Imperva 10-K 26 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 17, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	IMPV
Entity Registrant Name	IMPERVA INC
Entity Central Index Key	1,364,962
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		32,308,341
Entity Public Float			$ 1,800

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
CURRENT ASSETS:
Cash and cash equivalents	$ 168,252	$ 68,096
Short-term investments	96,555	41,624
Restricted cash	79	62
Accounts receivable, net of allowance of $1,438 and $ 215 as of December 31, 2015 and 2014, respectively	61,051	47,446
Inventory	815	259
Deferred tax assets	0	408
Prepaid expenses and other current assets	7,965	3,927
Total current assets	334,717	161,822
Property and equipment, net	12,164	7,618
Goodwill	34,972	34,972
Acquired intangible assets, net	7,991	9,399
Severance pay fund	4,530	3,980
Restricted cash	1,665	1,665
Deferred tax assets	588	329
Other assets	1,042	860
TOTAL ASSETS	397,669	220,645
CURRENT LIABILITIES:
Accounts payable	6,870	5,376
Accrued compensation and benefits	20,259	15,749
Accrued and other current liabilities	14,283	6,376
Deferred revenue	79,132	56,077
Total current liabilities	120,544	83,578
Other liabilities	4,515	10,408
Deferred revenue	27,525	25,098
Accrued severance pay	4,884	4,318
TOTAL LIABILITIES	$ 157,468	$ 123,402
Commitments and Contingencies (Note 11)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.0001 par value - 5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2015 and 2014, respectively	$ 0	$ 0
Common stock, $0.0001 par value - 145,000,000 shares authorized, 31,837,144 and 26,895,480 shares issued and outstanding as of December 31, 2015 and 2014, respectively	3	2
Additional paid-in capital	448,069	256,388
Accumulated deficit	(206,540)	(157,658)
Accumulated other comprehensive loss	(1,331)	(1,489)
TOTAL STOCKHOLDERS' EQUITY	240,201	97,243
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 397,669	$ 220,645

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,438	$ 215
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	31,837,144	26,895,480
Common stock, shares outstanding	31,837,144	26,895,480

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net revenue:
Products and license	$ 107,563	$ 74,299	$ 72,153
Services	126,735	89,711	65,606
Total net revenue	234,298	164,010	137,759
Cost of revenue:
Products and license	10,947	9,248	8,756
Services	36,633	27,335	20,940
Total cost of revenue	47,580	36,583	29,696
Gross profit	186,718	127,427	108,063
Operating expenses:
Research and development	53,376	43,052	27,556
Sales and marketing	136,292	106,382	81,500
General and administrative	43,440	34,499	24,436
Amortization of acquired intangible assets	1,408	1,269	0
Total operating expenses	234,516	185,202	133,492
Loss from operations	(47,798)	(57,775)	(25,429)
Other income (expense), net	(402)	(220)	(125)
Loss before provision for income taxes	(48,200)	(57,995)	(25,554)
Provision for income taxes	682	1,181	777
Net loss	(48,882)	(59,176)	(26,331)
Loss attributable to non - controlling interest	0	213	1,153
Net loss attributable to Imperva, Inc. stockholders	$ (48,882)	$ (58,963)	$ (25,178)
Net loss per share of common stock attributable to Imperva, Inc. stockholders, basic and diluted	$ (1.64)	$ (2.28)	$ (1.04)
Shares used in computing net loss per share of common stock, basic and diluted	29,849	25,806	24,300

Consolidated Statements of Comp

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

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interest [Member]
Beginning balance at Dec. 31, 2012	$ 84,231	$ 2	$ 157,989	$ (73,517)	$ 861	$ (1,104)
Beginning balance, shares at Dec. 31, 2012		24,296,076
Issuance of common stock, net of repurchases	4,796		4,796
Issuance of common stock, net of repurchases, shares		806,226
Vesting of restricted stock	801		801
Stock-based compensation	22,494		22,494
Issuance of common stock in connection with employee stock purchase plan	2,772		2,772
Issuance of common stock in connection with employee stock purchase plan, shares		96,502
Exercise of warrant, shares		7,694
Shares withheld for tax withholding on vesting of restricted stock units	(1,252)		(1,252)
Sale of additional ownership interest in Incapsula, Inc.			357			(357)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(172)				(172)
Change in unrealized loss on derivatives	(1,117)				(1,117)
Net loss	(26,331)			(25,178)		(1,153)
Comprehensive loss	(27,620)
Ending balance at Dec. 31, 2013	86,222	$ 2	187,957	(98,695)	(428)	(2,614)
Ending balance, shares at Dec. 31, 2013		25,206,498
Issuance of common stock related to acquisitions	24,163		24,163
Issuance of common stock related to acquisitions, shares		738,479
Issuance of common stock, net of repurchases	7,371		7,371
Issuance of common stock, net of repurchases, shares		672,832
Vesting of restricted stock	454		454
Stock-based compensation	37,273		37,273
Issuance of common stock in connection with employee stock purchase plan	3,332		3,332
Issuance of common stock in connection with employee stock purchase plan, shares		188,068
Income tax benefit from employee stock option exercises	385		385
Shares withheld for tax withholding on vesting of restricted stock units	(2,074)		(2,074)
Pre-combination service relating to acquired Skyfence option plan	354		354
Purchase of additional ownership interest in Incapsula, Inc.			(2,827)			2,827
Purchase of additional ownership interest in Incapsula, Inc. Shares		89,603
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(59)				(59)
Change in unrealized loss on derivatives	(1,002)				(1,002)
Net loss	(59,176)			(58,963)		$ (213)
Comprehensive loss	(60,237)
Ending balance at Dec. 31, 2014	97,243	$ 2	256,388	(157,658)	(1,489)
Ending balance, shares at Dec. 31, 2014		26,895,480
Proceeds from follow-on public offering, net of offering costs	127,741	$ 1	127,740
Proceeds from follow-on public offering, net of offering costs, shares		3,450,000
Issuance of common stock, net of repurchases	18,724		18,724
Issuance of common stock, net of repurchases, shares		670,844
Vesting of restricted stock	767		767
Vesting of restricted stock, shares		706,121
Stock-based compensation	50,964		50,964
Issuance of common stock in connection with employee stock purchase plan	4,785		4,785
Issuance of common stock in connection with employee stock purchase plan, shares		114,699
Income tax benefit from employee stock option exercises	165		165
Shares withheld for tax withholding on vesting of restricted stock units	(11,464)		(11,464)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(249)				(249)
Change in unrealized loss on derivatives	407				407
Net loss	(48,882)			(48,882)
Comprehensive loss	(48,724)
Ending balance at Dec. 31, 2015	$ 240,201	$ 3	$ 448,069	$ (206,540)	$ (1,331)
Ending balance, shares at Dec. 31, 2015		31,837,144

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (48,882)	$ (59,176)	$ (26,331)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	4,551	3,578	2,642
Stock-based compensation	50,964	37,273	22,494
Amortization of acquired intangibles	1,408	1,269	0
Amortization of premiums/accretion of discounts on short-term investments	496	416	639
Allowance for doubtful debts	(1,223)	195	2
Excess tax benefits from share-based compensation	(165)	(385)	0
Changes in operating assets and liabilities:
Accounts receivable, net	(14,828)	(2,805)	(8,868)
Inventory	(1,056)	253	(184)
Prepaid expenses and other assets	(4,220)	409	(1,161)
Accounts payable	977	1,150	159
Accrued compensation and benefits	4,510	2,630	3,672
Accrued and other liabilities	3,242	1,847	(206)
Severance pay (net)	16	93	(32)
Deferred revenue	25,482	18,123	16,761
Deferred tax assets	149	(354)	214
Net cash provided by operating activities	23,867	4,126	9,797
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales/maturities of short-term investments	(89,626)	29,821	42,162
Purchase of short-term investments	33,948	(33,267)	(38,021)
Acquisitions, net of cash acquired	0	(12,083)	0
Net purchases of property and equipment	(8,080)	(5,621)	(2,602)
Change in restricted cash	(17)	(441)	58
Net cash (used in) provided by investing activities	(63,775)	(21,591)	1,597
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from follow-on public offering, net of offering costs	127,853	0	0
Proceeds from issuance of common stock, net of repurchases	23,524	10,546	7,568
Shares withheld for tax withholding on vesting of restricted stock units	(11,464)	(2,074)	(1,252)
Excess tax benefits from share-based compensation	165	385	0
Net cash provided by financing activities	140,078	8,857	6,316
Effect of exchange rate changes on cash and cash equivalents	(14)	0	(207)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	100,156	(8,608)	17,503
CASH AND CASH EQUIVALENTS - Beginning of period	68,096	76,704	59,201
CASH AND CASH EQUIVALENTS - End of period	168,252	68,096	76,704
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	652	287	835
NONCASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued related to acquisitions of businesses	0	24,163	0
Property and equipment incurred but not yet paid	517	820	0
Vesting of restricted and early exercised stock options	$ 767	$ 454	$ 801

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	1. The Company 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 accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the fair presentation of the Company’s consolidated financial position, results of operations and cash flows for the periods presented. The consolidated financial statements include the accounts of Imperva Inc., and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Non-controlling Interest On March 20, 2014, the Company acquired the remaining interest it did not previously own in its majority-owned subsidiary, Incapsula, Inc. (“Incapsula”) (Refer to Note 2). The Company separately presented the non-controlling interest on its Consolidated Balance Sheets in Total Stockholders’ Equity, Consolidated Statements of Operations, Consolidated Statements of Comprehensive Loss and Consolidated Statements of Stockholders’ Equity for periods prior to such date. The Company had recorded a non - controlling interest in these consolidated financial statements for the 19% ownership interest of the minority owners of Incapsula as of December 31, 2013. Changes to the ownership interest in Incapsula held by the minority owners were accounted for as equity transactions in the consolidated statements of stockholders’ equity as the Company obtained control of Incapsula on November 5, 2009. Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company has 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 the cloud or on premises. Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include the fair value of accounts receivable, inventory intangible assets and goodwill, useful lives of intangible assets and property and equipment, and assumptions used in the calculation of revenue, income taxes and stock-based compensation, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts such estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Concentration of Supply Risk The Company relies on a single third party to manufacture its hardware appliances, and purchases its hardware appliances through such third party’s value-added resellers. Quality or performance failures of the Company’s products or changes in the Company’s suppliers’ financial or business condition could disrupt the Company’s ability to supply quality products to its customers and thereby have a material adverse effect on its business and consolidated financial statements. Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, short-term investments, restricted cash and derivative financial instruments. The Company’s cash, cash equivalents, short-term investments and restricted cash are invested in high-quality instruments with banks and financial institutions located in the United States and Israel. Such deposits may be in excess of insured limits provided on such deposits. The Company uses derivative financial instruments to manage exposures to foreign currency risks. The Company’s derivatives expose it to credit risk to the extent that the counterparty may be unable to meet the terms of the agreement. The Company seeks to mitigate such risk by limiting its counterparties to those with high or investment-grade credit ratings. The Company does not require collateral under these agreements and has not historically experienced any losses due to credit risk or lack of performance by counterparties. Derivative Financial Instruments The Company uses forward foreign currency exchange contracts to reduce its exposure to foreign currency rate changes for operating expenses that are forecasted to be incurred in currencies other than U.S. dollars. The Company records all of its derivative instruments at their gross fair value on the consolidated balance sheets. The Company classifies its cash flows from derivative financial instruments as operating activities. The accounting for changes in the fair value of a derivative instrument depends on whether the instrument has been designated and qualifies as a cash flow hedge for accounting purposes. For forward foreign currency exchange contracts that are designated and qualify as cash flow hedges, the effective portion of the gain or loss resulting from changes in the fair value of the derivative instruments is accounted for in accumulated other comprehensive income (loss) (“AOCI”) in the consolidated statements of stockholders’ equity and reclassified into operating expenses in the consolidated statements of operations in the period or periods during which the hedged transaction affects earnings. As of December 31, 2015, the Company estimated that $0.6 million of net derivative loss included in accumulated other comprehensive income (loss) will be reclassified into earnings within the next 12 months. The ineffective portion of the gain or loss resulting from the change in fair value is recognized in other income (expense), net in the consolidated statements of operations. 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 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 in 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 consolidated balance sheets, with any unrealized gains and losses reported in the consolidated statements of stockholders’ equity as a component of accumulated other comprehensive income (loss) 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 consolidated statements of operations. Restricted Cash The Company has restricted cash pledged as collateral representing a security deposit required for facility leases. As of December 31, 2015 and 2014, the Company has classified $1.7 million and $1.7 million, respectively, of security deposit as non-current assets relating to its facility lease arrangements. Inventory Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value where the cost is determined as the lower of an average cost basis or last invoice. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. For the years ended December 31, 2015, 2014 and 2013, the amount of inventory write-downs incurred by the Company were insignificant. Business Combination The Company accounts for its business acquisitions in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations. The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The fair value assigned to identifiable intangible assets acquired is determined using the income approach which discounts expected future cash flows to present value using estimated assumptions determined by management. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets, generally two to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term or the estimated useful lives of the assets. Upon the retirement or disposition of property and equipment, the related costs and accumulated depreciation is removed and any related gain or loss is recorded in the consolidated statements of operations. Repairs and maintenance that do not extend the life or improve an asset are expensed in the periods incurred. Goodwill and Acquired Intangibles Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. In reviewing goodwill, the Company bypasses the qualitative assessment and proceeds directly to performing the quantitative two step impairment test to test the reporting unit’s goodwill for impairment. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill and is used as a screening process for identifying a potential goodwill impairment loss. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value. The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the fiscal year ended December 31, 2015. Intangible assets consist of purchased technology which are amortized over the period of estimated benefit using the straight-line method, as the consumption pattern of the asset is not apparent, and estimated useful lives ranging from seven to ten years. The weighted average remaining useful life of the Company’s acquired technology intangible assets is six years as of December 31, 2015. No significant residual value is estimated for intangible assets. Impairment of Long-Lived Assets The Company evaluates its long-lived assets, which consist of property and equipment and acquired intangible assets, for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Impairment exists if the carrying amounts of such assets exceed the estimates of future net undiscounted 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. As of December 31, 2015 and 2014, the Company has not written down any of its long-lived assets as a result of impairment. Revenue Recognition The Company derives revenue from two sources: (i) products and license revenue, which includes hardware and perpetual software license revenue and (ii) services revenue, which includes maintenance and support, professional services, training and subscription arrangements. Substantially all of product and license sales have been sold in combination with maintenance and support services. Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery or performance has occurred; the sales price is fixed or determinable; and collection is reasonably assured. The Company defines each of the four criteria above as follows: · Persuasive evidence of an arrangement exists: Evidence of an arrangement consists of a purchase order or acknowledgment issued pursuant to the terms and conditions of a direct customer end user or distributor or value-added reseller (VAR) agreement and, in limited cases with said distributor or VAR, an end user agreement and/or purchase order · Delivery or performance has occurred: The Company uses shipping and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance. The Company recognizes product revenue upon transfer of title and risk of loss, which primarily is upon shipment to value-added resellers, distributors or end users. In most instances, the Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with the Company’s sales. In instances where final acceptance of the product or service is specified by the customer, revenue is deferred until all acceptance criteria have been met. · The sales price is fixed or determinable: The Company assesses whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. In the event payment terms are provided that differ from the Company’s standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized when the payments become due, provided the remaining criteria for revenue recognition have been met. · Collection is reasonably assured: The Company assesses probability of collection on a customer-by-customer basis. The Company’s customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. If the Company concludes that collection is not reasonably assured based upon an initial review, the Company does not recognize revenue until payment is received. Maintenance and support and subscription revenue includes arrangements for software maintenance and technical support for the Company’s products and subscription services revenue primarily related to the Company’s cloud-based services. The terms of the Company’s subscription service arrangements do not provide customers the right to take possession of the related software. Maintenance and support is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches and unspecified upgrades on a when-and-if-available basis. Maintenance and support and subscription revenue is initially deferred and recognized ratably over the life of the contract, with the related expenses recognized as incurred. Maintenance and support and subscription contracts usually have a term of one to three years. Unearned maintenance and support and subscription revenue is included in deferred revenue. Professional service revenue primarily consists of the fees the Company earns related to installation and consulting services. The Company recognizes revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 90 days from the start of service. Training services are recognized upon delivery of the training. Multiple Element Arrangements Most of the Company’s products are hardware appliances containing software components that function together to provide the essential functionality of the product. Therefore, the Company’s hardware appliances are considered non-software deliverables and are not subject to industry-specific software revenue recognition guidance. The Company’s product revenue also includes revenue from the sale of stand-alone software products. Stand-alone software may operate on the Company’s hardware appliance, but is not considered essential to the functionality of the hardware and is, therefore, subject to the industry-specific software revenue recognition guidance. Additionally, the Company provides unspecified software upgrades for its products, on a when-and-if available basis, and hardware replacements through maintenance and support contracts. These support arrangements when sold on a stand-alone basis are subject to the industry-specific software revenue recognition guidance. Under the software revenue recognition guidance, the Company uses the residual method to recognize revenue when a product agreement includes one or more elements to be delivered at a future date and Vendor Specific Objective Evidence (“VSOE”) of the fair value of all undelivered elements exists. In the majority of the Company’s contracts, the only element that remains undelivered at the time of delivery of the product is maintenance and support services and subscriptions. Under the residual method, the VSOE of fair value of the undelivered elements is deferred and the remaining portion of the contract fee is recognized as product revenue. If evidence of the VSOE of fair value of one or more undelivered elements does not exist, all revenue is generally deferred and recognized when delivery of those elements occurs or when fair value can be established. For certain arrangements with multiple deliverables, the Company allocates the arrangement fee to the non-software element based upon the relative selling price of such element and, if software and software-related elements (e.g., maintenance and support for the software element) are also included in the arrangement, the Company allocates the arrangement fee to each of those software and software-related elements as a group. After such allocations are made, the amount of the arrangement fee allocated to the software and software-related elements is accounted for using the residual method. When applying the relative selling price method, the Company determines the selling price for each element using VSOE of selling price, if it exists, or if not, Third-Party Evidence (“TPE”) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its Best Estimate of Selling Price (“BESP”) for that element. The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element. The Company limits the amount of revenue recognized for delivered elements to the amount that is not contingent on the future delivery of products or services, or subject to the Company’s future performance obligation. VSOE of fair value for elements of an arrangement is based upon the normal pricing and discounting practices for those services when sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices for a service fall within a reasonably narrow pricing range, evidenced by a substantial majority of such historical stand-alone transactions falling within a reasonably narrow range. In addition, the Company considers major service groups and geographies in determining VSOE. The Company is not able to determine TPE for its products or services. TPE is determined based on competitor prices for similar deliverables when sold separately. Generally, the Company’s go-to-market strategy differs from that of its peers and its offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine what similar competitor products’ selling prices are on a stand-alone basis. When the Company is unable to establish the selling price of its non-software deliverables using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company determines BESP for the purposes of allocating the arrangement by reviewing external and internal market factors including, but not limited to, pricing practices including discounting, the geographies in which the Company offers its products and services, the type of customer (i.e., distributor, value added reseller or direct end user) and competition. Additionally, the Company considers historical transactions, including transactions whereby the deliverable was sold on a stand-alone basis. The determination of BESP is made through consultation with and approval by the Company’s management. Selling prices are analyzed on a quarterly basis to identify if the Company has experienced significant changes in its selling prices. For its non-software deliverables the Company allocates the arrangement consideration based on the relative selling price of the deliverables. For its hardware appliances the Company uses BESP as its selling price. For its maintenance and support services, subscriptions and professional services and training, the Company primarily uses VSOE as the selling price and when the Company is unable to establish a selling price using VSOE, it uses BESP. Deferred Revenue Deferred revenue represents amounts invoiced to customers for which the related revenue has not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of the deferred revenues represents the amount that is expected to be recognized as revenue within one year of the consolidated balance sheet date. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. The Company generally does not require collateral from its customers; however, in certain circumstances, may require letters of credit, other collateral, additional guarantees or advance payments. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of its customer accounts. The Company regularly reviews its accounts receivable that remain outstanding past their applicable payment terms and establishes allowance and potential write-offs by considering certain factors such as historical experience, industry data, credit quality, age of balances and current economic conditions that may affect a customers’ ability to pay. 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 year ended December 31, 2015, we had one customer that represented 18% of our total revenue, and for the year ended December 31, 2013, a different customer represented 10% of our total revenue. For the year ended December 31, 2014, the Company did not have any customers that represented 10% or more of the Company’s total revenue. One customer represented 21% of gross accounts receivable as of December 31, 2015. There were no customers who represented 10% or more of gross accounts receivable as of December 31, 2014. Shipping and Handling Costs Costs related to shipping and handling are included in cost of revenue. Research and Development Costs Research and development costs, including direct and allocated expenses, are expensed as incurred. Software Development Costs The costs to develop software for sale have not been capitalized as the Company believes that the technological feasibility of the related software is not established until substantially all product development is complete. Warranty Costs The Company generally provides a 60-day warranty on hardware appliance products and software from the date of shipment to customers. To date, cost to repair or replace items sold to customers has been insignificant. Advertising Costs The Company expenses advertising costs as incurred. Advertising expense is included within sales and marketing expense in the consolidated statements of operations. For the years ended December 31, 2015, 2014 and 2013, advertising expenses were not material. Retirement Savings Plan The Company maintains a defined contribution 401(k) retirement savings plan for its U.S. employees. Each participant in the 401(k) retirement savings plan may elect to contribute a percentage of his or her annual compensation up to a specified maximum amount allowed under U.S. Internal Revenue Service regulations. There were no employer contributions to the 401(k) retirement savings plan for the years ended December 31, 2015, 2014 and 2013. Severance Pay Asset and Liability The Company has recorded a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. The Company’s liability for severance pay is calculated pursuant to Israeli severance pay law based on the most recent salary for the employees multiplied by the number of years of employment, as of the respective balance sheet date. Employees are entitled to one month salary for each year of employment or a portion thereof. The Company’s liability at each respective balance sheet date for all of its Israeli employees is fully accrued in the accompanying consolidated financial statements and is mainly funded through monthly deposits to the employee’s pension and management insurance policies. The carrying value of these policies is recorded as a severance fund asset in the Company’s consolidated balance sheets. The deposited funds may be withdrawn only upon the fulfillment of the obligation pursuant to Israeli severance pay law. The carrying value of the deposited funds is based on the cash surrender value of these policies and includes profits accumulated through the respective balance sheet date. The Company recognized severance expense related to the Israeli severance pay law during the years ended December 31, 2015, 2014 and 2013 of $1.3 million, $1.4 million, and $1.2 million, respectively. Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes. The Company uses the liability method for accounting for deferred income taxes, which requires recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements, but have not been reflected in its taxable income. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets and liabilities are expected to be realized or settled. The Company regularly assesses the likelihood that its deferred income tax assets will be realized from recoverable income taxes or recovered from future taxable income based on the realization criteria set forth in ASC 740. To the extent that the Company believes any amounts are more likely not to be realized, the Company records a valuation allowance to reduce the deferred income tax assets. In the event the Company determines that all or part of the net deferred tax assets are not realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period such determination is made. Similarly, if the Company subsequently realizes deferred income tax assets that were previously determined to be unrealizable, the respective valuation allowance would be reversed, resulting in an adjustment to earnings in the period such determination is made. In addition, the calculation of the Company’s tax liabilities involves addressing uncertainties in the application of complex tax regulations. The Company recognizes and measures potential liabilities based upon criteria set forth in ASC 740. Based upon these criteria, the Company estimates whether, and the extent to which, additional taxes will be due. If payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities may result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. If the Company’s estimate of tax liabilities is less than the amount ultimately assessed, a further charge to expense would result. Significant judgment is required in determining any valuation allowance recorded against deferred income tax assets. In assessing the need for a valuation allowance, the Company considers all available evidence, including past operating results, estimates of future taxable income, and the feasibility of tax planning strategies. In the event that the Company changes its determination as to the amount of deferred income tax assets that could be realized, it will adjust its valuation allowance with a corresponding effect to the provision for income taxes in the period in which such determination is made. Significant judgment is also required in evaluating the Company’s uncertain tax positions under ASC 740 and determining its provision for income taxes. Although the Company believes its reserves for uncertain tax positions are reasonable, no assurance can be given that the final tax outcome of these matters will not be different from that which is reflected in the Company’s historical income tax provisions and accruals. The Company adjusts these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different from the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the effect of reserves for uncertain tax positions and any changes to the reserves that are considered appropriate, as well as the related net interest and penalties, if applicable. Stock-Based Compensation Compensation costs related to employee stock option grants are based on the fair value of the options on the date of grant, net of estimated forfeitures. The Company determines the grant date fair value of the options using the Black-Scholes option-pricing model and the related stock-based compensation expense is generally recognized on a straight-line basis over the period in which an employee is required to provide service in exchange for the options, or the vesting period of the respective options. For performance based RSUs granted to employees which have multiple performance conditions and a market condition the Company used a Monte Carlo simulation model to determine the fair value of such awards. The key inputs used were the Company’s stock price on the date of grant, the expected volatility, the risk free in

Incapsula

Incapsula	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Incapsula	2. Incapsula On November 5, 2009, the Company entered into a license agreement for Incapsula to use certain developed technology of the Company. In lieu of any other fee or royalty under the license agreement, Incapsula issued to the Company 5,000,000 shares of its Series A Convertible Preferred Stock representing a 58% ownership interest at the date of issuance. The transaction was accounted for as a business combination. In March 2010, the Company entered into a Series A and Series A-1 Purchase Agreement whereby Incapsula issued 6,666,666 shares of its Series A Convertible Preferred Stock to the Company in exchange for cash consideration of $3.0 million. As a result of this transaction, the Company increased its ownership interest in Incapsula to 76% at the date of issuance. The purchase of the additional ownership interest in Incapsula was treated as an equity transaction. In July 2011, the Company purchased 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest to 82%. In January 2012, the Company purchased the remaining 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest in Incapsula to 85%. Under the terms of the agreements between the Company and Incapsula, the Company had the right, but not the obligation, to purchase the remaining ownership interest in Incapsula commencing on November 5, 2013 and ending on November 5, 2018 (the “Purchase Right”). In March 2014, the Company acquired the remaining outstanding capital stock in exchange for approximately 124,088 shares of Company common stock with an aggregate fair value of $7.7 million. As of the date of the acquisition, the remaining non-controlling interest on the Company’s balance sheet of $2.8 million was reclassified to additional paid-in capital given the Company’s complete ownership of Incapsula.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Acquisitions during 2014 were accounted for in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations, While management uses its best estimates and assumptions as part of the purchase price allocation process to value assets acquired and liabilities assumed at the business combination date, its estimates and assumptions are subject to refinement. As a result, during the preliminary purchase price allocation period, which may be up to one year from the business combination date, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. The Company record adjustments to assets acquired or liabilities assumed subsequent to the purchase price allocation period in its operating results in the period in which the adjustments were determined. The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The fair value assigned to identifiable intangible assets acquired is determined using the income approach which discounts expected future cash flows to present value using estimated assumptions determined by management. The Company believes that these identified intangible assets will have no residual value after their estimated economic useful lives. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets. The excess of the purchase price over the identified tangible and intangible assets, less liabilities assumed, is recorded as goodwill and primarily reflects the value of the synergies expected to be generated from combining the Company’s and the acquired entities’ technology and operations. Acquisition of Skyfence Networks Ltd. On February 7, 2014, the Company acquired Skyfence, a private company based and incorporated in Israel. Skyfence is a developer of a solution which allows real time visibility and control over corporate use of Software-as-a-Service (“SaaS”) applications, which enforces security policy, protects sensitive data from external and inside threats, as well as ensures compliance with standards. Per the terms of the acquisition agreement (as amended) with Skyfence and its security holders, the Company purchased all of the outstanding shares of capital stock of Skyfence in exchange for (a) approximately $8.6 million in cash, in addition to a holdback payment commitment due 24 months from the date the acquisition closes valued at approximately $7.2 million, and (b) 884,422 shares of Company common stock, of which 532,262 shares are subject to forfeiture based upon time-based vesting and continuing employment, and were therefore excluded from purchase consideration as such amounts will be recorded as compensation expense over the term of the corresponding four-year service period. In addition, 29,871 of the shares are subject to a holdback period of up to 24 months from the date of acquisition. The Company also assumed stock options outstanding in accordance with the terms of the applicable Skyfence stock option plan and Skyfence stock option agreement relating to that Skyfence stock option. Based on Skyfence’s stock options outstanding at February 7, 2014, Imperva converted options to purchase 164,000 shares of Skyfence stock into options to purchase 24,248 shares of Imperva common stock. The fair value of Imperva’s shares issued is based on Imperva’s closing price per share of $59.08 as reported on the New York Stock Exchange at the closing of the Acquisition on February 7, 2014. The fair values of the stock option awards assumed were estimated using a Black-Scholes option-pricing model. The estimated fair values of unvested equity awards of $1.1 million will be recorded as operating expense over the remaining requisite service periods as they relate to post-combination services, while the fair values of vested equity based awards of $0.3 million were included in total purchase price as they relate to pre-combination services. The total purchase consideration is as follows (in thousands): Cash $ 8,558 Cash holdback liability 7,157 Fair value of common stock 20,855 Estimated fair value of equity awards assumed and replaced 354 Total purchase price $ 36,924 The acquisition of Skyfence was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. The Company expensed the related acquisition costs in the amount of $0.9 million in general and administrative expenses. In addition, stock-based compensation expense totaling $7.3 million was recognized from the date of acquisition through December 31, 2014. The excess of the consideration for Skyfence over the fair values assigned to the assets acquired and liabilities assumed represents the goodwill resulting from the acquisition. The Company’s management believes that the goodwill represents the synergies expected from combining the products and technologies of Imperva with those of Skyfence, which will enhance the Company’s overall product portfolio. The purchased technology will be amortized straight-line over a seven-year estimated useful life. Also as part of the acquisition, the Company assumed deferred tax liabilities related to the fair value of the developed technology the Company obtained in the acquisition. Goodwill recorded in connection with the acquisition is not deductible for income tax purposes. The total purchase price was allocated using the information available at the business combination date. The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands): Net tangible assets $ 1,014 Existing technology 7,965 Deferred tax liability assumed (1,528 ) Goodwill 29,473 Total purchase price $ 36,924 The results of operations of Skyfence described above have been included in Imperva’s consolidated financial statements from the date of acquisition. The following table presents pro forma results of operations of the Company and Skyfence as if the companies had been combined as of January 1, 2013, and includes pro forma adjustments related to the amortization of acquired intangible assets and share-based compensation expense and the related income tax effects. Direct transaction costs are excluded from the December 31, 2014 pro forma condensed combined financial information presented below. The pro forma condensed combined financial information is presented for informational purposes only. The unaudited pro forma results of operations are not necessarily indicative of results that would have occurred had the acquisition taken place at the beginning of the earliest period presented, or of future results. Included in the pro forma results are fair value adjustments based on the fair values of assets acquired and liabilities assumed as of the acquisition date. Supplemental information on an unaudited pro forma basis, as if the Skyfence acquisition had been consummated on January 1, 2013 is presented as follows (in thousands): Year Ended December 2014 2013 Pro forma revenue $ 164,010 $ 137,759 Pro forma loss from operations $ (58,491 ) $ (36,629 ) Pro forma net loss $ (59,740 ) $ (37,414 ) Acquisition of Certain Assets and Liabilities of Tomium Software, LLC. On January 30, 2014, the Company acquired certain assets and liabilities of Tomium, a private company based in Texas. Tomium is a provider of real-time mainframe security auditing agents. The purchase price of approximately $8.3 million includes approximately $4.6 million in cash and assumption of a liability to pay cash of $0.3 million, and also the issuance of 60,556 shares of Company common stock valued at approximately $3.4 million based upon the closing price of the Company’s stock on the acquisition date of $55.45 per share. Imperva acquired certain tangible assets and also assumed a facility lease of Tomium. The following table summarizes the preliminary allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands): Intangible assets $ 2,704 Goodwill 5,499 Total intangible assets acquired 8,203 Other acquired tangible assets 60 Fair value of assets acquired $ 8,263 The total purchase price was allocated using the information available at the business combination date. Goodwill recorded in connection with the acquisition is deductible for U.S. income tax purposes. The acquisition of Tomium was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. The Company expensed the related acquisition costs, consisting primarily of legal costs in the amount of $0.3 million in general and administrative expenses. The Company’s management believes that the goodwill represents the synergies expected from combining the acquired technology and operations with those of Imperva. The intangible assets acquired by Imperva in conjunction with the acquisition of Tomium are being amortized straight-line over a ten-year estimated useful life. The results of operations related to the Tomium assets and liabilities have been included in the Company’s consolidated statements of operations from the acquisition date. Pro forma results of operations have not been presented because the acquisition was not material to the Company’s results of operations.

Cash, Cash Equivalents, and Sho

Cash, Cash Equivalents, and Short-Term Investments	12 Months Ended
	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	4. Cash, Cash Equivalents and Short-Term Investments Cash, cash equivalents and short-term investments consist of the following (in thousands): 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 As of December 31, 2014 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 26,284 $ — $ — $ 26,284 Bank deposits 11,877 — — 11,877 Commercial paper 18,341 — 2 18,339 Money market funds 11,596 — — 11,596 Total $ 68,098 $ — $ 2 $ 68,096 Short-term investments: Corporate debt obligations $ 31,404 $ 3 $ 53 31,354 Bank deposits 10,270 — — 10,270 Total $ 41,674 $ 3 $ 53 $ 41,624 The following table sets forth the cost and estimated fair value of short-term investments based on stated effective maturities as of December 31, 2015 (in thousands): As of December 31, 2015 Estimated Amortized Fair Cost Value Short-term investments: Due in 2016 $ 53,086 $ 53,003 Due in 2017 43,767 43,552 Total $ 96,853 $ 96,555 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 years ended December 31, 2015 and 2014, the Company did not consider any of its investments to be other-than-temporarily impaired. The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands): As of 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 As of December 31, 2014 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt obligations $ 12,735 $ 47 $ 12,088 $ 6 $ 24,823 $ 53

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	5. Fair Value of Financial Instruments The Company evaluates assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. The following table sets forth the Company’s assets and liabilities that were measured at fair value as of December 31, 2015 and 2014, by level within the fair value hierarchy (in thousands): As of December 31, 2015 Level I Level II Level III Fair 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 As of December 31, 2014 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Bank deposits $ — $ 11,877 $ — $ 11,877 Commercial paper — 18,339 — 18,339 Money market funds 11,596 — — 11,596 Short-term investments: Corporate debt obligations — 31,354 — 31,354 Bank deposits — 10,270 — 10,270 Total financial assets $ 11,596 $ 71,840 $ — $ 83,436 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ — $ 1,002 $ — $ 1,002 In addition to the amounts disclosed in the above table, the fair value of the Company’s Israeli severance pay assets, which were comprised of Level II assets, was $4.5 million and $4.0 million as of December 31, 2015 and 2014, respectively. The Company’s cash equivalents and short-term investments 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. Such instruments 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, term deposits and commercial paper. Such instruments are generally classified within Level 2 of the fair value hierarchy. There was no transfer between Level 1, Level 2 and Level 3 during the years ended December 31, 2015 and 2014.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments	6. Derivative Instruments The Company’s primary objective for holding derivative instruments is to reduce its exposure to foreign currency rate changes. The Company reduces its exposure by entering into forward foreign exchange contracts with respect to operating expenses that are forecast to be incurred in currencies other than U.S. dollars. Substantially all of the Company’s revenue and capital purchasing activities and a majority of its operating expenditures are transacted in U.S. dollars. However, certain operating expenditures are incurred in or exposed to other currencies, primarily the Israeli shekel and the Euro. The Company has established forecasted transaction currency risk management programs to protect against fluctuations in fair value and the volatility of future cash flows caused by changes in exchange rates. The Company’s currency risk management program includes forward foreign exchange contracts designated as cash flow hedges. These forward foreign exchange contracts generally mature within 12 months. The Company does not enter into derivative financial instruments for trading purposes. Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands): Liability as of December 31, 2015 2014 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in accrued and other current liabilities $ 47,231 $ 595 $ 25,990 $ 1,002 Gains (losses) on derivative instruments accounted for as hedges and their classification on the consolidated statement of operations, are presented in the following tables (in thousands): Years ended December 31, 2015 2014 2013 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 834 $ 191 $ 730 Losses recognized in OCI (a) $ (1,399 ) $ (1,846 ) $ (18 ) Gains recognized from accumulated OCI into net loss (b) $ — $ 55 $ 1,829 Losses recognized from accumulated OCI into net loss (b) $ (972 ) $ (708 ) $ — Foreign Exchange Forward Contract Derivatives not designated as hedging relationships: Gains recognized in net loss (c) $ — $ — $ 71 Losses recognized in net loss (c) $ — $ — $ (60 ) (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 income (loss), into net loss, of which $(107), $(72) and $117 were recognized within cost of sales for the years ended December 31, 2015, 2014 and 2013, respectively, and $(865), $(581), and $1,712 were recognized within operating expenses for the year ended December 31, 2015, 2014 and 2013, respectively. All amounts are reflected with the respective consolidated statement of operations. (c ) Classified in other income (expense), net.

Consolidated Balance Sheet Comp

Consolidated Balance Sheet Components	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Consolidated Balance Sheet Components	7. Consolidated Balance Sheet Components Allowance for Doubtful Accounts The allowance for doubtful accounts is comprised of the following activity (in thousands): Years Ended December 31, 2015 2014 2013 Allowance for doubtful accounts and sales returns reserve, beginning balance $ 215 $ 410 $ 412 Allowance for doubtful accounts, beginning balance $ 215 $ 410 $ 412 Charged to costs and expenses 1,044 418 46 Deductions (write-offs) (144 ) (613 ) (48 ) Allowance for doubtful accounts, ending balance 1,115 215 410 Sales returns reserve, beginning balance Charged to revenue 677 - - Deductions (write-offs) (354 ) - - Sales returns reserve, ending balance 323 - - Total allowance for doubtful accounts and sales returns reserve, ending balance $ 1,438 $ 215 $ 410 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, 2015 2014 Prepaid expenses $ 5,111 $ 3,263 Prepaid income taxes 585 45 Interest receivable 467 230 Other 1,802 389 Total prepaid expenses and other current assets $ 7,965 $ 3,927 Property and Equipment, net Property and equipment, net consist of the following (in thousands): As of December 31, 2015 2014 Computers and related equipment $ 15,953 $ 11,591 Office furniture and equipment 1,632 1,510 Leasehold improvements 7,791 3,751 Total property and equipment 25,376 16,852 Less: accumulated depreciation and amortization (13,212 ) (9,234 ) Total property and equipment, net $ 12,164 $ 7,618 Depreciation and amortization expense totaled $4.5 million, $3.6 million and $2.6 million, for the years ended December 31, 2015, 2014 and 2013, respectively. Accrued Compensation and Benefits Accrued compensation and benefits consist of the following (in thousands): As of December 31, 2015 2014 Salary and related benefits $ 7,215 $ 5,291 Accrued vacation 3,774 3,849 Accrued incentive payments 9,270 6,609 Total accrued compensation and benefits $ 20,259 $ 15,749 Accrued and Other Current Liabilities Accrued and other current liabilities consist of the following (in thousands): As of December 31, 2015 2014 Accrued expenses $ 4,633 $ 3,352 Derivative liability 595 1,002 Income tax payable 323 317 Short-term deferred rent 283 297 Short-term stock repurchase liability — 767 Skyfence holdback liability 7,556 - Other 893 641 Total accrued and other current liabilities $ 14,283 $ 6,376 Other Liabilities Other long-term liabilities consist of the following (in thousands): As of December 31, 2015 2014 Skyfence holdback liability $ — $ 7,343 Long-term deferred rent 1,926 841 Deferred tax liability 1,145 1,503 Other 1,444 721 Total other liabilities $ 4,515 $ 10,408

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	8. Goodwill and Acquired Intangible Assets During 2014, the Company completed two acquisitions of which $35.0 million was allocated to goodwill and $10.7 million to acquired intangible assets. The Company’s gross carrying amount of goodwill was $35.0 million as of December 31, 2015 and 2014, respectively. The Company did not have any goodwill impairments during 2015, 2014 or 2013. Acquired technology intangible assets subject to amortization as of December 31, 2015 were as follows (in thousands): As of December 31, 2015 2014 Acquired Technology $ 10,668 $ 10,668 Less: accumulated amortization (2,677 ) (1,269 ) Total acquired technology, net $ 7,991 $ 9,399 Amortization expense related to acquired intangible assets was $1.4 million for the year ended December 31, 2015. Acquired intangible assets are amortized over their estimated useful lives of seven to 10 years. As of December 31, 2015, the Company expects amortization expense in future periods to be as follows (in thousands): Acquired Fiscal Year Technology 2016 $ 1,408 2017 1,408 2018 1,408 2019 1,408 2020 1,408 Thereafter 951 Total expected amortization expense $ 7,991

Other Income (Expense), net

Other Income (Expense), net	12 Months Ended
	Dec. 31, 2015
Other Income And Expenses [Abstract]
Other Income (Expense), net	9. Other Income (Expense), net Other income (expense), net is comprised of the following (in thousands): Years Ended December 31, 2015 2014 2013 Other Income: Interest income $ 701 $ 163 $ 386 Foreign currency forward contract gains, net - - 12 Foreign currency exchange gains, net 5 8 — Total other income 706 171 398 Other Expense: Skyfence holdback liability accretion (212 ) (186 ) — Foreign currency exchange losses, net (322 ) — (373 ) Other (574 ) (205 ) (150 ) Total other expense (1,108 ) (391 ) (523 ) Total other income (expense), net $ (402 ) $ (220 ) $ (125 )

Revolving Credit Facility

Revolving Credit Facility	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Revolving Credit Facility	10. Revolving Credit Facility In September 2010, the Company entered into a revolving credit facility with a financial institution. The agreement, as amended, provides for maximum borrowing capacity of up to $7.5 million as of December 31, 2015. As of December 31, 2015 and 2014, there was no balance outstanding on the credit facility. The credit facility expires on April 1, 2019, 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 December 31, 2015, the Company was compliant with the amended covenant of the credit facility.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies (a) Operating Leases The Company rents its facilities under operating leases with lease periods expiring from 2015 through 2022. Future minimum payments under these facility operating leases are as follows as of December 31, 2015 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2016 $ 7,295 $ 436 2017 7,107 — 2018 7,412 — 2019 4,578 — 2020 4,210 — Thereafter 120 — Total $ 30,722 $ 436 Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Rent expense for the years ended December 31, 2015, 2014 and 2013 was $4.6 million, $3.9 million, and $3.3 million, respectively. In connection with leases for office space, the Company received tenant improvement allowances of $336,000 and $639,000 during the years ended December 31, 2012 and 2010, respectively, and is entitled to receive additional $791,000 under the lease amendments executed during the year ended December 31, 2015 from the lessor for certain improvements made to the leased property. 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 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 respective lease term. In addition, certain of the Company’s operating lease agreements for office space also include rent holidays and scheduled rent escalations during the initial lease term. The Company has recorded the rent holidays as a deferred rent within other liabilities on the 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 December 31, 2015 and 2014 the Company has $1.7 million and $1.7 million, respectively, in restricted deposits to secure bank guarantees provided to the lessor. (b) Cancelable Lease Agreement The Company leases motor vehicles under a cancelable operating lease agreement. The Company has an option to cancel the lease agreement, which may result in penalties in a maximum amount of $115,000 as of December 31, 2015. Motor vehicle lease expenses for the years ended December 31, 2015, 2014 and 2013 were $2.4 million, $2.6 million and $2.4 million, respectively. (c) Purchase Commitments As of both December 31, 2015 and 2014, the Company had purchase commitments of $5.8 million and $4.8 million, respectively, to purchase inventory, trial units, and research and development equipment from its vendors. The purchase commitments result from the Company’s contractual obligation to order or build inventory in advance of anticipated sales. According to the Company’s agreements with its vendors, the Company committed to purchase inventory within six months from the date the inventory arrived at the vendor’s warehouse. (d) Litigation From time to time, the Company may be subject to other legal proceedings and claims in the ordinary course of business. On April 11, 2014, a purported shareholder class action lawsuit was filed in the United States District Court for the Northern District of California against the Company and certain of its 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 the Company and certain of its current and former officers and purported to bring suit on behalf of those investors who purchased the Company’s publicly traded securities between May 2, 2013 and April 9, 2014. The plaintiff alleged that defendants made false and misleading statements about the Company’s 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 the Company’s operations and business and financial results, and seeking the same relief. On February 10, 2016, defendants filed a motion to dismiss the amended complaint. On June 27, 2014, a purported shareholder derivative lawsuit was filed in the Court of Chancery for the State of Delaware against the Company (as a nominal defendant), and naming certain of the Company’s officers and directors as individual defendants. The lawsuit relates to the acquisition of Skyfence Networks, Ltd. and the complaint asserts claims for breach of fiduciary duty and unjust enrichment, and seeks to recover unspecified compensatory damages allegedly sustained by the Company, corporate reforms, the recovery of plaintiffs’ attorney’s fees and other relief. On September 23, 2014, the Company and the individual defendants moved to dismiss the action. Plaintiffs filed an amended complaint on November 6, 2014. Defendants filed a motion to dismiss the amended complaint on January 14, 2015. 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. An oral argument before the Supreme Court of Delaware has been set for March 9, 2016. In addition, the Company has received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of their intellectual property rights. Future litigation may be necessary to defend the Company, its channel partners and its customers by determining the scope, enforceability and validity of third-party proprietary rights or to establish its proprietary rights. In the opinion of management, liabilities associated with these claims, while possible, are not probable at this time, and therefore the Company has not recorded any accrual for them as of December 31, 2015 and 2014. Further, any possible range of loss cannot be reasonably estimated at this time. The ultimate outcome of any litigation is uncertain and, regardless of outcome, litigation can have an adverse impact on 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 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.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Capital Stock	12. Capital Stock Common Stock Reserved for Issuance The Company had reserved shares of common stock, on an as if converted basis, for issuance as follows: As of December 31, 2015 2014 Issuance in connection with outstanding stock options 1,949,089 2,244,363 Issuance in connection with restricted stock units outstanding 1,898,025 2,279,081 Reserved for future stock option and restricted stock unit grants 650,527 1,166,742 Reserved for future issuance under the employee stock purchase plan 1,049,524 895,268 5,547,165 6,585,454 Preferred Stock Our board of directors is authorized, subject to any limitations prescribed by law, without stockholder approval, to issue from time to time up to an aggregate of 5,000,000 shares of preferred stock, in one or more series, each series to have such rights and preferences, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences as the Company’s board of directors determines. The rights of the holders of common stock will be subject to, and may be adversely affected by, the rights of holders of any preferred stock that may be issued in the future. The Company currently has no shares of preferred stock outstanding and the Company has no present plans to issue any shares of preferred stock. Stock Plans (a) 2003 Stock Plan During 2003, the Board of Directors adopted the 2003 Stock Plan (the “2003 Plan”), which allows for the granting of both incentive stock options and non-qualified stock options and the direct award or sale of shares of the Company’s common stock (including restricted common stock) to officers, employees, directors, consultants and other key persons. Incentive stock options may be granted to employees with exercise prices of no less than the fair value of the common stock on the grant date, and non-qualified options may be granted to employees, directors, or consultants at exercise prices of no less than 85% of the fair value of the common stock on the grant date, as determined by the Board of Directors. If, at the time the Company grants an option, the optionee directly or by attribution owns stock possessing more than 10% of the total combined voting power of all classes of stock of the Company, the option price shall be at least 110% of the fair value. Options granted under the Plan generally expire no later than ten years and in general vest four years from the date of grant. (b) 2011 Stock Option and Incentive Plan In September 2011, the Board of Directors adopted the 2011 Stock Option and Incentive Plan (the “2011 Plan”) which was subsequently approved by the Company’s stockholders. The 2011 Plan replaces the 2003 Plan as the Board has decided not to grant any additional awards under that plan. The Company has reserved a total of 1,000,000 shares of common stock for issuance under the 2011 Plan. In addition, any reserved but unissued shares under the 2003 Stock Plan will be added to the number of shares reserved for issuance under the 2011 Plan. The 2011 Plan also provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning in 2012 and ending in 2015, by 4% of the outstanding number of shares of common stock on the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. On January 1, 2015, the share reserve under the 2011 Plan was automatically increased by 1,075,819 shares. As of December 31, 2014, there were 1,166,742 shares available for grant under the 2011 Plan. The 2011 Plan permits the granting of incentive stock options, non-qualified stock options, 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. The Company began granting RSUs in February 2012, which generally vest either over 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, in conjunction with the Incapsula Acquisition, the Company granted performance-based RSUs to an employee of Incapsula for approximately 264,878 shares of Company common stock (Refer to Note 2). (c) 2011 Employee Stock Purchase Plan In September 2011, the Board of Directors adopted the 2011 Employee Stock Purchase Plan (the “ESPP”) which was subsequently approved by the Company’s stockholders. The ESPP took effect on the effective date of the registration statement for the Company’s IPO. The ESPP permits eligible employees to acquire shares of the Company’s common stock by accumulating funds through periodic payroll deductions of up to 15% of base salary. Each offering period may run for no more than 24 months and consist of no more than five purchase periods. The purchase price for shares of the Company’s common stock purchased under the ESPP will be 85% of the lesser of the fair market value of the Company’s common stock on the first day of the offering period or the last trading day of the applicable purchase period within that offering period. The Company has initially reserved a total of 500,000 shares of common stock for future issuance under the ESPP. The number of shares reserved for issuance under the ESPP will increase automatically on January 1 of each of the first eight years commencing in 2012 by the number of shares equal to 1% of the Company’s total outstanding shares as of the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. No more than 20,000,000 shares of common stock may be issued under the ESPP and no other shares may be added to the ESPP without the approval of the Company’s stockholders. On January 1, 2015, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 268,955 shares. (d) Inducement Stock Option Plans and Agreement and Inducement Restricted Stock Unit Plans and Agreement In August 2014 and August 2015, the Compensation Committee of the Board of Directors adopted Inducement Stock Option Plans and Agreements (the “Inducement Option Plans”) and Inducement Restricted Stock Unit Plans and Agreements (the “Inducement RSU Plans”), 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. The Company will issue a press release in connection with any stock options or RSUs awarded under the plan. (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 may grant to its employees and service providers options to purchase shares of its common stock, restricted shares, or RSUs. The total number of shares of common stock that may be granted under the Incapsula Plan shall not exceed 4,733,333 in the aggregate, subject to certain adjustments. In November 2013, the board of directors of Incapsula approved the grant of RSUs for 7,095,461 shares of Incapsula’s common stock (“Incapsula RSUs”). As part of the Incapsula Acquisition, the Incapsula RSUs were assumed and replaced by RSUs for Company Common Stock issued to continuing employees of Incapsula . The Incapsula RSU’s vest according to performance-based vesting terms tied to 2014 revenue for Incapsula and Incapsula-related products and services, which were converted into approximately 198,825 shares of Company Common Stock at the same exchange ratio applicable to the Incapsula Acquisition. In addition to performance conditions, the awards are dependent on future market price of Imperva’s common stock, which is deemed a market condition under ASC 718. The following table summarizes option activity under the Incapsula Plan and related: Shares Available for Grant Number of Performance- base d Stock Units Outstanding Number of Stock Options Outstanding Weighted Average Exercise Price of Stock Options Outstanding Outstanding - December 31, 2012 2,753,708 — 1,836,500 $ 0.10 Additional shares authorized 5,529,878 $ — Granted, performance RSUs (7,095,461 ) 7,095,461 — $ — Granted, stock options (1,240,000 ) — 1,240,000 $ 0.58 Exercised/Released — — (1,128,438 ) $ 0.02 Forfeited 141,562 — (141,562 ) $ 0.22 Outstanding - December 31, 2013 89,687 7,095,461 1,806,500 $ 0.47 Granted (95,000 ) — 95,000 $ 1.25 Forfeited 15,213 (12,713 ) (2,500 ) $ 1.25 Transferred to Imperva 2011 stock option plan (9,900 ) (7,082,748 ) (1,899,000 ) $ 0.16 Outstanding - December 31, 2014 — — — $ — The options outstanding and performance restricted share units under the Incapsula 2010 Share Incentive Plan were assumed as part of the Incapsula Acquisition and are equivalent to 247,184 shares of Company common stock on an as-converted basis. The Company does not intend to grant any additional shares under the Incapsula 2010 Share Incentive Plan. 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 Outstanding - December 31, 2012 1,989,237 $ 14.08 8.09 $ 35,513 Granted 631,775 $ 36.55 Exercised or released (687,719 ) $ 6.94 Cancelled or forfeited (257,787 ) $ 25.11 Outstanding - December 31, 2013 1,675,506 $ 23.78 8.01 $ 40,813 Granted 1,256,559 $ 41.39 Options assumed in acquisitions 72,607 $ 13.30 Exercised or released (496,297 ) $ 14.85 Cancelled or forfeited (264,012 ) $ 35.85 Balances - December 31, 2014 2,244,363 $ 33.83 8.27 $ 38,457 Granted 696,971 $ 49.20 Exercised or released (636,424 ) $ 29.44 Cancelled or forfeited (355,821 ) $ 42.00 Balances - December 31, 2015 1,949,089 $ 39.27 8.09 $ 47,480 Vested and expected to vest - December 31, 2015 1,700,981 $ 38.26 8.01 $ 43,108 Exercisable - December 31, 2015 609,137 $ 29.57 6.91 $ 20,557 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $63.31 of the Company’s common stock on December 31, 2015 Additional information regarding the Company’s stock options outstanding and exercisable as of December 31, 2015 is summarized below: Options Outstanding Options Exercisable Exercise Prices Number of Stock Options Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price per Share Shares Subject to Stock Options Weighted Average Exercise Price per Share $0.02 to $10.70 157,918 4.86 $ 6.66 148,074 $ 7.07 $10.71 to $29.10 242,340 7.66 $ 25.34 118,092 $ 24.95 $29.11 to $32.54 269,777 8.51 $ 29.43 72,161 $ 29.66 $32.55 to $34.55 206,863 7.26 $ 33.72 99,746 $ 33.62 $34.56 to $54.48 581,938 8.79 $ 43.19 74,298 $ 41.88 $54.49 to $61.55 275,131 8.14 $ 54.98 82,179 $ 54.76 $61.56 to $69.55 184,232 9.21 $ 64.87 14,587 $ 62.81 $69.56 to $77.00 30,890 9.79 $ 71.72 - $ - 1,949,089 8.09 $ 39.27 609,137 $ 29.57 (g) RSU Activity A summary of RSU activity for the year ended December 31, 2015, is as follows: Number of Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - December 31, 2013 1,044,651 $ 31.64 Granted 1,368,761 $ 41.66 Granted, performance RSUs 131,143 $ 31.42 PRSUs assumed in acquisitions 198,825 $ 61.14 Released (238,446 ) $ 34.84 Cancelled or expired (225,853 ) $ 39.83 Unvested - December 31, 2014 2,279,081 $ 39.07 Granted 911,734 $ 53.02 Granted, performance RSUs 249,220 $ 42.58 Released (898,205 ) $ 34.97 Cancelled or expired (643,805 ) $ 35.09 Unvested - December 31, 2015 1,898,025 $ 49.53 (h) Stock-Based Compensation Expense The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2015 2014 2013 Cost of revenue $ 3,862 $ 2,058 $ 1,440 Research and development 13,831 8,799 3,660 Sales and marketing 16,717 13,558 8,537 General and administrative 16,554 12,858 8,857 Total stock-based compensation expense $ 50,964 $ 37,273 $ 22,494 (i) Determining the Fair Value of RSUs, Performance RSUs, Stock Options, and ESPP The fair value of RSUs is determined using the closing price of the Company’s stock on the date of grant. Compensation is recognized on a straight-line basis over the requisite service period of each grant adjusted for estimated forfeitures. The fair value of RSUs granted to employees which have multiple performance conditions and a market condition is determined by the Company using a Monte Carlo simulation model. The key inputs used were the Company’s stock price on the date of grant, the expected volatility, the risk free interest rate and a revenue forecast. The Company updates the estimated expense, net of forfeitures, at the end of each reporting period. The expense is recognized on an accelerated basis over the requisite service period, which is generally the vesting period of the respective awards. The fair value of each stock option and ESPP grant to employees was determined by the Company and its board of directors using the Black-Scholes option-pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment to determine. Expected Term — The expected term represents the period that the Company’s stock-based awards are expected to be outstanding. For option grants that are considered to be “plain vanilla,” the Company used the simplified method to determine the expected term as provided by the Securities and Exchange Commission. The simplified method is calculated as the average of the time-to-vesting and the contractual life of the options. For option grants that are not considered “plain vanilla”, the expected term is derived from historical data on employee exercises and post-vesting employment termination behavior taking into account the contractual life of the award. For ESPP grants, the expected term is based on the length of the offering period, which is six months. Expected Volatility —The expected volatility was based on a combination of our historical volatilities and the Company’s publicly listed peers because we do not have sufficient trading history for our common stocks. The volatility is over a period equal to the expected terms of the stock option grants and the offering period for employee stock purchase plan. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero coupon U.S. Treasury notes with maturities approximately equal to the grant’s expected term. Expected Dividend — The Company has never paid dividends and does not expect to pay dividends. Forfeiture Rate —The Company estimates its forfeiture rate based on an analysis of its actual forfeitures and will continue to evaluate the adequacy of the forfeiture rate based on actual forfeiture experience, analysis of employee turnover behavior, and other factors. The impact from a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual number of future forfeitures differs from that estimated by the Company, the Company may be required to record adjustments to stock-based compensation expense in future periods. A summary of the weighted-average assumptions is as follows: Years Ended December 31 2015 2014 2013 Stock option grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 1.8 % 1.8 % 1.2 % Expected term (in years) 6.1 6.1 6.1 Expected volatility 49 % 46 % 46 % ESPP grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 0.4 % 0.1 % 0.1 % Expected term (in years) 0.5 0.5 0.5 Expected volatility 65 % 45 % 27 % The weighted-average grant date fair value of the Company’s stock options granted during the years ended December 31, 2015, 2014 and 2013 was $23.75, $19.36, and $16.48 per share, respectively. The aggregate grant date fair value of the Company’s stock options granted to employees during the years ended December 31, 2015, 2014 and 2013 was $16.6 million, $24.3 million, and $7.3 million, respectively. The aggregate grant date fair value of the Company’s stock options vested during the years ended December 31, 2015, 2014, and 2013 was $11.7 million, $7.2 million, and $4.6 million, respectively. The fair value of the Company’s RSUs vested during the year ended December 31, 2015, 2014 and 2013 was $31.4 million, $8.3 million and $6.0 million, respectively. The aggregate intrinsic value of options exercised under the Plans was $21.6 million, $14.7 million, and $23.2 million for the years ended December 31, 2015, 2014 and 2013, respectively. The aggregate intrinsic value of options exercised 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. As of December 31, 2015, total compensation cost related to unvested stock-based awards granted to employees under the Plans, but not yet recognized, was $92.6 million, net of estimated forfeitures. As of December 31, 2015, this cost will be amortized to expense over a weighted-average remaining period of 2.6 years, and will be adjusted for subsequent changes in estimated forfeitures. Future option grants will increase the amount of compensation expense to be recorded in these periods. Net cash proceeds from the exercise of stock options and the issuance of common stock in connection with the employee stock purchase plan were $12.1 million, $8.5 million, and $6.3 million for the years ended December 31, 2015, 2014 and 2013, respectively. There was no capitalized stock-based compensation cost during the years ended December 31, 2015, 2014 and 2013. Recognized stock-based compensation tax benefits during the year ended December 31, 2015 and 2014 was $165,000 and $385,000, respectively. There was no recognized stock-based compensation tax benefit during the year ended December 31, 2013. (j) Common Stock Subject to Repurchase Pursuant to restricted stock agreements with the Company’s former CEO, the Company had the right, but not the obligation, to repurchase the unvested shares of common stock upon termination of employment at the original purchase price per share. The repurchase rights with respect to the common stock lapse over the vesting period, which ranges from 48 months to 60 months. The amounts received in exchange for these shares have been included in other liabilities in the accompanying condensed consolidated balance sheet and are reclassified to equity as the shares vest. The Company granted 843,819 shares of restricted common stock with a weighted-average grant date fair value per share of $1.94 during the year ended December 31, 2010. There were no grants of shares of restricted common stock during years ended December 31, 2015, 2014 and 2013. All these shares were fully vested as of December 31, 2015. As of December 31, 2014, 210,954 shares of restricted common stock held by the Company’s former CEO were unvested and subject to repurchase by the Company. In connection with the acquisition of Skyfence in the first quarter of 2014, the Company issued 532,262 shares of the Company’s common stock with a fair value per share of $59.08 which are subject to forfeiture based upon time-based vesting and continuing employment over the term of the corresponding four-year service period. 236,537 shares were fully vested as of December 31, 2015. None of these shares were vested as of December 31, 2014. (k) Early Exercise of Stock Options In 2010 and 2011, the Company’s board of directors allowed for the early exercise of stock options granted to certain members of the Company’s board of directors. The amounts received in exchange for these shares have been included in accrued and other current liabilities and other liabilities in the accompanying condensed consolidated balance sheet and are reclassified to equity as the shares vest. As of December 31, 2015 there were no unvested shares. As of December 31, 2014 and 2013, 6,667 shares and 45,000 shares were unvested amounting to $71,000 and $0.4 million, respectively. (l) Equity Awards Issued in Acquisitions In connection with the Skyfence and Incapsula acquisitions, the Company assumed stock options covering an aggregate of 72,607 shares of its common stock (in addition to the Incapsula RSUs discussed above). At the date of the acquisition, vested stock options and the associated fair value was recorded as part of the purchase consideration. The fair value related to the assumed unvested stock options are recognized as post-combination compensation costs and is being recorded as post-combination compensation expense ratably over the respective remaining service periods. (m) 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 Income (Loss)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	13. Accumulated Other Comprehensive Income (Loss) The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands): Years ended December 31, 2015 2014 2013 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,428 ) $ (61 ) $ (1,489 ) $ (426 ) $ (2 ) $ (428 ) $ 691 $ 170 $ 861 Other comprehensive income (loss) before reclassifications (565 ) (249 ) (814 ) (1,655 ) (59 ) (1,714 ) 712 34 746 Amounts reclassified to net loss 972 — 972 653 — 653 (1,829 ) (206 ) (2,035 ) Change in other comprehensive income (loss) 407 (249 ) 158 (1,002 ) (59 ) (1,061 ) (1,117 ) (172 ) (1,289 ) Balance at December 31 $ (1,021 ) $ (310 ) $ (1,331 ) $ (1,428 ) $ (61 ) $ (1,489 ) $ (426 ) $ (2 ) $ (428 ) The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the years 2015, 2014, and 2013 (in thousands): Year ended December 31, 2015 2014 2013 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ (565 ) - $ (565 ) $ (1,655 ) $ — $ (1,655 ) $ 712 $ — $ 712 Reclassification adjustments 1 972 - 972 653 — 653 (1,829 ) — $ (1,829 ) Unrealized gains (losses) on cash flow hedges, net 407 - 407 (1,002 ) — (1,002 ) (1,117 ) — (1,117 ) Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ (249 ) - (249 ) (59 ) — (59 ) 34 — 34 Reclassification adjustments 2 — - — — — — (206 ) — (206 ) Unrealized gains (losses) on investments: (249 ) — (249 ) (59 ) — (59 ) (172 ) — (172 ) Other comprehensive income (loss) $ 158 $ — $ 158 $ (1,061 ) $ — $ (1,061 ) $ (1,289 ) $ — $ (1,289 ) 1 Refer to Note 6 for the affected line items in the consolidated statement of operations 2 Amount included in other income (expense), net, in the consolidated statement of operations

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes The Company’s geographical breakdown of its loss before provision for income taxes is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic $ (50,892 ) $ (55,330 ) $ (28,831 ) Foreign 2,692 (2,665 ) 3,277 Loss before provision for taxes $ (48,200 ) $ (57,995 ) $ (25,554 ) The components of the provision for income taxes are as follows (in thousands): Years Ended December 31, 2015 2014 2013 Current Federal $ — $ — State 34 66 127 Foreign 857 1,523 700 Total current provision 891 1,589 827 Deferred Federal 63 109 — State (1 ) 6 — Foreign (271 ) (523 ) (50 ) Total deferred provision (209 ) (408 ) (50 ) Total $ 682 $ 1,181 $ 777 Reconciliation of the provision for income taxes at the statutory rate to the Company’s provision for income tax is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Tax benefit at federal statutory tax rate $ (16,388 ) $ (19,718 ) $ (8,688 ) Tax benefit at state statutory tax rate (499 ) (1,169 ) (829 ) Foreign tax rate differential (826 ) (526 ) (705 ) Unbenefitted loss of consolidated investment - 2,366 2,402 Change in valuation allowance 9,738 12,407 7,400 Meals and entertainment 44 34 197 Stock compensation 8,492 7,160 810 Nondeductible expenses and other 121 627 190 Provision for income taxes $ 682 $ 1,181 $ 777 Significant components of the Company’s net deferred tax assets are as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Reserves and accruals $ 2,662 $ 1,387 Deferred revenue 8,724 8,429 Stock-based compensation 4,772 5,776 Net operating loss carryforwards 37,793 25,519 Loss on OCI 374 380 Other 32 41 Gross deferred tax assets 54,357 41,532 Valuation allowance (53,468 ) (40,488 ) Total deferred tax assets 889 1,044 Deferred tax liabilities: Stock-based compensation (21 ) (53 ) Depreciation and amortization (1,425 ) (1,757 ) Total deferred tax liabilities (1,446 ) (1,810 ) Net deferred tax assets $ (557 ) $ (766 ) Recognition of deferred tax assets is appropriate when realization of these assets is more likely than not. Based upon the weight of available evidence, which includes the Company’s historical operating performance and the recorded cumulative net losses in all prior fiscal periods, the Company has provided a full valuation allowance against its U.S. deferred tax assets. The Company’s valuation allowance increased by $13.0 million, $7.8 million, and $8.4 million in the years ended December 31, 2015, 2014 and 2013, respectively. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes, related to balance sheet classification of deferred taxes. The ASU requires that deferred tax assets and liabilities be classified as noncurrent in the statement of financial position, thereby simplifying the current guidance that requires an entity to separate deferred assets and liabilities into current and noncurrent amounts. In the fourth quarter of 2015, the Company early adopted this guidance prospectively and our statement of financial position as of this date reflects the revised classification of current deferred tax assets and liabilities as noncurrent. There is no other impact on our financial statements of early-adopting the ASU. As of December 31, 2015, the Company had U.S. federal and state net operating loss carryforwards of approximately $153.0 million and $73.7 million, respectively. The U.S. federal net operating loss carryforwards will expire at various dates beginning in 2023 through 2035 if not utilized. Most state net operating loss carryforwards will expire at various dates beginning in 2018 through 2035. The Company uses the “with-and-without” approach to determine the recognition and measurement of excess tax benefits. Accordingly, the Company has elected to recognize excess income tax benefits from stock option exercises in additional paid in capital only if an incremental income tax benefit would be realized after considering all other tax attributes presently available to the Company. As of December 31, 2015, the amount of such excess tax benefits from stock options included in deferred tax assets for federal and state net operating losses were $49.9 million and $13.5 million, respectively. In addition, the Company has elected to account for the indirect effects of stock-based awards on other tax attributes, such as the research and alternative minimum tax credits, through the statement of operations. Net operating loss carryforwards reflected above may be subject to limitations due to ownership changes as provided in the Internal Revenue Code and similar state provisions. The Company has not provided U.S. income tax on certain foreign earnings that are deemed to be indefinitely invested outside the U.S. For fiscal years 2015, 2014, and 2013 the amount of accumulated unremitted earnings from the Company’s foreign subsidiaries is approximately $13.6 million, $12.9 million and $9.8 million, respectively. Determination of the amount of unrecognized deferred U.S. income tax liability is not practical due to the complexities associated with the hypothetical calculation. As of December 31, 2015 and 2014, the Company had gross unrecognized tax benefits of approximately $1.2 million and $672,000, respectively, all of which would impact the effective tax rate if recognized. While it is often difficult to predict the final outcome of any particular uncertain tax position, the Company does not believe that the amount of unrecognized tax benefits will change significantly in the next twelve months. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its income tax provision. For the years ended December 31, 2015 and 2014, the Company accrued interest of $83,000 and $43,000 in income tax expense, respectively. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2015 2014 2013 Balance at January 1 $ 672 $ 353 $ 239 Additions based on tax positions taken during the current period 401 222 134 Reductions based on tax positions taken during the prior period (50 ) (47 ) (20 ) Additions based on tax positions taken during a prior period 131 144 — Balance at December 31 $ 1,154 $ 672 $ 353 The Company’s material income tax jurisdictions are the United States (federal), California and Israel. The Israeli Tax Authorities have now settled the audit of income tax returns of the Israeli subsidiary for the tax years 2006 through 2010. As a result of net operating loss carryforwards, the Company is subject to audit for tax years 2003 and forward for federal purposes and 2005 and forward for California purposes. There are tax years which remain subject to examination in various other jurisdictions that are not material to the Company’s financial statements. The Company’s Israeli subsidiaries (“Israeli subsidiaries”) research and development intercompany services activity (“R&D activity”) have a “Beneficiary Enterprise” status for a separate investment program that was elected by the Israel subsidiaries starting 2012 under the Law for Encouragement of Capital Investments, 1959 (the “Investments Law”), amended from time to time. The entitlement to the above benefits is conditional upon the Israeli subsidiaries fulfilling the conditions stipulated by the Investments Law and regulations published there under. In December 2010 the “Knesset” (Israeli Parliament) passed the Law for Economic Policy for 2011 and 2012 (Amended Legislation), which prescribes, among others, amendments in the Investment Law (the “Amendment”). The Amendment became effective as of January 1, 2011. According to the Amendment, a flat tax rate applies to the Israeli subsidiary’s R&D activities as follows: 2011 and 2012—15%, 2013 and 2014—12.5% and in 2015 and thereafter—12%. The Israeli subsidiaries fully adopted the provisions of the Amendment in 2012. On July 30, 2013, the Knesset approved an amended Economic Plan for 2013-2014 (“Amended Budget Law”) to raise the Israeli corporate tax rate from 25% to 26.5%, in addition to increasing the flat tax rate applicable to the Israeli subsidiaries R&D activities starting in 2014 to 16%. Activities other than R&D will be taxed at the rate of 26.5%.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	15. 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 the 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 services revenue was comprised of the following (in thousands): Years Ended December 31, 2015 2014 2013 Maintenance and support $ 66,380 $ 54,795 $ 44,353 Professional services and training 14,084 11,414 9,890 Subscriptions 46,271 23,502 11,363 Total net services revenue $ 126,735 $ 89,711 $ 65,606 The Company’s revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands): Years Ended December 31, 2015 2014 2013 Americas $ 149,766 $ 94,266 $ 83,736 EMEA 57,180 43,111 33,183 APAC 27,352 26,633 20,840 Total net revenue $ 234,298 $ 164,010 $ 137,759 The following table presents long-lived assets by location (in thousands): As of December 31, 2015 2014 2013 United States $ 9,913 $ 6,761 $ 3,039 Israel 10,224 10,221 2,422 Other 18 35 14 Total long-lived assets $ 20,155 $ 17,017 $ 5,475

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss per Share	16. Net Loss per Share The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock (in thousands, except per share amounts): Years Ended December 31, 2015 2014 2013 Net loss attributable to Imperva, Inc. stockholders $ (48,882 ) $ (58,963 ) $ (25,178 ) Shares used in computing net loss per share of common stock, basic and diluted 29,849 25,806 24,300 Net loss per share of common stock, basic and diluted $ (1.64 ) $ (2.28 ) $ (1.04 ) The following outstanding shares of common stock equivalents 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: Years Ended December 31, 2015 2014 2013 Stock options to purchase common stock 1,949,089 2,244,363 1,675,506 Restricted stock units for common stock 1,898,025 2,279,081 1,044,651 Restricted shares of common stock subject to repurchase - 217,621 335,062 Restricted stock issued in connection with Skyfence acquisition 118,961 355,499 —

The Company and Summary of Si24

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Business	Business Imperva, Inc. (together with its subsidiaries, the “Company”) was incorporated in April 2002 in Delaware. The Company is headquartered in Redwood Shores, California and has subsidiaries located throughout the world including Israel, Asia and Europe. The Company is engaged in the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises.
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the fair presentation of the Company’s consolidated financial position, results of operations and cash flows for the periods presented. The consolidated financial statements include the accounts of Imperva Inc., and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Non - controlling Interest	Non-controlling Interest On March 20, 2014, the Company acquired the remaining interest it did not previously own in its majority-owned subsidiary, Incapsula, Inc. (“Incapsula”) (Refer to Note 2). The Company separately presented the non-controlling interest on its Consolidated Balance Sheets in Total Stockholders’ Equity, Consolidated Statements of Operations, Consolidated Statements of Comprehensive Loss and Consolidated Statements of Stockholders’ Equity for periods prior to such date. The Company had recorded a non - controlling interest in these consolidated financial statements for the 19% ownership interest of the minority owners of Incapsula as of December 31, 2013. Changes to the ownership interest in Incapsula held by the minority owners were accounted for as equity transactions in the consolidated statements of stockholders’ equity as the Company obtained control of Incapsula on November 5, 2009.
Segment Information	Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company has 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 the cloud or on premises.
Use of Estimates	Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include the fair value of accounts receivable, inventory intangible assets and goodwill, useful lives of intangible assets and property and equipment, and assumptions used in the calculation of revenue, income taxes and stock-based compensation, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts such estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates.
Concentration of Supply Risk	Concentration of Supply Risk The Company relies on a single third party to manufacture its hardware appliances, and purchases its hardware appliances through such third party’s value-added resellers. Quality or performance failures of the Company’s products or changes in the Company’s suppliers’ financial or business condition could disrupt the Company’s ability to supply quality products to its customers and thereby have a material adverse effect on its business and consolidated financial statements.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, short-term investments, restricted cash and derivative financial instruments. The Company’s cash, cash equivalents, short-term investments and restricted cash are invested in high-quality instruments with banks and financial institutions located in the United States and Israel. Such deposits may be in excess of insured limits provided on such deposits. The Company uses derivative financial instruments to manage exposures to foreign currency risks. The Company’s derivatives expose it to credit risk to the extent that the counterparty may be unable to meet the terms of the agreement. The Company seeks to mitigate such risk by limiting its counterparties to those with high or investment-grade credit ratings. The Company does not require collateral under these agreements and has not historically experienced any losses due to credit risk or lack of performance by counterparties.
Derivative Financial Instruments	Derivative Financial Instruments The Company uses forward foreign currency exchange contracts to reduce its exposure to foreign currency rate changes for operating expenses that are forecasted to be incurred in currencies other than U.S. dollars. The Company records all of its derivative instruments at their gross fair value on the consolidated balance sheets. The Company classifies its cash flows from derivative financial instruments as operating activities. The accounting for changes in the fair value of a derivative instrument depends on whether the instrument has been designated and qualifies as a cash flow hedge for accounting purposes. For forward foreign currency exchange contracts that are designated and qualify as cash flow hedges, the effective portion of the gain or loss resulting from changes in the fair value of the derivative instruments is accounted for in accumulated other comprehensive income (loss) (“AOCI”) in the consolidated statements of stockholders’ equity and reclassified into operating expenses in the consolidated statements of operations in the period or periods during which the hedged transaction affects earnings. As of December 31, 2015, the Company estimated that $0.6 million of net derivative loss included in accumulated other comprehensive income (loss) will be reclassified into earnings within the next 12 months. The ineffective portion of the gain or loss resulting from the change in fair value is recognized in other income (expense), net in the consolidated statements of operations.
Cash, Cash Equivalents and Short-Term Investments	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 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 in 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 consolidated balance sheets, with any unrealized gains and losses reported in the consolidated statements of stockholders’ equity as a component of accumulated other comprehensive income (loss) 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 consolidated statements of operations.
Restricted Cash	Restricted Cash The Company has restricted cash pledged as collateral representing a security deposit required for facility leases. As of December 31, 2015 and 2014, the Company has classified $1.7 million and $1.7 million, respectively, of security deposit as non-current assets relating to its facility lease arrangements.
Inventory	Inventory Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value where the cost is determined as the lower of an average cost basis or last invoice. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. For the years ended December 31, 2015, 2014 and 2013, the amount of inventory write-downs incurred by the Company were insignificant.
Business Combination	Business Combination The Company accounts for its business acquisitions in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations. The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The fair value assigned to identifiable intangible assets acquired is determined using the income approach which discounts expected future cash flows to present value using estimated assumptions determined by management. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets
Property and Equipment	Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets, generally two to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term or the estimated useful lives of the assets. Upon the retirement or disposition of property and equipment, the related costs and accumulated depreciation is removed and any related gain or loss is recorded in the consolidated statements of operations. Repairs and maintenance that do not extend the life or improve an asset are expensed in the periods incurred.
Goodwill and Acquired Intangibles	Goodwill and Acquired Intangibles Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. In reviewing goodwill, the Company bypasses the qualitative assessment and proceeds directly to performing the quantitative two step impairment test to test the reporting unit’s goodwill for impairment. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill and is used as a screening process for identifying a potential goodwill impairment loss. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value. The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the fiscal year ended December 31, 2015. Intangible assets consist of purchased technology which are amortized over the period of estimated benefit using the straight-line method, as the consumption pattern of the asset is not apparent, and estimated useful lives ranging from seven to ten years. The weighted average remaining useful life of the Company’s acquired technology intangible assets is six years as of December 31, 2015. No significant residual value is estimated for intangible assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets, which consist of property and equipment and acquired intangible assets, for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Impairment exists if the carrying amounts of such assets exceed the estimates of future net undiscounted 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. As of December 31, 2015 and 2014, the Company has not written down any of its long-lived assets as a result of impairment.
Revenue Recognition	Revenue Recognition The Company derives revenue from two sources: (i) products and license revenue, which includes hardware and perpetual software license revenue and (ii) services revenue, which includes maintenance and support, professional services, training and subscription arrangements. Substantially all of product and license sales have been sold in combination with maintenance and support services. Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery or performance has occurred; the sales price is fixed or determinable; and collection is reasonably assured. The Company defines each of the four criteria above as follows: · Persuasive evidence of an arrangement exists: Evidence of an arrangement consists of a purchase order or acknowledgment issued pursuant to the terms and conditions of a direct customer end user or distributor or value-added reseller (VAR) agreement and, in limited cases with said distributor or VAR, an end user agreement and/or purchase order · Delivery or performance has occurred: The Company uses shipping and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance. The Company recognizes product revenue upon transfer of title and risk of loss, which primarily is upon shipment to value-added resellers, distributors or end users. In most instances, the Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with the Company’s sales. In instances where final acceptance of the product or service is specified by the customer, revenue is deferred until all acceptance criteria have been met. · The sales price is fixed or determinable: The Company assesses whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. In the event payment terms are provided that differ from the Company’s standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized when the payments become due, provided the remaining criteria for revenue recognition have been met. · Collection is reasonably assured: The Company assesses probability of collection on a customer-by-customer basis. The Company’s customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. If the Company concludes that collection is not reasonably assured based upon an initial review, the Company does not recognize revenue until payment is received. Maintenance and support and subscription revenue includes arrangements for software maintenance and technical support for the Company’s products and subscription services revenue primarily related to the Company’s cloud-based services. The terms of the Company’s subscription service arrangements do not provide customers the right to take possession of the related software. Maintenance and support is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches and unspecified upgrades on a when-and-if-available basis. Maintenance and support and subscription revenue is initially deferred and recognized ratably over the life of the contract, with the related expenses recognized as incurred. Maintenance and support and subscription contracts usually have a term of one to three years. Unearned maintenance and support and subscription revenue is included in deferred revenue. Professional service revenue primarily consists of the fees the Company earns related to installation and consulting services. The Company recognizes revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 90 days from the start of service. Training services are recognized upon delivery of the training. Multiple Element Arrangements Most of the Company’s products are hardware appliances containing software components that function together to provide the essential functionality of the product. Therefore, the Company’s hardware appliances are considered non-software deliverables and are not subject to industry-specific software revenue recognition guidance. The Company’s product revenue also includes revenue from the sale of stand-alone software products. Stand-alone software may operate on the Company’s hardware appliance, but is not considered essential to the functionality of the hardware and is, therefore, subject to the industry-specific software revenue recognition guidance. Additionally, the Company provides unspecified software upgrades for its products, on a when-and-if available basis, and hardware replacements through maintenance and support contracts. These support arrangements when sold on a stand-alone basis are subject to the industry-specific software revenue recognition guidance. Under the software revenue recognition guidance, the Company uses the residual method to recognize revenue when a product agreement includes one or more elements to be delivered at a future date and Vendor Specific Objective Evidence (“VSOE”) of the fair value of all undelivered elements exists. In the majority of the Company’s contracts, the only element that remains undelivered at the time of delivery of the product is maintenance and support services and subscriptions. Under the residual method, the VSOE of fair value of the undelivered elements is deferred and the remaining portion of the contract fee is recognized as product revenue. If evidence of the VSOE of fair value of one or more undelivered elements does not exist, all revenue is generally deferred and recognized when delivery of those elements occurs or when fair value can be established. For certain arrangements with multiple deliverables, the Company allocates the arrangement fee to the non-software element based upon the relative selling price of such element and, if software and software-related elements (e.g., maintenance and support for the software element) are also included in the arrangement, the Company allocates the arrangement fee to each of those software and software-related elements as a group. After such allocations are made, the amount of the arrangement fee allocated to the software and software-related elements is accounted for using the residual method. When applying the relative selling price method, the Company determines the selling price for each element using VSOE of selling price, if it exists, or if not, Third-Party Evidence (“TPE”) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its Best Estimate of Selling Price (“BESP”) for that element. The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element. The Company limits the amount of revenue recognized for delivered elements to the amount that is not contingent on the future delivery of products or services, or subject to the Company’s future performance obligation. VSOE of fair value for elements of an arrangement is based upon the normal pricing and discounting practices for those services when sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices for a service fall within a reasonably narrow pricing range, evidenced by a substantial majority of such historical stand-alone transactions falling within a reasonably narrow range. In addition, the Company considers major service groups and geographies in determining VSOE. The Company is not able to determine TPE for its products or services. TPE is determined based on competitor prices for similar deliverables when sold separately. Generally, the Company’s go-to-market strategy differs from that of its peers and its offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine what similar competitor products’ selling prices are on a stand-alone basis. When the Company is unable to establish the selling price of its non-software deliverables using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company determines BESP for the purposes of allocating the arrangement by reviewing external and internal market factors including, but not limited to, pricing practices including discounting, the geographies in which the Company offers its products and services, the type of customer (i.e., distributor, value added reseller or direct end user) and competition. Additionally, the Company considers historical transactions, including transactions whereby the deliverable was sold on a stand-alone basis. The determination of BESP is made through consultation with and approval by the Company’s management. Selling prices are analyzed on a quarterly basis to identify if the Company has experienced significant changes in its selling prices. For its non-software deliverables the Company allocates the arrangement consideration based on the relative selling price of the deliverables. For its hardware appliances the Company uses BESP as its selling price. For its maintenance and support services, subscriptions and professional services and training, the Company primarily uses VSOE as the selling price and when the Company is unable to establish a selling price using VSOE, it uses BESP.
Deferred Revenue	Deferred Revenue Deferred revenue represents amounts invoiced to customers for which the related revenue has not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of the deferred revenues represents the amount that is expected to be recognized as revenue within one year of the consolidated balance sheet date.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. The Company generally does not require collateral from its customers; however, in certain circumstances, may require letters of credit, other collateral, additional guarantees or advance payments. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of its customer accounts. The Company regularly reviews its accounts receivable that remain outstanding past their applicable payment terms and establishes allowance and potential write-offs by considering certain factors such as historical experience, industry data, credit quality, age of balances and current economic conditions that may affect a customers’ ability to pay.
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 year ended December 31, 2015, we had one customer that represented 18% of our total revenue, and for the year ended December 31, 2013, a different customer represented 10% of our total revenue. For the year ended December 31, 2014, the Company did not have any customers that represented 10% or more of the Company’s total revenue. One customer represented 21% of gross accounts receivable as of December 31, 2015. There were no customers who represented 10% or more of gross accounts receivable as of December 31, 2014.
Shipping and Handling Costs	Shipping and Handling Costs Costs related to shipping and handling are included in cost of revenue.
Research and Development Costs	Research and Development Costs Research and development costs, including direct and allocated expenses, are expensed as incurred.
Software Development Costs	Software Development Costs The costs to develop software for sale have not been capitalized as the Company believes that the technological feasibility of the related software is not established until substantially all product development is complete.
Warranty Costs	Warranty Costs The Company generally provides a 60-day warranty on hardware appliance products and software from the date of shipment to customers. To date, cost to repair or replace items sold to customers has been insignificant.
Advertising Costs	Advertising Costs The Company expenses advertising costs as incurred. Advertising expense is included within sales and marketing expense in the consolidated statements of operations. For the years ended December 31, 2015, 2014 and 2013, advertising expenses were not material.
Retirement Savings Plan	Retirement Savings Plan The Company maintains a defined contribution 401(k) retirement savings plan for its U.S. employees. Each participant in the 401(k) retirement savings plan may elect to contribute a percentage of his or her annual compensation up to a specified maximum amount allowed under U.S. Internal Revenue Service regulations. There were no employer contributions to the 401(k) retirement savings plan for the years ended December 31, 2015, 2014 and 2013.
Severance Pay Asset and Liability	Severance Pay Asset and Liability The Company has recorded a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. The Company’s liability for severance pay is calculated pursuant to Israeli severance pay law based on the most recent salary for the employees multiplied by the number of years of employment, as of the respective balance sheet date. Employees are entitled to one month salary for each year of employment or a portion thereof. The Company’s liability at each respective balance sheet date for all of its Israeli employees is fully accrued in the accompanying consolidated financial statements and is mainly funded through monthly deposits to the employee’s pension and management insurance policies. The carrying value of these policies is recorded as a severance fund asset in the Company’s consolidated balance sheets. The deposited funds may be withdrawn only upon the fulfillment of the obligation pursuant to Israeli severance pay law. The carrying value of the deposited funds is based on the cash surrender value of these policies and includes profits accumulated through the respective balance sheet date. The Company recognized severance expense related to the Israeli severance pay law during the years ended December 31, 2015, 2014 and 2013 of $1.3 million, $1.4 million, and $1.2 million, respectively.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes. The Company uses the liability method for accounting for deferred income taxes, which requires recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements, but have not been reflected in its taxable income. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets and liabilities are expected to be realized or settled. The Company regularly assesses the likelihood that its deferred income tax assets will be realized from recoverable income taxes or recovered from future taxable income based on the realization criteria set forth in ASC 740. To the extent that the Company believes any amounts are more likely not to be realized, the Company records a valuation allowance to reduce the deferred income tax assets. In the event the Company determines that all or part of the net deferred tax assets are not realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period such determination is made. Similarly, if the Company subsequently realizes deferred income tax assets that were previously determined to be unrealizable, the respective valuation allowance would be reversed, resulting in an adjustment to earnings in the period such determination is made. In addition, the calculation of the Company’s tax liabilities involves addressing uncertainties in the application of complex tax regulations. The Company recognizes and measures potential liabilities based upon criteria set forth in ASC 740. Based upon these criteria, the Company estimates whether, and the extent to which, additional taxes will be due. If payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities may result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. If the Company’s estimate of tax liabilities is less than the amount ultimately assessed, a further charge to expense would result. Significant judgment is required in determining any valuation allowance recorded against deferred income tax assets. In assessing the need for a valuation allowance, the Company considers all available evidence, including past operating results, estimates of future taxable income, and the feasibility of tax planning strategies. In the event that the Company changes its determination as to the amount of deferred income tax assets that could be realized, it will adjust its valuation allowance with a corresponding effect to the provision for income taxes in the period in which such determination is made. Significant judgment is also required in evaluating the Company’s uncertain tax positions under ASC 740 and determining its provision for income taxes. Although the Company believes its reserves for uncertain tax positions are reasonable, no assurance can be given that the final tax outcome of these matters will not be different from that which is reflected in the Company’s historical income tax provisions and accruals. The Company adjusts these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different from the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the effect of reserves for uncertain tax positions and any changes to the reserves that are considered appropriate, as well as the related net interest and penalties, if applicable.
Stock-Based Compensation	Stock-Based Compensation Compensation costs related to employee stock option grants are based on the fair value of the options on the date of grant, net of estimated forfeitures. The Company determines the grant date fair value of the options using the Black-Scholes option-pricing model and the related stock-based compensation expense is generally recognized on a straight-line basis over the period in which an employee is required to provide service in exchange for the options, or the vesting period of the respective options. For performance based RSUs granted to employees which have multiple performance conditions and a market condition the Company used a Monte Carlo simulation model to determine the fair value of such awards. The key inputs used were the Company’s stock price on the date of grant, the expected volatility, the risk free interest rate and revenues achieved. The Company updates the estimated expense, net of forfeitures, at the end of each reporting period. The expense is recognized on an accelerated basis over the requisite service period, which is generally the vesting period of the respective awards.
Foreign Currency	Foreign Currency The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are re-measured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are re-measured at historical exchange rates. Gains and losses related to remeasurement are recorded in other income (expense) in the consolidated statements of operations.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company measures and reports its cash equivalents, short-term investments, derivative instruments, and the Israeli severance pay fund assets at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level I—Unadjusted quoted prices in active markets for identical assets or liabilities; Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III—Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level I and Level II assets. Level I securities include highly liquid money market funds and mutual funds. Level II instruments include deposits maintained with financial institutions and derivative instruments.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock The Company’s basic net loss per share of common stock is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The weighted-average number of shares of common stock used to calculate the Company’s basic net loss per share of common stock excludes those shares subject to repurchase as these shares are not deemed to be issued for accounting purposes until they vest. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, stock options to purchase common stock, common stock subject to repurchase, and warrants to purchase common stock are considered to be common stock equivalents. Basic and diluted net loss per share of common stock was the same for each period presented as the inclusion of all potential common shares outstanding was anti-dilutive.
Reclassifications	Reclassifications From time to time the Company reclassifies certain prior period balances to conform to the current year presentation. Starting first quarter 2015, we present tax withholdings on vesting of restricted stock units separately from proceeds from issuance of common stock in connection with employee stock purchase plan, in the Consolidated Statements of Stockholders’ Equity and Consolidated Statements of Cash Flows. The change was made to better reflect nature of the transactions, and prior period balances were reclassified accordingly. These reclassifications have no material impact on previously reported total assets, total liabilities, stockholders’ equity, results of operations or cash flows.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2016, the FASB issued ASU 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This guidance relates accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. This guidance will be effective for the Company beginning January 1, 2018, early adoption is permitted only for certain provisions. Adoption of the guidance is retrospective with a cumulative adjustment to retained earnings or accumulated deficit as of the adoption date. The Company is evaluating the impact of adopting this new accounting standard on its consolidated financial statements. In November 2015, the FASB issued ASU 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes. This guidance requires that deferred tax assets and liabilities be classified as noncurrent in a classified statement of financial position. This guidance is effective beginning January 1, 2017, with early adoption permitted. Adoption of the ASU is either retrospective to each prior period presented or prospective. In the fourth quarter of 2015, the Company early adopted this guidance prospectively. As a result, the Company no longer presents any current deferred income tax assets or liabilities but did not reclassify prior period deferred income tax assets or liabilities, as permitted by the guidance. See "Note 14 - Income Taxes" for additional information. In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. ASU 2015-16 eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Instead, an acquirer will recognize a measurement-period adjustment during the period in which it determines the amount of the adjustment. This guidance will be effective for the Company beginning January 1, 2016, with early adoption permitted. The Company does not believe the implementation of this standard will result in a material impact to its consolidated financial statements. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, which changes the measurement principle for inventory from the lower of cost or market to the lower of cost and net realizable value. ASU No. 2015-11 defines net realizable value as estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. This guidance will be effective for the Company beginning January 1, 2017, with early adoption permitted. The Company does not believe the implementation of this standard will result in a material impact to its 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.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Skyfence Networks Ltd. [Member]
Schedule of Total Purchase Consideration	The total purchase consideration is as follows (in thousands): Cash $ 8,558 Cash holdback liability 7,157 Fair value of common stock 20,855 Estimated fair value of equity awards assumed and replaced 354 Total purchase price $ 36,924
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands): Net tangible assets $ 1,014 Existing technology 7,965 Deferred tax liability assumed (1,528 ) Goodwill 29,473 Total purchase price $ 36,924
Summary of Supplemental Information on Unaudited Pro Forma Basis	Supplemental information on an unaudited pro forma basis, as if the Skyfence acquisition had been consummated on January 1, 2013 is presented as follows (in thousands): Year Ended December 2014 2013 Pro forma revenue $ 164,010 $ 137,759 Pro forma loss from operations $ (58,491 ) $ (36,629 ) Pro forma net loss $ (59,740 ) $ (37,414 )
Tomium Software, LLC. [Member]
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands): Intangible assets $ 2,704 Goodwill 5,499 Total intangible assets acquired 8,203 Other acquired tangible assets 60 Fair value of assets acquired $ 8,263

Cash, Cash Equivalents, and S26

Cash, Cash Equivalents, and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Short-Term Investments	Cash, cash equivalents and short-term investments consist of the following (in thousands): As of 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 As of December 31, 2014 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 26,284 $ — $ — $ 26,284 Bank deposits 11,877 — — 11,877 Commercial paper 18,341 — 2 18,339 Money market funds 11,596 — — 11,596 Total $ 68,098 $ — $ 2 $ 68,096 Short-term investments: Corporate debt obligations $ 31,404 $ 3 $ 53 31,354 Bank deposits 10,270 — — 10,270 Total $ 41,674 $ 3 $ 53 $ 41,624
Summary of Cost and Estimated Fair Value of Short-Term Investments	The following table sets forth the cost and estimated fair value of short-term investments based on stated effective maturities as of December 31, 2015 (in thousands): As of December 31, 2015 Estimated Amortized Fair Cost Value Short-term investments: Due in 2016 $ 53,086 $ 53,003 Due in 2017 43,767 43,552 Total $ 96,853 $ 96,555
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 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 As of December 31, 2014 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate debt obligations $ 12,735 $ 47 $ 12,088 $ 6 $ 24,823 $ 53

Fair Value of Financial Instr27

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis	The following table sets forth the Company’s assets and liabilities that were measured at fair value as of December 31, 2015 and 2014, by level within the fair value hierarchy (in thousands): As of December 31, 2015 Level I Level II Level III Fair 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 As of December 31, 2014 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Bank deposits $ — $ 11,877 $ — $ 11,877 Commercial paper — 18,339 — 18,339 Money market funds 11,596 — — 11,596 Short-term investments: Corporate debt obligations — 31,354 — 31,354 Bank deposits — 10,270 — 10,270 Total financial assets $ 11,596 $ 71,840 $ — $ 83,436 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ — $ 1,002 $ — $ 1,002

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments Measured at Fair Value and Classification on Consolidated Balance Sheets	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands): Liability as of December 31, 2015 2014 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in accrued and other current liabilities $ 47,231 $ 595 $ 25,990 $ 1,002
Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations	Gains (losses) on derivative instruments accounted for as hedges and their classification on the consolidated statement of operations, are presented in the following tables (in thousands): Years ended December 31, 2015 2014 2013 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 834 $ 191 $ 730 Losses recognized in OCI (a) $ (1,399 ) $ (1,846 ) $ (18 ) Gains recognized from accumulated OCI into net loss (b) $ — $ 55 $ 1,829 Losses recognized from accumulated OCI into net loss (b) $ (972 ) $ (708 ) $ — Foreign Exchange Forward Contract Derivatives not designated as hedging relationships: Gains recognized in net loss (c) $ — $ — $ 71 Losses recognized in net loss (c) $ — $ — $ (60 ) (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 income (loss), into net loss, of which $(107), $(72) and $117 were recognized within cost of sales for the years ended December 31, 2015, 2014 and 2013, respectively, and $(865), $(581), and $1,712 were recognized within operating expenses for the year ended December 31, 2015, 2014 and 2013, respectively. All amounts are reflected with the respective consolidated statement of operations. (c ) Classified in other income (expense), net.

Consolidated Balance Sheet Co29

Consolidated Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Allowance for Doubtful Accounts	The allowance for doubtful accounts is comprised of the following activity (in thousands): Years Ended December 31, 2015 2014 2013 Allowance for doubtful accounts and sales returns reserve, beginning balance $ 215 $ 410 $ 412 Allowance for doubtful accounts, beginning balance $ 215 $ 410 $ 412 Charged to costs and expenses 1,044 418 46 Deductions (write-offs) (144 ) (613 ) (48 ) Allowance for doubtful accounts, ending balance 1,115 215 410 Sales returns reserve, beginning balance Charged to revenue 677 - - Deductions (write-offs) (354 ) - - Sales returns reserve, ending balance 323 - - Total allowance for doubtful accounts and sales returns reserve, ending balance $ 1,438 $ 215 $ 410
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, 2015 2014 Prepaid expenses $ 5,111 $ 3,263 Prepaid income taxes 585 45 Interest receivable 467 230 Other 1,802 389 Total prepaid expenses and other current assets $ 7,965 $ 3,927
Property and Equipment, Net	Property and equipment, net consist of the following (in thousands): As of December 31, 2015 2014 Computers and related equipment $ 15,953 $ 11,591 Office furniture and equipment 1,632 1,510 Leasehold improvements 7,791 3,751 Total property and equipment 25,376 16,852 Less: accumulated depreciation and amortization (13,212 ) (9,234 ) Total property and equipment, net $ 12,164 $ 7,618
Accrued Compensation and Benefits	Accrued compensation and benefits consist of the following (in thousands): As of December 31, 2015 2014 Salary and related benefits $ 7,215 $ 5,291 Accrued vacation 3,774 3,849 Accrued incentive payments 9,270 6,609 Total accrued compensation and benefits $ 20,259 $ 15,749
Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following (in thousands): As of December 31, 2015 2014 Accrued expenses $ 4,633 $ 3,352 Derivative liability 595 1,002 Income tax payable 323 317 Short-term deferred rent 283 297 Short-term stock repurchase liability — 767 Skyfence holdback liability 7,556 - Other 893 641 Total accrued and other current liabilities $ 14,283 $ 6,376
Other Long-term Liabilities	Other long-term liabilities consist of the following (in thousands): As of December 31, 2015 2014 Skyfence holdback liability $ — $ 7,343 Long-term deferred rent 1,926 841 Deferred tax liability 1,145 1,503 Other 1,444 721 Total other liabilities $ 4,515 $ 10,408

Goodwill and Acquired Intangi30

Goodwill and Acquired Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Acquired Technology Intangible Assets Subject to Amortization	Acquired technology intangible assets subject to amortization as of December 31, 2015 were as follows (in thousands): As of December 31, 2015 2014 Acquired Technology $ 10,668 $ 10,668 Less: accumulated amortization (2,677 ) (1,269 ) Total acquired technology, net $ 7,991 $ 9,399
Schedule of Expected Amortization Expense in Future Periods	As of December 31, 2015, the Company expects amortization expense in future periods to be as follows (in thousands): Acquired Fiscal Year Technology 2016 $ 1,408 2017 1,408 2018 1,408 2019 1,408 2020 1,408 Thereafter 951 Total expected amortization expense $ 7,991

Other Income (Expense), net (Ta

Other Income (Expense), net (Tables)	12 Months Ended
	Dec. 31, 2015
Other Income And Expenses [Abstract]
Schedule of Other Income (Expense), Net	Other income (expense), net is comprised of the following (in thousands): Years Ended December 31, 2015 2014 2013 Other Income: Interest income $ 701 $ 163 $ 386 Foreign currency forward contract gains, net - - 12 Foreign currency exchange gains, net 5 8 — Total other income 706 171 398 Other Expense: Skyfence holdback liability accretion (212 ) (186 ) — Foreign currency exchange losses, net (322 ) — (373 ) Other (574 ) (205 ) (150 ) Total other expense (1,108 ) (391 ) (523 ) Total other income (expense), net $ (402 ) $ (220 ) $ (125 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Payments Under Operating Leases	Future minimum payments under these facility operating leases are as follows as of December 31, 2015 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2016 $ 7,295 $ 436 2017 7,107 — 2018 7,412 — 2019 4,578 — 2020 4,210 — Thereafter 120 — Total $ 30,722 $ 436

Capital Stock (Tables)

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2015
Reserved Shares of Common Stock	The Company had reserved shares of common stock, on an as if converted basis, for issuance as follows: As of December 31, 2015 2014 Issuance in connection with outstanding stock options 1,949,089 2,244,363 Issuance in connection with restricted stock units outstanding 1,898,025 2,279,081 Reserved for future stock option and restricted stock unit grants 650,527 1,166,742 Reserved for future issuance under the employee stock purchase plan 1,049,524 895,268 5,547,165 6,585,454
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 Outstanding - December 31, 2012 1,989,237 $ 14.08 8.09 $ 35,513 Granted 631,775 $ 36.55 Exercised or released (687,719 ) $ 6.94 Cancelled or forfeited (257,787 ) $ 25.11 Outstanding - December 31, 2013 1,675,506 $ 23.78 8.01 $ 40,813 Granted 1,256,559 $ 41.39 Options assumed in acquisitions 72,607 $ 13.30 Exercised or released (496,297 ) $ 14.85 Cancelled or forfeited (264,012 ) $ 35.85 Balances - December 31, 2014 2,244,363 $ 33.83 8.27 $ 38,457 Granted 696,971 $ 49.20 Exercised or released (636,424 ) $ 29.44 Cancelled or forfeited (355,821 ) $ 42.00 Balances - December 31, 2015 1,949,089 $ 39.27 8.09 $ 47,480 Vested and expected to vest - December 31, 2015 1,700,981 $ 38.26 8.01 $ 43,108 Exercisable - December 31, 2015 609,137 $ 29.57 6.91 $ 20,557 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $63.31 of the Company’s common stock on December 31, 2015
Additional Information Regarding Company's Stock Options Outstanding and Exercisable	Additional information regarding the Company’s stock options outstanding and exercisable as of December 31, 2015 is summarized below: Options Outstanding Options Exercisable Exercise Prices Number of Stock Options Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price per Share Shares Subject to Stock Options Weighted Average Exercise Price per Share $0.02 to $10.70 157,918 4.86 $ 6.66 148,074 $ 7.07 $10.71 to $29.10 242,340 7.66 $ 25.34 118,092 $ 24.95 $29.11 to $32.54 269,777 8.51 $ 29.43 72,161 $ 29.66 $32.55 to $34.55 206,863 7.26 $ 33.72 99,746 $ 33.62 $34.56 to $54.48 581,938 8.79 $ 43.19 74,298 $ 41.88 $54.49 to $61.55 275,131 8.14 $ 54.98 82,179 $ 54.76 $61.56 to $69.55 184,232 9.21 $ 64.87 14,587 $ 62.81 $69.56 to $77.00 30,890 9.79 $ 71.72 - $ - 1,949,089 8.09 $ 39.27 609,137 $ 29.57
Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value	A summary of RSU activity for the year ended December 31, 2015, is as follows: Number of Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - December 31, 2013 1,044,651 $ 31.64 Granted 1,368,761 $ 41.66 Granted, performance RSUs 131,143 $ 31.42 PRSUs assumed in acquisitions 198,825 $ 61.14 Released (238,446 ) $ 34.84 Cancelled or expired (225,853 ) $ 39.83 Unvested - December 31, 2014 2,279,081 $ 39.07 Granted 911,734 $ 53.02 Granted, performance RSUs 249,220 $ 42.58 Released (898,205 ) $ 34.97 Cancelled or expired (643,805 ) $ 35.09 Unvested - December 31, 2015 1,898,025 $ 49.53
Stock-Based Compensation Expense	The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2015 2014 2013 Cost of revenue $ 3,862 $ 2,058 $ 1,440 Research and development 13,831 8,799 3,660 Sales and marketing 16,717 13,558 8,537 General and administrative 16,554 12,858 8,857 Total stock-based compensation expense $ 50,964 $ 37,273 $ 22,494
Weighted Average Assumptions for Fair Value of Stock Options Grants and ESPP Grants	A summary of the weighted-average assumptions is as follows: Years Ended December 31 2015 2014 2013 Stock option grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 1.8 % 1.8 % 1.2 % Expected term (in years) 6.1 6.1 6.1 Expected volatility 49 % 46 % 46 % ESPP grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 0.4 % 0.1 % 0.1 % Expected term (in years) 0.5 0.5 0.5 Expected volatility 65 % 45 % 27 %
Incapsula Plan [Member]
Summary of Option Activity under Plans and Related Information	The following table summarizes option activity under the Incapsula Plan and related: Shares Available for Grant Number of Performance- base d Stock Units Outstanding Number of Stock Options Outstanding Weighted Average Exercise Price of Stock Options Outstanding Outstanding - December 31, 2012 2,753,708 — 1,836,500 $ 0.10 Additional shares authorized 5,529,878 $ — Granted, performance RSUs (7,095,461 ) 7,095,461 — $ — Granted, stock options (1,240,000 ) — 1,240,000 $ 0.58 Exercised/Released — — (1,128,438 ) $ 0.02 Forfeited 141,562 — (141,562 ) $ 0.22 Outstanding - December 31, 2013 89,687 7,095,461 1,806,500 $ 0.47 Granted (95,000 ) — 95,000 $ 1.25 Forfeited 15,213 (12,713 ) (2,500 ) $ 1.25 Transferred to Imperva 2011 stock option plan (9,900 ) (7,082,748 ) (1,899,000 ) $ 0.16 Outstanding - December 31, 2014 — — — $ —

Accumulated Other Comprehensi34

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Changes in Balances of Accumulated Other Comprehensive Income (Loss)	The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands): Years ended December 31, 2015 2014 2013 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,428 ) $ (61 ) $ (1,489 ) $ (426 ) $ (2 ) $ (428 ) $ 691 $ 170 $ 861 Other comprehensive income (loss) before reclassifications (565 ) (249 ) (814 ) (1,655 ) (59 ) (1,714 ) 712 34 746 Amounts reclassified to net loss 972 — 972 653 — 653 (1,829 ) (206 ) (2,035 ) Change in other comprehensive income (loss) 407 (249 ) 158 (1,002 ) (59 ) (1,061 ) (1,117 ) (172 ) (1,289 ) Balance at December 31 $ (1,021 ) $ (310 ) $ (1,331 ) $ (1,428 ) $ (61 ) $ (1,489 ) $ (426 ) $ (2 ) $ (428 )
Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the years 2015, 2014, and 2013 (in thousands): Year ended December 31, 2015 2014 2013 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ (565 ) - $ (565 ) $ (1,655 ) $ — $ (1,655 ) $ 712 $ — $ 712 Reclassification adjustments 1 972 - 972 653 — 653 (1,829 ) — $ (1,829 ) Unrealized gains (losses) on cash flow hedges, net 407 - 407 (1,002 ) — (1,002 ) (1,117 ) — (1,117 ) Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ (249 ) - (249 ) (59 ) — (59 ) 34 — 34 Reclassification adjustments 2 — - — — — — (206 ) — (206 ) Unrealized gains (losses) on investments: (249 ) — (249 ) (59 ) — (59 ) (172 ) — (172 ) Other comprehensive income (loss) $ 158 $ — $ 158 $ (1,061 ) $ — $ (1,061 ) $ (1,289 ) $ — $ (1,289 ) 1 Refer to Note 6 for the affected line items in the consolidated statement of operations 2 Amount included in other income (expense), net, in the consolidated statement of operations

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Loss Before Provision for Income Taxes	The Company’s geographical breakdown of its loss before provision for income taxes is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic $ (50,892 ) $ (55,330 ) $ (28,831 ) Foreign 2,692 (2,665 ) 3,277 Loss before provision for taxes $ (48,200 ) $ (57,995 ) $ (25,554 )
Provision for Income Taxes	The components of the provision for income taxes are as follows (in thousands): Years Ended December 31, 2015 2014 2013 Current Federal $ — $ — State 34 66 127 Foreign 857 1,523 700 Total current provision 891 1,589 827 Deferred Federal 63 109 — State (1 ) 6 — Foreign (271 ) (523 ) (50 ) Total deferred provision (209 ) (408 ) (50 ) Total $ 682 $ 1,181 $ 777
Reconciliation of Provision for Income Taxes at Statutory Rate	Reconciliation of the provision for income taxes at the statutory rate to the Company’s provision for income tax is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Tax benefit at federal statutory tax rate $ (16,388 ) $ (19,718 ) $ (8,688 ) Tax benefit at state statutory tax rate (499 ) (1,169 ) (829 ) Foreign tax rate differential (826 ) (526 ) (705 ) Unbenefitted loss of consolidated investment - 2,366 2,402 Change in valuation allowance 9,738 12,407 7,400 Meals and entertainment 44 34 197 Stock compensation 8,492 7,160 810 Nondeductible expenses and other 121 627 190 Provision for income taxes $ 682 $ 1,181 $ 777
Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets are as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Reserves and accruals $ 2,662 $ 1,387 Deferred revenue 8,724 8,429 Stock-based compensation 4,772 5,776 Net operating loss carryforwards 37,793 25,519 Loss on OCI 374 380 Other 32 41 Gross deferred tax assets 54,357 41,532 Valuation allowance (53,468 ) (40,488 ) Total deferred tax assets 889 1,044 Deferred tax liabilities: Stock-based compensation (21 ) (53 ) Depreciation and amortization (1,425 ) (1,757 ) Total deferred tax liabilities (1,446 ) (1,810 ) Net deferred tax assets $ (557 ) $ (766 )
Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2015 2014 2013 Balance at January 1 $ 672 $ 353 $ 239 Additions based on tax positions taken during the current period 401 222 134 Reductions based on tax positions taken during the prior period (50 ) (47 ) (20 ) Additions based on tax positions taken during a prior period 131 144 — Balance at December 31 $ 1,154 $ 672 $ 353

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Company's Services Revenue	The Company’s services revenue was comprised of the following (in thousands): Years Ended December 31, 2015 2014 2013 Maintenance and support $ 66,380 $ 54,795 $ 44,353 Professional services and training 14,084 11,414 9,890 Subscriptions 46,271 23,502 11,363 Total net services revenue $ 126,735 $ 89,711 $ 65,606
Company's Revenue by Geographic Region, Based on Customer's Location	The Company’s revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands): Years Ended December 31, 2015 2014 2013 Americas $ 149,766 $ 94,266 $ 83,736 EMEA 57,180 43,111 33,183 APAC 27,352 26,633 20,840 Total net revenue $ 234,298 $ 164,010 $ 137,759
Long-Lived Assets by Location	The following table presents long-lived assets by location (in thousands): As of December 31, 2015 2014 2013 United States $ 9,913 $ 6,761 $ 3,039 Israel 10,224 10,221 2,422 Other 18 35 14 Total long-lived assets $ 20,155 $ 17,017 $ 5,475

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Computation of Company's Basic and Diluted Net Loss Per Share of Common Stock	The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock (in thousands, except per share amounts): Years Ended December 31, 2015 2014 2013 Net loss attributable to Imperva, Inc. stockholders $ (48,882 ) $ (58,963 ) $ (25,178 ) Shares used in computing net loss per share of common stock, basic and diluted 29,849 25,806 24,300 Net loss per share of common stock, basic and diluted $ (1.64 ) $ (2.28 ) $ (1.04 )
Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock	The following outstanding shares of common stock equivalents 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: Years Ended December 31, 2015 2014 2013 Stock options to purchase common stock 1,949,089 2,244,363 1,675,506 Restricted stock units for common stock 1,898,025 2,279,081 1,044,651 Restricted shares of common stock subject to repurchase - 217,621 335,062 Restricted stock issued in connection with Skyfence acquisition 118,961 355,499 —

The Company and Summary of Si38

The Company and Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)SegmentPartyCustomer	Dec. 31, 2014USD ($)Customer	Dec. 31, 2013USD ($)Customer
Revenue, Major Customer [Line Items]
Non - controlling interest of minority owners			19.00%
Number of operating segments | Segment	1
Number of third party | Party	1
Net derivative loss included in AOCI to be reclassified into earnings	$ 600,000
Security deposit as non-current assets	1,665,000	$ 1,665,000
Impairment of goodwill	$ 0	0	$ 0
Weighted average useful lives of acquired technology intangible assets	6 years
Period to complete Professional service arrangements	90 days
Warranty period	60 days
Employer contributions to the 401(k) retirement savings plan	$ 0	0	0
Salary in calculation for severance pay by severance pay law	1 month
Severance expense	$ 1,300,000	$ 1,400,000	$ 1,200,000
Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Number of customers representing 10% or more of gross accounts receivable | Customer		0
Number of customers representing 21% or more of gross accounts receivable | Customer	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	18.00%		10.00%
Number of customers representing 10% or more of revenue | Customer	1	0	1
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	21.00%
Minimum [Member]
Revenue, Major Customer [Line Items]
Estimated useful lives	2 years
Estimated useful life	7 years
Standard payment terms to customers range	30 days
Term of maintenance and support and subscription contracts	1 year
Maximum [Member]
Revenue, Major Customer [Line Items]
Estimated useful lives	7 years
Estimated useful life	10 years
Standard payment terms to customers range	90 days
Term of maintenance and support and subscription contracts	3 years

Incapsula - Additional Informat

Incapsula - Additional Information (Detail) - USD ($) $ in Millions	Nov. 05, 2009	Mar. 31, 2014	Jan. 31, 2012	Jul. 31, 2011	Mar. 31, 2010
Subsidiary or Equity Method Investee [Line Items]
Non-controlling interest reclassified to additional paid-in capital		$ 2.8
Incapsula Acquisition [Member]
Subsidiary or Equity Method Investee [Line Items]
Amount paid for remaining outstanding capital stock		$ 7.7
Business acquisition, shares issued		124,088
Series A Convertible Preferred Stock [Member] | Incapsula [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity method investments, shares	5,000,000				6,666,666
Ownership interest	58.00%				76.00%
Cash consideration					$ 3
Series A-1 Preferred Stock [Member] | Incapsula [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity method investments, shares			4,375,000	4,375,000
Ownership interest			85.00%	82.00%
Cash consideration			$ 3.5	$ 3.5

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($)	Feb. 07, 2014	Jan. 30, 2014	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Residual value of intangible assets				$ 0
Business acquisition purchase price, cash paid				$ 0	$ 12,083,000	$ 0
Compensation expense, service period				2 years 7 months 6 days
Recognized compensation expense				$ 50,964,000	$ 37,273,000	$ 22,494,000
Maximum [Member]
Business Acquisition [Line Items]
Estimated useful life				10 years
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Date of acquisition				Feb. 7, 2014
Business acquisition purchase price, cash paid	$ 8,558,000
Holdback payment commitment period	24 months
Holdback liability	$ 7,157,000
Business acquisition purchase price, shares issued	884,422
Compensation expense, service period	4 years
Closing price of stock	$ 59.08
Unvested equity awards to be recorded as operating expense	$ 1,100,000
Vested equity awards	300,000
Related acquisition costs	900,000
Recognized compensation expense			$ 7,300,000
Total purchase price	36,924,000
Business acquisition purchase price, common stock value	$ 20,855,000
Skyfence Networks Ltd. [Member] | Purchased Technology [Member]
Business Acquisition [Line Items]
Estimated useful life	7 years
Skyfence Networks Ltd. [Member] | Subject to a Holdback [Member]
Business Acquisition [Line Items]
Business acquisition purchase price, shares issued	29,871
Skyfence Networks Ltd. [Member] | Restricted Shares of Common Stock Subject to Repurchase [Member]
Business Acquisition [Line Items]
Business acquisition purchase price, shares issued	532,262
Skyfence Networks Ltd. [Member] | Skyfence Options [Member]
Business Acquisition [Line Items]
Options converted to purchase shares	164,000
Skyfence Networks Ltd. [Member] | Converted Imperva Options [Member]
Business Acquisition [Line Items]
Options converted to purchase shares	24,248
Skyfence Networks Ltd. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Common stock subject to holdback, period	24 months
Tomium Software, LLC. [Member]
Business Acquisition [Line Items]
Date of acquisition				Jan. 30, 2014
Business acquisition purchase price, cash paid		$ 4,600,000
Business acquisition purchase price, shares issued		60,556
Closing price of stock		$ 55.45
Related acquisition costs		$ 300,000
Estimated useful life		10 years
Total purchase price		$ 8,263,000
Business acquisition purchase price, assumption of liability to pay cash		300,000
Business acquisition purchase price, common stock value		$ 3,400,000

Acquisitions - Schedule of Tota

Acquisitions - Schedule of Total Purchase Consideration (Detail) - USD ($) $ in Thousands	Feb. 07, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Cash		$ 0	$ 12,083	$ 0
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Cash	$ 8,558
Cash holdback liability	7,157
Fair value of common stock	20,855
Estimated fair value of equity awards assumed and replaced	354
Total purchase price	$ 36,924

Acquisitions - Summary of Alloc

Acquisitions - Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Feb. 07, 2014	Jan. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill			$ 34,972	$ 34,972
Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]
Net tangible assets	$ 1,014
Intangible assets	7,965
Deferred tax liability assumed	(1,528)
Goodwill	29,473
Total purchase price	$ 36,924
Tomium Software, LLC. [Member]
Business Acquisition [Line Items]
Intangible assets		$ 2,704
Goodwill		5,499
Total intangible assets acquired		8,203
Other acquired tangible assets		60
Total purchase price		$ 8,263

Acquisitions - Summary of Suppl

Acquisitions - Summary of Supplemental Information on Unaudited Pro Forma Basis (Detail) - Skyfence Networks Ltd. [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Pro forma revenue	$ 164,010	$ 137,759
Pro forma loss from operations	(58,491)	(36,629)
Pro forma net loss	$ (59,740)	$ (37,414)

Cash, Cash Equivalents, and S44

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 168,255	$ 68,098
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	3	2
Cash and cash equivalents, Fair Value	168,252	68,096
Short-term investments, Amortized Cost	96,853	41,674
Short-term investments, Gross Unrealized Gains	2	3
Short-term investments, Gross Unrealized Losses	300	53
Short-term investments, Estimated Fair Value	96,555	41,624
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	57,906	26,284
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	57,906	26,284
Bank Deposits [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	10,253	11,877
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	10,253	11,877
Short-term investments, Amortized Cost	10,263	10,270
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,263	10,270
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	13,896	18,341
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	3	2
Cash and cash equivalents, Fair Value	13,893	18,339
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	86,200	11,596
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	86,200	11,596
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	86,590	31,404
Short-term investments, Gross Unrealized Gains	2	3
Short-term investments, Gross Unrealized Losses	300	53
Short-term investments, Estimated Fair Value	$ 86,292	$ 31,354

Cash, Cash Equivalents, and S45

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Short Term Investments [Abstract]
Amortized Cost of short-term investments, Due in 2016	$ 53,086
Amortized Cost of short-term investments, Due in 2017	43,767
Short-term investments, Amortized Cost	96,853	$ 41,674
Estimated fair value of short-term investments, Due in 2016	53,003
Estimated fair value of short-term investments, Due in 2017	43,552
Short-term investments, Estimated Fair Value	$ 96,555	$ 41,624

Cash, Cash Equivalents, and S46

Cash, Cash Equivalents, and Short-Term Investments - Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position (Detail) - Corporate Debt Obligations [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 73,673	$ 12,735
Less than 12 Months, Unrealized Losses	286	47
12 Months or Greater, Fair Value	10,609	12,088
12 Months or Greater, Unrealized Losses	14	6
Total, Fair Value	84,282	24,823
Total, Unrealized Losses	$ 300	$ 53

Fair Value of Financial Instr47

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	$ 168,252	$ 68,096
Short-term investments	96,555	41,624
Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	10,253	11,877
Short-term investments	10,263	10,270
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	13,893	18,339
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	86,200	11,596
Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	86,292	31,354
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	206,901	83,436
Fair Value, Measurements, Recurring [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	86,200	11,596
Fair Value, Measurements, Recurring [Member] | Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	120,701	71,840
Fair Value, Measurements, Recurring [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total financial assets	0	0
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	10,253	11,877
Short-term investments	10,263	10,270
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring 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 Basis [Line Items]
Cash equivalents	10,253	11,877
Short-term investments	10,263	10,270
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring 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 Basis [Line Items]
Cash equivalents	13,893	18,339
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring 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 Basis [Line Items]
Cash equivalents	13,893	18,339
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	86,200	11,596
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	86,200	11,596
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring 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 Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	86,292	31,354
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring 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 Basis [Line Items]
Short-term investments	86,292	31,354
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term investments	0	0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	595	1,002
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	0	0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	595	1,002
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts	$ 0	$ 0

Fair Value of Financial Instr48

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value transfers between level 1 to level 2	$ 0	$ 0
Fair value transfers between level 2 to level 1	0	0
Fair value transfers into level 3	0	0
Fair value transfers out of level 3	0	0
Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Severance pay assets	$ 4,500,000	$ 4,000,000

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
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 Consolidated Balance Sheets (Detail) - Forward Foreign Exchange Contracts [Member] - Accrued and Other Current Liabilities [Member] - Designated As Hedging Instrument [Member] - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$ 47,231,000	$ 25,990,000
Derivative Fair Value	$ 595,000	$ 1,002,000

Derivative Instruments - Gains

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Gains recognized in OCI	$ 834	$ 191	$ 730
Losses recognized in OCI	(1,399)	(1,846)	(18)
Gains recognized from accumulated OCI into net loss		55	1,829
Losses recognized from accumulated OCI into net loss	$ (972)	$ (708)
Not Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Gains recognized in net loss			71
Losses recognized in net loss			$ (60)

Derivative Instruments - Gain52

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Parenthetical) (Detail) - Designated As Hedging Instrument [Member] - Unrealized Gain (Loss) on Cash Flow Hedges [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cost of revenues [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ (107)	$ (72)	$ 117
Operating Expenses [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ (865)	$ (581)	$ 1,712

Consolidated Balance Sheet Co53

Consolidated Balance Sheet Components - Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts and sales returns reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	$ 215	$ 410	$ 412
Allowance for doubtful accounts, ending balance	1,438	215	410
Allowance for doubtful accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	215	410	412
Charged to costs and expenses	1,044	418	46
Deductions (write-offs)	(144)	(613)	(48)
Allowance for doubtful accounts, ending balance	1,115	215	410
Sales returns reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	0	0
Charged to revenue	677	0	0
Deductions (write-offs)	(354)	0	0
Allowance for doubtful accounts, ending balance	$ 323	$ 0	$ 0

Consolidated Balance Sheet Co54

Consolidated Balance Sheet Components - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Prepaid Expense And Other Assets Current [Abstract]
Prepaid expenses	$ 5,111	$ 3,263
Prepaid income taxes	585	45
Interest receivable	467	230
Other	1,802	389
Total prepaid expenses and other current assets	$ 7,965	$ 3,927

Consolidated Balance Sheet Co55

Consolidated Balance Sheet Components - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 25,376	$ 16,852
Less: accumulated depreciation and amortization	(13,212)	(9,234)
Total property and equipment, net	12,164	7,618
Computers and related equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	15,953	11,591
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,632	1,510
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 7,791	$ 3,751

Consolidated Balance Sheet Co56

Consolidated Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 4,551	$ 3,578	$ 2,642

Consolidated Balance Sheet Co57

Consolidated Balance Sheet Components - Accrued Compensation and Benefits (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Employee Related Liabilities Current [Abstract]
Salary and related benefits	$ 7,215	$ 5,291
Accrued vacation	3,774	3,849
Accrued incentive payments	9,270	6,609
Total accrued compensation and benefits	$ 20,259	$ 15,749

Consolidated Balance Sheet Co58

Consolidated Balance Sheet Components - Accrued and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Liabilities And Other Liabilities [Abstract]
Accrued expenses	$ 4,633	$ 3,352
Derivative liability	595	1,002
Income tax payable	323	317
Short-term deferred rent	283	297
Short-term stock repurchase liability	0	767
Skyfence holdback liability	7,556	0
Other	893	641
Total accrued and other current liabilities	$ 14,283	$ 6,376

Consolidated Balance Sheet Co59

Consolidated Balance Sheet Components - Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Liabilities Noncurrent [Abstract]
Skyfence holdback liability	$ 0	$ 7,343
Long-term deferred rent	1,926	841
Deferred tax liability	1,145	1,503
Other	1,444	721
Total other liabilities	$ 4,515	$ 10,408

Goodwill and Acquired Intangi60

Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Goodwill acquired		$ 35,000,000
Intangible assets acquired	$ 10,668,000	10,668,000
Gross carrying amount of goodwill	34,972,000	34,972,000
Goodwill impairments	0	0	$ 0
Amortization of acquired intangibles	$ 1,408,000	$ 1,269,000	$ 0
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

Goodwill and Acquired Intangi61

Goodwill and Acquired Intangible Assets - Summary of Acquired Technology Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets Net Excluding Goodwill [Abstract]
Acquired Technology	$ 10,668	$ 10,668
Less: accumulated amortization	(2,677)	(1,269)
Total acquired technology, net	$ 7,991	$ 9,399

Goodwill and Acquired Intangi62

Goodwill and Acquired Intangible Assets - Schedule of Expected Amortization Expense in Future Periods (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Total acquired technology, net	$ 7,991	$ 9,399
Purchased Technology [Member]
Finite-Lived Intangible Assets [Line Items]
2,016	1,408
2,017	1,408
2,018	1,408
2,019	1,408
2,020	1,408
Thereafter	951
Total acquired technology, net	$ 7,991

Other Income (Expense), Net - S

Other Income (Expense), Net - Schedule of Other Income (Expense), Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Income:
Interest income	$ 701	$ 163	$ 386
Foreign currency forward contract gains, net	0	0	12
Foreign currency exchange gains, net	5	8	0
Total other income	706	171	398
Other Expense:
Skyfence holdback liability accretion	(212)	(186)	0
Foreign currency exchange losses, net	(322)	0	(373)
Other	(574)	(205)	(150)
Total other expense	(1,108)	(391)	(523)
Total other income (expense), net	$ (402)	$ (220)	$ (125)

Revolving Credit Facility - Add

Revolving Credit Facility - Additional Information (Detail) - Revolving Credit Facility [Member] - London Interbank Offered Rate (LIBOR) [Member] - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 7,500,000
Outstanding credit facility	$ 0	$ 0
Credit facility expiration date	Apr. 1, 2019
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 - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Operating Leases
2,016	$ 7,295
2,017	7,107
2,018	7,412
2,019	4,578
2,020	4,210
Thereafter	120
Total	30,722
Estimated Sublease Income
2,016	436
2,017	0
2,018	0
2,019	0
2,020	0
Thereafter	0
Total	$ 436

Commitments and Contingencies66

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010
Loss Contingencies [Line Items]
Rent expense	$ 4,600,000	$ 3,900,000	$ 3,300,000
Tenant improvement allowances	791,000			$ 336,000	$ 639,000
Restricted cash	1,665,000	1,665,000
Purchase commitments	$ 5,800,000	4,800,000
Period of purchase commitment of inventory from specified date	6 months
Loss contingency accrual	$ 0	0
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Motor vehicle lease expenses	$ 2,400,000	$ 2,600,000	$ 2,400,000
Minimum [Member]
Loss Contingencies [Line Items]
Operating lease expiration year	2,015
Maximum [Member]
Loss Contingencies [Line Items]
Operating lease expiration year	2,022
Maximum [Member] | Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	$ 115,000

Capital Stock - Reserved Shares

Capital Stock - Reserved Shares of Common Stock (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Issuance in connection with outstanding stock options	1,949,089	2,244,363	1,675,506	1,989,237
Issuance in connection with restricted stock units outstanding	1,898,025	2,279,081	1,044,651
Reserved for future stock option and restricted stock unit grants	650,527	1,166,742
Reserved for future issuance under the employee stock purchase plan	1,049,524	895,268
Total	5,547,165	6,585,454

Capital Stock - Additional Info

Capital Stock - Additional Information (Detail)

Feb. 07, 2014$ / sharesshares

Oct. 31, 2015shares

Mar. 31, 2015USD ($)$ / sharesshares

Aug. 31, 2014shares

Mar. 31, 2014shares

Nov. 30, 2013shares

Jan. 31, 2012

Sep. 30, 2011Periodshares

Dec. 31, 2015USD ($)$ / sharesshares

Dec. 31, 2014USD ($)$ / sharesshares

Dec. 31, 2013USD ($)$ / sharesshares

Dec. 31, 2010$ / sharesshares

Mar. 31, 2010shares

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

Preferred stock, shares authorized

5,000,000

5,000,000

Preferred stock, shares outstanding

0

0

Preferred stock, shares issued

0

0

Reserve of common stock for future issuance

5,547,165

6,585,454

Performance-based restricted stock units granted

911,734

1,368,761

Number of stock option outstanding, granted

696,971

1,256,559

631,775

Weighted-average grant date fair value | $ / shares

$ 23.75

$ 19.36

$ 16.48

Aggregate grant date fair value, stock options granted | $

$ 16,600,000

$ 24,300,000

$ 7,300,000

Aggregate grant date fair value, stock options vested | $

11,700,000

7,200,000

4,600,000

Intrinsic value of options exercised | $

21,600,000

14,700,000

23,200,000

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

$ 92,600,000

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

2 years 7 months 6 days

Net cash proceeds from the exercise of stock options | $

$ 12,100,000

8,500,000

6,300,000

Capitalized stock-based compensation cost | $

0

0

0

Recognized stock-based compensation tax benefits | $

$ 165,000

$ 385,000

$ 0

Weighted-average grant date fair value | $ / shares

$ 53.02

$ 41.66

Issuance in connection with restricted stock units outstanding

1,898,025

2,279,081

1,044,651

Assumed common stock options in acquisitions

72,607

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

$ 23,524,000

$ 10,546,000

$ 7,568,000

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

Incapsula Acquisition [Member]

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

Business acquisition purchase price, shares issued

124,088

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

Common stock, shares vested

236,537

0

Business acquisition purchase price, shares issued

884,422

Closing price of stock | $ / shares

$ 59.08

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

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

Assumed common stock options in acquisitions

72,607

Stock options [Member] | Director [Member]

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

Unvested shares

0

6,667

45,000

Unvested shares, value | $

$ 71,000

$ 400,000

Restricted Stock Units for Common Stock [Member]

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

Number of Restricted Stock Units Vested in Period | $

$ 31,400,000

$ 8,300,000

$ 6,000,000

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

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

Shares issuable, as-converted to common stock-basis

198,825

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

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

Shares issuable, as-converted to common stock-basis

247,184

Restricted Shares of Common Stock Subject to Repurchase [Member]

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

Performance-based restricted stock units granted

0

0

0

843,819

Weighted-average grant date fair value | $ / shares

$ 1.94

Common stock, shares vested

843,819

Issuance in connection with restricted stock units outstanding

210,954

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

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

Business acquisition purchase price, shares issued

532,262

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

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

Vesting period

60 months

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

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

Vesting period

48 months

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] | Maximum [Member] | Stock options [Member]

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

Expiration period

10 years

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

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

Vesting period

4 years

2011 Stock Option and Incentive Plan [Member]

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

Reserve of common stock for future issuance

1,000,000

Increase percentage of common stock outstanding

4.00%

Shares available for grant

1,166,742

Increase in reserve share

1,075,819

2011 Stock Option and Incentive Plan [Member] | 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 began granting RSUs in February 2012, which generally vest either over a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter or they completely vest at the end of a three-year period.

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

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

Vesting percentage at the end of period

25.00%

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

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

Performance-based restricted stock units granted

264,878

2011 Employee Stock Purchase Plan [Member]

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

Reserve of common stock for future issuance

500,000

Increase percentage of common stock outstanding

1.00%

Increase in reserve share

268,955

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

15.00%

Offering period

24 months

Percentage of fair value of common stock on offering period

85.00%

Number of years, shares reserved for issuance will increase

8 years

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

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

Reserve of common stock for future issuance

20,000,000

Number of purchase periods for offering | 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]

Shares available for grant

290,000

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.

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] | 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

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

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

Reserve of common stock for future issuance

4,733,333

Greater 10% Ownership [Member] | 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

110.00%

Minimum percentage of combined voting power

10.00%

Capital Stock - Option and Perf

Capital Stock - Option and Performance-Based Restricted Share Unit Activity Under Incapsula Plan (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	2,279,081	1,044,651
Number of Restricted Stock Units Outstanding, Granted	911,734	1,368,761
Number of Restricted Stock Units Outstanding, Exercised/Released	898,205	238,446
Number of Restricted Stock Units Outstanding, Forfeited	(643,805)	(225,853)
Number of Restricted Stock Units Outstanding, Unvested - Ending balance	1,898,025	2,279,081	1,044,651
Number of Stock Options Outstanding, Outstanding - Beginning balance	2,244,363	1,675,506	1,989,237
Number of Stock Options Outstanding, Granted	696,971	1,256,559	631,775
Number of Stock Options Outstanding, Exercised/Released	(636,424)	(496,297)	(687,719)
Number of Stock Options Outstanding, Forfeited	(355,821)	(264,012)	(257,787)
Number of Stock Options Outstanding, Outstanding - Ending balance	1,949,089	2,244,363	1,675,506
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.27	$ 33.83	$ 23.78	$ 14.08
Weighted Average Exercise Price of Stock Options Outstanding, Granted	49.20	41.39	36.55
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released	29.44	14.85	6.94
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited	$ 42	$ 35.85	$ 25.11
Incapsula Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Outstanding - Beginning Balance	0	89,687	2,753,708
Additional shares authorized			5,529,878
Shares Available for Grant, Granted		(95,000)
Shares Available for Grant, Exercised/Released			0
Shares Available for Grant, Forfeited		15,213	141,562
Shares Available for Grant, Transferred to Imperva 2011 stock option plan		(9,900)
Shares Available for Grant, Outstanding - Ending Balance		0	89,687
Number of Stock Options Outstanding, Outstanding - Beginning balance	0	1,806,500	1,836,500
Number of Stock Options Outstanding, Granted		95,000
Number of Stock Options Outstanding, Exercised/Released			(1,128,438)
Number of Stock Options Outstanding, Forfeited		(2,500)	(141,562)
Number of Stock Options Outstanding, Transferred to Imperva 2011 stock option plan		(1,899,000)
Number of Stock Options Outstanding, Outstanding - Ending balance		0	1,806,500
Weighted Average Exercise Price of Stock Options Outstanding		$ 0	$ 0.47	$ 0.10
Weighted Average Exercise Price of Stock Options Outstanding, Granted		1.25
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released			0.02
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited		1.25	0.22
Weighted Average Exercise Price of Stock Options Outstanding, Transferred to Imperva 2011 stock option plan		$ 0.16	$ 0
Incapsula Plan [Member] | Performance RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Granted			(7,095,461)
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	0	7,095,461	0
Number of Restricted Stock Units Outstanding, Additional Stock authorized			0
Number of Restricted Stock Units Outstanding, Granted		0	7,095,461
Number of Restricted Stock Units Outstanding, Exercised/Released			0
Number of Restricted Stock Units Outstanding, Forfeited		(12,713)	0
Number of Restricted Stock Units Outstanding, Transferred to Imperva 2011 stock option plan		(7,082,748)
Number of Restricted Stock Units Outstanding, Unvested - Ending balance		0	7,095,461
Number of Stock Options Outstanding, Granted			0
Weighted Average Exercise Price of Stock Options Outstanding, Granted			$ 0
Incapsula Plan [Member] | Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Granted			(1,240,000)
Number of Restricted Stock Units Outstanding, Granted			0
Number of Stock Options Outstanding, Granted			1,240,000
Weighted Average Exercise Price of Stock Options Outstanding, Granted			$ 0.58

Capital Stock - Summary of Opti

Capital Stock - Summary of Option Activity under Plans and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options Outstanding, Outstanding - Beginning balance	2,244,363	1,675,506	1,989,237
Number of Stock Options Outstanding, Granted	696,971	1,256,559	631,775
Number of Shares, Options assumed in acquisitions		72,607
Number of Stock Options Outstanding, Exercised or released	(636,424)	(496,297)	(687,719)
Number of Stock Options Outstanding, Cancelled or forfeited	(355,821)	(264,012)	(257,787)
Number of Stock Options Outstanding, Outstanding - Ending balance	1,949,089	2,244,363	1,675,506	1,989,237
Number of Shares, Vested and expected to vest	1,700,981
Number of Shares, Exercisable	609,137
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.27	$ 33.83	$ 23.78	$ 14.08
Weighted Average Exercise Price, Granted	49.20	41.39	36.55
Weighted Average Exercise Price, Options assumed in acquisitions		13.30
Weighted Average Exercise Price, Exercised	29.44	14.85	6.94
Weighted Average Exercise Price, Cancelled or forfeited	42	$ 35.85	$ 25.11
Weighted-Average Exercise Price, Vested and expected to vest	38.26
Weighted Average Exercise Price, Exercisable	$ 29.57
Weighted Average Remaining Contractual Term (in years)	8 years 1 month 2 days	8 years 3 months 7 days	8 years 4 days	8 years 1 month 2 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	8 years 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable	6 years 10 months 28 days
Aggregate Intrinsic Value	$ 47,480	$ 38,457	$ 40,813	$ 35,513
Aggregate Intrinsic Value, Vested and expected to vest	43,108
Aggregate Intrinsic Value, Exercisable	$ 20,557

Capital Stock - Summary of Op71

Capital Stock - Summary of Option Activity under Plans and Related Information (Parenthetical) (Detail)	Dec. 31, 2015$ / shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Closing stock price	$ 63.31

Capital Stock - Additional In72

Capital Stock - Additional Information Regarding Company's Stock Options Outstanding and Exercisable (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Stock Options Outstanding | shares	1,949,089
Weighted Average Remaining Contractual Life (Years)	8 years 1 month 2 days
Weighted Average Exercise Price per Share	$ 39.27
Shares Subject to Stock Options | shares	609,137
Weighted Average Exercise Price per Share	$ 29.57
Exercise price range one [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	0.02
Company's stock options outstanding and exercisable, Upper Range	$ 10.70
Number of Stock Options Outstanding | shares	157,918
Weighted Average Remaining Contractual Life (Years)	4 years 10 months 10 days
Weighted Average Exercise Price per Share	$ 6.66
Shares Subject to Stock Options | shares	148,074
Weighted Average Exercise Price per Share	$ 7.07
Exercise price range two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	10.71
Company's stock options outstanding and exercisable, Upper Range	$ 29.10
Number of Stock Options Outstanding | shares	242,340
Weighted Average Remaining Contractual Life (Years)	7 years 7 months 28 days
Weighted Average Exercise Price per Share	$ 25.34
Shares Subject to Stock Options | shares	118,092
Weighted Average Exercise Price per Share	$ 24.95
Exercise price range three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	29.11
Company's stock options outstanding and exercisable, Upper Range	$ 32.54
Number of Stock Options Outstanding | shares	269,777
Weighted Average Remaining Contractual Life (Years)	8 years 6 months 4 days
Weighted Average Exercise Price per Share	$ 29.43
Shares Subject to Stock Options | shares	72,161
Weighted Average Exercise Price per Share	$ 29.66
Exercise price range four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	32.55
Company's stock options outstanding and exercisable, Upper Range	$ 34.55
Number of Stock Options Outstanding | shares	206,863
Weighted Average Remaining Contractual Life (Years)	7 years 3 months 4 days
Weighted Average Exercise Price per Share	$ 33.72
Shares Subject to Stock Options | shares	99,746
Weighted Average Exercise Price per Share	$ 33.62
Exercise price range five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	34.56
Company's stock options outstanding and exercisable, Upper Range	$ 54.48
Number of Stock Options Outstanding | shares	581,938
Weighted Average Remaining Contractual Life (Years)	8 years 9 months 15 days
Weighted Average Exercise Price per Share	$ 43.19
Shares Subject to Stock Options | shares	74,298
Weighted Average Exercise Price per Share	$ 41.88
Exercise price range six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	54.49
Company's stock options outstanding and exercisable, Upper Range	$ 61.55
Number of Stock Options Outstanding | shares	275,131
Weighted Average Remaining Contractual Life (Years)	8 years 1 month 21 days
Weighted Average Exercise Price per Share	$ 54.98
Shares Subject to Stock Options | shares	82,179
Weighted Average Exercise Price per Share	$ 54.76
Exercise price range seven [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	61.56
Company's stock options outstanding and exercisable, Upper Range	$ 69.55
Number of Stock Options Outstanding | shares	184,232
Weighted Average Remaining Contractual Life (Years)	9 years 2 months 16 days
Weighted Average Exercise Price per Share	$ 64.87
Shares Subject to Stock Options | shares	14,587
Weighted Average Exercise Price per Share	$ 62.81
Exercise price range eight [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	69.56
Company's stock options outstanding and exercisable, Upper Range	$ 77
Number of Stock Options Outstanding | shares	30,890
Weighted Average Remaining Contractual Life (Years)	9 years 9 months 15 days
Weighted Average Exercise Price per Share	$ 71.72
Shares Subject to Stock Options | shares	0
Weighted Average Exercise Price per Share	$ 0

Capital Stock - Summary of RSU

Capital Stock - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	2,279,081	1,044,651
Number of Restricted Stock Units Outstanding, Granted	911,734	1,368,761
Number of Restricted Stock Units Outstanding, Granted, performance RSUs	249,220	131,143
Number of Restricted Stock Units Outstanding, PRSUs assumed in acquisitions		198,825
Number of Restricted Stock Units Outstanding, Released	(898,205)	(238,446)
Number of Restricted Stock Units Outstanding, Cancelled or expired	(643,805)	(225,853)
Number of Restricted Stock Units Outstanding, Unvested - Ending balance	1,898,025	2,279,081	1,044,651
Weighted-Average Grant Date Fair Value, Unvested	$ 49.53	$ 39.07	$ 31.64
Weighted-Average Grant Date Fair Value, Granted	53.02	41.66
Weighted-Average Grant Date Fair Value, Granted, performance RSUs	42.58	31.42
Weighted-Average Grant Date Fair Value, PRSUs assumed in acquisitions		61.14
Weighted-Average Grant Date Fair Value, Released	34.97	34.84
Weighted-Average Grant Date Fair Value, Cancelled or expired	$ 35.09	$ 39.83

Capital Stock - Stock-Based Com

Capital Stock - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 50,964	$ 37,273	$ 22,494
Cost of revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,862	2,058	1,440
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	13,831	8,799	3,660
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	16,717	13,558	8,537
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 16,554	$ 12,858	$ 8,857

Capital Stock - Weighted Averag

Capital Stock - Weighted Average Assumptions for Fair Value of Stock Options Grants and ESPP Grants (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%	0.00%
Risk-free interest rate	0.40%	0.10%	0.10%
Expected term (in years)	6 months	6 months	6 months
Expected volatility	65.00%	45.00%	27.00%
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%	0.00%
Risk-free interest rate	1.80%	1.80%	1.20%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	49.00%	46.00%	46.00%

Accumulated Other Comprehensi76

Accumulated Other Comprehensive Income (Loss) - Changes in Balances of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (1,489)	$ (428)	$ 861
Other comprehensive income (loss) before reclassifications	(814)	(1,714)	746
Amounts reclassified to net loss	972	653	(2,035)
Other comprehensive income (loss)	158	(1,061)	(1,289)
Ending Balance	(1,331)	(1,489)	(428)
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,428)	(426)	691
Other comprehensive income (loss) before reclassifications	(565)	(1,655)	712
Amounts reclassified to net loss	972	653	(1,829)
Other comprehensive income (loss)	407	(1,002)	(1,117)
Ending Balance	(1,021)	(1,428)	(426)
Unrealized Gain (Loss) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(61)	(2)	170
Other comprehensive income (loss) before reclassifications	(249)	(59)	34
Amounts reclassified to net loss	0	0	(206)
Other comprehensive income (loss)	(249)	(59)	(172)
Ending Balance	$ (310)	$ (61)	$ (2)

Accumulated Other Comprehensi77

Accumulated Other Comprehensive Income (Loss) - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Current period unrealized gain (loss) on cash flow hedges, Pre-Tax Amount	$ (565)	$ (1,655)	$ 712
Reclassification adjustments on cash flow hedges, Pre-Tax Amount	972	653	(1,829)
Unrealized gains (losses) on cash flow hedges, net, Pre-Tax Amount	407	(1,002)	(1,117)
Current period unrealized gain (loss) on investments, Pre-Tax Amount	(249)	(59)	34
Reclassification adjustments on investments, Pre-Tax Amount	0	0	(206)
Unrealized gains (losses) on investments, net, Pre-Tax Amount	(249)	(59)	(172)
Other comprehensive income (loss), Pre-Tax Amount	158	(1,061)	(1,289)
Current period unrealized gain (loss) on cash flow hedges, Tax Expense (Benefit)	0	0	0
Reclassification adjustments on cash flow hedges, Tax Expense (Benefit)	0	0	0
Unrealized gains (losses) on cash flow hedges, net, Tax Expense (Benefit)	0	0	0
Current period unrealized gain (loss) on investments, Tax Expense (Benefit)	0	0	0
Reclassification adjustments on investments, Tax Expense (Benefit)	0	0	0
Unrealized gains (losses) on investments, net, Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss), Tax Expense (Benefit)	0	0	0
Current period unrealized gain (loss) on cash flow hedges, After-Tax Amount	(565)	(1,655)	712
Reclassification adjustments on cash flow hedges, After-Tax Amount	972	653	(1,829)
Unrealized gains (losses) on cash flow hedges, net, After-Tax Amount	407	(1,002)	(1,117)
Current period unrealized gain (loss) on investments, After-Tax Amount	(249)	(59)	34
Reclassification adjustments on investments, After-Tax Amount	0	0	(206)
Unrealized gains (losses) on investments, After-Tax Amount	(249)	(59)	(172)
Other comprehensive income (loss)	$ 158	$ (1,061)	$ (1,289)

Income Taxes - Loss Before Prov

Income Taxes - Loss Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ (50,892)	$ (55,330)	$ (28,831)
Foreign	2,692	(2,665)	3,277
Loss before provision for income taxes	$ (48,200)	$ (57,995)	$ (25,554)

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current
Federal		$ 0	$ 0
State	$ 34	66	127
Foreign	857	1,523	700
Total current provision	891	1,589	827
Deferred
Federal	63	109	0
State	(1)	6	0
Foreign	(271)	(523)	(50)
Total deferred provision	(209)	(408)	(50)
Provision for income taxes	$ 682	$ 1,181	$ 777

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Provision for Income Taxes at Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory tax rate	$ (16,388)	$ (19,718)	$ (8,688)
Tax benefit at state statutory tax rate	(499)	(1,169)	(829)
Foreign tax rate differential	(826)	(526)	(705)
Unbenefitted loss of consolidated investment	0	2,366	2,402
Change in valuation allowance	9,738	12,407	7,400
Meals and entertainment	44	34	197
Stock compensation	8,492	7,160	810
Nondeductible expenses and other	121	627	190
Provision for income taxes	$ 682	$ 1,181	$ 777

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Reserves and accruals	$ 2,662	$ 1,387
Deferred revenue	8,724	8,429
Stock-based compensation	4,772	5,776
Net operating loss carryforwards	37,793	25,519
Loss on OCI	374	380
Other	32	41
Gross deferred tax assets	54,357	41,532
Valuation allowance	(53,468)	(40,488)
Total deferred tax assets	889	1,044
Deferred tax liabilities:
Stock-based compensation	(21)	(53)
Depreciation and amortization	(1,425)	(1,757)
Total deferred tax liabilities	(1,446)	(1,810)
Net deferred tax assets	$ (557)	$ (766)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Expenses [Line Items]
Valuation allowance		$ 13,000,000	$ 7,800,000	$ 8,400,000
U.S. federal, net operating loss carryforwards		153,000,000
State net operating loss carryforwards		73,700,000
Excess tax benefits from stock options included in deferred tax assets for federal net operating losses		49,900,000
Excess tax benefits from stock options included in deferred tax assets for state net operating losses		13,500,000
Accumulated unremitted earnings		13,600,000	12,900,000	9,800,000
Unrecognized tax benefits		1,154,000	672,000	$ 353,000	$ 239,000
Accrued interest on income tax expense		$ 83,000	$ 43,000
2014 [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		12.50%
2015 and Thereafter [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		12.00%
Israeli Tax Authority [Member]
Income Tax Expenses [Line Items]
Corporate tax rate		26.50%
Israeli Tax Authority [Member] | Previous [Member]
Income Tax Expenses [Line Items]
Corporate tax rate	25.00%
Israeli Tax Authority [Member] | Non R&D Activities [Member]
Income Tax Expenses [Line Items]
Corporate tax rate		26.50%
Israeli Tax Authority [Member] | 2011 [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		15.00%
Israeli Tax Authority [Member] | 2012 [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		15.00%
Israeli Tax Authority [Member] | 2013 [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		12.50%
Israeli Tax Authority [Member] | 2014 [Member]
Income Tax Expenses [Line Items]
Tax rate applicable for R&D activities		16.00%
Maximum [Member] | State [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,035
Maximum [Member] | Federal [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,035
Maximum [Member] | Israeli Tax Authority [Member]
Income Tax Expenses [Line Items]
Tax years		2,010
Minimum [Member] | State [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,018
Minimum [Member] | Federal [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,023
Minimum [Member] | Israeli Tax Authority [Member]
Income Tax Expenses [Line Items]
Tax years		2,006

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Beginning Balance	$ 672,000	$ 353,000	$ 239,000
Additions based on tax positions taken during the current period	401,000	222,000	134,000
Reductions based on tax positions taken during the prior period	(50,000)	(47,000)	(20,000)
Additions based on tax positions taken during a prior period	131,000	144,000	0
Ending Balance	$ 1,154,000	$ 672,000	$ 353,000

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Segment
Segment Reporting [Abstract]
Number of operating segments	1

Segment Information - Company's

Segment Information - Company's of Services Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer [Line Items]
Total net services revenue	$ 126,735	$ 89,711	$ 65,606
Maintenance and Support [Member]
Revenue from External Customer [Line Items]
Total net services revenue	66,380	54,795	44,353
Professional Services and Training [Member]
Revenue from External Customer [Line Items]
Total net services revenue	14,084	11,414	9,890
Subscriptions [Member]
Revenue from External Customer [Line Items]
Total net services revenue	$ 46,271	$ 23,502	$ 11,363

Segment Information - Company86

Segment Information - Company's Revenue by Geographic Region, Based on Customer's Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 234,298	$ 164,010	$ 137,759
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	149,766	94,266	83,736
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	57,180	43,111	33,183
APAC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 27,352	$ 26,633	$ 20,840

Segment Information - Long-Live

Segment Information - Long-Lived Assets by Location (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 20,155	$ 17,017	$ 5,475
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	9,913	6,761	3,039
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	10,224	10,221	2,422
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 18	$ 35	$ 14

Net Loss per Share - Computatio

Net Loss per Share - Computation of Company's Basic and Diluted Net Loss Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss attributable to Imperva, Inc. stockholders	$ (48,882)	$ (58,963)	$ (25,178)
Shares used in computing net loss per share of common stock, basic and diluted	29,849	25,806	24,300
Net loss per share of common stock, basic and diluted	$ (1.64)	$ (2.28)	$ (1.04)

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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	1,949,089	2,244,363	1,675,506
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	1,898,025	2,279,081	1,044,651
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	217,621	335,062
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	118,961	355,499	0