impact on us because of defense costs, potential negative publicity, diversion of management resources and other factors. Accordingly, there can be no assurance that existing or future legal proceedings arising in the ordinary course of business or otherwise will not have a material adverse effect on the Company’s business, consolidated financial position, results of operations or cash flows.
	(e) Indemnification
	Under the indemnification provisions of its standard sales contracts, the Company agrees to defend its channel partners and end customers against third-party claims asserting infringement of certain intellectual property rights, which may include patents, copyrights, trademarks, or trade secrets, and to pay judgments and settlements entered on such claims. The Company’s exposure under these indemnifications provisions is generally limited to the total amount paid under the agreement. However, certain agreements included indemnification provisions that could potentially expose the Company to losses in excess of the amount received under the agreement. To date, there have been no claims under such indemnification provisions. Accordingly, the Company has not recorded a liability on its consolidated balance sheets for these indemnification provisions.
	In addition to the foregoing, the Company maintains director and officer insurance, which may cover certain liabilities arising from its obligation to indemnify its directors and officers.

Stock_Plans

Stock Plans	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Plans	10. Stock Plans
	(a) 2003 Stock Plan
	During 2003, the Board of Directors adopted the 2003 Stock Plan (the “2003 Plan”), which allows for the granting of both incentive stock options and non-qualified stock options and the direct award or sale of shares of the Company’s common stock (including restricted common stock) to officers, employees, directors, consultants and other key persons. Incentive stock options may be granted to employees with exercise prices of no less than the fair value of the common stock on the grant date, and non-qualified options may be granted to employees, directors, or consultants at exercise prices of no less than 85% of the fair value of the common stock on the grant date, as determined by the Board of Directors. If, at the time the Company grants an option, the optionee directly or by attribution owns stock possessing more than 10% of the total combined voting power of all classes of stock of the Company, the option price shall be at least 110% of the fair value. Options granted under the Plan generally expire no later than ten years and, in general, vest four years from the date of grant.
	(b) 2011 Stock Option and Incentive Plan
	In September 2011, the Board of Directors adopted the 2011 Stock Option and Incentive Plan (the “2011 Plan”) which was subsequently approved by the Company’s stockholders. The 2011 Plan replaces the 2003 Plan as the Board has decided not to grant any additional awards under that plan. The Company has reserved a total of 1,000,000 shares of common stock for issuance under the 2011 Plan. In addition, any reserved but unissued shares under the 2003 Stock Plan will be added to the number of shares reserved for issuance under the 2011 Plan. The 2011 Plan also provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning in 2012 and ending in 2015, by 4% of the outstanding number of shares of common stock on the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. On January 1, 2015, the share reserve under the 2011 Plan was automatically increased by 1,075,819 shares. As of December 31, 2014, there were 1,166,742 shares available for grant under the 2011 Plan.
	The 2011 Plan permits the granting of incentive stock options, non-qualified stock options, restricted stock units (RSUs), stock appreciation rights, restricted shares of common stock and performance share awards. The exercise price of stock options may not be less than the 100% of the fair market value of the common stock on the date of grant. Options granted pursuant to the 2011 Plan generally expire in no later than ten years. The Company also grants RSUs, which generally vest over either a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter or they completely vest at the end of a three-year period. Additionally, from time to time the Company grants performance-based restricted stock units to its executives and employees.
	(c) 2011 Employee Stock Purchase Plan
	In September 2011, the Board of Directors adopted the 2011 Employee Stock Purchase Plan (the “ESPP”) which was subsequently approved by the Company’s stockholders. The ESPP took effect on the effective date of the registration statement for the Company’s IPO. The ESPP permits eligible employees to acquire shares of the Company’s common stock by accumulating funds through periodic payroll deductions of up to 15% of base salary. Each offering period may run for no more than 24 months and consist of no more than five purchase periods. The purchase price for shares of the Company’s common stock purchased under the ESPP will be 85% of the lesser of the fair market value of the Company’s common stock on the first day of the offering period or the last trading day of the applicable purchase period within that offering period.
	The Company has initially reserved a total of 500,000 shares of common stock for future issuance under the ESPP. The number of shares reserved for issuance under the ESPP will increase automatically on January 1 of each of the first eight years commencing in 2012 by the number of shares equal to 1% of the Company’s total outstanding shares as of the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. No more than 20,000,000 shares of common stock may be issued under the ESPP and no other shares may be added to the ESPP without the approval of the Company’s stockholders. On January 1, 2015, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 268,955 shares.
	(d) Inducement Stock Option Plan and Agreement and Inducement Restricted Stock Unit Plan and Agreement
	In August 2014, the Board of Directors adopted the Inducement Stock Option Plan and Agreement (the “Inducement Option Plan”) and the Inducement Restricted Stock Unit Plan and Agreement (the “Inducement RSU Plan”) which were both created in connection with the appointment of the Company’s new Chief Executive Officer. In accordance with the terms of the Inducement Option Plan, the Company can issue an option to purchase up to 265,000 shares of the Company’s common stock at an exercise price equal to the fair market value of a share of the Company’s common stock on the date of grant of the option. The option, which will have a ten-year term, will vest at the rate of 25% of the shares on the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the option vesting each quarter thereafter so long as the participant has not been terminated. In accordance with the terms of the Inducement RSU Plan, the Company can issue RSUs representing a total of 265,000 shares of the Company’s common stock (the RSUs”). The RSUs, which will expire following settlement, will vest at the rate of 25% of the shares on the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the RSU vesting each quarter thereafter so long as participant has not been terminated.
	(e) Incapsula 2010 Share Incentive Plan
	In March 2010, Incapsula’s board of directors adopted the Incapsula 2010 Share Incentive Plan (the “Incapsula Plan”), pursuant to which Incapsula may grant to its employees and service providers options to purchase shares of its common stock, restricted shares, or RSUs. The total number of shares of common stock that may be granted under the Incapsula Plan shall not exceed 4,733,333 in the aggregate, subject to certain adjustments.
	In November 2013, the board of directors of Incapsula approved the grant of RSUs for 7,095,461 shares of Incapsula’s common stock (“Incapsula RSUs”). As part of the Incapsula Acquisition, the Incapsula RSUs were assumed and replaced by RSUs for Company Common Stock issued to continuing employees of Incapsula. The Incapsula RSU’s vest according to performance-based vesting terms tied to 2014 revenue for Incapsula and Incapsula-related products and services, which were converted into approximately 198,825 shares of Company Common Stock at the same exchange ratio applicable to the Incapsula Acquisition. In addition to performance conditions, the awards are dependent on future market price of Imperva’s common stock, which is deemed a market condition under ASC 718.
	The options outstanding and performance restricted share units under the Incapsula 2010 Share Incentive Plan were assumed as part of the Incapsula Acquisition and are equivalent to 247,184 shares of Company common stock on an as-converted basis. The Company does not intend to grant any additional shares under the Incapsula 2010 Share Incentive Plan.
	Option Activity
	The following table summarizes option activity under the Plans and related information:
			Options Outstanding
			Number of			Weighted			Weighted		Aggregate
			Shares			Average			Average		Intrinsic Value
						Exercise Price			Remaining		(in thousands) (1)
									Contractual
									Life (in years)
	Balances - January 1, 2015			2,244,363		$	33.83			8.27	$	38,457
	Granted			452,791		$	42.83
	Exercised or released			(73,005	)	$	22.16
	Cancelled or forfeited			(90,004	)	$	41.74
	Balances - March 31, 2015			2,534,145		$	35.49			8.34	$	25,400
	Vested and expected to vest - March 31, 2015			2,267,701		$	34.91			8.27	$	23,883
	Exercisable - March 31, 2015			729,987		$	28			6.73	$	12,428
	-1	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $42.70 of the Company’s common stock on March 31, 2015.
	RSU Activity
	The following table summarizes RSU activity under the Plans and related information:
			Number of			Weighted-
			Restricted			Average
			Stock Units			Grant Date
			Outstanding			Fair Value
	Unvested - January 1, 2015			2,279,081		$	39.07
	Granted			463,497		$	42.9
	Granted, performance RSUs			249,220		$	42.58
	Released			(224,739	)	$	45.5
	Cancelled or expired			(208,578	)	$	36.67
	Unvested - March 31, 2015			2,558,481		$	39.74
	The aggregate intrinsic value of options exercised under the Plans was $1.7 million for the three months ended March 31, 2015. The aggregate intrinsic value is calculated as the difference between the fair market value of the Company’s common stock on the date of the exercise and the exercise price of each option multiplied by the number of options exercised. As reported in the Wall Street Journal, the market value as of March 31, 2015 was $42.70 per share. As of March 31, 2015, total compensation cost related to unvested stock-based awards granted to employees under the Plans, but not yet recognized, was $108.8 million, net of estimated forfeitures. As of March 31, 2015, this cost will be amortized to expense over a weighted-average remaining period of 2.9 years, and will be adjusted for subsequent changes in estimated forfeitures. Future stock-based award grants will increase the amount of compensation expense to be recorded in these periods.
	There was no capitalized stock-based compensation cost during the three months ended March 31, 2015 and 2014. Recognized stock-based compensation tax benefits during the three months ended March 31, 2015 was $43,000. There was no recognized stock-based compensation tax benefit during the  three months ended March 31, 2014.
	(f) Stock Compensation Expense
	The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands):
			For the three months ended
			March 31,
			2015			2014
	Cost of revenues		$	914		$	374
	Research and development			3,328			1,792
	Sales and marketing			4,465			2,430
	General and administrative			3,839			2,070
	Total stock-based compensation expense		$	12,546		$	6,666
	The fair value of stock option grants for the three months ended March 31, 2015 and 2014 was estimated using the following weighted average assumptions:
			For the three months ended
			March 31,
			2015			2014
	Stock option grants:
	Dividend rate			0	%		0	%
	Risk-free interest rate			1.7	%		1.8	%
	Expected term (in years)			6.1			6.1
	Expected volatility			50	%		45	%
The fair value of the RSUs is determined using the closing price of the Company’s common stock on the date of the grant. Compensation is recognized on a straight-line basis over the requisite service period of each grant adjusted for estimated forfeitures.
(g) Common Stock Subject to Repurchase
Pursuant to restricted stock agreements with the Company’s former CEO and current Chairman of the Board of Directors, the Company has the right, but not the obligation, to repurchase the unvested shares of common stock upon termination of the provision of services at the original purchase price per share. The repurchase rights with respect to the common stock lapse over the vesting period, which ranges from 48 months to 60 months. The amounts received in exchange for these shares have been included in other liabilities in the accompanying condensed consolidated balance sheet and are reclassified to equity as the shares vest. The Company granted 843,819 shares of restricted common stock with a weighted-average grant date fair value per share of $1.94 during the year ended December 31, 2010. There were no grants of shares of restricted common stock during the three months ended March 31, 2015 and the year ended December 31, 2014. As of March 31, 2015, 210,954 shares of restricted common stock held by the Company’s former CEO and current Chairman of the Board of Directors were unvested and subject to repurchase by the Company.
In connection with the acquisition of Skyfence in the first quarter of 2014, the Company issued 532,262 shares of the Company’s common stock with a fair value per share of $59.08 which are subject to forfeiture based upon time-based vesting and continuing employment over the term of the corresponding four-year service period of which the first vesting anniversary will not be earlier than November 7, 2015. None of these shares were vested as of March 31, 2015.
(h) Early Exercise of Stock Options
In 2010 and 2011, the Company’s board of directors allowed for the early exercise of stock options granted to certain members of the Company’s board of directors. The amounts received in exchange for these shares have been included in accrued and other current liabilities and other liabilities in the accompanying condensed consolidated balance sheet and are reclassified to equity as the shares vest. As of March 31, 2015 and December 31, 2014 there were 4,167 and 6,667 shares, respectively, unvested amounting to $45,000 and $71,000, respectively.
(i) Equity Awards Issued in Acquisitions
In connection with the Skyfence and Incapsula acquisitions, the Company assumed stock options covering an aggregate of 72,607 shares of its common stock (in addition to the Incapsula RSUs discussed above). At the date of the acquisition, vested stock options and the associated fair value was recorded as part of the purchase consideration. The fair value related to the assumed unvested stock options are recognized as post-combination compensation costs and is being recorded as post-combination compensation expense ratably over the respective remaining service periods.
(j) Follow-On Public Offering
In March 2015, the Company completed a follow-on public offering whereby the Company sold 3,450,000 shares of common stock at a price of $39.00 per share, for aggregate net proceeds of $127.9 million, after deducting underwriting discounts, commissions and other offering costs  of approximately $6.7 million.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Loss	11. Accumulated Other Comprehensive Loss
	The changes in the balances of accumulated other comprehensive loss by component are as follows (in thousands):
			For the three months ended
			31-Mar-15
			Unrealized			Unrealized			Total
			gain (loss)			gain (loss) on
			on cash flow			investments
			hedges
	Balance at January 1		$	(1,428	)	$	(61	)	$	(1,489	)
	Other comprehensive income (loss) before reclassifications			(450	)		44			(406	)
	Amounts reclassified to net loss			320			—			320
	Change in other comprehensive income (loss)			(130	)		44			(86	)
	Balance at March 31		$	(1,558	)	$	(17	)	$	(1,575	)
			For the three months ended
			31-Mar-14
			Unrealized			Unrealized			Total
			gain (loss)			gain (loss) on
			on cash flow			investments
			hedges
	Balance at January 1		$	(426	)	$	(2	)	$	(428	)
	Other comprehensive income (loss) before reclassifications			—			3			3
	Amounts reclassified to net loss			—			—			—
	Change in other comprehensive income (loss)			—			3			3
	Balance at March 31		$	(426	)	$	1		$	(425	)
	The following is a summary of reclassifications out of accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014 (in thousands):
			For the three months ended
			31-Mar-15
			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount
						(Benefit)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)		$	44		$	—		$	44
	Unrealized gains (losses) on investments			44			—			44
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)			(450	)		—			(450	)
	Reclassification adjustments 1			320			—			320
	Unrealized gains (losses) on cash flow hedges, net			(130	)		—			(130	)
	Other comprehensive income/(loss)		$	(86	)	$	—		$	(86	)
			For the three months ended
			31-Mar-14
			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount
						(Benefit)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)		$	5		$	2		$	3
	Other comprehensive income/(loss)		$	5		$	2		$	3
	1	Refer to note 6 for the affected line items in the condensed consolidated statement of operations.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes
	The Company is subject to income tax in the United States as well as other tax jurisdictions in which it conducts business. Earnings from non-U.S. activities are subject to local country income tax. The Company does not provide for federal income taxes on the undistributed earnings of its foreign subsidiaries as such earnings are to be reinvested indefinitely. For the three months ended March 31, 2015 and 2014, the Company recorded income tax expense of $0.4 million and an income tax benefit of $0.4 million, respectively. The income tax expense amount in 2015 was primarily attributable to foreign and state income taxes. The income tax benefit recorded in 2014 relates primarily to the recognition of deferred tax assets attributable to foreign losses.
	Factors that impact the income tax provision include, but are not limited to, stock-based compensation expense, permanent tax adjustments, foreign operations and a valuation allowance against the Company’s deferred tax assets.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	13. Segment Information
	The Company operates its business in one operating segment, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in cloud or on premises. Operating segments are defined as components of an enterprise that engage in business activities for which separate financial information is available and evaluated by the chief operating decision maker in deciding how to allocate resources and assessing performance. The chief operating decision maker is the Company’s Chief Executive Officer.
	The Company’s net services revenue is comprised of the following (in thousands):
		For the three months ended
		March 31,
		2015		2014
	Maintenance and support	$	15,048	$	12,663
	Professional services and training		3,932		2,299
	Subscriptions		8,673		4,583
	Total net services revenue	$	27,653	$	19,545
	The Company’s net revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands):
		For the three months ended
		March 31,
		2015		2014
	Americas	$	26,557	$	18,076
	EMEA		12,202		8,210
	APAC		5,998		5,230
	Total net revenue	$	44,757	$	31,516
	The following table presents long-lived assets by location (in thousands):
		As of		As of
		March 31,		December 31,
		2015		2014
	United States	$	6,735	$	6,761
	Israel		10,003		10,221
	Other		31		35
	Total long-lived assets	$	16,769	$	17,017

Net_Loss_per_Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Net Loss per Share	14. Net Loss per Share
	Basic and diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding during the period. The computation of net loss per share for each period, including the number of weighted-average shares outstanding, is shown on the face of the condensed consolidated statements of operations.
	The following outstanding shares of common stock and potential common shares were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		For the three months ended
		March 31,
		2015		2014
	Stock options to purchase common stock		2,534,145		2,113,995
	Restricted stock units for common stock		2,558,481		1,694,129
	Restricted shares of common stock subject to repurchase		215,121		286,125
	Restricted stock issued in connection with Skyfence acquisition		355,499		354,678

Basis_of_Presentation_and_Summ1

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Business	Business
	Imperva, Inc. (together with its subsidiaries, the “Company”) was incorporated in April 2002 in Delaware. The Company is headquartered in Redwood Shores, California and has subsidiaries located throughout the world including Israel, Asia and Europe. The Company is engaged in the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises.
Basis of Presentation	Basis of Presentation
	The Company has prepared the accompanying unaudited Condensed Consolidated Financial Statements in accordance with Article 10 of Regulation S-X and pursuant to the rules and regulations for Form 10-Q of the Securities and Exchange Commission (the “SEC”). Pursuant to those rules and regulations, the Company has condensed or omitted certain information and footnote disclosure it normally includes in its annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the Company has made all adjustments (consisting only of normal, recurring adjustments, except as otherwise indicated) necessary to fairly present its consolidated financial position, results of operations, and cash flows. The Company’s interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the consolidated financial statements and notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014, which was filed with the SEC on March 2, 2015 (the “Annual Report”).
	The condensed consolidated financial statements include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications
	From time to time the Company reclassifies certain period balances to conform to the current year presentation. These reclassifications have no material impact on previously reported total assets, total liabilities, stockholders’ equity, results of operations or cash flows.
Concentration of Revenue and Accounts Receivable	Concentration of Revenue and Accounts Receivable
	Significant customers are those which represent 10% or more of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the three months ended March 31, 2015 and 2014, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There were no customers who represented greater than 10% of gross accounts receivable as of March 31, 2015 and December 31, 2014.
Significant Accounting Policies	Significant Accounting Policies
	There have been no material changes to the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	There have been no new accounting pronouncements during the three months ended March 31, 2015, as compared to the recent accounting pronouncements described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2014 that are of significance, or potential significance, to the Company.

Acquisitions_Tables

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2015
Skyfence Networks Ltd. [Member]
Schedule of Total Purchase Consideration	The total purchase consideration is as follows (in thousands):
	Cash	$	8,558
	Cash holdback liability		7,157
	Fair value of common stock		20,855
	Estimated fair value of equity awards assumed and replaced		354
		$	36,924
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands):
	Net tangible assets	$	1,014
	Existing technology		7,965
	Deferred tax liability assumed		(1,528	)
	Goodwill		29,473
	Total purchase price	$	36,924
Tomium Software, LLC. [Member]
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands):
	Intangible assets	$	2,704
	Goodwill		5,499
	Total intangible assets acquired		8,203
	Other acquired tangible assets		60
	Fair value of assets acquired	$	8,263

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents, and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Cash and Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Short-Term Investments	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		As of March 31, 2015
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	34,742	$	—	$	—	$	34,742
	Commercial paper		23,698		—		1		23,697
	Bank deposits		11,231		—		—		11,231
	Money market funds		126,816		—		—		126,816
	Total	$	196,487	$	—	$	1	$	196,486
	Short-term investments:
	Corporate debt obligations	$	35,956	$	14	$	21	$	35,949
	Bank deposits		10,302		—		—		10,302
	Total	$	46,258	$	14	$	21	$	46,251
		As of December 31, 2014
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	26,284	$	—	$	—	$	26,284
	Bank deposits		11,877				—		11,877
	Commercial paper		18,341		—		2		18,339
	Money market funds		11,596		—		—		11,596
	Total	$	68,098	$	—	$	2	$	68,096
	Short-term investments:
	Corporate debt obligations	$	31,404	$	3	$	53	$	31,354
	Bank deposits		10,270		—		—		10,270
	Total	$	41,674	$	3	$	53	$	41,624
Summary of Cost and Estimated Fair Value of Short-Term Investments	The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of March 31, 2015 (in thousands):
		As of March 31, 2015
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	27,361	$	27,365
	Due within two years		18,897		18,886
	Total	$	46,258	$	46,251
Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position	The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands):
		As of March 31, 2015
		Less than 12 Months				12 Months or Greater				Total
		Fair Value		Unrealized		Fair Value		Unrealized		Fair Value		Unrealized
				Losses				Losses				Losses
	Corporate debt obligations	$	15,559	$	20	$	2,003	$	1	$	17,562	$	21
		As of December 31, 2014
		Less than 12 Months				12 Months or Greater				Total
		Fair Value		Unrealized		Fair Value		Unrealized		Fair Value		Unrealized
				Losses				Losses				Losses
	Corporate debt obligations	$	12,735	$	47	$	12,088	$	6	$	24,823	$	53

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis	The following table sets forth the Company’s assets and liabilities that were measured at fair value as of March 31, 2015 and December 31, 2014, by level within the fair value hierarchy (in thousands):
		As of March 31, 2015
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	23,697	$	—	$	23,697
	Bank deposits		—		11,231		—		11,231
	Money market funds		126,816		—		—		126,816
	Short-term investments:
	Corporate debt obligations		—		35,949		—		35,949
	Bank deposits		—		10,302		—		10,302
	Total financial assets	$	126,816	$	81,179	$	—	$	207,995
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	1,132	$	—	$	1,132
		As of December 31, 2014
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash equivalents:
	Bank deposits	$	—	$	11,877	$	—	$	11,877
	Commercial paper		—		18,339		—		18,339
	Money market funds		11,596		—		—		11,596
	Short-term investments:
	Corporate debt obligations		—		31,354		—		31,354
	Bank deposits		—		10,270		—		10,270
	Total financial assets	$	11,596	$	71,840	$	—	$	83,436
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	1,002	$	—	$	1,002

Derivative_Instruments_Tables

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments Measured at Fair Value	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands):
			As of March 31, 2015						As of December 31, 2014
			(unaudited)
			Notional			Fair			Notional		Fair
			Amount			Value			Amount		Value
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships - included in accrued and other current liabilities		$	19,497		$	(1,132	)	$	25,990	$	(1,002	)
Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations	Gains (losses) on derivative instruments and their classification on the condensed consolidated statement of operations are presented in the following table (in thousands):
			Three months ended
			March 31,
			2015			2014
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Losses recognized in OCI (a)		$	(450	)	$	—
	Losses reclassified from accumulated OCI into net loss (b)		$	(320	)	$	—
	(a)	Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”).
	(b)	Effective portion of cash flow hedges reclassified from accumulated other comprehensive income (loss) into net loss, of which $32 and $288 losses were recognized within cost of sales and operating expenses, respectively, for the three months ended March 31, 2015. All amounts are reflected within the respective condensed consolidated statement of operations.

Acquired_Intangible_Assets_Tab

Acquired Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Acquired Technology Intangible Assets Subject to Amortization	Acquired technology intangible assets subject to amortization are presented as follows (in thousands):
		As of March 31, 2015							As of December 31, 2014
		Cost		Accumulated			Net		Cost		Accumulated			Net
				Amortization							Amortization
	Acquired Technology	$	10,668	$	(1,621	)	$	9,047	$	10,668	$	(1,269	)	$	9,399
Schedule of Expected Amortization Expense in Future Periods	As of March 31, 2015, the amortization expense in future periods is expected to be as follows (in thousands):
	Fiscal Year	Acquired
		Technology
	2015 (remaining 9 months)	$	1,056
	2016		1,408
	2017		1,408
	2018		1,408
	2019		1,408
	Thereafter		2,359
	Total expected amortization expense	$	9,047

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases	Future minimum payments under these facility operating leases and minimum rentals to be received under non-cancellable subleases are as follows as of March 31, 2015 (in thousands):
	Fiscal Year	Operating		Estimated
		Leases		Sublease Income
	2015 (remaining 9 months)	$	3,680	$	354
	2016		5,730		105
	2017		5,367		—
	2018		3,411		—
	2019		513		—
	Thereafter		253		—
	Total	$	18,954	$	459

Stock_Plans_Tables

Stock Plans (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Option Activity under Plans and Related Information	The following table summarizes option activity under the Plans and related information:
			Options Outstanding
			Number of			Weighted			Weighted		Aggregate
			Shares			Average			Average		Intrinsic Value
						Exercise Price			Remaining		(in thousands) (1)
									Contractual
									Life (in years)
	Balances - January 1, 2015			2,244,363		$	33.83			8.27	$	38,457
	Granted			452,791		$	42.83
	Exercised or released			(73,005	)	$	22.16
	Cancelled or forfeited			(90,004	)	$	41.74
	Balances - March 31, 2015			2,534,145		$	35.49			8.34	$	25,400
	Vested and expected to vest - March 31, 2015			2,267,701		$	34.91			8.27	$	23,883
	Exercisable - March 31, 2015			729,987		$	28			6.73	$	12,428
	-1	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $42.70 of the Company’s common stock on March 31, 2015.
Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value	The following table summarizes RSU activity under the Plans and related information:
			Number of			Weighted-
			Restricted			Average
			Stock Units			Grant Date
			Outstanding			Fair Value
	Unvested - January 1, 2015			2,279,081		$	39.07
	Granted			463,497		$	42.9
	Granted, performance RSUs			249,220		$	42.58
	Released			(224,739	)	$	45.5
	Cancelled or expired			(208,578	)	$	36.67
	Unvested - March 31, 2015			2,558,481		$	39.74
Stock-Based Compensation Expense	The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands):
			For the three months ended
			March 31,
			2015			2014
	Cost of revenues		$	914		$	374
	Research and development			3,328			1,792
	Sales and marketing			4,465			2,430
	General and administrative			3,839			2,070
	Total stock-based compensation expense		$	12,546		$	6,666
Weighted Average Assumptions for Fair Value of Stock Options Grants	The fair value of stock option grants for the three months ended March 31, 2015 and 2014 was estimated using the following weighted average assumptions:
			For the three months ended
			March 31,
			2015			2014
	Stock option grants:
	Dividend rate			0	%		0	%
	Risk-free interest rate			1.7	%		1.8	%
	Expected term (in years)			6.1			6.1
	Expected volatility			50	%		45	%

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Changes in Balances of Accumulated Other Comprehensive Loss	The changes in the balances of accumulated other comprehensive loss by component are as follows (in thousands):
			For the three months ended
			31-Mar-15
			Unrealized			Unrealized			Total
			gain (loss)			gain (loss) on
			on cash flow			investments
			hedges
	Balance at January 1		$	(1,428	)	$	(61	)	$	(1,489	)
	Other comprehensive income (loss) before reclassifications			(450	)		44			(406	)
	Amounts reclassified to net loss			320			—			320
	Change in other comprehensive income (loss)			(130	)		44			(86	)
	Balance at March 31		$	(1,558	)	$	(17	)	$	(1,575	)
			For the three months ended
			31-Mar-14
			Unrealized			Unrealized			Total
			gain (loss)			gain (loss) on
			on cash flow			investments
			hedges
	Balance at January 1		$	(426	)	$	(2	)	$	(428	)
	Other comprehensive income (loss) before reclassifications			—			3			3
	Amounts reclassified to net loss			—			—			—
	Change in other comprehensive income (loss)			—			3			3
	Balance at March 31		$	(426	)	$	1		$	(425	)
Summary of Reclassifications Out of Accumulated Other Comprehensive Loss	The following is a summary of reclassifications out of accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014 (in thousands):
			For the three months ended
			31-Mar-15
			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount
						(Benefit)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)		$	44		$	—		$	44
	Unrealized gains (losses) on investments			44			—			44
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)			(450	)		—			(450	)
	Reclassification adjustments 1			320			—			320
	Unrealized gains (losses) on cash flow hedges, net			(130	)		—			(130	)
	Other comprehensive income/(loss)		$	(86	)	$	—		$	(86	)
			For the three months ended
			31-Mar-14
			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount
						(Benefit)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)		$	5		$	2		$	3
	Other comprehensive income/(loss)		$	5		$	2		$	3
	1	Refer to note 6 for the affected line items in the condensed consolidated statement of operations.

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Company's Net Services Revenue	The Company’s net services revenue is comprised of the following (in thousands):
		For the three months ended
		March 31,
		2015		2014
	Maintenance and support	$	15,048	$	12,663
	Professional services and training		3,932		2,299
	Subscriptions		8,673		4,583
	Total net services revenue	$	27,653	$	19,545
Company's Net Revenue by Geographic Region, Based on Customer's Location	The Company’s net revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands):
		For the three months ended
		March 31,
		2015		2014
	Americas	$	26,557	$	18,076
	EMEA		12,202		8,210
	APAC		5,998		5,230
	Total net revenue	$	44,757	$	31,516
Long-Lived Assets by Location	The following table presents long-lived assets by location (in thousands):
		As of		As of
		March 31,		December 31,
		2015		2014
	United States	$	6,735	$	6,761
	Israel		10,003		10,221
	Other		31		35
	Total long-lived assets	$	16,769	$	17,017

Net_Loss_per_Share_Tables

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock	The following outstanding shares of common stock and potential common shares were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		For the three months ended
		March 31,
		2015		2014
	Stock options to purchase common stock		2,534,145		2,113,995
	Restricted stock units for common stock		2,558,481		1,694,129
	Restricted shares of common stock subject to repurchase		215,121		286,125
	Restricted stock issued in connection with Skyfence acquisition		355,499		354,678

Basis_of_Presentation_and_Summ2

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
	Customer	Customer	Customer
Revenue [Member] | Customer Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers	10.00%	10.00%
Number of customers representing 10% or more of revenue	0	0
Gross Accounts Receivable [Member] | Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers	10.00%		10.00%
Number of customers representing 10% or more of gross accounts receivable	0		0

Incapsula_Additional_Informati

Incapsula - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended	1 Months Ended
	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2013	Nov. 05, 2009	Mar. 31, 2010	Jan. 31, 2012	Jul. 31, 2011	Dec. 31, 2014
Subsidiary or Equity Method Investee [Line Items]
Value of goodwill on the acquisition date		$34,972,000						$34,972,000	[1]
Purchase Right valuation description		Exercise of the Purchase Right was solely within the Company's control and the price for the remaining ownership interest was to be based on an Incapsula enterprise valuation calculated as the greater of (i) eight times Incapsula's prior 12 months trailing revenues or (ii) seven times the aggregate amount Incapsula had raised in connection with its Series A Convertible Preferred Stock financings.
Non-controlling interest reclassified to additional paid-in capital	2,827,000
Performance-Based Award [Member] | Restricted Stock Units for Common Stock [Member]
Subsidiary or Equity Method Investee [Line Items]
Business acquisition, shares issued			264,878
Incapsula Acquisition [Member]
Subsidiary or Equity Method Investee [Line Items]
Amount paid for remaining outstanding capital stock	7,700,000
Business acquisition, shares issued	124,088
Incapsula Acquisition [Member] | Assumed Outstanding Options [Member]
Subsidiary or Equity Method Investee [Line Items]
Business acquisition, shares issued	48,359
Incapsula Acquisition [Member] | 15-Month Holdback [Member]
Subsidiary or Equity Method Investee [Line Items]
Business acquisition, shares issued	34,485
Common stock subject to holdback, period	15 months
Incapsula [Member] | Restricted Stock Units for Common Stock [Member]
Subsidiary or Equity Method Investee [Line Items]
Shares issued or issuable, as-converted to common stock-basis			198,825
Series A Convertible Preferred Stock [Member] | Incapsula [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity method investments, shares				5,000,000	6,666,666
Ownership interest				58.00%	76.00%
Value assigned to license				0
Net assets				0
Value of goodwill on the acquisition date				0
Cash consideration					3,000,000
Value assigned to Purchase Right		0
Series A-1 Convertible Preferred Stock [Member] | Incapsula [Member]
Subsidiary or Equity Method Investee [Line Items]
Number of shares to be purchased if certain milestones were achieved					8,750,000
Cash consideration for milestones achieved					7,000,000
Value assigned to forward contract					0
Series A-1 Preferred Stock [Member] | Incapsula [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity method investments, shares						4,375,000	4,375,000
Ownership interest						85.00%	82.00%
Cash consideration						$3,500,000	$3,500,000
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended	14 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 07, 2014	Mar. 31, 2015	Jan. 30, 2014
Business Acquisition [Line Items]
Residual value of intangible assets	$0			$0
Business acquisition purchase price, cash paid	0	12,083,000
Recognized compensation expense	12,546,000	6,666,000
Maximum [Member]
Business Acquisition [Line Items]
Estimated useful life	10 years
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Date of acquisition	7-Feb-14
Business acquisition purchase price, cash paid			8,558,000
Holdback payment commitment period			24 months
Holdback liability			7,157,000
Business acquisition purchase price, shares issued			884,422
Compensation expense, service period			4 years
Closing price of stock			$59.08
Unvested equity awards to be recorded as operating expense			1,100,000
Vested equity awards			300,000
Related acquisition costs			900,000
Recognized compensation expense				9,400,000
Total purchase price			36,924,000
Business acquisition purchase price, common stock value			20,855,000
Skyfence Networks Ltd. [Member] | Subject to a Holdback [Member]
Business Acquisition [Line Items]
Business acquisition purchase price, shares issued			29,871
Skyfence Networks Ltd. [Member] | Restricted Shares of Common Stock Subject to Repurchase [Member]
Business Acquisition [Line Items]
Business acquisition purchase price, shares issued			532,262
Skyfence Networks Ltd. [Member] | Skyfence Options [Member]
Business Acquisition [Line Items]
Options converted to purchase shares			164,000
Skyfence Networks Ltd. [Member] | Converted Imperva Options [Member]
Business Acquisition [Line Items]
Options converted to purchase shares			24,248
Skyfence Networks Ltd. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Common stock subject to holdback, period			24 months
Skyfence Networks Ltd. [Member] | Purchased Technology [Member]
Business Acquisition [Line Items]
Estimated useful life			7 years
Tomium Software, LLC. [Member]
Business Acquisition [Line Items]
Date of acquisition	30-Jan-14
Business acquisition purchase price, cash paid					4,600,000
Business acquisition purchase price, shares issued					60,556
Closing price of stock					$55.45
Related acquisition costs					300,000
Estimated useful life					10 years
Total purchase price					8,300,000
Business acquisition purchase price, assumption of liability to pay cash					300,000
Business acquisition purchase price, common stock value					$3,400,000

Acquisitions_Schedule_of_Total

Acquisitions - Schedule of Total Purchase Consideration (Detail) (USD $)	3 Months Ended		0 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Feb. 07, 2014
Business Acquisition [Line Items]
Cash	$0	$12,083
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Cash			8,558
Cash holdback liability			7,157
Fair value of common stock			20,855
Estimated fair value of equity awards assumed and replaced			354
Total purchase price			$36,924

Acquisitions_Summary_of_Alloca

Acquisitions - Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed (Detail) (USD $)	0 Months Ended
In Thousands, unless otherwise specified	Feb. 07, 2014	Jan. 30, 2014	Mar. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill			$34,972	$34,972	[1]
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Net tangible assets	1,014
Intangible assets	7,965
Deferred tax liability assumed	-1,528
Goodwill	29,473
Total purchase price	36,924
Tomium Software, LLC. [Member]
Business Acquisition [Line Items]
Intangible assets		2,704
Goodwill		5,499
Total purchase price		8,300
Total intangible assets acquired		8,203
Other acquired tangible assets		60
Fair value of assets acquired		$8,263
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$196,487	$68,098
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	2
Cash and cash equivalents, Fair Value	196,486	68,096
Short-term investments, Amortized Cost	46,258	41,674
Short-term investments, Gross Unrealized Gains	14	3
Short-term investments, Gross Unrealized Losses	21	53
Short-term investments, Estimated Fair Value	46,251	41,624	[1]
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	35,956	31,404
Short-term investments, Gross Unrealized Gains	14	3
Short-term investments, Gross Unrealized Losses	21	53
Short-term investments, Estimated Fair Value	35,949	31,354
Bank Deposits [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	11,231	11,877
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	11,231	11,877
Short-term investments, Amortized Cost	10,302	10,270
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,302	10,270
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	34,742	26,284
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	34,742	26,284
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	23,698	18,341
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	2
Cash and cash equivalents, Fair Value	23,697	18,339
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	126,816	11,596
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	$126,816	$11,596
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Cash_Cash_Equivalents_and_Shor3

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Short-term Investments [Abstract]
Amortized Cost of short-term investments, Due within one year	$27,361
Amortized Cost of short-term investments, Due within two years	18,897
Short-term investments, Amortized Cost	46,258	41,674
Estimated fair value of short-term investments, Due within one year	27,365
Estimated fair value of short-term investments, Due within two years	18,886
Short-term investments, Estimated Fair Value	$46,251	$41,624	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Cash_Cash_Equivalents_and_Shor4

Cash, Cash Equivalents, and Short-Term Investments - Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position (Detail) (Corporate Debt Obligations [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Corporate Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$15,559	$12,735
Less than 12 Months, Unrealized Losses	20	47
12 Months or Greater, Fair Value	2,003	12,088
12 Months or Greater, Unrealized Losses	1	6
Total, Fair Value	17,562	24,823
Total, Unrealized Losses	$21	$53

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value transfers between level 1 to level 2	$0
Fair value transfers between level 2 to level 1	0
Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Severance pay assets	$4,100,000	$4,000,000

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	$196,486	$68,096
Short-term investments	46,251	41,624	[1]
Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	11,231	11,877
Short-term investments	10,302	10,270
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	23,697	18,339
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	126,816	11,596
Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	35,949	31,354
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	207,995	83,436
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	11,231	11,877
Short-term investments	10,302	10,270
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	23,697	18,339
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	126,816	11,596
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	35,949	31,354
Fair Value, Measurements, Recurring [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	1,132	1,002
Level I [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	126,816	11,596
Level I [Member] | Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Level I [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Level I [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	126,816	11,596
Level I [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Level I [Member] | Fair Value, Measurements, Recurring [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	0	0
Level II [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	81,179	71,840
Level II [Member] | Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	11,231	11,877
Short-term investments	10,302	10,270
Level II [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	23,697	18,339
Level II [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Level II [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	35,949	31,354
Level II [Member] | Fair Value, Measurements, Recurring [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	1,132	1,002
Level III [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	0	0
Level III [Member] | Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Level III [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Level III [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Level III [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Level III [Member] | Fair Value, Measurements, Recurring [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	$0	$0
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Forward foreign exchange contracts maturity	12 months

Derivative_Instruments_Derivat

Derivative Instruments - Derivative Instruments Measured at Fair Value (Detail) (Forward Foreign Exchange Contracts [Member], Accrued and Other Current Liabilities [Member], Designated As Hedging Instrument [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member] | Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$19,497,000	$25,990,000
Derivative Fair Value	($1,132,000)	($1,002,000)

Derivative_Instruments_Gains_L

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Detail) (Designated As Hedging Instrument [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Losses recognized in OCI	($450)	$0
Losses recognized from accumulated OCI into net loss	($320)	$0

Derivative_Instruments_Gains_L1

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Parenthetical) (Detail) (Designated As Hedging Instrument [Member], Unrealized Gain (Loss) on Cash Flow Hedges [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Cost of revenues [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge loss reclassified	($32)
Operating Expenses [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge loss reclassified	($288)

Acquired_Intangible_Assets_Sum

Acquired Intangible Assets - Summary of Acquired Technology Intangible Assets Subject to Amortization (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cost	$10,668,000	$10,668,000
Accumulated Amortization	-1,621,000	-1,269,000
Acquired intangible assets, net	$9,047,000	$9,399,000	[1]	$0
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquired_Intangible_Assets_Add

Acquired Intangible Assets - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Acquired intangible assets	$9,047,000	$9,399,000	[1]	$0
Impairment of intangible assets	$0
Weighted Average Remaining Useful Life	7 years
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	7 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	10 years
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquired_Intangible_Assets_Sch

Acquired Intangible Assets - Schedule of Expected Amortization Expense in Future Periods (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Acquired intangible assets, net	$9,047,000	$9,399,000	[1]	$0
Purchased Technology [Member]
Finite-Lived Intangible Assets [Line Items]
2015 (remaining 9 months)	1,056,000
2016	1,408,000
2017	1,408,000
2018	1,408,000
2019	1,408,000
Thereafter	2,359,000
Acquired intangible assets, net	$9,047,000
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Revolving_Credit_Facility_Addi

Revolving Credit Facility - Additional Information (Detail) (London Interbank Offered Rate (LIBOR) [Member], USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$4,500,000
Outstanding credit facility	0	0
Credit facility expiration date	1-May-16
Minimum cash and cash equivalents	$3,000,000
Percentage in payment of unused line fee	0.25%
Interest rate spread	2.75%
Compliance of credit facility, description	The Company was compliant with the amended covenant of the credit facility.

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2014
Loss Contingencies [Line Items]
Operating lease expiration year	2019
Rent expense	$1,000,000	$1,000,000
Tenant improvement allowances			336,000	639,000
Restricted cash	1,665,000				1,665,000	[1]
Commitments purchased	5,600,000				4,800,000
Period of purchase commitment of inventory from specified date	9 months
Loss contingency accrual	0
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	95,000
Motor vehicle lease expenses	$600,000	$700,000
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Operating Leases
2015 (remaining 9 months)	$3,680
2016	5,730
2017	5,367
2018	3,411
2019	513
Thereafter	253
Total	18,954
Estimated Sublease Income
2015 (remaining 9 months)	354
2016	105
2017	0
2018	0
2019	0
Thereafter	0
Total	$459

Stock_Plans_Additional_Informa

Stock Plans - Additional Information (Detail) (USD $)

3 Months Ended

1 Months Ended

0 Months Ended

12 Months Ended

1 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Mar. 31, 2015

Feb. 07, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2010

Feb. 29, 2012

Jan. 31, 2012

Sep. 30, 2011

Nov. 30, 2013

Aug. 31, 2014

Mar. 31, 2010

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of stock option outstanding, granted

452,791

Performance-based restricted stock units granted

463,497

Market value of common stock

$42.70

$42.70

Capitalized stock-based compensation cost

$0

$0

Recognized stock-based compensation tax benefits

43,000

0

Weighted-average grant date fair value

$42.90

Unvested shares

2,558,481

2,558,481

2,279,081

Aggregate net proceeds from sale of common stock, net of underwriting discounts, commissions and offering costs

1,618,000

2,471,000

Follow-On Public Offering [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Issuance of common stock, shares

3,450,000

Sale of common stock, price per share

$39

$39

Aggregate net proceeds from sale of common stock, net of underwriting discounts, commissions and offering costs

127,900,000

Underwriting discounts, commissions and other offering expenses

6,700,000

Skyfence Networks Ltd. [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation cost related to unvested stock-based awards granted, but not yet recognized

1,100,000

Nonvested awards, compensation cost not yet recognized, period for recognition

4 years

Business acquisition purchase price, shares issued

884,422

Closing price of stock

$59.08

Common stock, shares vested

0

Incapsula [Member] | Skyfence Networks Ltd. [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Assumed common stock options in acquisitions

72,607

Restricted Stock Units for Common Stock [Member] | Incapsula [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares issuable, as-converted to common stock-basis

198,825

Restricted Stock Units And Options Outstanding [Member] | Incapsula [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares issuable, as-converted to common stock-basis

247,184

Restricted Shares of Common Stock Subject to Repurchase [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance-based restricted stock units granted

0

0

843,819

Weighted-average grant date fair value

$1.94

Unvested shares

210,954

210,954

Restricted Shares of Common Stock Subject to Repurchase [Member] | Skyfence Networks Ltd. [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Business acquisition purchase price, shares issued

532,262

Restricted Shares of Common Stock Subject to Repurchase [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

60 months

Restricted Shares of Common Stock Subject to Repurchase [Member] | Minimum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

48 months

Stock options [Member] | Director [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Unvested shares

4,167

4,167

6,667

Unvested shares, value

45,000

45,000

71,000

2011 Stock Option and Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Reserve of common stock for future issuance

1,000,000

Increase percentage of common stock outstanding

4.00%

Shares available for grant

1,166,742

Increase in reserve share

1,075,819

2011 Stock Option and Incentive Plan [Member] | Restricted Stock Units for Common Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

4 years

Description of vesting terms

The Company also grants RSUs in February 2012, which generally vest over either a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter or they completely vest at the end of a three-year period.

2011 Stock Option and Incentive Plan [Member] | Restricted Stock Units for Common Stock [Member] | Share-based Compensation Award, Tranche One [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percentage at the end of period

25.00%

2011 Stock Option and Incentive Plan [Member] | Stock options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Maximum percentage of fair value of common stock on grant date

100.00%

Expiration period

10 years

2011 Employee Stock Purchase Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Reserve of common stock for future issuance

500,000

Increase percentage of common stock outstanding

1.00%

Increase in reserve share

268,955

Percentage in payroll of deduction base salary to acquire shares of common stock

15.00%

Offering period

24 months

Percentage of fair value of common stock on offering period

85.00%

Number of years, shares reserved for issuance will increase

8 years

2011 Employee Stock Purchase Plan [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Reserve of common stock for future issuance

20,000,000

Number of purchase periods for offering

5

Incapsula 2010 Share Incentive Plan [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Reserve of common stock for future issuance

4,733,333

Incapsula 2010 Share Incentive Plan [Member] | Restricted Stock Units for Common Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance-based restricted stock units granted

7,095,461

2003 Stock Plan [Member] | Stock options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Maximum percentage of fair value of common stock on grant date

85.00%

2003 Stock Plan [Member] | Stock options [Member] | Greater 10% Ownership [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Maximum percentage of fair value of common stock on grant date

110.00%

Minimum percentage of combined voting power

10.00%

2003 Stock Plan [Member] | Stock options [Member] | Maximum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expiration period

10 years

2003 Stock Plan [Member] | Stock options [Member] | Minimum [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting period

4 years

Inducement Stock Option Plan And Agreement [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Description of vesting terms

In accordance with the terms of the Inducement Option Plan, the Company can issue an option to purchase up to 265,000 shares of the Companybs common stock at an exercise price equal to the fair market value of a share of the Companybs common stock on the date of grant of the option. The option, which will have a ten-year term, will vest at the rate of 25% of the shares on the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the option vesting each quarter thereafter so long as the participant has not been terminated.

Number of stock option outstanding, granted

265,000

Inducement Stock Option Plan And Agreement [Member] | Share-based Compensation Award, Tranche One [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percentage at the end of period

25.00%

Inducement Stock Option Plan And Agreement [Member] | Quarterly Vesting [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percentage at the end of period

6.25%

Inducement Restricted Stock Unit Plan and Agreement [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Shares available for grant

265,000

Description of vesting terms

In accordance with the terms of the Inducement RSU Plan, the Company can issue RSUs representing a total of 265,000 shares of the Companybs common stock (the RSUsb). The RSUs, which will expire following settlement, will vest at the rate of 25% of the shares on the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the RSU vesting each quarter thereafter so long as participant has not been terminated.

Inducement Restricted Stock Unit Plan and Agreement [Member] | Share-based Compensation Award, Tranche One [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percentage at the end of period

25.00%

Inducement Restricted Stock Unit Plan and Agreement [Member] | Quarterly Vesting [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percentage at the end of period

6.25%

2003 Stock and 2011 Imperva Stock Option and Incentive Plans [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Intrinsic value of options exercised

1,700,000

Market value of common stock

$42.70

$42.70

Compensation cost related to unvested stock-based awards granted, but not yet recognized

$108,800,000

$108,800,000

Nonvested awards, compensation cost not yet recognized, period for recognition

2 years 10 months 24 days

Stock_Plans_Summary_of_Option_

Stock Plans - Summary of Option Activity under Plans and Related Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Stock Options Outstanding, Beginning balance	2,244,363
Number of Stock Options Outstanding, Granted	452,791
Number of Stock Options Outstanding, Exercised or released	-73,005
Number of Stock Options Outstanding, Cancelled or forfeited	-90,004
Number of Stock Options Outstanding, Ending balance	2,534,145	2,244,363
Number of Shares, Vested and expected to vest	2,267,701
Number of Shares, Exercisable	729,987
Weighted Average Exercise Price, Outstanding- Beginning balance	$33.83
Weighted Average Exercise Price, Granted	$42.83
Weighted Average Exercise Price, Exercised or released	$22.16
Weighted Average Exercise Price, Cancelled or forfeited	$41.74
Weighted Average Exercise Price, Outstanding - Ending balance	$35.49	$33.83
Weighted-Average Exercise Price, Vested and expected to vest	$34.91
Weighted Average Exercise Price, Exercisable	$28
Weighted Average Remaining Contractual Life (in years)	8 years 4 months 2 days	8 years 3 months 7 days
Weighted Average Remaining Contractual Life (in years), Vested and expected to vest	8 years 3 months 7 days
Weighted Average Remaining Contractual Life (in years), Exercisable	6 years 8 months 23 days
Aggregate Intrinsic Value - Beginning balance	$38,457
Aggregate Intrinsic Value - Ending balance	25,400	38,457
Aggregate Intrinsic Value, Vested and expected to vest	23,883
Aggregate Intrinsic Value, Exercisable	$12,428

Stock_Plans_Summary_of_Option_1

Stock Plans - Summary of Option Activity under Plans and Related Information (Parenthetical) (Detail) (USD $)	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Closing stock price	$42.70

Stock_Plans_Summary_of_RSU_Act

Stock Plans - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	2,279,081
Number of Restricted Stock Units Outstanding, Granted	463,497
Number of Restricted Stock Units Outstanding, Granted, performance RSUs	249,220
Number of Restricted Stock Units Outstanding, Released	-224,739
Number of Restricted Stock Units Outstanding, Cancelled or expired	-208,578
Number of Restricted Stock Units Outstanding, Unvested - Ending Balance	2,558,481
Weighted-Average Grant Date Fair Value, Unvested - Beginning Balance	$39.07
Weighted-Average Grant Date Fair Value, Granted	$42.90
Weighted-Average Grant Date Fair Value, Granted, performance RSUs	$42.58
Weighted-Average Grant Date Fair Value, Released	$45.50
Weighted-Average Grant Date Fair Value, Cancelled or expired	$36.67
Weighted-Average Grant Date Fair Value, Unvested - Ending Balance	$39.74

Stock_Plans_StockBased_Compens

Stock Plans - Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$12,546	$6,666
Cost of revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	914	374
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,328	1,792
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,465	2,430
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$3,839	$2,070

Stock_Plans_Weighted_Average_A

Stock Plans - Weighted Average Assumptions for Fair Value of Stock Options Granted to Employees (Detail) (Stock options [Member])	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%
Risk-free interest rate	1.70%	1.80%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	50.00%	45.00%

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Loss - Changes in Balances of Accumulated Other Comprehensive Loss (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	($1,489)	[1]	($428)
Other comprehensive income (loss) before reclassifications	-406		3
Amounts reclassified to net loss	320		0
Other comprehensive income (loss)	-86		3
Ending Balance	-1,575		-425
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	-1,428		-426
Other comprehensive income (loss) before reclassifications	-450		0
Amounts reclassified to net loss	320		0
Other comprehensive income (loss)	-130		0
Ending Balance	-1,558		-426
Unrealized Gain (Loss) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	-61		-2
Other comprehensive income (loss) before reclassifications	44		3
Amounts reclassified to net loss	0		0
Other comprehensive income (loss)	44		3
Ending Balance	($17)		$1
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2014 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Loss - Summary of Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Current period unrealized gain (loss) on investments, Pre-Tax Amount	$44	$5
Unrealized gains (losses) on investments, net, Pre-Tax Amount	44
Current period unrealized gain (loss) on cash flow hedges, Pre-Tax Amount	-450
Reclassification adjustments on cash flow hedges, Pre-Tax Amount	320
Unrealized gains (losses) on cash flow hedges, net, Pre-Tax Amount	-130
Other comprehensive income (loss), Pre-Tax Amount	-86	5
Current period unrealized gain (loss) on investments, Tax Expense (Benefit)	0	2
Unrealized gains (losses) on investments, net, Tax Expense (Benefit)	0
Current period unrealized gain (loss) on cash flow hedges, Tax Expense (Benefit)	0
Reclassification adjustments on cash flow hedges, Tax Expense (Benefit)	0
Unrealized gains (losses) on cash flow hedges, net, Tax Expense (Benefit)	0
Other comprehensive income (loss), Tax Expense (Benefit)	0	2
Current period unrealized gain (loss) on investments, After-Tax Amount	44	3
Unrealized gains (losses) on investments, After-Tax Amount	44	3
Current period unrealized gain (loss) on cash flow hedges, After-Tax Amount	-450
Reclassification adjustments on cash flow hedges, After-Tax Amount	320
Unrealized gains (losses) on cash flow hedges, net, After-Tax Amount	-130	0
Other comprehensive income (loss)	($86)	$3

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$351	($371)

Segment_Information_Additional

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
	Segment
Segment Reporting [Abstract]
Number of operating segments	1

Segment_Information_Companys_N

Segment Information - Company's Net Services Revenue (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Total net services revenue	$27,653	$19,545
Maintenance and Support [Member]
Revenue from External Customer [Line Items]
Total net services revenue	15,048	12,663
Professional Services and Training [Member]
Revenue from External Customer [Line Items]
Total net services revenue	3,932	2,299
Subscriptions [Member]
Revenue from External Customer [Line Items]
Total net services revenue	$8,673	$4,583

Segment_Information_Companys_N1

Segment Information - Company's Net Revenue by Geographic Region, Based on Customer's Location (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$44,757	$31,516
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	26,557	18,076
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	12,202	8,210
APAC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$5,998	$5,230

Segment_Information_LongLived_

Segment Information - Long-Lived Assets by Location (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$16,769	$17,017
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	6,735	6,761
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	10,003	10,221
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$31	$35

Net_Loss_per_Share_Antidilutiv

Net Loss per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
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	2,534,145	2,113,995
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	2,558,481	1,694,129
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	215,121	286,125
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	355,499	354,678