Imperva 10-Q 9 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	May. 02, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Trading Symbol	IMPV
Entity Registrant Name	IMPERVA INC
Entity Central Index Key	1,364,962
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		32,261,081

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,595	$ 1,438
Preferred stock, par value, per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	32,259,601	31,837,144
Common stock, shares outstanding	32,259,601	31,837,144

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	[1]
CURRENT ASSETS:
Cash and cash equivalents	$ 158,691	$ 168,252
Short-term investments	100,054	96,555
Restricted cash	69	79
Accounts receivable, net of allowance of $1,595 and $ 1,438 as of March 31, 2016 and December 31, 2015, respectively	43,570	61,051
Inventory	860	815
Prepaid expenses and other current assets	9,476	7,965
Total current assets	312,720	334,717
Property and equipment, net	17,486	12,164
Goodwill	34,972	34,972
Acquired intangible assets, net	7,639	7,991
Severance pay fund	4,789	4,530
Restricted cash	1,665	1,665
Deferred tax assets	683	588
Other assets	1,157	1,042
TOTAL ASSETS	381,111	397,669
CURRENT LIABILITIES:
Accounts payable	7,772	6,870
Accrued compensation and benefits	17,195	20,259
Accrued and other current liabilities	6,462	14,283
Deferred revenue	82,119	79,132
Total current liabilities	113,548	120,544
Other liabilities	5,005	4,515
Deferred revenue	25,936	27,525
Accrued severance pay	5,454	4,884
TOTAL LIABILITIES	149,943	157,468
Commitments and Contingencies (Note 7)	0	0
STOCKHOLDERS' EQUITY:
Preferred stock, $0.0001 par value - 5,000,000 shares authorized, no shares issued and outstanding as of March 31, 2016 and December 31, 2015, respectively	0	0
Common stock, $0.0001 par value - 145,000,000 shares authorized, 32,259,601 and 31,837,144 shares issued and outstanding as of March 31, 2016 and December 31, 2015, respectively	3	3
Additional paid-in capital	461,958	448,069
Accumulated deficit	(230,547)	(206,540)
Accumulated other comprehensive loss	(246)	(1,331)
TOTAL STOCKHOLDERS' EQUITY	231,168	240,201
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 381,111	$ 397,669
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net revenue:
Products and license	$ 20,841	$ 17,104
Services	38,932	27,653
Total net revenue	59,773	44,757
Cost of revenue:
Products and license	2,184	1,998
Services	10,784	8,332
Total cost of revenue	12,968	10,330
Gross profit	46,805	34,427
Operating expenses:
Research and development	16,019	12,678
Sales and marketing	40,740	31,253
General and administrative	13,886	9,743
Amortization of acquired intangible assets	352	352
Total operating expenses	70,997	54,026
Loss from operations	(24,192)	(19,599)
Other income (expense), net	83	(80)
Loss before (benefit) provision for income taxes	(24,109)	(19,679)
(Benefit) provision for income taxes	(102)	351
Net loss	$ (24,007)	$ (20,030)
Net loss per share of common stock stockholders, basic and diluted	$ (0.75)	$ (0.74)
Shares used in computing net loss per share of common stock, basic and diluted	31,843	26,973

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (24,007)	$ (20,030)
Other comprehensive gain (loss) (net of tax):
Net change in net unrealized loss on investments	169	44
Net change in unrealized gain (loss) on hedging instruments	916	(130)
Other comprehensive income (loss)	1,085	(86)
Comprehensive loss	$ (22,922)	$ (20,116)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2014	$ 97,243		$ 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 (deficiencies) benefit from employee stock option exercises	43			43
Shares withheld for tax withholding on vesting of restricted stock units	(2,137)			(2,137)
Components of other comprehensive income (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
Beginning balance at Dec. 31, 2015	240,201	[1]	$ 3	448,069	(206,540)	(1,331)
Beginning balance, shares at Dec. 31, 2015			31,837,144
Issuance of common stock under employee equity plans, net of repurchases	590			590
Issuance of common stock under employee equity plans, net of repurchases, shares			215,958
Issuance of holdback shares in connection with acquisitions, shares			402,983
Stock-based compensation	15,655			15,655
Income tax (deficiencies) benefit from employee stock option exercises	(4)			(4)
Shares withheld for tax withholding on vesting of restricted stock units	(2,352)			(2,352)
Components of other comprehensive income (loss), net of tax
Change in unrealized gain (loss) on investments	169					169
Change in unrealized gain (loss) on derivatives	916					916
Net loss	(24,007)				(24,007)
Comprehensive loss	(22,922)
Ending balance at Mar. 31, 2016	$ 231,168		$ 3	$ 461,958	$ (230,547)	$ (246)
Ending balance, shares at Mar. 31, 2016			32,259,601
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (24,007)		$ (20,030)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	1,308		1,056
Stock-based compensation	15,655		12,546
Amortization of acquired intangibles	352		352
Amortization of premiums/accretion of discounts on short-term investments	136		92
Allowance for doubtful debts	157		65
Excess tax deficiencies (benefits) from share-based compensation	4		(43)
Other	(172)		114
Changes in operating assets and liabilities:
Accounts receivable, net	17,324		14,016
Inventory	(45)		(296)
Prepaid expenses and other assets	(809)		(515)
Accounts payable	(2,302)		(1,812)
Accrued compensation and benefits	(3,064)		(1,268)
Accrued and other liabilities	(169)		79
Severance pay (net)	311		(64)
Deferred revenue	1,398		2,508
Deferred tax assets	(95)		4
Net cash provided by operating activities	5,982		6,804
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales/maturities of short-term investments	22,909		18,168
Purchase of short-term investments	(26,285)		(22,843)
Net purchases of property and equipment	(3,426)		(991)
Change in restricted cash	10		(11)
Net cash used in investing activities	(6,792)		(5,677)
CASH FLOWS FROM FINANCING ACTIVITIES:
Settlement of holdback liability	(7,157)
Proceeds from follow-on public offering, net of offering costs			127,854
Proceeds from issuance of common stock, net of repurchases	590		1,618
Shares withheld for tax withholding on vesting of restricted stock units	(2,352)		(2,137)
Excess tax (deficiencies) benefits from share-based compensation	(4)		43
Net cash (used in) provided by financing activities	(8,923)		127,378
Effect of exchange rate changes on cash and cash equivalents	172		(115)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(9,561)		128,390
CASH AND CASH EQUIVALENTS - Beginning of period	168,252	[1]	68,096
CASH AND CASH EQUIVALENTS - End of period	158,691		196,486
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment incurred but not yet paid	$ 3,721		169
Vesting of restricted and early exercised stock options			$ 27
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 Summa

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2016
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, 2015, which was filed with the SEC on February 26, 2016 (the “Annual Report”). The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Reclassifications From time to time the Company reclassifies certain prior 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, 2016, the Company had one customer that represented 14% of the Company’s total revenue. The same customer represented 17% and 21% of gross accounts receivable as of March 31, 2016 and December 31, 2015 respectively. For the three months ended March 31, 2015, the Company did not have any customers that represented more than 10% of the Company’s total revenue. 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, 2015. Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) Issued ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The updated guidance changes how companies account for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The standard will be effective for the Company beginning January 1, 2017, with early application permitted. We are evaluating the impact of adopting this new accounting guidance on our consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 regarding ASC Topic 842 "Leases." The amendments in this guidance require balance sheet recognition of lease assets and lease liabilities by lessees for leases classified as operating leases, with an optional policy election to not recognize lease assets and lease liabilities for leases with a term of 12 months or less. The amendments also require new disclosures, including qualitative and quantitative requirements, providing additional information about the amounts recorded in the financial statements. The standard will be effective for the Company beginning January 1, 2019. The amendments require a modified retrospective approach with optional practical expedients. We are evaluating the impact of adopting this new accounting guidance on our consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09—Revenue (Topic 606): Revenue from Contracts with Customers. ASU No. 2014-09 will replace most existing U.S. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In July 2015, the FASB approved a one-year deferral of the effective date for the new revenue reporting standard for entities reporting under U.S. GAAP. In accordance with the deferral, this guidance will be effective for the Company beginning January 1, 2018 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. The Company is evaluating the impact of adopting this new accounting standard on its consolidated financial statements and has not selected a transition method.

Cash, Cash Equivalents, and Sho

Cash, Cash Equivalents, and Short-Term Investments	3 Months Ended
	Mar. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	2. 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, 2016 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 51,182 $ — $ — $ 51,182 Bank deposits 10,262 — — 10,262 Commercial paper 20,921 — 2 20,919 Money market funds 76,328 — — 76,328 Total $ 158,693 $ — $ 2 $ 158,691 Short-term investments: Commercial paper $ 11,548 $ — $ — $ 11,548 Corporate debt obligations 63,665 16 64 63,617 US government agencies 14,514 12 3 14,523 Bank deposits 10,366 — — 10,366 Total $ 100,093 $ 28 $ 67 $ 100,054 As of December 31, 2015 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 57,906 $ — $ — $ 57,906 Bank deposits 10,253 — — 10,253 Commercial paper 13,896 — 3 13,893 Money market funds 86,200 — — 86,200 Total $ 168,255 $ — $ 3 $ 168,252 Short-term investments: Corporate debt obligations $ 86,590 $ 2 $ 300 $ 86,292 Bank deposits 10,263 — — 10,263 Total $ 96,853 $ 2 $ 300 $ 96,555 The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of March 31, 2016 (in thousands): As of March 31, 2016 Estimated Amortized Fair Cost Value Short-term investments: Due within one year $ 66,464 $ 66,422 Due within two years 33,629 33,632 Total $ 100,093 $ 100,054 The gross unrealized loss related to these securities was due primarily to changes in interest rates. 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, 2016 and 2015, 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, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 11,548 $ — $ — $ — $ 11,548 $ — Corporate debt obligations 33,916 55 13,116 9 47,032 $ 64 US government agencies 3,999 3 3,999 3 $ 49,463 $ 58 $ 13,116 $ 9 $ 62,579 $ 67 As of December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt obligations $ 73,673 $ 286 $ 10,609 $ 14 $ 84,282 $ 300 $ 73,673 $ 286 $ 10,609 $ 14 $ 84,282 $ 300

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. 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, 2016. 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, 2016 and December 31, 2015, by level within the fair value hierarchy (in thousands): As of March 31, 2016 Level I Level II Level III Fair Financial Assets: Cash equivalents: Bank deposits $ — $ 10,262 $ — $ 10,262 Commercial paper — 20,919 — 20,919 Money market funds 76,328 — — 76,328 Short-term investments: Commercial paper and debt obligations — 11,548 — 11,548 Corporate debt obligations 63,617 63,617 US government agencies 14,523 14,523 Bank deposits — 10,366 — 10,366 Prepaid expenses and other current assets - Forward foreign exchange contracts — 817 — 817 Total financial assets $ 76,328 $ 132,052 $ — $ 208,380 As of December 31, 2015 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Bank deposits $ — $ 10,253 $ — $ 10,253 Commercial paper — 13,893 — 13,893 Money market funds 86,200 — — 86,200 Short-term investments: Corporate debt obligations — 86,292 — 86,292 Bank deposits — 10,263 — 10,263 Total financial assets $ 86,200 $ 120,701 $ — $ 206,901 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ — $ 595 $ — $ 595 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 $4.8 million and $4.5 million as of March 31, 2016 and December 31, 2015, respectively.

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments	4. 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 condensed consolidated balance sheets are presented in the following tables (in thousands): As of March 31, 2016 As of December 31, 2015 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in prepaid expenses and other current assets (accrued and other current liabilities) $ 38,988 $ 817 $ 47,231 $ (595 ) Gains (losses) on derivative instruments and their classification on the condensed consolidated statement of operations are presented in the following table (in thousands): For the three months ended March 31 2016 2015 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 1,316 $ — Losses recognized in OCI (a) $ (99 ) $ (450 ) Gains recognized from accumulated OCI into net loss (b) $ — $ — Losses recognized from accumulated OCI into net loss (b) $ (194 ) $ (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 $13 and $181 were recognized within cost of sales and operating expenses, respectively, for the three months ended March 31, 2016 and $32 and $288 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, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Acquired Intangible Assets	5. Acquired Intangible Assets The Company amortizes intangible assets, which consist of purchased technologies that have estimated useful lives ranging from 7 to 10 years, using the straight-line method when the consumption pattern of the asset is not apparent. The Company reviews such assets 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, 2016 and 2015. The weighted average remaining useful life of the Company’s acquired technology intangible assets is 6 years as of March 31, 2016. Acquired technology intangible assets subject to amortization are presented as follows (in thousands): As of March As of December Acquired Technology $ 10,668 $ 10,668 Less: accumulated amortization (3,029 ) (2,677 ) Total acquired technology, net $ 7,639 $ 7,991 Acquired intangible assets are amortized over their estimated useful lives of seven to ten years. As of March 31, 2016, the amortization expense in future periods is expected to be as follows (in thousands): Acquired Fiscal Year Technology 2016 $ 1,056 2017 1,408 2018 1,408 2019 1,408 2020 1,408 Thereafter 951 Total expected amortization expense $ 7,639

Revolving Credit Facility

Revolving Credit Facility	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Revolving Credit Facility	6. Revolving Credit Facility In September 2010, the Company entered into a revolving credit facility with a financial institution. The credit facility agreement, as amended, provides for borrowing capacity up to $7.5 million. The credit facility expires on April 1, 2019. As of March 31, 2016 and December 31, 2015, 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, standby letter of credit fees of 1% per annum of the stated amount of each letter of credit and bears interest at LIBOR plus 2.75%. As of March 31, 2016, the Company was compliant with the amended covenant of the credit facility.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies (a) Operating Leases The Company rents its facilities under operating leases with lease periods expiring through 2022. 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, 2016 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2016 $ 5,214 $ 686 2017 7,221 — 2018 7,524 — 2019 4,603 — 2020 4,222 — Thereafter 124 — Total $ 28,908 $ 686 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, 2016 and 2015 was $1.5 million and $1.0 million, respectively. In connection with leases of office space, the Company has received tenant improvement allowances 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. For the three months ending March 31, 2016 and 2015, the Company did not receive any tenant improvement allowances. 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, 2016 and December 31, 2015 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 cancelable operating lease agreements. The Company has an option to cancel the lease agreements, which may result in penalties in a maximum amount of $0.1 million as of March 31, 2016. Motor vehicle lease expenses for the three months ended March 31, 2016 and 2015 were $0.7 million and $0.6 million, respectively. (c) Purchase Commitments As of March 31, 2016 and December 31, 2015, the Company had purchase commitments of $6.1 million and $5.8 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 us and certain of our current and former 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 named us and certain of our current and former officers and purported to bring suit on behalf of those investors who purchased our publicly traded securities between May 2, 2013 and April 9, 2014. The plaintiff alleged that defendants made false and misleading statements about our operations and business and financial results and purported to assert claims for violations of the federal securities laws. The amended complaint sought 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. On September 17, 2015, the Court granted defendants’ motion to dismiss with leave to amend. The lead plaintiff filed an amended complaint on January 13, 2016, again naming the same current and former officers, alleging false and misleading statements about our operations and business and financial results, and seeking the same relief. On February 10, 2016, defendants filed a motion to dismiss the amended complaint. That motion is pending. On June 27, 2014, a purported shareholder derivative lawsuit was filed in the Court of Chancery for the State of Delaware against us (as a nominal defendant), and naming certain of our 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 us, corporate reforms, the recovery of plaintiffs’ attorney’s fees and other relief. On September 23, 2014, we 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. On September 2, 2015, the Court granted the motion to dismiss with prejudice. Plaintiffs filed a notice of appeal with the Supreme Court of Delaware on October 1, 2015. Following briefing and oral argument, the Supreme Court of Delaware issued an order on March 11, 2016, affirming the Court of Chancery’s decision dismissing the case with prejudice. In addition, we have 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 ourselves, our channel partners and our customers by determining the scope, enforceability and validity of third-party proprietary rights or to establish our 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, 2016 and December 31, 2015. 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 the Company 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 condensed 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, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Plans	8. Stock Plans (a) 2003 Stock Plan During 2003, the Board of Directors adopted the 2003 Stock Plan (the “2003 Plan”), which allowed for the grant 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. In connection with the Company’s initial public offering, which was completed in November 2011, the Board of Directors determined not to grant any further awards under the 2003 Plan upon completion of the public offering. The 2011 Stock Option and Incentive Plan (the “2011 Plan”) replaced the 2003 Plan in November 2011. Under the 2003 Plan, incentive stock options could have been 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 could have been 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 granted an option, the optionee directly or by attribution owned stock possessing more than 10% of the total combined voting power of all classes of stock of the Company, the option price had to have been at least 110% of the fair value. Options granted under the 2003 Plan generally expire no later than ten years from the date of grant 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 replaced the 2003 Plan and the Company no longer grants awards under the 2003 Plan. The Company initially reserved a total of 1,000,000 shares of common stock for issuance under the 2011 Plan. In addition, 955,568 reserved but unissued shares under the 2003 Stock Plan were added to the number of shares reserved for issuance under the 2011 Plan. The 2011 Plan also provided that the number of shares reserved and available for issuance under the plan would 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 last automatic increase occurred on January 1, 2015. 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 100% of the fair market value of the common stock on the date of grant. Options granted pursuant to the 2011 Plan generally expire no later than ten years from the date of grant. 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 RSUs 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 November 8, 2011, the effective date of the registration statement for the Company’s initial public offering. 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 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 increases 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, 2016, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 318,371 shares. (d) Inducement Stock Option Plan and Agreement and Inducement Restricted Stock Unit Plan and Agreement In August 2014 and August 2015, the Compensation Committee of the Board of Directors adopted an Inducement Stock Option Plan and Agreement (the “Inducement Option Plan”) and an Inducement Restricted Stock Unit Plan and Agreement (the “Inducement RSU Plan”), in each case created as employment inducement awards. In accordance with the terms of the Inducement Option Plans, the Company issued options to purchase up to 290,000 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 dates of grant of the options. The options, which will have a ten-year term, will vest at the rate of 25% of the shares on each of 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 Plans, the Company issued RSUs representing a total of 290,000 shares of the Company’s common stock. The RSUs, which will expire following settlement, will vest at the rate of 25% of the shares on each of 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 the participant has not been terminated. (e) 2015 Equity Inducement Plan In October 2015, the Board of Directors adopted the 2015 Equity Inducement Plan, a non-stockholder approved plan that provides for the granting of stock options and RSUs as employment inducement awards and in connection with acquisitions, subject to compliance with applicable securities laws and stock exchange requirements for such plans. The Company has reserved 100,000 shares of common stock for issuance under the 2015 Equity Inducement Plan. No awards have been made under the 2015 Equity Inducement Plan and the entire reserve remains available for grant. Under the terms of the 2015 Equity Inducement Plan, the exercise price of stock options may not be less than 100% of the fair market value of common stock on the date of grant and generally expire no later than ten years from the date of grant. (f) 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 was able to grant to its employees and service providers options to purchase shares of its common stock, restricted shares, or RSUs. As of November 2013, the total number of shares of common stock that could have been granted under the Incapsula Plan was not to exceed 10,263,211 shares 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 performance-based RSUs for Company Common Stock to be issued to continuing employees of Incapsula. The Incapsula RSUs were earned upon Incapsula’s achievement of revenue targets for Incapsula and Incapsula-related products and services for fiscal year 2014 and were converted into approximately 198,825 shares of Company Common Stock at the same exchange ratio applicable to the shares of Incapsula common stock acquired in the acquisition. In addition to performance conditions, the awards were dependent on the market price of Imperva’s common stock during February 2014, which was deemed a market condition under ASC 718. The outstanding options and RSUs under the Incapsula 2010 Stock 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 Stock Incentive Plan. Option Activity The following table summarizes option activity under the Plans and related information: Options Outstanding Weighted- Average Remaining Number of Shares Weighted Average Exercis e Contractual Term (in years) Aggregate Intrinsic Value (i n Balances - January 1, 2016 1,949,089 $ 39.27 8.09 $ 47,480 Granted 48,260 $ 53.59 Exercised or released (19,474 ) $ 30.29 Cancelled or forfeited (41,422 ) $ 43.68 Balances - March 31, 2016 1,936,453 $ 39.62 7.86 $ 25,732 Vested and expected to vest - March 31, 2016 1,729,309 $ 38.72 7.78 $ 24,226 Exercisable - March 31, 2016 784,409 $ 32.48 6.94 $ 14,863 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $50.50 of the Company’s common stock on March 31, 2016. RSU Activity The following table summarizes RSU activity under the Plans and related information: Number of Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - January 1, 2016 1,898,025 $ 49.53 Granted 704,760 $ 51.32 Granted, performance RSUs 273,900 $ 51.55 Released (261,627 ) $ 41.73 Cancelled or expired (61,460 ) $ 47.19 Unvested - March 31, 2016 2,553,598 $ 51.09 The aggregate intrinsic value of options exercised under the Plans was $0.3 million for the three months ended March 31, 2016. 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 of March 31, 2016, total compensation cost related to unvested stock-based awards granted to employees under the Plans, but not yet recognized, was $115.8 million, net of estimated forfeitures. As of March 31, 2016, this cost will be amortized to expense over a weighted-average remaining period of 2.7 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 expense during the three months ended March 31, 2016 and 2015. Recognized stock-based compensation tax deficiencies (benefits) during the three months ended March 31, 2016 and 2015 was $4,000 and ($43,000), respectively. (g) 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 condensed consolidated statements of operations as follows (in thousands): For the three months ended March 31 2016 2015 Cost of revenue $ 1,393 $ 914 Research and development 4,249 3,328 Sales and marketing 5,094 4,465 General and administrative 4,919 3,839 Total stock-based compensation expense $ 15,655 $ 12,546 The fair value of stock option grants for the three months ended March 31, 2016 and 2015 was estimated using the following weighted average assumptions: For the three months ended March 31 2016 2015 Stock option grants: Dividend rate 0 % 0 % Risk-free interest rate 1.5 % 1.7 % Expected term (in years) 6.1 6.1 Expected volatility 58 % 50 % 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. (h) Common Stock Subject to Repurchase 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. 236,537 shares were fully vested as of March 31, 2016. (i) 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 Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Accumulated Other Comprehensive Loss	9. 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 March 31, 2016 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,021 ) $ (310 ) $ (1,331 ) Other comprehensive income (loss) before reclassifications 722 169 891 Amounts reclassified to net loss 194 — 194 Change in other comprehensive income (loss) 916 169 1,085 Balance at March 31 $ (105 ) $ (141 ) $ (246 ) For the three months ended March 31, 2015 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total 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 ) The following is a summary of reclassifications out of accumulated other comprehensive loss for the three months ended March 31, 2016 and 2015 (in thousands): For the three months ended March 31, 2016 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ 1,217 (495 ) $ 722 Reclassification adjustments 1 194 — 194 Unrealized gains (losses) on cash flow hedges, net 1,411 (495 ) 916 Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ 260 (91 ) 169 Unrealized gains (losses) on investments: 260 (91 ) 169 Other comprehensive income (loss) $ 1,671 $ (586 ) $ 1,085 For the three months ended March 31, 2015 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount 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 ) Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ 44 — 44 Unrealized gains (losses) on investments: 44 — 44 Other comprehensive income (loss) $ (86 ) $ — $ (86 ) 1 Refer to note 4 for the affected line items in the condensed consolidated statement of operations.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	10. 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, 2016 and 2015, the Company recorded income tax benefit of $0.1 million and an income tax expense $0.4 million respectively. The income tax benefit for the three months ended March 31, 2016 was primarily attributable to an intraperiod tax expense allocation related to unrealized gains reported in other comprehensive income, offset in part, by foreign and state income taxes. The income tax expense for the three months ended March 31, 2015 was primarily attributable to foreign and state income taxes. 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 domestic deferred tax assets.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Segment Information	11. 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 revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands): For the three months ended March 31, 2016 2015 Americas $ 34,802 $ 26,557 EMEA 14,749 12,202 APAC 10,222 5,998 Total net revenue $ 59,773 $ 44,757 The following table presents long-lived assets by location (in thousands): As of March 31, As of December 31, 2016 2015 United States $ 14,725 $ 9,913 Israel 10,386 10,224 Other 14 18 Total long-lived assets $ 25,125 $ 20,155

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Net Loss per Share	12. 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, 2016 2015 Stock options to purchase common stock 1,936,453 2,534,145 Restricted stock units for common stock 2,553,598 2,558,481 Restricted shares of common stock subject to repurchase — 215,121 Restricted stock issued in connection with Skyfence acquisition 219,969 355,499

Basis of Presentation and Sum20

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2016
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, 2015, which was filed with the SEC on February 26, 2016 (the “Annual Report”). The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications From time to time the Company reclassifies certain prior 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, 2016, the Company had one customer that represented 14% of the Company’s total revenue. The same customer represented 17% and 21% of gross accounts receivable as of March 31, 2016 and December 31, 2015 respectively. For the three months ended March 31, 2015, the Company did not have any customers that represented more than 10% of the Company’s total revenue.
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, 2015.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) Issued ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The updated guidance changes how companies account for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The standard will be effective for the Company beginning January 1, 2017, with early application permitted. We are evaluating the impact of adopting this new accounting guidance on our consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 regarding ASC Topic 842 "Leases." The amendments in this guidance require balance sheet recognition of lease assets and lease liabilities by lessees for leases classified as operating leases, with an optional policy election to not recognize lease assets and lease liabilities for leases with a term of 12 months or less. The amendments also require new disclosures, including qualitative and quantitative requirements, providing additional information about the amounts recorded in the financial statements. The standard will be effective for the Company beginning January 1, 2019. The amendments require a modified retrospective approach with optional practical expedients. We are evaluating the impact of adopting this new accounting guidance on our consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09—Revenue (Topic 606): Revenue from Contracts with Customers. ASU No. 2014-09 will replace most existing U.S. GAAP guidance on this topic. The new revenue recognition standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. In July 2015, the FASB approved a one-year deferral of the effective date for the new revenue reporting standard for entities reporting under U.S. GAAP. In accordance with the deferral, this guidance will be effective for the Company beginning January 1, 2018 and can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. Early adoption is permitted beginning January 1, 2017. The Company is evaluating the impact of adopting this new accounting standard on its consolidated financial statements and has not selected a transition method.

Cash, Cash Equivalents, and S21

Cash, Cash Equivalents, and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2016
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, 2016 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 51,182 $ — $ — $ 51,182 Bank deposits 10,262 — — 10,262 Commercial paper 20,921 — 2 20,919 Money market funds 76,328 — — 76,328 Total $ 158,693 $ — $ 2 $ 158,691 Short-term investments: Commercial paper $ 11,548 $ — $ — $ 11,548 Corporate debt obligations 63,665 16 64 63,617 US government agencies 14,514 12 3 14,523 Bank deposits 10,366 — — 10,366 Total $ 100,093 $ 28 $ 67 $ 100,054 As of December 31, 2015 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 57,906 $ — $ — $ 57,906 Bank deposits 10,253 — — 10,253 Commercial paper 13,896 — 3 13,893 Money market funds 86,200 — — 86,200 Total $ 168,255 $ — $ 3 $ 168,252 Short-term investments: Corporate debt obligations $ 86,590 $ 2 $ 300 $ 86,292 Bank deposits 10,263 — — 10,263 Total $ 96,853 $ 2 $ 300 $ 96,555
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, 2016 (in thousands): As of March 31, 2016 Estimated Amortized Fair Cost Value Short-term investments: Due within one year $ 66,464 $ 66,422 Due within two years 33,629 33,632 Total $ 100,093 $ 100,054
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, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 11,548 $ — $ — $ — $ 11,548 $ — Corporate debt obligations 33,916 55 13,116 9 47,032 $ 64 US government agencies 3,999 3 3,999 3 $ 49,463 $ 58 $ 13,116 $ 9 $ 62,579 $ 67 As of December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt obligations $ 73,673 $ 286 $ 10,609 $ 14 $ 84,282 $ 300 $ 73,673 $ 286 $ 10,609 $ 14 $ 84,282 $ 300

Fair Value of Financial Instr22

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2016
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, 2016 and December 31, 2015, by level within the fair value hierarchy (in thousands): As of March 31, 2016 Level I Level II Level III Fair Financial Assets: Cash equivalents: Bank deposits $ — $ 10,262 $ — $ 10,262 Commercial paper — 20,919 — 20,919 Money market funds 76,328 — — 76,328 Short-term investments: Commercial paper and debt obligations — 11,548 — 11,548 Corporate debt obligations 63,617 63,617 US government agencies 14,523 14,523 Bank deposits — 10,366 — 10,366 Prepaid expenses and other current assets - Forward foreign exchange contracts — 817 — 817 Total financial assets $ 76,328 $ 132,052 $ — $ 208,380 As of December 31, 2015 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Bank deposits $ — $ 10,253 $ — $ 10,253 Commercial paper — 13,893 — 13,893 Money market funds 86,200 — — 86,200 Short-term investments: Corporate debt obligations — 86,292 — 86,292 Bank deposits — 10,263 — 10,263 Total financial assets $ 86,200 $ 120,701 $ — $ 206,901 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ — $ 595 $ — $ 595

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments Measured at Fair Value and Classification on Condensed Consolidated Balance Sheets	Derivative instruments measured at fair value and their classification on the condensed consolidated balance sheets are presented in the following tables (in thousands): As of March 31, 2016 As of December 31, 2015 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in prepaid expenses and other current assets (accrued and other current liabilities) $ 38,988 $ 817 $ 47,231 $ (595 )
Gains (Losses) on Derivative Instruments and Classification on Condensed 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): For the three months ended March 31 2016 2015 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 1,316 $ — Losses recognized in OCI (a) $ (99 ) $ (450 ) Gains recognized from accumulated OCI into net loss (b) $ — $ — Losses recognized from accumulated OCI into net loss (b) $ (194 ) $ (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 $13 and $181 were recognized within cost of sales and operating expenses, respectively, for the three months ended March 31, 2016 and $32 and $288 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, 2016
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 As of December Acquired Technology $ 10,668 $ 10,668 Less: accumulated amortization (3,029 ) (2,677 ) Total acquired technology, net $ 7,639 $ 7,991
Schedule of Expected Amortization Expense in Future Periods	Acquired intangible assets are amortized over their estimated useful lives of seven to ten years. As of March 31, 2016, the amortization expense in future periods is expected to be as follows (in thousands): Acquired Fiscal Year Technology 2016 $ 1,056 2017 1,408 2018 1,408 2019 1,408 2020 1,408 Thereafter 951 Total expected amortization expense $ 7,639

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Payments Under Operating Leases	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, 2016 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2016 $ 5,214 $ 686 2017 7,221 — 2018 7,524 — 2019 4,603 — 2020 4,222 — Thereafter 124 — Total $ 28,908 $ 686

Stock Plans (Tables)

Stock Plans (Tables)	3 Months Ended
	Mar. 31, 2016
Disclosure Of Compensation Related Costs Sharebased 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 Weighted- Average Remaining Number of Shares Weighted Average Exercis e Contractual Term (in years) Aggregate Intrinsic Value (i n Balances - January 1, 2016 1,949,089 $ 39.27 8.09 $ 47,480 Granted 48,260 $ 53.59 Exercised or released (19,474 ) $ 30.29 Cancelled or forfeited (41,422 ) $ 43.68 Balances - March 31, 2016 1,936,453 $ 39.62 7.86 $ 25,732 Vested and expected to vest - March 31, 2016 1,729,309 $ 38.72 7.78 $ 24,226 Exercisable - March 31, 2016 784,409 $ 32.48 6.94 $ 14,863 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $50.50 of the Company’s common stock on March 31, 2016.
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 Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - January 1, 2016 1,898,025 $ 49.53 Granted 704,760 $ 51.32 Granted, performance RSUs 273,900 $ 51.55 Released (261,627 ) $ 41.73 Cancelled or expired (61,460 ) $ 47.19 Unvested - March 31, 2016 2,553,598 $ 51.09
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 condensed consolidated statements of operations as follows (in thousands): For the three months ended March 31 2016 2015 Cost of revenue $ 1,393 $ 914 Research and development 4,249 3,328 Sales and marketing 5,094 4,465 General and administrative 4,919 3,839 Total stock-based compensation expense $ 15,655 $ 12,546
Weighted Average Assumptions for Fair Value of Stock Options Grants	The fair value of stock option grants for the three months ended March 31, 2016 and 2015 was estimated using the following weighted average assumptions: For the three months ended March 31 2016 2015 Stock option grants: Dividend rate 0 % 0 % Risk-free interest rate 1.5 % 1.7 % Expected term (in years) 6.1 6.1 Expected volatility 58 % 50 %

Accumulated Other Comprehensi27

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Mar. 31, 2016
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 March 31, 2016 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,021 ) $ (310 ) $ (1,331 ) Other comprehensive income (loss) before reclassifications 722 169 891 Amounts reclassified to net loss 194 — 194 Change in other comprehensive income (loss) 916 169 1,085 Balance at March 31 $ (105 ) $ (141 ) $ (246 ) For the three months ended March 31, 2015 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total 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 )
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, 2016 and 2015 (in thousands): For the three months ended March 31, 2016 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ 1,217 (495 ) $ 722 Reclassification adjustments 1 194 — 194 Unrealized gains (losses) on cash flow hedges, net 1,411 (495 ) 916 Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ 260 (91 ) 169 Unrealized gains (losses) on investments: 260 (91 ) 169 Other comprehensive income (loss) $ 1,671 $ (586 ) $ 1,085 For the three months ended March 31, 2015 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount 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 ) Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ 44 — 44 Unrealized gains (losses) on investments: 44 — 44 Other comprehensive income (loss) $ (86 ) $ — $ (86 ) 1 Refer to note 4 for the affected line items in the condensed consolidated statement of operations.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Company's 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, 2016 2015 Americas $ 34,802 $ 26,557 EMEA 14,749 12,202 APAC 10,222 5,998 Total net revenue $ 59,773 $ 44,757
Long-Lived Assets by Location	The following table presents long-lived assets by location (in thousands): As of March 31, As of December 31, 2016 2015 United States $ 14,725 $ 9,913 Israel 10,386 10,224 Other 14 18 Total long-lived assets $ 25,125 $ 20,155

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2016
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, 2016 2015 Stock options to purchase common stock 1,936,453 2,534,145 Restricted stock units for common stock 2,553,598 2,558,481 Restricted shares of common stock subject to repurchase — 215,121 Restricted stock issued in connection with Skyfence acquisition 219,969 355,499

Basis of Presentation and Sum30

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - Customer	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Number of customers representing 17% or more of gross accounts receivable	1
Number of customers representing 21% or more of gross accounts receivable			1
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	14.00%
Number of customers representing 10% or more of revenue		0
Accounts Receivable | Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers	17.00%		21.00%

Cash, Cash Equivalents, and S31

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 158,693	$ 168,255
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	3
Cash and cash equivalents, Fair Value	158,691	168,252
Short-term investments, Amortized Cost	100,093	96,853
Short-term investments, Gross Unrealized Gains	28	2
Short-term investments, Gross Unrealized Losses	67	300
Short-term investments, Estimated Fair Value	100,054	96,555	[1]
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	51,182	57,906
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	51,182	57,906
Bank Deposits [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	10,262	10,253
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	10,262	10,253
Short-term investments, Amortized Cost	10,366	10,263
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,366	10,263
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	20,921	13,896
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	2	3
Cash and cash equivalents, Fair Value	20,919	13,893
Short-term investments, Amortized Cost	11,548
Short-term investments, Gross Unrealized Gains	0
Short-term investments, Gross Unrealized Losses	0
Short-term investments, Estimated Fair Value	11,548
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	76,328	86,200
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	76,328	86,200
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	63,665	86,590
Short-term investments, Gross Unrealized Gains	16	2
Short-term investments, Gross Unrealized Losses	64	300
Short-term investments, Estimated Fair Value	63,617	$ 86,292
US Government Agencies [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	14,514
Short-term investments, Gross Unrealized Gains	12
Short-term investments, Gross Unrealized Losses	3
Short-term investments, Estimated Fair Value	$ 14,523
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 S32

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Short Term Investments [Abstract]
Amortized Cost of short-term investments, Due within one year	$ 66,464
Amortized Cost of short-term investments, Due within two years	33,629
Short-term investments, Amortized Cost	100,093	$ 96,853
Estimated fair value of short-term investments, Due within one year	66,422
Estimated fair value of short-term investments, Due within two years	33,632
Short-term investments, Estimated Fair Value	$ 100,054	$ 96,555	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 S33

Cash, Cash Equivalents, and Short-Term Investments - Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 49,463	$ 73,673
Less than 12 Months, Unrealized Losses	58	286
12 Months or Greater, Fair Value	13,116	10,609
12 Months or Greater, Unrealized Losses	9	14
Total, Fair Value	62,579	84,282
Total, Unrealized Losses	67	300
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	11,548
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	0
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	11,548
Total, Unrealized Losses	0
Corporate Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	33,916	73,673
Less than 12 Months, Unrealized Losses	55	286
12 Months or Greater, Fair Value	13,116	10,609
12 Months or Greater, Unrealized Losses	9	14
Total, Fair Value	47,032	84,282
Total, Unrealized Losses	64	$ 300
US Government Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 Months, Fair Value	3,999
Less than 12 Months, Unrealized Losses	3
12 Months or Greater, Fair Value	0
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	3,999
Total, Unrealized Losses	$ 3

Fair Value of Financial Instr34

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value transfers between level 1 to level 2	$ 0
Fair value transfers between level 2 to level 1	0
Fair value transfers into level 3	0
Fair value transfers out of level 3	0
Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Severance pay assets	$ 4,800,000	$ 4,500,000

Fair Value of Financial Instr35

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 158,691	$ 168,252
Short-term investments	100,054	96,555	[1]
Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	10,262	10,253
Short-term investments	10,366	10,263
Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	20,919	13,893
Short-term investments	11,548
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	76,328	86,200
Corporate Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	63,617	86,292
US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	14,523
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	208,380	206,901
Fair Value, Measurements, Recurring [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	76,328	86,200
Fair Value, Measurements, Recurring [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	132,052	120,701
Fair Value, Measurements, Recurring [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	0	0
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	10,262	10,253
Short-term investments	10,366	10,263
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	10,262	10,253
Short-term investments	10,366	10,263
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	20,919	13,893
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	20,919	13,893
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	76,328	86,200
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	76,328	86,200
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Commercial Paper And Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	11,548
Fair Value, Measurements, Recurring [Member] | Commercial Paper And Debt Obligations [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0
Fair Value, Measurements, Recurring [Member] | Commercial Paper And Debt Obligations [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	11,548
Fair Value, Measurements, Recurring [Member] | Commercial Paper And Debt Obligations [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	63,617	86,292
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	63,617	86,292
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	14,523
Fair Value, Measurements, Recurring [Member] | US Government Agencies [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0
Fair Value, Measurements, Recurring [Member] | US Government Agencies [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	14,523
Fair Value, Measurements, Recurring [Member] | US Government Agencies [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0
Forward Foreign Exchange Contracts [Member] | Prepaid Expenses and Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	817
Forward Foreign Exchange Contracts [Member] | Prepaid Expenses and Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	0
Forward Foreign Exchange Contracts [Member] | Prepaid Expenses and Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	817
Forward Foreign Exchange Contracts [Member] | Prepaid Expenses and Other Current Assets [Member] | Fair Value, Measurements, Recurring [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	$ 0
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		595
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		0
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		595
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		$ 0
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 - Additi

Derivative Instruments - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Forward foreign exchange contracts maturity	12 months

Derivative Instruments - Deriva

Derivative Instruments - Derivative Instruments Measured at Fair Value and Classification on Condensed Consolidated Balance Sheets (Detail) - Forward Foreign Exchange Contracts [Member] - Designated As Hedging Instrument [Member] - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$ 38,988,000
Derivative Fair Value	$ 817,000
Accrued and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount		$ 47,231,000
Derivative Fair Value		$ (595,000)

Derivative Instruments - Gains

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Condensed Consolidated Statement of Operations (Detail) - Designated As Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivatives, Fair Value [Line Items]
Gains recognized in OCI	$ 1,316	$ 0
Losses recognized in OCI	(99)	(450)
Gains recognized from accumulated OCI into net loss		0
Losses recognized from accumulated OCI into net loss	$ (194)	$ (320)

Derivative Instruments - Gain39

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Condensed Consolidated Statement of Operations (Parenthetical) (Detail) - Designated As Hedging Instrument [Member] - Unrealized Gain (Loss) on Cash Flow Hedges [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cost of revenues [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ 13	$ 32
Operating Expenses [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ 181	$ 288

Acquired Intangible Assets - Ad

Acquired Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 0	$ 0
Weighted average remaining useful life	6 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

Acquired Intangible Assets - Su

Acquired Intangible Assets - Summary of Acquired Technology Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Intangible Assets Net Excluding Goodwill [Abstract]
Acquired Technology	$ 10,668	$ 10,668
Less: accumulated amortization	(3,029)	(2,677)
Total acquired technology, net	$ 7,639	$ 7,991	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 - Sc

Acquired Intangible Assets - Schedule of Expected Amortization Expense in Future Periods (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	[1]
Finite-Lived Intangible Assets [Line Items]
Total acquired technology, net	$ 7,639	$ 7,991
Purchased Technology [Member]
Finite-Lived Intangible Assets [Line Items]
2,016	1,056
2,017	1,408
2,018	1,408
2,019	1,408
2,020	1,408
Thereafter	951
Total acquired technology, net	$ 7,639
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 - Add

Revolving Credit Facility - Additional Information (Detail) - Revolving Credit Facility [Member] - London Interbank Offered Rate (LIBOR) [Member] - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 7,500,000
Credit facility expiration date	Apr. 1, 2019
Outstanding credit facility	$ 0	$ 0
Minimum cash and cash equivalents	$ 3,000,000
Percentage in payment of unused line fee	0.25%
Stand by letter of credit fees	1.00%
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 -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Loss Contingencies [Line Items]
Operating lease expiration year	2,022
Rent expense	$ 1,500,000	$ 1,000,000
Tenant improvement allowances	0	0
Restricted cash	1,665,000		$ 1,665,000	[1]
Purchase commitments	$ 6,100,000		5,800,000
Period of purchase commitment of inventory from specified date	9 months
Loss contingency accrual	$ 0		$ 0
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Motor vehicle lease expenses	700,000	$ 600,000
Maximum [Member] | Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	$ 100,000
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 Contingencies45

Commitments and Contingencies - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) $ in Thousands	Mar. 31, 2016USD ($)
Operating Leases
2,016	$ 5,214
2,017	7,221
2,018	7,524
2,019	4,603
2,020	4,222
Thereafter	124
Total	28,908
Estimated Sublease Income
2,016	686
2,017	0
2,018	0
2,019	0
2,020	0
Thereafter	0
Total	$ 686

Stock Plans - Additional Inform

Stock Plans - Additional Information (Detail)	Jan. 01, 2016shares	Oct. 31, 2015shares	Aug. 31, 2014shares	Nov. 30, 2013shares	Jan. 31, 2012	Sep. 30, 2011Periodshares	Mar. 31, 2016USD ($)$ / sharesshares	Mar. 31, 2015USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option outstanding, granted							48,260
Performance-based restricted stock units granted							704,760
Capitalized stock-based compensation expense | $							$ 0	$ 0
Recognized stock-based compensation tax deficiencies (benefits) | $							4,000	(43,000)
Aggregate net proceeds from sale of common stock, net of underwriting discounts, commissions and offering costs | $							$ 590,000	$ 1,618,000
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 | $ / shares								$ 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]
Nonvested awards, compensation cost not yet recognized, period for recognition							4 years
Business acquisition purchase price, shares issued							532,262
Closing price of stock | $ / shares							$ 59.08
Common stock, shares vested							236,537
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
Outstanding Options and RSUs [Member] | Incapsula [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issuable, as-converted to common stock-basis							247,184
2003 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in reserve share						955,568
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] | 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
2003 Stock Plan [Member] | Greater 10% Ownership [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							110.00%
Minimum percentage of combined voting power							10.00%
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%
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 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, 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 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 in reserve share	318,371
Increase percentage of common stock outstanding					1.00%
Program effective date						Nov. 8, 2011
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 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 | Period						5
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 Plans, the Company issued options to purchase up to 290,000 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 dates of grant of the options. The options, which will have a ten-year term, will vest at the rate of 25% of the shares on each of 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			290,000
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]
Description of vesting terms							In accordance with the terms of the Inducement RSU Plans, the Company issued RSUs representing a total of 290,000 shares of the Company’s common stock. The RSUs, which will expire following settlement, will vest at the rate of 25% of the shares on each of 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 the participant has not been terminated.
Shares available for grant			290,000
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%
2015 Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserve of common stock for future issuance		100,000
2015 Equity Inducement 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
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				10,263,211
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 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 | $							$ 300,000
Compensation cost related to unvested stock-based awards granted, but not yet recognized | $							$ 115,800,000
Nonvested awards, compensation cost not yet recognized, period for recognition							2 years 8 months 12 days

Stock Plans - Summary of Option

Stock Plans - Summary of Option Activity under Plans and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options Outstanding, Beginning balance	1,949,089
Number of Stock Options Outstanding, Granted	48,260
Number of Stock Options Outstanding, Exercised or released	(19,474)
Number of Stock Options Outstanding, Cancelled or forfeited	(41,422)
Number of Stock Options Outstanding, Ending balance	1,936,453	1,949,089
Number of Shares, Vested and expected to vest	1,729,309
Number of Shares, Exercisable	784,409
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.62	$ 39.27
Weighted Average Exercise Price, Granted	53.59
Weighted Average Exercise Price, Exercised or released	30.29
Weighted Average Exercise Price, Cancelled or forfeited	43.68
Weighted-Average Exercise Price, Vested and expected to vest	38.72
Weighted Average Exercise Price, Exercisable	$ 32.48
Weighted Average Remaining Contractual Term (in years)	7 years 10 months 10 days	8 years 1 month 2 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	7 years 9 months 11 days
Weighted Average Remaining Contractual Term (in years), Exercisable	6 years 11 months 9 days
Aggregate Intrinsic Value	$ 25,732	$ 47,480
Aggregate Intrinsic Value, Vested and expected to vest	24,226
Aggregate Intrinsic Value, Exercisable	$ 14,863

Stock Plans - Summary of Opti48

Stock Plans - Summary of Option Activity under Plans and Related Information (Parenthetical) (Detail)	Mar. 31, 2016$ / shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Closing stock price	$ 50.50

Stock Plans - Summary of RSU Ac

Stock Plans - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	1,898,025
Number of Restricted Stock Units Outstanding, Granted	704,760
Number of Restricted Stock Units Outstanding, Granted, performance RSUs	273,900
Number of Restricted Stock Units Outstanding, Released	(261,627)
Number of Restricted Stock Units Outstanding, Cancelled or expired	(61,460)
Number of Restricted Stock Units Outstanding, Unvested - Ending Balance	2,553,598
Weighted-Average Grant Date Fair Value, Unvested	$ 51.09	$ 49.53
Weighted-Average Grant Date Fair Value, Granted	51.32
Weighted-Average Grant Date Fair Value, Granted, performance RSUs	51.55
Weighted-Average Grant Date Fair Value, Released	41.73
Weighted-Average Grant Date Fair Value, Cancelled or expired	$ 47.19

Stock Plans - Stock-Based Compe

Stock Plans - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 15,655	$ 12,546
Cost of revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,393	914
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,249	3,328
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,094	4,465
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,919	$ 3,839

Stock Plans - Weighted Average

Stock Plans - Weighted Average Assumptions for Fair Value of Stock Options Grants (Detail) - Stock options [Member]	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%
Risk-free interest rate	1.50%	1.70%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	58.00%	50.00%

Accumulated Other Comprehensi52

Accumulated Other Comprehensive Loss - Changes in Balances of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (1,331)	[1]	$ (1,489)
Other comprehensive income (loss) before reclassifications	891		(406)
Amounts reclassified to net loss	194		320
Other comprehensive income (loss)	1,085		(86)
Ending Balance	(246)		(1,575)
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,021)		(1,428)
Other comprehensive income (loss) before reclassifications	722		(450)
Amounts reclassified to net loss	194		320
Other comprehensive income (loss)	916		(130)
Ending Balance	(105)		(1,558)
Unrealized Gain (Loss) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(310)		(61)
Other comprehensive income (loss) before reclassifications	169		44
Other comprehensive income (loss)	169		44
Ending Balance	$ (141)		$ (17)
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2015 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 Comprehensi53

Accumulated Other Comprehensive Loss - Summary of Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity [Abstract]
Current period unrealized gain (loss) on cash flow hedges, Pre-Tax Amount	$ 1,217	$ (450)
Reclassification adjustments on cash flow hedges, Pre-Tax Amount	194	320
Unrealized gains (losses) on cash flow hedges, net, Pre-Tax Amount	1,411	(130)
Current period unrealized gain (loss) on investments, Pre-Tax Amount	260	44
Unrealized gains (losses) on investments, net, Pre-Tax Amount	260	44
Other comprehensive income (loss), Pre-Tax Amount	1,671	(86)
Current period unrealized gain (loss) on cash flow hedges, Tax Expense (Benefit)	(495)
Unrealized gains (losses) on cash flow hedges, net, Tax Expense (Benefit)	(495)
Current period unrealized gain (loss) on investments, Tax Expense (Benefit)	(91)
Unrealized gains (losses) on investments, net, Tax Expense (Benefit)	(91)
Other comprehensive income (loss), Tax Expense (Benefit)	(586)
Current period unrealized gain (loss) on cash flow hedges, After-Tax Amount	722	(450)
Reclassification adjustments on cash flow hedges, After-Tax Amount	194	320
Unrealized gains (losses) on cash flow hedges, net, After-Tax Amount	916	(130)
Current period unrealized gain (loss) on investments, After-Tax Amount	169	44
Unrealized gains (losses) on investments, After-Tax Amount	169	44
Other comprehensive income (loss)	$ 1,085	$ (86)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ (102)	$ 351

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016Segment
Segment Reporting [Abstract]
Number of operating segments	1

Segment Information - Company's

Segment Information - Company's Revenue by Geographic Region, Based on Customer's Location (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 59,773	$ 44,757
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	34,802	26,557
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	14,749	12,202
APAC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 10,222	$ 5,998

Segment Information - Long-Live

Segment Information - Long-Lived Assets by Location (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 25,125	$ 20,155
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	14,725	9,913
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	10,386	10,224
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 14	$ 18

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
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	1,936,453	2,534,145
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	2,553,598	2,558,481
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	0	215,121
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	219,969	355,499