Imperva 10-K 28 Feb 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 15, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'IMPV	'	'
Entity Registrant Name	'IMPERVA INC	'	'
Entity Central Index Key	'0001364962	'	'
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	'	26,089,704	'
Entity Public Float	'	'	$922.90

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
CURRENT ASSETS:	'	'
Cash and cash equivalents	$76,704	$59,201
Short-term investments	38,381	43,126
Restricted cash	34	591
Accounts receivable, net of allowance for doubtful accounts of $410 and $412 as of December 31, 2013 and 2012, respectively	44,446	35,576
Inventory	512	328
Deferred tax assets	341	597
Prepaid expenses and other current assets	3,972	4,356
Total current assets	164,390	143,775
Property and equipment, net	5,475	5,515
Severance pay fund	4,140	3,150
Restricted cash	1,252	753
Deferred tax assets	42	'
Other assets	1,192	764
TOTAL ASSETS	176,491	153,957
CURRENT LIABILITIES:	'	'
Accounts payable	3,948	3,789
Accrued compensation and benefits	12,930	9,258
Accrued and other current liabilities	3,961	4,323
Deferred revenue	40,337	33,609
Total current liabilities	61,176	50,979
Other liabilities	1,993	2,638
Deferred revenue	22,715	12,682
Accrued severance pay	4,385	3,427
TOTAL LIABILITIES	90,269	69,726
Commitments and Contingencies (Note 9)	'	'
STOCKHOLDERS' EQUITY:	'	'
Preferred stock, $0.0001 par value-5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2013 and 2012, respectively	'	'
Common stock, $0.0001 par value-145,000,000 shares authorized, 25,206,498 and 24,296,076 shares issued and outstanding as of December 31, 2013 and 2012, respectively	2	2
Additional paid-in capital	187,957	157,989
Accumulated deficit	-98,695	-73,517
Accumulated other comprehensive income (loss)	-428	861
TOTAL IMPERVA, INC. STOCKHOLDERS' EQUITY	88,836	85,335
Noncontrolling interest	-2,614	-1,104
TOTAL STOCKHOLDERS' EQUITY	86,222	84,231
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$176,491	$153,957

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$410	$412
Preferred stock, par value	$0.00	$0.00
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	$0.00	$0.00
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	25,206,498	24,296,076
Common stock, shares outstanding	25,206,498	24,296,076

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net revenue:	'	'	'
Products and license	$72,153	$59,490	$47,600
Services	65,606	44,745	30,702
Total net revenue	137,759	104,235	78,302
Cost of revenue:	'	'	'
Products and license	8,756	8,530	6,711
Services	20,940	13,374	9,510
Total cost of revenue	29,696	21,904	16,221
Gross profit	108,063	82,331	62,081
Operating expenses:	'	'	'
Research and development	27,556	20,555	17,598
Sales and marketing	81,500	53,509	42,682
General and administrative	24,436	15,371	11,807
Total operating expenses	133,492	89,435	72,087
Loss from operations	-25,429	-7,104	-10,006
Other income (expense), net	-125	-243	-190
Loss before provision for income taxes	-25,554	-7,347	-10,196
Provision for income taxes	777	545	662
Net loss	-26,331	-7,892	-10,858
Loss attributable to noncontrolling interest	1,153	505	589
Net loss attributable to Imperva, Inc. stockholders	($25,178)	($7,387)	($10,269)
Net loss per share of common stock attributable to Imperva, Inc. stockholders, basic and diluted	($1.04)	($0.32)	($1.34)
Shares used in computing net loss per share of common stock, basic and diluted	24,300,198	22,916,426	7,674,554

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]	'	'	'
Net loss	($26,331)	($7,892)	($10,858)
Other comprehensive loss (net of tax):	'	'	'
Net change in net unrealized gain (loss) on investments	-172	227	-57
Net change in unrealized gains and losses on hedging instruments	-1,117	1,250	-1,011
Other comprehensive income (loss)	-1,289	1,477	-1,068
Comprehensive loss	-27,620	-6,415	-11,926
Comprehensive loss attributable to noncontrolling interest	1,153	505	589
Comprehensive loss attributable to Imperva, Inc. stockholders	($26,467)	($5,910)	($11,337)

Consolidated_Statements_of_Con

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
In Thousands, except Share data, unless otherwise specified
Beginning balance at Dec. 31, 2010	($52,419)	$53,442	$1	$3,340	($55,861)	$452	($351)
Beginning balance, shares at Dec. 31, 2010	'	10,761,511	6,143,018	'	'	'	'
Initial public offering shares issued, net of issuance costs	86,245	'	'	86,245	'	'	'
Initial public offering shares issued, net of issuance costs, shares	'	'	5,500,000	'	'	'	'
Exercise of warrant on preferred shares, amount	'	178	'	'	'	'	'
Exercise of warrant on preferred shares	'	9,721	'	'	'	'	'
Conversion of preferred shares, amount	53,621	-53,620	1	53,620	'	'	'
Conversion of preferred shares	'	-10,771,232	10,771,232	'	'	'	'
Conversion of preferred stock warrant to common stock warrant	129	'	'	129	'	'	'
Issuance of common stock upon exercise of stock options	1,145	'	'	1,145	'	'	'
Issuance of common stock upon exercise of stock options, shares	563,916	'	473,916	'	'	'	'
Issuance of common stock upon early exercise of stock options, shares	'	'	90,000	'	'	'	'
Vesting of restricted stock	1,046	'	'	1,046	'	'	'
Stock-based compensation	1,727	'	'	1,727	'	'	'
Purchase of additional ownership interest in Incapsula, Inc.	'	'	'	-167	'	'	167
Components of other comprehensive income (loss), net of tax	'	'	'	'	'	'	'
Change in unrealized gain (loss) on investments	-57	'	'	'	'	-57	'
Change in unrealized gain (loss) on derivatives	-1,011	'	'	'	'	-1,011	'
Net loss	-10,858	'	'	'	-10,269	'	-589
Comprehensive loss	-11,926	'	'	'	'	'	'
Ending balance at Dec. 31, 2011	79,568	'	2	147,085	-66,130	-616	-773
Ending balance, shares at Dec. 31, 2011	'	'	22,978,166	'	'	'	'
Issuance of common stock upon exercise of stock options	3,093	'	'	3,093	'	'	'
Issuance of common stock upon exercise of stock options, shares	1,272,941	'	1,272,940	'	'	'	'
Vesting of restricted stock	881	'	'	881	'	'	'
Stock-based compensation	5,968	'	'	5,968	'	'	'
Issuance of common stock in connection with employee stock purchase plan	1,117	'	'	1,117	'	'	'
Issuance of common stock in connection with employee stock purchase plan, shares	'	'	44,970	'	'	'	'
Income tax benefit from employee stock option exercises	19	'	'	19	'	'	'
Purchase of additional ownership interest in Incapsula, Inc.	'	'	'	-174	'	'	174
Components of other comprehensive income (loss), net of tax	'	'	'	'	'	'	'
Change in unrealized gain (loss) on investments	227	'	'	'	'	227	'
Change in unrealized gain (loss) on derivatives	1,250	'	'	'	'	1,250	'
Net loss	-7,892	'	'	'	-7,387	'	-505
Comprehensive loss	-6,415	'	'	'	'	'	'
Ending balance at Dec. 31, 2012	84,231	'	2	157,989	-73,517	861	-1,104
Ending balance, shares at Dec. 31, 2012	'	'	24,296,076	'	'	'	'
Issuance of common stock, net of repurchases	3,544	'	'	3,544	'	'	'
Issuance of common stock, net of repurchases, shares	'	'	806,226	'	'	'	'
Issuance of common stock upon exercise of stock options, shares	687,719	'	'	'	'	'	'
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	'	'	'	'
Sale of ownership interest in Incapsula, Inc.	'	'	'	357	'	'	-357
Components of other comprehensive income (loss), net of tax	'	'	'	'	'	'	'
Change in unrealized gain (loss) on investments	-172	'	'	'	'	-172	'
Change in unrealized gain (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	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES :	'	'	'
Net loss	($26,331)	($7,892)	($10,858)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:	'	'	'
Depreciation and amortization	2,642	1,841	1,540
Stock-based compensation	22,494	5,968	1,727
Revaluation of convertible preferred stock warrant liability	'	'	238
Amortization of premiums/accretion of discounts on short-term investments	639	496	'
Excess tax benefits from share-based compensation	'	-19	'
Changes in operating assets and liabilities:	'	'	'
Accounts receivable, net	-8,870	-9,840	-12,572
Inventory	-184	114	-55
Prepaid expenses and other assets	-1,161	-2,174	-95
Accounts payable	159	255	1,019
Accrued compensation and benefits	3,672	1,767	1,623
Accrued and other liabilities	-206	703	-622
Severance pay (net)	-32	169	-60
Deferred revenue	16,761	13,366	11,707
Deferred tax assets	214	-286	-121
Other	'	-1	-8
Net cash provided by (used in) operating activities	9,797	4,467	-6,537
CASH FLOWS FROM INVESTING ACTIVITIES:	'	'	'
Purchase of short-term investments	-38,021	-58,158	-2,948
Proceeds from sales/maturities of short-term investments	42,162	16,305	2,611
Net purchases of property and equipment	-2,602	-3,330	-1,465
Purchase of other assets	'	-400	'
Change in restricted cash	58	9	160
Net cash used provided by (used in) investing activities	1,597	-45,574	-1,642
CASH FLOWS FROM FINANCING ACTIVITIES:	'	'	'
Proceeds from issuance of common stock, net of repurchases	6,316	4,211	1,149
Proceeds from initial public offering, net of offering costs	'	'	86,245
Proceeds from issuance of restricted stock	'	'	963
Borrowings on revolving credit facility	'	'	4,000
Repayments of revolving credit facility	'	'	-4,501
Excess tax benefits from share-based compensation	'	19	'
Net cash provided by financing activities	6,316	4,230	87,856
Effect of exchange rate changes on cash and cash equivalents	-207	53	-62
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	17,503	-36,824	79,615
CASH AND CASH EQUIVALENTS - Beginning of period	59,201	96,025	16,410
CASH AND CASH EQUIVALENTS - End of period	76,704	59,201	96,025
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:	'	'	'
Cash paid for interest	'	'	25
Cash paid for income taxes	835	1,430	369
NONCASH INVESTING AND FINANCING ACTIVITIES:	'	'	'
Vesting of restricted and early exercised stock options	801	881	1,046
Conversion of convertible preferred stock to common stock	'	'	$53,620

The_Company_and_Summary_of_Sig

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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 data center security solutions that protect high value applications and data assets in physical and virtual data centers.
	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., its wholly-owned subsidiaries and one majority owned subsidiary, Incapsula, Inc. (“Incapsula”). All intercompany accounts and transactions have been eliminated in consolidation.
	Noncontrolling Interest
	The Company has recorded a noncontrolling interest in its consolidated balance sheets, consolidated statements of operations, comprehensive loss and convertible preferred stock and stockholders’ equity (deficit) for the 19%, 15%, and 18% ownership interest of the minority owners of Incapsula as of December 31, 2013, 2012 and 2011, respectively. Changes to the ownership interest in Incapsula held by the minority owners are accounted for as equity transactions in the consolidated statements of convertible preferred stock and stockholders’ equity (deficit) as the Company obtained control of Incapsula on November 5, 2009.
	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 and inventory, and assumptions used in the calculation of 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 convertible preferred stock and stockholders’ equity (deficit) 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, 2013, there were no outstanding forward foreign currency exchange contracts thus no derivative gains or losses were included in accumulated other comprehensive loss. 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 convertible preferred stock and stockholders’ equity (deficit) 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 a facility lease, and collateral for the Company’s contract manufacturer in regards to the Company’s obligation to purchase inventory. As of December 31, 2012, the Company had classified $591,000 of restricted cash as a current asset relating to inventory purchase commitments. In addition, as of December 31, 2013 and 2012, the Company has classified $1.3 million and $753,000, respectively, of security deposit as non-current assets relating to its facility lease arrangement.
	Inventory
	Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value determined on an average cost basis. 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, 2013, 2012 and 2011, there was no inventory write-down incurred by the Company.
	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.
	Impairment of Long-Lived Assets
	The Company evaluates its long-lived assets, which consist of property and equipment, 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, 2013 and 2012, 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 issued pursuant to the terms and conditions of a distributor or value-added reseller agreement and, in limited cases, 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. The Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with its sales.
		•	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 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. 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, TPE of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its 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 our 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, 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 more than 10% of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the year ended December 31, 2013 the Company had one customer that represented 10% of the Company’s total revenue. For the years ended December 31, 2012 and 2011, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There were no customers who represented greater than 10% of gross accounts receivable as of December 31, 2013 and 2012.
	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, 2013, 2012 and 2011, 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, 2013, 2012 and 2011.
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, 2013, 2012 and 2011 of $1.2 million, $1.0 million, and $1.0 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 makes certain estimates and judgments in determining income tax expense for financial statement purposes. These estimates and judgments occur in the calculation of tax credits, tax benefits and deductions and in the calculation of certain tax assets and liabilities, which arise from differences in the timing of recognition of revenue and expense for tax and financial statement purposes. Significant changes to these estimates may result in an increase or decrease to the Company’s tax provision in the subsequent period when such a change in estimate occurs.
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.
At December 31, 2013, the Company had net deferred income tax assets, related primarily to net operating loss carry forwards , deferred revenue, stock based compensation and accruals and reserves that are not currently deductible of $33.0 million, which have been partially offset by $32.7 million of valuation allowance. At December 31, 2012, the Company had net deferred income tax assets, related primarily to net operating loss carry forwards, deferred revenue, stock based compensation and accruals and reserves that are not currently deductible of $24.6 million, which have been partially offset by $24.3 million of valuation allowance.
Liability Associated with Warrants to Purchase Convertible Preferred Stock
The Company accounts for freestanding warrants to purchase shares of convertible preferred stock that are contingently redeemable as liabilities on the consolidated balance sheet at their estimated fair value because the warrants may obligate the Company to redeem these warrants at some point in the future. At the end of each reporting period, changes in the estimated fair value of the warrants to purchase shares of the convertible preferred stock are recorded through other income (expense), net in the consolidated statements of operations. In connection with our IPO, the warrants to purchase convertible preferred stock were converted into warrants to purchase common stock. Accordingly, as of December 31, 2013 and 2012, there were no outstanding warrants to purchase shares of convertible preferred stock.
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 Incapsula 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 a revenue forecast. The Company updates the estimated expense, net of forfeitures, at the end of each reporting period. Based on forecasted revenue for 2014 until the actual 2014 revenue performance becomes known, the expense is recognized on an accelerated basis over the requisite service period, generally vesting period of the respective awards.
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
The Company measures and reports its cash equivalents, short-term investments, derivative instruments, the Israeli severance pay fund assets, and the liability associated with the warrants to purchase convertible preferred stock 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
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, convertible preferred stock, stock options to purchase common stock, common stock subject to repurchase, warrants to purchase convertible preferred stock 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.
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 two operating segments which are both reportable business segments: (i) Imperva, which is comprised of Imperva’s and its wholly-owned subsidiaries’ financial position and results of operations; and (ii) Incapsula, which is comprised of Incapsula’s financial position and results from operations.
Recent Accounting Pronouncements
From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Incapsula

Incapsula	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interest [Abstract]	'
Incapsula	'
	2. Incapsula
	On November 5, 2009, the Company entered into a license agreement for Incapsula to use certain developed technology of the Company. In lieu of any other fee or royalty under the license agreement, Incapsula issued to the Company 5,000,000 shares of its Series A Convertible Preferred Stock representing a 58% ownership interest at the date of issuance. The transaction was accounted for as a business combination. No value was assigned to the license on the acquisition date as the use of the license will stay within the control of the Company. Therefore, the Company’s historical carrying value of the developed technology immediately prior to the acquisition was used to determine the value of the purchase consideration exchanged in the transaction. As Incapsula was a newly-formed entity with no net assets on the acquisition date and the value of the license was determined to be zero, no goodwill was recorded by the Company on the acquisition.
	Under the terms of the agreements between the Company and Incapsula, the Company has the right, but not the obligation, to purchase the remaining ownership interest in Incapsula commencing on November 5, 2013 and ending on November 5, 2018 (the “Purchase Right”). Exercise of the Purchase Right is solely within the Company’s control and the price for the remaining ownership interest will be based on an Incapsula enterprise valuation calculated as the greater of (i) eight times Incapsula’s prior 12 months trailing revenues or (ii) seven times the aggregate amount Incapsula has raised in connection with its Series A Convertible Preferred Stock financings. On the acquisition date, no value was assigned to this Purchase Right as the option does not meet the definition of a derivative instrument as it does not contain a net settlement feature. Specifically, the Purchase Right can only be gross physically settled as Incapsula is a non-publicly traded company whose stock is not readily convertible to cash.
	On March 9, 2010, the Company entered into a Series A and Series A-1 Purchase Agreement whereby Incapsula issued 6,666,666 shares of its Series A Convertible Preferred Stock to the Company in exchange for cash consideration of $3.0 million. As a result of this transaction, the Company increased its ownership interest in Incapsula to 76% at the date of issuance. The purchase of the additional ownership interest in Incapsula was treated as an equity transaction.
	Under the terms of the Series A and Series A-1 Purchase Agreement, the Company entered into a forward contract with Incapsula to purchase 8,750,000 shares of Incapsula’s Series A-1 Convertible Preferred Stock in exchange for $7.0 million in cash consideration if certain milestones were achieved no later than September 2011. On the transaction date, no value was assigned to the forward contract as the option did not meet the definition of a derivative instrument as it did not contain a net settlement feature. Specifically, the forward contract could only be gross physically settled as Incapsula is a non-publicly traded company whose stock was not readily convertible to cash.
	In July 2011, Incapsula achieved the respective performance milestones. As a result, the Company purchased 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest to 82%. In January 2012, the Company purchased the remaining 4,375,000 shares of Incapsula’s Series A-1 Preferred Stock for $3.5 million thereby increasing its ownership interest in Incapsula to 85% at the date of issuance.
	As of December 31, 2013 and 2012, all of the outstanding shares of Incapsula’s Series A and A-1 Convertible Preferred Stock were held by the Company.
	In March 2010, the board of directors of Incapsula adopted the Incapsula 2010 Share Incentive Plan pursuant to which Incapsula may grant to its employees options to purchase shares of Incapsula’s common stock or restricted share units (RSUs). If the Company exercises the Purchase Right option discussed above, awards under the Incapsula 2010 Share Incentive Plan would be assumed by the Company, substituted with Company stock options, restricted shares or cashed out, and all outstanding awards and the Incapsula 2010 Share Plan would terminate.
	In October 2013, the Company loaned $1.1 million to Incapsula at a rate of 2% with a maturity date of December 31, 2014 (“the Incapsula Loan”). In November 2013, the Company reached an agreement in principle with the major stockholders of Incapsula (other than Imperva) to acquire the remaining outstanding capital stock and assume outstanding options to acquire capital stock of Incapsula not already owned by Imperva (the “Incapsula Purchase”). The aggregate consideration for the Incapsula Purchase is to be substantially on the same terms of the Purchase Right less the outstanding principal and interest under the Incapsula Loan. Subsequent to year end, the Company entered into a binding definitive agreement with all of the Incapsula stockholders other than Imperva with respect to such acquisition, the completion of which is subject to customary closing conditions, including regulatory clearance. The Company also issued RSUs for approximately 264,878 shares of Imperva common stock with performance-based vesting tied to 2014 revenue for Incapsula and Incapsula-related products and services (effectively valuing such revenues similarly to the Purchase Right) less the outstanding principal and interest under the Incapsula Loan. At the same time, Incapsula issued similar RSUs for approximately 204,820 shares on an as-converted to Imperva common stock-basis, which the Company will assume in connection with the Incapsula Acquisition, in addition to the consideration for the Incapsula Purchase. These performance-based RSUs granted by Imperva and Incapsula were issued to continuing employees of Incapsula. See Note 16 (Subsequent Events) for more information regarding the Incapsula Acquisition.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2013
Cash And Cash Equivalents [Abstract]	'
Cash, Cash Equivalents and Short-Term Investments	'
	3. Cash, Cash Equivalents and Short-Term Investments
	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		As of December 31, 2013
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	41,973	$	—	$	—	$	41,973
	Bank deposits		10,165				—		10,165
	Commercial paper		21,948		—		1		21,947
	Money market funds		2,619		—		—		2,619
	Total	$	76,705	$	—	$	1	$	76,704
	Short-term investments:
	Corporate debt obligations	$	28,220	$	22	$	14	$	28,228
	Bank deposits		10,153		—		—		10,153
	Total	$	38,373	$	22	$	14	$	38,381
		As of December 31, 2012
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	27,602	$	—	$	—	$	27,602
	Bank deposits		10,107				—		10,107
	Commercial paper		17,748		—		3		17,745
	Money market funds		3,045		—		—		3,045
	Corporate debt obligations		702						702
	Total		59,204		—		3		59,201
	Short-term investments:
	Commercial paper	$	1,000	$	—	$	—	$	1,000
	Corporate debt obligations		29,040		22		—		29,062
	Bank deposits		10,057		—		—		10,057
	US agency securities		1,001		—		—		1,001
	Mutual funds		1,847		159		—		2,006
	Total	$	42,945	$	181	$	—	$	43,126
	None of the Company’s short-term investments have been in an unrealized loss position for more than twelve months as of December 31, 2013 and 2012.
	The following table sets forth the cost and estimated fair value of short-term investments based on stated effective maturities as of December 31, 2013 (in thousands):
		As of December 31, 2013
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	19,466	$	19,470
	Due within two years		18,907		18,911
	Total	$	38,373	$	38,381
	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, 2013 and 2012, the Company did not consider any of its investments to be other-than-temporarily impaired.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	4. 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, 2013 and 2012, by level within the fair value hierarchy (in thousands):
		As of December 31, 2013
		Level I			Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Bank deposits	$	—		$	10,165	$	—	$	10,165
	Commercial paper		—			21,947		—		21,947
	Money market funds		2,619			—		—		2,619
	Short-term investments:
	Corporate debt obligations	$	—		$	28,228	$	—	$	28,228
	Bank deposits		—			10,153		—		10,153
	Total financial assets	$	2,619		$	70,493	$	—	$	73,112
		As of December 31, 2012
		Level I			Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Bank deposits	$	—		$	10,107	$	—	$	10,107
	Commercial paper		—			17,745		—		17,745
	Corporate debt obligations		—			702		—		702
	Money market funds		3,045			—		—		3,045
	Short-term investments:
	Corporate debt obligations	$	—		$	29,062	$	—	$	29,062
	Bank deposits		—			10,057		—		10,057
	Commercial paper		—			1,000		—		1,000
	US agency securities		—			1,001		—		1,001
	Mutual funds		2,006			—		—		2,006
	Total financial assets	$	5,051		$	69,674	$	—	$	74,725
	Prepaid expenses and other current assets—Forward foreign exchange contracts	$	—		$	1,226	$	—	$	1,226
	In addition to the amounts disclosed in the above table, the fair value of the Company’s Israeli severance pay assets, which were comprised of Level II assets, was $4.1 million and $3.2 million as of December 31, 2013 and 2012, respectively.
	Our 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, 2013 and 2012.
	The following table sets forth a summary of the changes in the fair value of the Company’s Level III financial liabilities (in thousands):
	Fair value—January 1, 2011	$	69
	Change in fair value of convertible preferred stock warrant liability		238
	Reclassification to additional paid-in capital upon conversion to common stock warrant		(129	)
	Reclassification to preferred stock upon exercise of warrants		(178	)
	Fair value—December 31, 2011	$	—

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	5. 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.
	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands):
			Asset as of December 31,
			2013						2012
			Notional			Fair Value			Notional			Fair Value
			Amount						Amount
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships -
	Forward foreign exchange contracts included in prepaid expenses and other current assets		$	—		$	—		$	20,513		$	1,117
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships -
	Forward foreign exchange contracts included in prepaid expenses and other current assets		$	—		$	—		$	2,296		$	109
	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):
			2013			2012			2011
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Gains recognized in OCI (a)		$	730		$	1,304		$	—
	Losses recognized in OCI (a)			(18	)		(225	)		(1,231	)
	Gains recognized from accumulated OCI into net loss (b)			1,829			—			220
	Losses recognized from accumulated OCI into net loss (b)			—			(598	)		—
	Losses recognized in net loss (c)			—			(5	)		(38	)
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships:
	Gains recognized in net loss (d)			71			181			—
	Losses recognized in net loss (d)		$	(60	)	$	(121	)	$	—
	(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 $117, $(45) and $16 were recognized within cost of sales for the years ended December 31, 2013, 2012 and 2011, respectively, and $1,712, $(553), and $204 were recognized within operating expenses for the year ended December 31, 2013, 2012 and 2011, respectively. All amounts are reflected with the respective consolidated statement of operations.
	(c)	Ineffective portion and amount excluded from effectiveness testing classified in other income (expense), net.
	(d)	Classified in other income (expense), net.

Consolidated_Balance_Sheet_Com

Consolidated Balance Sheet Components	12 Months Ended
	Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Consolidated Balance Sheet Components	'
	6. Consolidated Balance Sheet Components
	Accounts Receivable Allowance for Doubtful Accounts
	The allowance for doubtful accounts is comprised of the following activity (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Allowance for doubtful accounts, beginning balance	$	412		$	225		$	407
	Charged to costs and expenses		46			269			202
	Recoveries		—			—			(37	)
	Deductions (write-offs)		(48	)		(82	)		(347	)
	Allowance for doubtful accounts, ending balance	$	410		$	412		$	225
	Prepaid and Other Current Assets
	Prepaid and other current assets consist of the following (in thousands):
		As of December 31,
		2013			2012
	Prepaid expenses	$	2,632		$	1,646
	Derivative asset		—			1,226
	Prepaid income taxes		786			631
	Interest receivable		268			326
	Other		286			527
	Total prepaid and other current assets	$	3,972		$	4,356
	Property and Equipment
	Property and equipment consist of the following (in thousands):
		As of December 31,
		2013			2012
	Computers and related equipment	$	8,989		$	7,088
	Office furniture and equipment		1,403			1,438
	Leasehold improvements		2,773			2,670
	Total property and equipment		13,165			11,196
	Less: accumulated depreciation and amortization		(7,690	)		(5,681	)
	Total property and equipment, net	$	5,475		$	5,515
	Depreciation and amortization expense totaled $2.6 million, $1.8 million and $1.5 million, and for the years ended December 31, 2013, 2012 and 2011, respectively.
	Accrued Compensation and Benefits
	Accrued compensation and benefits consist of the following (in thousands):
		As of December 31,
		2013			2012
	Salary and related benefits	$	4,399		$	2,761
	Accrued vacation		4,122			3,373
	Accrued incentive payments		4,409			3,124
	Total accrued compensation and benefits	$	12,930		$	9,258
	Accrued and Other Current Liabilities
	Accrued and other current liabilities consist of the following (in thousands):
		As of December 31,
		2013			2012
	Accrued expenses	$	2,295		$	2,602
	Income tax payable		325			396
	Short-term deferred rent		226			65
	Short-term stock repurchase liability		521			801
	Other		594			459
	Total accrued and other current liabilities	$	3,961		$	4,323
	Other Long-term Liabilities
	Other long-term liabilities consist of the following (in thousands):
		As of December 31,
		2013			2012
	Stock repurchase liability	$	857		$	1,377
	Long-term deferred rent		725			716
	Other		411			545
	Total other long-term liabilities	$	1,993		$	2,638

Other_Income_Expense_net

Other Income (Expense), net	12 Months Ended
	Dec. 31, 2013
Other Income And Expenses [Abstract]	'
Other Income (Expense), net	'
	7. Other Income (Expense), net
	Other income (expense), net is comprised of the following (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Other Income:
	Interest income	$	386		$	460		$	28
	Forward foreign exchange contract gains, net		12			—			—
	Foreign currency exchange gains, net		—			—			203
	Total		398			460			231
	Other Expense:
	Convertible preferred stock warrant liability losses		—			—			(238	)
	Forward foreign exchange contract losses, net		—			(19	)		(39	)
	Foreign currency exchange losses, net		(373	)		(497	)		—
	Other		(150	)		(187	)		(144	)
	Total		(523	)		(703	)		(421	)
	Total other income (expense), net	$	(125	)	$	(243	)	$	(190	)

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Debt	'
	8. Debt
	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 $6.0 million as of December 31, 2013. As of December 31, 2013 and 2012, there was no balance outstanding on the credit facility.
	The credit facility expires on May 1, 2014, is secured by the assets of the Company, and contains a restrictive covenant that requires the Company to maintain a minimum cash and cash equivalents balance of $3.0 million. The terms of this agreement requires payment of an unused line fee of 0.25% per quarter of the unused portion and bears interest at LIBOR plus 2.75%. As of December 31, 2013, the Company was compliant with the amended covenant of the credit facility.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	9. Commitments and Contingencies
	Operating Leases
	The Company rents its facilities under operating leases with lease periods expiring from 2013 to 2018. Future minimum payments under these facility operating leases are as follows as of December 31, 2013 (in thousands):
		Operating		Estimated
		Leases		Sublease
				Income
	Year Ending December 31:
	2014	$	4,693	$	578
	2015		2,338		244
	2016		2,390		82
	2017		1,917		—
	2018		272		—
	Total	$	11,610	$	904
	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, 2013, 2012 and 2011 was $3.3 million, $2.1 million, and $1.9 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, 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, 2013, 2012 and 2011 the Company has $1.3 million, $753,000 and $666,000, respectively, in restricted deposits to secure bank guarantees provided to the lessor.
	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 $80,000 as of December 31, 2013. Motor vehicle lease expenses for the years ended December 31, 2013, 2012 and 2011 were $2.4 million, $2.2 million and $2.1 million, respectively.
	Purchase Commitments
	As of both December 31, 2013 and 2012, the Company had purchase commitments of $3.2 million 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.
	The Company also provided stand-by letters of credit to its vendors to secure its obligation to purchase the inventory. As of December 31, 2012 the Company had $562,000 of restricted deposits to secure the stand-by letters of credit provided. There were no restricted deposits related to inventory as of December 31, 2013.
	Litigation
	From time to time, the Company may be subject to other legal proceedings and claims in the ordinary course of business. The Company is not currently a party to any material litigation; however, the Company has received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of intellectual property rights. While the outcome of these matters is remote, the Company does not expect that the ultimate costs to resolve these matters will have a material effect on the Company’s consolidated financial position, results of operations, or cash flows. The Company will record a liability when it believes that it is both probable that a loss has been incurred and the amount can be reasonably estimated.
	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 indemnification provisions is generally limited to the total amount paid under the agreement. However, certain agreements include 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.

Capital_Stock

Capital Stock	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Capital Stock	'
	10. 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,
		2013			2012
	Issuance upon exercise of common stock warrant		—			8,333
	Issuance in connection with outstanding stock options		1,675,506			1,989,237
	Issuance in connection with restricted stock units outstanding		1,044,651			446,915
	Reserved for future stock option and restricted stock unit grants		1,847,752			1,967,336
	Reserved for future issuance under the employee stock purchase plan		831,271			684,812
			5,399,180			5,096,633
	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 our 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. We currently have no shares of preferred stock outstanding and we have no present plans to issue any shares of preferred stock.
	Stock Plans
	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 our 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.
	2011 Stock Option and Incentive Plan
	On September 9, 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. As of December 31, 2013, there were 1,847,752 shares available for grant under the 2011 Plan. On January 1, 2014 and January 1, 2013, the share reserve under the 2011 Plan was automatically increased by 1,008,260 and 971,843 shares, respectively.
	The 2011 Plan permits the granting of incentive stock options, non-qualified stock options, restricted stock units (RSUs), stock appreciation rights, restricted shares of common stock and performance share awards. The exercise price of stock options may not be less than the 100% of the fair market value of the common stock on the date of grant. Options granted pursuant to the 2011 Plan generally expire 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 restricted stock units to an employee of Incapsula for approximately 264,878 shares of Company common stock (Refer to Note 2).
	2011 Employee Stock Purchase Plan
	On September 9, 2012, 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 our common stock purchased under the ESPP will be 85% of the lesser of the fair market value of our 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 our stockholders. On January 1, 2014 and 2013, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 252,065 and 242,961 shares, respectively.
	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 restricted share units. The total number of shares of common stock that were initially reserved for grant under the Incapsula Plan was 4,733,333 in the aggregate, subject to certain adjustments. In November 2013, the board of directors of Incapsula approved an increase in the number of shares reserved for grant under the Incapsula Plan to 10,263,211 in the aggregate. The increase in shares reserved was in conjunction with the issuance of performance-based restricted share awards as part of the Incapsula Acquisition further discussed in Note 2.
	In November 2013, the board of directors of Incapsula approved the grant of restricted stock units for 7,095,461 shares of Incapsula’s common stock (“Incapsula RSUs”). If the closing of the Incapsula Acquisition occurs, the Incapsula RSUs will be 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 are expected to convert into approximately 204,820 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 and performance-based restricted share unit activity under the Incapsula Plan and related information:
		Shares			Number of			Number of			Weighted
		Available			Performance-			Stock Options			Average Exercise
		for Grant			based Restricted			Outstanding			Price of Stock
					Share Units						Options
					Outstanding						Oustanding
	Outstanding—December 31, 2010		3,589,333			—			1,144,000		$	0.01
	Granted		(1,050,000	)		—			1,050,000			0.18
	Exercised		—			—			(37,500	)		0.11
	Forfeited		382,500			—			(382,500	)		0.16
	Outstanding—December 31, 2011		2,921,833			—			1,774,000		$	0.08
	Granted		(232,500	)		—			232,500			0.25
	Exercised		—			—			(105,625	)		0.15
	Forfeited		64,375			—			(64,375	)		0.18
	Outstanding—December 31, 2012		2,753,708			—			1,836,500		$	0.1
	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
	The following table summarizes option activity under the 2003 Plan and the 2011 Plan and related information:
		Options Outstanding						Weighted-			Aggregate
								Average			Intrinsic Value
								Remaining			(in thousands)
								Contractual
		Number of			Weighted Average			Term (in years)
		Shares			Exercise Price
	Outstanding—December 31, 2010		2,763,908		$	1.9			8.09		$	4,999
	Granted		1,067,050			9.74
	Exercised or released		(563,916	)		3.73
	Cancelled or forfeited		(396,037	)		4.02
	Outstanding—December 31, 2011		2,871,005			4.15			7.86			88,012
	Granted		698,240			31.8
	Exercised or released		(1,272,941	)		2.41
	Cancelled or forfeited		(307,067	)		9.98
	Balances—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
Balances—December 31, 2013		1,675,506		$	23.78			8.01		$	40,813
Vested and expected to vest—December 31, 2013		1,454,729		$	23.08			7.93		$	36,463
Exercisable—December 31, 2013		512,536		$	12.87			6.85		$	18,074
Additional information regarding the Company’s stock options outstanding and exercisable as of December 31, 2013 is summarized below:
Exercise Prices	Options Outstanding									Options Exercisable
	Number of			Weighted			Weighted			Shares Subject		Weighted
	Stock Options			Average			Average			to Stock Options		Average
	Outstanding			Remaining			Exercise Price					Exercise Price
				Contractual			per Share					per Share
				Life (Years)
$0.72 to $9.04		474,906			6.26		$	3.29			302,269	$	2.7
$9.05 to $17.35		107,947			7.65		$	10.7			33,116	$	10.7
$17.36 to $25.67		44,064			7.92		$	25.61			18,461	$	25.61
$25.68 to $33.99		498,384			8.45		$	31.34			147,217	$	30.73
$34.00 to $42.30		477,785			9.12		$	35.71			11,473	$	37.23
$42.31 to $50.62		72,420			9.69		$	45.87			—	$	—
		1,675,506			8.01		$	23.78			512,536	$	12.87
RSU Activity
A summary of RSU activity for the year ended December 31, 2013, is as follows:
	Number of			Weighted—
	Restricted			Average Grant
	Stock Units			Date Fair Value
	Outstanding
Unvested—December 31, 2011		—		$	—
Granted		458,790			31.24
Released		—			—
Cancelled or expired		(11,875	)		32.88
Unvested—December 31, 2012		446,915		$	31.2
Granted		577,528			36.94
Granted, performance RSUs		264,878			20.76
Released		(149,531	)		30.64
Cancelled or expired		(95,139	)		34.3
Unvested—December 31, 2013		1,044,651		$	31.64
Stock-Based Compensation Expense
The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, 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,
	2013			2012			2011
Cost of revenue	$	1,440		$	469		$	118
Research and development		3,660			1,227			130
Sales and marketing		8,537			2,543			412
General and administrative		8,857			1,729			1,067
Total stock-based compensation expense	$	22,494		$	5,968		$	1,727
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 Incapsula 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. Based on forecasted revenue for 2014 until the actual 2014 revenue performance becomes known, the expense is recognized on an accelerated basis over the requisite service period, generally 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 the average historical stock volatilities of several of the Company’s publicly listed peers over a period equal to the expected terms of the stock option grants and the offering period for employee stock purchase plan grants as the Company did not have a sufficient trading history to use the volatility of its own common stock.
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
	2013			2012			2011
Stock option grants:
Dividend rate		0	%		0	%		0	%
Risk-free interest rate		1.2	%		1	%		1.7	%
Expected term (in years)		6.1			6			5.4
Expected volatility		46	%		48	%		49	%
ESPP grants:
Dividend rate		0	%		0	%		—
Risk-free interest rate		0.1	%		0.1	%		—
Expected term (in years)		0.5			0.5			—
Expected volatility		27	%		39	%		—
The weighted-average grant date fair value of the Company’s stock options granted during the years ended December 31, 2013, 2012 and 2011 was $16.48, $14.54, and $5.03 per share, respectively. The aggregate grant date fair value of the Company’s stock options granted to employees during the years ended December 31, 2013, 2012 and 2011 was $7.3 million, $10.1 million, and $5.4 million, respectively. The aggregate grant date fair value of the Company’s stock options vested during the years ended December 31, 2013, 2012, and 2011 was $4.6 million, $2.1 million, and $1.5 million, respectively. The fair value of the Company’s restricted stock units vested during the year ended December 31, 2013 was $6.0 million. There were no restricted units that vested for the years ended December 31, 2012 and 2011.
The aggregate intrinsic value of options exercised under the Plan was $23.2 million, $34.6 million, and $5.8 million for the years ended December 31, 2013, 2012 and 2011, respectively. The aggregate intrinsic value is calculated as the difference between the per-share exercise price and the deemed fair value of the Company’s common stock for each share subject to an option multiplied by the number of shares subject to options at the date of exercise.
As of December 31, 2013, total compensation cost related to unvested stock-based awards granted to employees under the Plan, but not yet recognized, was $10.6 million, net of estimated forfeitures. As of December 31, 2013, this cost will be amortized to expense over a weighted-average remaining period of 2.3 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 $6.3 million, $4.2 million, and $2.1 million for the years ended December 31, 2013, 2012 and 2011, respectively. There was no capitalized stock-based compensation cost during the years ended December 31, 2013, 2012 and 2011. Recognized stock-based compensation tax benefits during the year ended December 31, 2012 was $19,000. There was no recognized stock-based compensation tax benefit during the years ended December 31, 2013 and 2011.
Common Stock Subject to Repurchase
Pursuant to restricted stock agreements with the Company’s CEO, the Company has 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 consolidated balance sheet and are reclassified to equity as the shares vest. The Company granted 843,819 shares of restricted common stock with a weighted-average grant date fair value per share of $1.94 during the year ended December 31, 2010. There were no grants of shares of restricted common stock during the years ended December 31, 2013 and 2012. As of December 31, 2013 and 2012, 290,062 and 448,279 shares of restricted common stock, respectively, held by the Company’s CEO were unvested and subject to repurchase by the Company.
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 total amount received in exchange for these shares of $1.1 million has been included in other liabilities in the accompanying consolidated balance sheet and is reclassified to equity as the shares vest. As of December 31, 2013 and 2012, 45,000 and 82,500 shares were unvested amounting to $1.4 million and $2.2 million in other liabilities, respectively.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	11. 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,
			2013									2012									2011
			Unrealized			Unrealized			Total			Unrealized			Unrealized			Total			Unrealized			Unrealized			Total
			gain			gain (loss)						gain			gain (loss)						gain			gain (loss)
			(loss) on			on						(loss)  on			on						(loss) on			on
			cash flow			investments						cash flow			investments						cash flow			investments
			hedges									hedges									hedges
	Balance at January 1		$	691		$	170		$	861		$	(559	)	$	(57	)	$	(616	)	$	452		$	—		$	452
	Other comprehensive income (loss) before reclassifications			712			34			746			652			284			936			(1,231	)		(55	)		(1,286	)
	Amounts reclassified to net loss			(1,829	)		(206	)		(2,035	)		598			(57	)		541			220			(2	)		218
	Change in other comprehensive income (loss)			(1,117	)		(172	)		(1,289	)		1,250			227			1,477			(1,011	)		(57	)		(1,068	)
	Balance at December 31		$	(426	)	$	(2	)	$	(428	)	$	691		$	170		$	861		$	(559	)	$	(57	)	$	(616	)
	The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the years 2013, 2012, and 2011 (in thousands):
			Year ended December 31,
			2013									2012									2011
			Pre-Tax			Tax			After-Tax			Pre-Tax			Tax			After-Tax			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount			Amount			Expense			Amount			Amount			Expense			Amount
						(Benefit)									(Benefit)									(Benefit)
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	712		$	—		$	712		$	1,079		$	427		$	652		$	(1,231	)	$	—		$	(1,231	)
	Reclassification adjustments(1)			(1,829	)		—			(1,829	)		598			—			598			220			—			220
	Unrealized gains (losses) on cash flow hedges, net			(1,117	)		—			(1,117	)		1,677			427			1,250			(1,011	)		—			(1,011	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			34			—			34			291			7			284			(55	)		—			(55	)
	Reclassification adjustments(2)			(206	)		—			(206	)		(57	)		—			(57	)		(2	)		—			(2	)
	Unrealized gains (losses) on investments:			(172	)		—			(172	)		234			7			227			(57	)		—			(57	)
	Other comprehensive income (loss)		$	(1,289	)	$	—		$	(1,289	)	$	1,911		$	434		$	1,477		$	(1,068	)	$	—		$	(1,068	)
	-1	Refer to note 5 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, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	12. Income Taxes
	The Company’s geographical breakdown of its loss before provision for income taxes is as follows (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Domestic	$	(28,831	)	$	(9,373	)	$	(12,747	)
	Foreign		3,277			2,026			2,551
	Loss before provision for taxes	$	(25,554	)	$	(7,347	)	$	(10,196	)
	The components of the provision for income taxes are as follows (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Current
	Federal	$	—		$	51		$	—
	State		127			47			63
	Foreign		700			889			618
	Total current provision		827			987			681
	Deferred
	Federal		—			(386	)		—
	State		—			(49	)		—
	Foreign		(50	)		(7	)		(19	)
	Total deferred provision		(50	)		(442	)		(19	)
	Total	$	777		$	545		$	662
	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,
		2013			2012			2011
	Tax benefit at federal statutory tax rate	$	(8,688	)	$	(2,497	)	$	(3,465	)
	Tax benefit at state statutory tax rate		(829	)		(282	)		(390	)
	Tax benefit resulting from “Beneficiary Enterprise”		—			(95	)		(191	)
	Foreign tax rate differential		(705	)		(232	)		(302	)
	Foreign repatriation		—			179			—
	Unbenefitted loss of consolidated investment		2,402			1,193			1,026
	Change in valuation allowance		7,400			1,373			3,072
	Meals and entertainment		197			162			145
	Warrants fair value adjustment		—			—			95
	Stock compensation		810			497			543
	Nondeductible expenses and other		190			247			129
	Provision for income taxes	$	777		$	545		$	662
	Basic net loss per share amounts of benefits resulting from	$	—		$	—		$	0.02
	Beneficiary Enterprise Status
	Significant components of the Company’s net deferred tax assets are as follows (in thousands):
		As of December 31,
		2013			2012
	Deferred tax assets:
	Reserves and accruals	$	1,345		$	1,169
	Deferred revenue		4,297			5,642
	Stock-based compensation		7,042			1,470
	Net operating loss carryforwards		20,361			17,530
	Other		194
	Gross deferred tax assets		33,239			25,811
	Valuation allowance		(32,656	)		(24,266	)
	Deferred tax assets		583			1,545
	Deferred tax liabilities:
	Stock-based compensation		(166	)		(314	)
	Depreciation and amortization		(31	)		(497	)
	Gain on OCI		(2	)		(435	)
	Total deferred tax liabilities		(200	)		(1,246	)
	Net deferred tax assets	$	383		$	299
	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 $8.4 million, $1.8 million, and $3.1 million in the years ended December 31, 2013, 2012 and 2011, respectively.
	As of December 31, 2013, the Company had U.S. federal and state net operating loss carryforwards of approximately $82.6 million and $65.3 million, respectively. The U.S. federal net operating loss carryforwards will expire at various dates beginning in 2023 through 2033 if not utilized. Most state net operating loss carryforwards will expire at various dates beginning in 2018 through 2033.
	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, 2013, the amount of such excess tax benefits from stock options included in deferred tax assets for federal and state net operating losses were $28.9 million and $21.8 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 2013, 2012, and 2011 the amount of accumulated unremitted earnings from the Company’s foreign subsidiaries is approximately $9.8 million, $7.2 million and $5.6 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, 2013 and 2012, the Company had gross unrecognized tax benefits of approximately $353,000 and $239,000, 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, 2013 and 2012, the Company accrued interest of $22,000 and $7,000 in income tax expense, respectively.
A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
	2013			2012			2011
Balance at January 1	$	239		$	267		$	171
Additions based on tax positions taken during the current period		134			141			96
Reductions based on tax positions taken during a prior period		(20	)		(169	)		—
Balance at December 31	$	353		$	239		$	267
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 2002 and forward for federal purposes and 2003 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 subsidiary’s research and development intercompany services have a “Beneficiary Enterprise” status for a separate investment program that was elected by the Israel subsidiary under the Law for Encouragement of Capital Investments, 1959 (the “Investments Law”), which was amended on April 1, 2005. Undistributed Israeli income derived from its “Beneficiary Enterprise” program entitles the Israeli subsidiary to a tax exemption for a period of two years and to a reduced tax rate of 10%—25% for an additional period of five to eight years (depending on the level of non-Israeli investment in the Company). These tax benefits are subject to a limitation of 12 years from activation of the program.
The entitlement to the above benefits is conditional upon the Israeli subsidiary fulfilling the conditions stipulated by the Investments Law and regulations published there under.
Through December 31, 2012, the Israeli subsidiary had $2.4 million of tax exempt income attributed to its Beneficiary Enterprise program (“exempt profits”). If such exempt profits are distributed as dividends, in a merger or a regular distribution or upon complete liquidation of the Israeli subsidiary, it would be taxed at the corporate tax rate applicable to such profits and an income tax liability of up to $0.6 million would be incurred as of December 31, 2012.
According to a temporary provision of the Investment Law, the Israeli subsidiary has paid a onetime payment in November 2013 of approximately $0.2 million to the Israeli Tax Authority for the purpose of “releasing” the exempt profits (10% of the exempt profits).
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 subsidiary 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 subsidiary’s 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, 2013
Segment Reporting [Abstract]	'
Segment Information	'
	13. Segment Information
	The Company has two operating segments which are also both reportable business segments: (i) Imperva, which is comprised of Imperva’s and its wholly-owned subsidiaries’ financial position and results of operations; and (ii) Incapsula, which is comprised entirely of the financial position and results from operations of the Company’s majority owned subsidiary, which commenced operations in late 2009.
	The following table presents a summary of our operating segments (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Imperva:
	Net revenue	$	134,691		$	103,410		$	78,214
	Operating loss		(18,853	)		(4,119	)		(7,436	)
	Provision for income tax		740			527			646
	Net loss		(19,874	)		(4,757	)		(8,144	)
	Depreciation and amortization		2,298			1,703			1,529
	Stock-based compensation		19,559			5,947			1,706
	Total assets	$	174,554		$	149,998		$	130,742
	Incapsula:
	Net revenue	$	3,068		$	825		$	88
	Operating loss		(6,576	)		(2,985	)		(2,570	)
	Provision for income tax		37			18			16
	Net loss		(6,457	)		(3,135	)		(2,714	)
	Depreciation and amortization		344			138			11
	Stock-based compensation		2,935			21			21
	Total assets	$	1,937		$	3,959		$	2,800
	The Company’s services revenue was comprised of the following (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Maintenance and support	$	44,353		$	33,647		$	24,497
	Professional services and training		9,890			6,428			4,730
	Subscriptions		11,363			4,670			1,475
	Total net services revenue	$	65,606		$	44,745		$	30,702
	The Company’s revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Americas	$	83,736		$	61,588		$	47,851
	EMEA		33,183			24,958			18,464
	APAC		20,840			17,689			11,987
	Total net revenue	$	137,759		$	104,235		$	78,302
	The following table presents long-lived assets by location (in thousands):
		As of December 31,
		2013			2012			2011
	United States	$	3,039		$	2,851		$	1,815
	Israel		2,422			2,642			2,196
	Other		14			22			15
	Total long-lived assets	$	5,475		$	5,515		$	4,026

Net_Loss_per_Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Net Loss per Share	'
	14. 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 for share and per share amounts):
		Years Ended December 31,
		2013			2012			2011
	Net loss attributable to Imperva, Inc. stockholders	$	(25,178	)	$	(7,387	)	$	(10,269	)
	Shares used in computing net loss per share of common stock, basic and diluted		24,300,198			22,916,426			7,674,554
	Net loss per share of common stock, basic and diluted	$	(1.04	)	$	(0.32	)	$	(1.34	)
	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,
		2013			2012			2011
	Stock options to purchase common stock		1,675,506			1,989,237			2,871,005
	Restricted stock units for common stock		1,044,651			446,915			—
	Restricted shares of common stock subject to repurchase		335,062			530,779			733,995
	Common stock warrants		—			8,333			8,333

Related_Party_Transaction

Related Party Transaction	12 Months Ended
	Dec. 31, 2013
Related Party Transactions [Abstract]	'
Related Party Transaction	'
	15. Related Party Transaction
	The Company indirectly sells its products, licenses and services through a third party to Seagate Technology, a President of which is also director of the Company. Net revenues recorded from indirect sales to Seagate Technology were approximately $0.1 million for the year ended December 31, 2013. Net revenues for the year ended December 31, 2012 was approximately $0.4 million and there was no revenue for the year ended December 31, 2011. As of December 31, 2013, Imperva had accounts receivable of $19,000 from the reseller for the indirect sales to Seagate.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	16. Subsequent Events
	Acquisition of Certain Assets and Liabilities of Tomium Software, LLC.
	On January 30, 2014, the Company acquired certain assets and liabilities of Tomium Software, LLC (“Tomium”), a private company based in Texas. Tomium is a provider of real-time mainframe security auditing agents. The purchase price of approximately $8.1 million includes approximately $4.7 million in cash as well as 60,556 shares of Company common stock valued at approximately $3.4 million. Imperva assumed a facility lease and certain liabilities of Tomium. Management is currently evaluating the purchase price allocation for this transaction.
	Acquisition of SkyFence Networks, Ltd.
	On February 7, 2014, we acquired SkyFence Networks Ltd. (“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 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 agreement (as amended) with SkyFence and its security holders, we purchased all of the outstanding shares of capital stock of SkyFence in exchange for approximately $16.1 million in cash, 884,422 shares of Company common stock valued at approximately $52.3 million and the assumption of stock options exercisable for an aggregate of up to 24,248 shares of our common stock, for total consideration of approximately $69.8 million.
	The Company’s CEO and Chief Technology Officer were both SkyFence shareholders, owning 42.67% and 3.16%, respectively of the outstanding fully diluted stock of SkyFence. In that capacity, they received similar percentages of the SkyFence consideration in the form of (i) with respect to the CEO, cash and shares of Company common stock and (ii) with respect to the Chief Technology Officer, shares of Company common stock.
	Acquisition of Incapsula, Inc.
	On February 11, 2014, the Company entered into an agreement with Incapsula and its security holders to acquire the remaining interest in Incapsula not already owned by Imperva in exchange for approximately $8.1 million, based on the lower price collar of Company stock of $31.40, in Company common stock in addition to the assumption of Incapsula options outstanding and conversion into options to purchase Company common stock. For purposes of determining the exchange ratio and number of shares to be issued at closing, each share of Company stock issued as part of the consideration will have an ascribed value equal to the average closing price of Company stock for the ten (10) trading days ending on the third day prior to the closing, with the maximum and minimum values ascribed being subject to an upper and lower price collar of $47.10 and $31.40, respectively. The Company also agreed to assume the Incapsula RSUs for performance-based vesting tied to 2014 revenue for Incapsula and Incapsula-related products and services, which are expected to convert into approximately 180,890 shares of Company common stock. The Incapsula consideration is net of certain deductions, including deductions for transaction expenses and a deduction for the cancellation of the Incapsula Loan of approximately $1.1 million.

The_Company_and_Summary_of_Sig1

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
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 data center security solutions that protect high value applications and data assets in physical and virtual data centers.
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., its wholly-owned subsidiaries and one majority owned subsidiary, Incapsula, Inc. (“Incapsula”). All intercompany accounts and transactions have been eliminated in consolidation.
Noncontrolling Interest	'
	Noncontrolling Interest
	The Company has recorded a noncontrolling interest in its consolidated balance sheets, consolidated statements of operations, comprehensive loss and convertible preferred stock and stockholders’ equity (deficit) for the 19%, 15%, and 18% ownership interest of the minority owners of Incapsula as of December 31, 2013, 2012 and 2011, respectively. Changes to the ownership interest in Incapsula held by the minority owners are accounted for as equity transactions in the consolidated statements of convertible preferred stock and stockholders’ equity (deficit) as the Company obtained control of Incapsula on November 5, 2009.
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 and inventory, and assumptions used in the calculation of 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 convertible preferred stock and stockholders’ equity (deficit) 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, 2013, there were no outstanding forward foreign currency exchange contracts thus no derivative gains or losses were included in accumulated other comprehensive loss. 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 convertible preferred stock and stockholders’ equity (deficit) 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 a facility lease, and collateral for the Company’s contract manufacturer in regards to the Company’s obligation to purchase inventory. As of December 31, 2012, the Company had classified $591,000 of restricted cash as a current asset relating to inventory purchase commitments. In addition, as of December 31, 2013 and 2012, the Company has classified $1.3 million and $753,000, respectively, of security deposit as non-current assets relating to its facility lease arrangement.
Inventory	'
	Inventory
	Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value determined on an average cost basis. 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, 2013, 2012 and 2011, there was no inventory write-down incurred by the Company.
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.
Impairment of Long-Lived Assets	'
	Impairment of Long-Lived Assets
	The Company evaluates its long-lived assets, which consist of property and equipment, 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, 2013 and 2012, 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 issued pursuant to the terms and conditions of a distributor or value-added reseller agreement and, in limited cases, 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. The Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with its sales.
		•	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 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. 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, TPE of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its 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 our 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, 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 more than 10% of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the year ended December 31, 2013 the Company had one customer that represented 10% of the Company’s total revenue. For the years ended December 31, 2012 and 2011, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There were no customers who represented greater than 10% of gross accounts receivable as of December 31, 2013 and 2012.
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, 2013, 2012 and 2011, 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, 2013, 2012 and 2011.
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, 2013, 2012 and 2011 of $1.2 million, $1.0 million, and $1.0 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 makes certain estimates and judgments in determining income tax expense for financial statement purposes. These estimates and judgments occur in the calculation of tax credits, tax benefits and deductions and in the calculation of certain tax assets and liabilities, which arise from differences in the timing of recognition of revenue and expense for tax and financial statement purposes. Significant changes to these estimates may result in an increase or decrease to the Company’s tax provision in the subsequent period when such a change in estimate occurs.
	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.
	At December 31, 2013, the Company had net deferred income tax assets, related primarily to net operating loss carry forwards , deferred revenue, stock based compensation and accruals and reserves that are not currently deductible of $33.0 million, which have been partially offset by $32.7 million of valuation allowance. At December 31, 2012, the Company had net deferred income tax assets, related primarily to net operating loss carry forwards, deferred revenue, stock based compensation and accruals and reserves that are not currently deductible of $24.6 million, which have been partially offset by $24.3 million of valuation allowance.
Liability Associated with Warrants to Purchase Convertible Preferred Stock	'
	Liability Associated with Warrants to Purchase Convertible Preferred Stock
	The Company accounts for freestanding warrants to purchase shares of convertible preferred stock that are contingently redeemable as liabilities on the consolidated balance sheet at their estimated fair value because the warrants may obligate the Company to redeem these warrants at some point in the future. At the end of each reporting period, changes in the estimated fair value of the warrants to purchase shares of the convertible preferred stock are recorded through other income (expense), net in the consolidated statements of operations. In connection with our IPO, the warrants to purchase convertible preferred stock were converted into warrants to purchase common stock. Accordingly, as of December 31, 2013 and 2012, there were no outstanding warrants to purchase shares of convertible preferred stock.
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 Incapsula 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 a revenue forecast. The Company updates the estimated expense, net of forfeitures, at the end of each reporting period. Based on forecasted revenue for 2014 until the actual 2014 revenue performance becomes known, the expense is recognized on an accelerated basis over the requisite service period, generally 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, the Israeli severance pay fund assets, and the liability associated with the warrants to purchase convertible preferred stock 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, convertible preferred stock, stock options to purchase common stock, common stock subject to repurchase, warrants to purchase convertible preferred stock 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.
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 two operating segments which are both reportable business segments: (i) Imperva, which is comprised of Imperva’s and its wholly-owned subsidiaries’ financial position and results of operations; and (ii) Incapsula, which is comprised of Incapsula’s financial position and results from operations.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	41,973	$	—	$	—	$	41,973
	Bank deposits		10,165				—		10,165
	Commercial paper		21,948		—		1		21,947
	Money market funds		2,619		—		—		2,619
	Total	$	76,705	$	—	$	1	$	76,704
	Short-term investments:
	Corporate debt obligations	$	28,220	$	22	$	14	$	28,228
	Bank deposits		10,153		—		—		10,153
	Total	$	38,373	$	22	$	14	$	38,381
		As of December 31, 2012
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	27,602	$	—	$	—	$	27,602
	Bank deposits		10,107				—		10,107
	Commercial paper		17,748		—		3		17,745
	Money market funds		3,045		—		—		3,045
	Corporate debt obligations		702						702
	Total		59,204		—		3		59,201
	Short-term investments:
	Commercial paper	$	1,000	$	—	$	—	$	1,000
	Corporate debt obligations		29,040		22		—		29,062
	Bank deposits		10,057		—		—		10,057
	US agency securities		1,001		—		—		1,001
	Mutual funds		1,847		159		—		2,006
	Total	$	42,945	$	181	$	—	$	43,126
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, 2013 (in thousands):
		As of December 31, 2013
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	19,466	$	19,470
	Due within two years		18,907		18,911
	Total	$	38,373	$	38,381

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013 and 2012, by level within the fair value hierarchy (in thousands):
		As of December 31, 2013
		Level I			Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Bank deposits	$	—		$	10,165	$	—	$	10,165
	Commercial paper		—			21,947		—		21,947
	Money market funds		2,619			—		—		2,619
	Short-term investments:
	Corporate debt obligations	$	—		$	28,228	$	—	$	28,228
	Bank deposits		—			10,153		—		10,153
	Total financial assets	$	2,619		$	70,493	$	—	$	73,112
		As of December 31, 2012
		Level I			Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Bank deposits	$	—		$	10,107	$	—	$	10,107
	Commercial paper		—			17,745		—		17,745
	Corporate debt obligations		—			702		—		702
	Money market funds		3,045			—		—		3,045
	Short-term investments:
	Corporate debt obligations	$	—		$	29,062	$	—	$	29,062
	Bank deposits		—			10,057		—		10,057
	Commercial paper		—			1,000		—		1,000
	US agency securities		—			1,001		—		1,001
	Mutual funds		2,006			—		—		2,006
	Total financial assets	$	5,051		$	69,674	$	—	$	74,725
	Prepaid expenses and other current assets—Forward foreign exchange contracts	$	—		$	1,226	$	—	$	1,226
Summary of Changes in Fair Value of Level III Financial Liabilities	'
	The following table sets forth a summary of the changes in the fair value of the Company’s Level III financial liabilities (in thousands):
	Fair value—January 1, 2011	$	69
	Change in fair value of convertible preferred stock warrant liability		238
	Reclassification to additional paid-in capital upon conversion to common stock warrant		(129	)
	Reclassification to preferred stock upon exercise of warrants		(178	)
	Fair value—December 31, 2011	$	—

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Derivative Instruments Measured at Fair Value	'
	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands):
			Asset as of December 31,
			2013						2012
			Notional			Fair Value			Notional			Fair Value
			Amount						Amount
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships -
	Forward foreign exchange contracts included in prepaid expenses and other current assets		$	—		$	—		$	20,513		$	1,117
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships -
	Forward foreign exchange contracts included in prepaid expenses and other current assets		$	—		$	—		$	2,296		$	109
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):
			2013			2012			2011
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Gains recognized in OCI (a)		$	730		$	1,304		$	—
	Losses recognized in OCI (a)			(18	)		(225	)		(1,231	)
	Gains recognized from accumulated OCI into net loss (b)			1,829			—			220
	Losses recognized from accumulated OCI into net loss (b)			—			(598	)		—
	Losses recognized in net loss (c)			—			(5	)		(38	)
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships:
	Gains recognized in net loss (d)			71			181			—
	Losses recognized in net loss (d)		$	(60	)	$	(121	)	$	—
	(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 $117, $(45) and $16 were recognized within cost of sales for the years ended December 31, 2013, 2012 and 2011, respectively, and $1,712, $(553), and $204 were recognized within operating expenses for the year ended December 31, 2013, 2012 and 2011, respectively. All amounts are reflected with the respective consolidated statement of operations.
	(c)	Ineffective portion and amount excluded from effectiveness testing classified in other income (expense), net.
	(d)	Classified in other income (expense), net.

Consolidated_Balance_Sheet_Com1

Consolidated Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2013
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,
		2013			2012			2011
	Allowance for doubtful accounts, beginning balance	$	412		$	225		$	407
	Charged to costs and expenses		46			269			202
	Recoveries		—			—			(37	)
	Deductions (write-offs)		(48	)		(82	)		(347	)
	Allowance for doubtful accounts, ending balance	$	410		$	412		$	225
Prepaid and Other Current Assets	'
	Prepaid and other current assets consist of the following (in thousands):
		As of December 31,
		2013			2012
	Prepaid expenses	$	2,632		$	1,646
	Derivative asset		—			1,226
	Prepaid income taxes		786			631
	Interest receivable		268			326
	Other		286			527
	Total prepaid and other current assets	$	3,972		$	4,356
Property and Equipment	'
	Property and equipment consist of the following (in thousands):
		As of December 31,
		2013			2012
	Computers and related equipment	$	8,989		$	7,088
	Office furniture and equipment		1,403			1,438
	Leasehold improvements		2,773			2,670
	Total property and equipment		13,165			11,196
	Less: accumulated depreciation and amortization		(7,690	)		(5,681	)
	Total property and equipment, net	$	5,475		$	5,515
Accrued Compensation and Benefits	'
	Accrued compensation and benefits consist of the following (in thousands):
		As of December 31,
		2013			2012
	Salary and related benefits	$	4,399		$	2,761
	Accrued vacation		4,122			3,373
	Accrued incentive payments		4,409			3,124
	Total accrued compensation and benefits	$	12,930		$	9,258
Accrued and Other Current Liabilities	'
	Accrued and other current liabilities consist of the following (in thousands):
		As of December 31,
		2013			2012
	Accrued expenses	$	2,295		$	2,602
	Income tax payable		325			396
	Short-term deferred rent		226			65
	Short-term stock repurchase liability		521			801
	Other		594			459
	Total accrued and other current liabilities	$	3,961		$	4,323
Other Long-term Liabilities	'
	Other long-term liabilities consist of the following (in thousands):
		As of December 31,
		2013			2012
	Stock repurchase liability	$	857		$	1,377
	Long-term deferred rent		725			716
	Other		411			545
	Total other long-term liabilities	$	1,993		$	2,638

Other_Income_Expense_net_Table

Other Income (Expense), net (Tables)	12 Months Ended
	Dec. 31, 2013
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,
		2013			2012			2011
	Other Income:
	Interest income	$	386		$	460		$	28
	Forward foreign exchange contract gains, net		12			—			—
	Foreign currency exchange gains, net		—			—			203
	Total		398			460			231
	Other Expense:
	Convertible preferred stock warrant liability losses		—			—			(238	)
	Forward foreign exchange contract losses, net		—			(19	)		(39	)
	Foreign currency exchange losses, net		(373	)		(497	)		—
	Other		(150	)		(187	)		(144	)
	Total		(523	)		(703	)		(421	)
	Total other income (expense), net	$	(125	)	$	(243	)	$	(190	)

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases	'
	Future minimum payments under these facility operating leases are as follows as of December 31, 2013 (in thousands):
		Operating		Estimated
		Leases		Sublease
				Income
	Year Ending December 31:
	2014	$	4,693	$	578
	2015		2,338		244
	2016		2,390		82
	2017		1,917		—
	2018		272		—
	Total	$	11,610	$	904

Capital_Stock_Tables

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
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,
		2013			2012
	Issuance upon exercise of common stock warrant		—			8,333
	Issuance in connection with outstanding stock options		1,675,506			1,989,237
	Issuance in connection with restricted stock units outstanding		1,044,651			446,915
	Reserved for future stock option and restricted stock unit grants		1,847,752			1,967,336
	Reserved for future issuance under the employee stock purchase plan		831,271			684,812
			5,399,180			5,096,633
Option and Performance-Based Restricted Share Unit Activity Under Incapsula Plan	'
	The following table summarizes option and performance-based restricted share unit activity under the Incapsula Plan and related information:
		Shares			Number of			Number of			Weighted
		Available			Performance-			Stock Options			Average Exercise
		for Grant			based Restricted			Outstanding			Price of Stock
					Share Units						Options
					Outstanding						Oustanding
	Outstanding—December 31, 2010		3,589,333			—			1,144,000		$	0.01
	Granted		(1,050,000	)		—			1,050,000			0.18
	Exercised		—			—			(37,500	)		0.11
	Forfeited		382,500			—			(382,500	)		0.16
	Outstanding—December 31, 2011		2,921,833			—			1,774,000		$	0.08
	Granted		(232,500	)		—			232,500			0.25
	Exercised		—			—			(105,625	)		0.15
	Forfeited		64,375			—			(64,375	)		0.18
	Outstanding—December 31, 2012		2,753,708			—			1,836,500		$	0.1
	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
Summary of Option Activity under 2003 Plan and 2011 Plan and Related Information	'
	The following table summarizes option activity under the 2003 Plan and the 2011 Plan and related information:
		Options Outstanding						Weighted-			Aggregate
								Average			Intrinsic Value
								Remaining			(in thousands)
								Contractual
		Number of			Weighted Average			Term (in years)
		Shares			Exercise Price
	Outstanding—December 31, 2010		2,763,908		$	1.9			8.09		$	4,999
	Granted		1,067,050			9.74
	Exercised or released		(563,916	)		3.73
	Cancelled or forfeited		(396,037	)		4.02
	Outstanding—December 31, 2011		2,871,005			4.15			7.86			88,012
	Granted		698,240			31.8
	Exercised or released		(1,272,941	)		2.41
	Cancelled or forfeited		(307,067	)		9.98
	Balances—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
	Balances—December 31, 2013		1,675,506		$	23.78			8.01		$	40,813
	Vested and expected to vest—December 31, 2013		1,454,729		$	23.08			7.93		$	36,463
	Exercisable—December 31, 2013		512,536		$	12.87			6.85		$	18,074
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, 2013 is summarized below:
	Exercise Prices	Options Outstanding									Options Exercisable
		Number of			Weighted			Weighted			Shares Subject		Weighted
		Stock Options			Average			Average			to Stock Options		Average
		Outstanding			Remaining			Exercise Price					Exercise Price
					Contractual			per Share					per Share
					Life (Years)
	$0.72 to $9.04		474,906			6.26		$	3.29			302,269	$	2.7
	$9.05 to $17.35		107,947			7.65		$	10.7			33,116	$	10.7
	$17.36 to $25.67		44,064			7.92		$	25.61			18,461	$	25.61
	$25.68 to $33.99		498,384			8.45		$	31.34			147,217	$	30.73
	$34.00 to $42.30		477,785			9.12		$	35.71			11,473	$	37.23
	$42.31 to $50.62		72,420			9.69		$	45.87			—	$	—
			1,675,506			8.01		$	23.78			512,536	$	12.87
Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value	'
	A summary of RSU activity for the year ended December 31, 2013, is as follows:
		Number of			Weighted—
		Restricted			Average Grant
		Stock Units			Date Fair Value
		Outstanding
	Unvested—December 31, 2011		—		$	—
	Granted		458,790			31.24
	Released		—			—
	Cancelled or expired		(11,875	)		32.88
	Unvested—December 31, 2012		446,915		$	31.2
	Granted		577,528			36.94
	Granted, performance RSUs		264,878			20.76
	Released		(149,531	)		30.64
	Cancelled or expired		(95,139	)		34.3
	Unvested—December 31, 2013		1,044,651		$	31.64
Stock-Based Compensation Expense	'
	The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, 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,
		2013			2012			2011
	Cost of revenue	$	1,440		$	469		$	118
	Research and development		3,660			1,227			130
	Sales and marketing		8,537			2,543			412
	General and administrative		8,857			1,729			1,067
	Total stock-based compensation expense	$	22,494		$	5,968		$	1,727
Weighted Average Assumptions for Fair Value of Stock Options Granted to Employees	'
	A summary of the weighted-average assumptions is as follows:
		Years Ended December 31
		2013			2012			2011
	Stock option grants:
	Dividend rate		0	%		0	%		0	%
	Risk-free interest rate		1.2	%		1	%		1.7	%
	Expected term (in years)		6.1			6			5.4
	Expected volatility		46	%		48	%		49	%
	ESPP grants:
	Dividend rate		0	%		0	%		—
	Risk-free interest rate		0.1	%		0.1	%		—
	Expected term (in years)		0.5			0.5			—
	Expected volatility		27	%		39	%		—

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Changes in Balances of Accumulated Other Comprehensive Income	'
	The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands):
			Years ended December 31,
			2013									2012									2011
			Unrealized			Unrealized			Total			Unrealized			Unrealized			Total			Unrealized			Unrealized			Total
			gain			gain (loss)						gain			gain (loss)						gain			gain (loss)
			(loss) on			on						(loss)  on			on						(loss) on			on
			cash flow			investments						cash flow			investments						cash flow			investments
			hedges									hedges									hedges
	Balance at January 1		$	691		$	170		$	861		$	(559	)	$	(57	)	$	(616	)	$	452		$	—		$	452
	Other comprehensive income (loss) before reclassifications			712			34			746			652			284			936			(1,231	)		(55	)		(1,286	)
	Amounts reclassified to net loss			(1,829	)		(206	)		(2,035	)		598			(57	)		541			220			(2	)		218
	Change in other comprehensive income (loss)			(1,117	)		(172	)		(1,289	)		1,250			227			1,477			(1,011	)		(57	)		(1,068	)
	Balance at December 31		$	(426	)	$	(2	)	$	(428	)	$	691		$	170		$	861		$	(559	)	$	(57	)	$	(616	)
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 2013, 2012, and 2011 (in thousands):
			Year ended December 31,
			2013									2012									2011
			Pre-Tax			Tax			After-Tax			Pre-Tax			Tax			After-Tax			Pre-Tax			Tax			After-Tax
			Amount			Expense			Amount			Amount			Expense			Amount			Amount			Expense			Amount
						(Benefit)									(Benefit)									(Benefit)
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	712		$	—		$	712		$	1,079		$	427		$	652		$	(1,231	)	$	—		$	(1,231	)
	Reclassification adjustments(1)			(1,829	)		—			(1,829	)		598			—			598			220			—			220
	Unrealized gains (losses) on cash flow hedges, net			(1,117	)		—			(1,117	)		1,677			427			1,250			(1,011	)		—			(1,011	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			34			—			34			291			7			284			(55	)		—			(55	)
	Reclassification adjustments(2)			(206	)		—			(206	)		(57	)		—			(57	)		(2	)		—			(2	)
	Unrealized gains (losses) on investments:			(172	)		—			(172	)		234			7			227			(57	)		—			(57	)
	Other comprehensive income (loss)		$	(1,289	)	$	—		$	(1,289	)	$	1,911		$	434		$	1,477		$	(1,068	)	$	—		$	(1,068	)
	-1	Refer to note 5 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, 2013
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,
		2013			2012			2011
	Domestic	$	(28,831	)	$	(9,373	)	$	(12,747	)
	Foreign		3,277			2,026			2,551
	Loss before provision for taxes	$	(25,554	)	$	(7,347	)	$	(10,196	)
Provision for Income Taxes	'
	The components of the provision for income taxes are as follows (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Current
	Federal	$	—		$	51		$	—
	State		127			47			63
	Foreign		700			889			618
	Total current provision		827			987			681
	Deferred
	Federal		—			(386	)		—
	State		—			(49	)		—
	Foreign		(50	)		(7	)		(19	)
	Total deferred provision		(50	)		(442	)		(19	)
	Total	$	777		$	545		$	662
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,
		2013			2012			2011
	Tax benefit at federal statutory tax rate	$	(8,688	)	$	(2,497	)	$	(3,465	)
	Tax benefit at state statutory tax rate		(829	)		(282	)		(390	)
	Tax benefit resulting from “Beneficiary Enterprise”		—			(95	)		(191	)
	Foreign tax rate differential		(705	)		(232	)		(302	)
	Foreign repatriation		—			179			—
	Unbenefitted loss of consolidated investment		2,402			1,193			1,026
	Change in valuation allowance		7,400			1,373			3,072
	Meals and entertainment		197			162			145
	Warrants fair value adjustment		—			—			95
	Stock compensation		810			497			543
	Nondeductible expenses and other		190			247			129
	Provision for income taxes	$	777		$	545		$	662
	Basic net loss per share amounts of benefits resulting from	$	—		$	—		$	0.02
	Beneficiary Enterprise Status
Net Deferred Tax Assets	'
	Significant components of the Company’s net deferred tax assets are as follows (in thousands):
		As of December 31,
		2013			2012
	Deferred tax assets:
	Reserves and accruals	$	1,345		$	1,169
	Deferred revenue		4,297			5,642
	Stock-based compensation		7,042			1,470
	Net operating loss carryforwards		20,361			17,530
	Other		194
	Gross deferred tax assets		33,239			25,811
	Valuation allowance		(32,656	)		(24,266	)
	Deferred tax assets		583			1,545
	Deferred tax liabilities:
	Stock-based compensation		(166	)		(314	)
	Depreciation and amortization		(31	)		(497	)
	Gain on OCI		(2	)		(435	)
	Total deferred tax liabilities		(200	)		(1,246	)
	Net deferred tax assets	$	383		$	299
Unrecognized Tax Benefits	'
	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
		2013			2012			2011
	Balance at January 1	$	239		$	267		$	171
	Additions based on tax positions taken during the current period		134			141			96
	Reductions based on tax positions taken during a prior period		(20	)		(169	)		—
	Balance at December 31	$	353		$	239		$	267

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2013
Summary of Company's Operating Segments	'
	The following table presents a summary of our operating segments (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Imperva:
	Net revenue	$	134,691		$	103,410		$	78,214
	Operating loss		(18,853	)		(4,119	)		(7,436	)
	Provision for income tax		740			527			646
	Net loss		(19,874	)		(4,757	)		(8,144	)
	Depreciation and amortization		2,298			1,703			1,529
	Stock-based compensation		19,559			5,947			1,706
	Total assets	$	174,554		$	149,998		$	130,742
	Incapsula:
	Net revenue	$	3,068		$	825		$	88
	Operating loss		(6,576	)		(2,985	)		(2,570	)
	Provision for income tax		37			18			16
	Net loss		(6,457	)		(3,135	)		(2,714	)
	Depreciation and amortization		344			138			11
	Stock-based compensation		2,935			21			21
	Total assets	$	1,937		$	3,959		$	2,800
Company's Net Revenue by Geographic Region, Based on Customer's Location	'
	The Company’s services revenue was comprised of the following (in thousands):
		Years Ended December 31,
		2013			2012			2011
	Maintenance and support	$	44,353		$	33,647		$	24,497
	Professional services and training		9,890			6,428			4,730
	Subscriptions		11,363			4,670			1,475
	Total net services revenue	$	65,606		$	44,745		$	30,702
Long-Lived Assets by Location	'
	The following table presents long-lived assets by location (in thousands):
		As of December 31,
		2013			2012			2011
	United States	$	3,039		$	2,851		$	1,815
	Israel		2,422			2,642			2,196
	Other		14			22			15
	Total long-lived assets	$	5,475		$	5,515		$	4,026
Geographic Location [Member]	'
Company's Net 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,
		2013			2012			2011
	Americas	$	83,736		$	61,588		$	47,851
	EMEA		33,183			24,958			18,464
	APAC		20,840			17,689			11,987
	Total net revenue	$	137,759		$	104,235		$	78,302

Net_Loss_per_Share_Tables

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2013
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 for share and per share amounts):
		Years Ended December 31,
		2013			2012			2011
	Net loss attributable to Imperva, Inc. stockholders	$	(25,178	)	$	(7,387	)	$	(10,269	)
	Shares used in computing net loss per share of common stock, basic and diluted		24,300,198			22,916,426			7,674,554
	Net loss per share of common stock, basic and diluted	$	(1.04	)	$	(0.32	)	$	(1.34	)
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,
		2013			2012			2011
	Stock options to purchase common stock		1,675,506			1,989,237			2,871,005
	Restricted stock units for common stock		1,044,651			446,915			—
	Restricted shares of common stock subject to repurchase		335,062			530,779			733,995
	Common stock warrants		—			8,333			8,333

The_Company_and_Summary_of_Sig2

The Company and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Parties	Customer	Customer
	Segment
	Customer
Significant Accounting Policies [Line Items]	'	'	'
Noncontrolling interest of minority owners	19.00%	15.00%	18.00%
Number of third party	1	'	'
Outstanding forward foreign currency exchange contracts	$0	'	'
Net derivative gains or losses included in accumulated other comprehensive income (loss)	0	'	'
Restricted cash	34,000	591,000	'
Security deposit as non-current assets	1,252,000	753,000	'
Inventory write down	0	0	0
Period to complete Professional service arrangements	'90 days	'	'
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers	10.00%	'	'
Number of customers representing more than 10% of revenue	1	0	0
Number of customers representing greater than 10% of gross accounts receivable	0	0	'
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	1,200,000	1,000,000	1,000,000
Deferred income tax assets	33,239,000	25,811,000	'
Deferred income tax assets, valuation allowance	$32,656,000	$24,266,000	'
Outstanding warrants	0	0	'
Number of operating segments	2	'	'
Minimum [Member]	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Estimated useful lives	'2 years	'	'
Standard payment terms to customers range	'30 days	'	'
Term of maintenance and support and subscription contracts	'1 year	'	'
Maximum [Member]	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Estimated useful lives	'7 years	'	'
Standard payment terms to customers range	'90 days	'	'
Term of maintenance and support and subscription contracts	'3 years	'	'

Incapsula_Additional_Informati

Incapsula - Additional Information (Detail) (USD $)	1 Months Ended			0 Months Ended		12 Months Ended		0 Months Ended		1 Months Ended
	Oct. 31, 2013	Oct. 31, 2013	Oct. 31, 2013	Mar. 09, 2010	Nov. 05, 2009	Dec. 31, 2013	Dec. 31, 2013	Mar. 09, 2010	Mar. 09, 2010	Jan. 31, 2012	Jul. 31, 2011
	Incapsula [Member]	Incapsula [Member]	Imperva [Member]	Series A convertible preferred stock [Member]	Series A convertible preferred stock [Member]	Series A convertible preferred stock [Member]	Trailing revenues [Member]	Series A-1 convertible preferred stock [Member]	Series A-1 convertible preferred stock [Member]	Series A-1 preferred stock [Member]	Series A-1 preferred stock [Member]
		Restricted stock units for common stock [Member]	Restricted stock units for common stock [Member]			Times	Times		Forward contract [Member]
Subsidiary or Equity Method Investee [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Equity method investments, shares	'	'	'	6,666,666	5,000,000	'	'	8,750,000	'	4,375,000	4,375,000
Ownership interest	'	'	'	76.00%	58.00%	'	'	'	'	85.00%	82.00%
Value assigned to license	'	'	'	'	$0	'	'	'	'	'	'
Net assets	'	'	'	'	0	'	'	'	'	'	'
Value of goodwill on the acquisition date	'	'	'	'	0	'	'	'	'	'	'
Enterprise valuation for computation of share price	'	'	'	'	'	7	8	'	'	'	'
Value assigned to Purchase Right	'	'	'	'	'	0	'	'	'	'	'
Cash consideration	'	'	'	3,000,000	'	'	'	7,000,000	'	'	'
Value assigned to forward contract	'	'	'	'	'	'	'	'	0	'	'
Cash consideration	'	'	'	'	'	'	'	'	'	3,500,000	3,500,000
Loaned to subsidiaries	$1,100,000	'	'	'	'	'	'	'	'	'	'
Interest rate on loans	2.00%	'	'	'	'	'	'	'	'	'	'
Maturity of loans	31-Dec-14	'	'	'	'	'	'	'	'	'	'
Business acquisition, shares issued	'	'	264,878	'	'	'	'	'	'	'	'
Shares issuable, as-converted to common stock-basis	'	204,820	'	'	'	'	'	'	'	'	'

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
In Thousands, unless otherwise specified
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	$76,705	$59,204	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	1	3	'	'
Cash and cash equivalents, Fair Value	76,704	59,201	96,025	16,410
Short-term investments, Amortized Cost	38,373	42,945	'	'
Short-term investments, Gross Unrealized Gains	22	181	'	'
Short-term investments, Gross Unrealized Losses	14	'	'	'
Short-term investments, Estimated Fair Value	38,381	43,126	'	'
Corporate debt obligations [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	'	702	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	'	'	'	'
Cash and cash equivalents, Fair Value	'	702	'	'
Short-term investments, Amortized Cost	28,220	29,040	'	'
Short-term investments, Gross Unrealized Gains	22	22	'	'
Short-term investments, Gross Unrealized Losses	14	'	'	'
Short-term investments, Estimated Fair Value	28,228	29,062	'	'
Bank deposits [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	10,165	10,107	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	'	'	'	'
Cash and cash equivalents, Fair Value	10,165	10,107	'	'
Short-term investments, Amortized Cost	10,153	10,057	'	'
Short-term investments, Gross Unrealized Gains	'	'	'	'
Short-term investments, Gross Unrealized Losses	'	'	'	'
Short-term investments, Estimated Fair Value	10,153	10,057	'	'
Commercial paper [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	21,948	17,748	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	1	3	'	'
Cash and cash equivalents, Fair Value	21,947	17,745	'	'
Short-term investments, Amortized Cost	'	1,000	'	'
Short-term investments, Gross Unrealized Gains	'	'	'	'
Short-term investments, Gross Unrealized Losses	'	'	'	'
Short-term investments, Estimated Fair Value	'	1,000	'	'
US agency securities [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Short-term investments, Amortized Cost	'	1,001	'	'
Short-term investments, Gross Unrealized Gains	'	'	'	'
Short-term investments, Gross Unrealized Losses	'	'	'	'
Short-term investments, Estimated Fair Value	'	1,001	'	'
Mutual funds [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Short-term investments, Amortized Cost	'	1,847	'	'
Short-term investments, Gross Unrealized Gains	'	159	'	'
Short-term investments, Gross Unrealized Losses	'	'	'	'
Short-term investments, Estimated Fair Value	'	2,006	'	'
Cash [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	41,973	27,602	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	'	'	'	'
Cash and cash equivalents, Fair Value	41,973	27,602	'	'
Money market funds [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Cash and cash equivalents, Amortized Cost	2,619	3,045	'	'
Cash and cash equivalents, Gross Unrealized Gains	'	'	'	'
Cash and cash equivalents, Gross Unrealized Losses	'	'	'	'
Cash and cash equivalents, Fair Value	$2,619	$3,045	'	'

Cash_Cash_Equivalents_and_Shor3

Cash, Cash Equivalents and Short-Term Investments - Additional Information (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Short Term Investments [Abstract]	'	'
Short-term investments continuous unrealized loss position twelve months or longer value	$0	$0

Cash_Cash_Equivalents_and_Shor4

Cash, Cash Equivalents and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Short Term Investments [Abstract]	'	'
Amortized Cost of short-term investments, Due within one year	$19,466	'
Amortized Cost of short-term investments, Due within two years	18,907	'
Short-term investments, Amortized Cost	38,373	42,945
Estimated fair value of short-term investments, Due within one year	19,470	'
Estimated fair value of short-term investments, Due within two years	18,911	'
Short-term investments, Estimated Fair Value	$38,381	$43,126

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	$73,112	$74,725
Cash and cash equivalents [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	10,165	10,107
Cash and cash equivalents [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	21,947	17,745
Cash and cash equivalents [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	702
Cash and cash equivalents [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	2,619	3,045
Short-term investments [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	10,153	10,057
Short-term investments [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	1,000
Short-term investments [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	28,228	29,062
Short-term investments [Member] | US agency securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	1,001
Short-term investments [Member] | Mutual funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	2,006
Forward foreign exchange contracts [Member] | Prepaid expenses and other current assets [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Prepaid expenses and other current assets-Forward foreign exchange contracts	'	1,226
Level I [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	2,619	5,051
Level I [Member] | Cash and cash equivalents [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level I [Member] | Cash and cash equivalents [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level I [Member] | Cash and cash equivalents [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level I [Member] | Cash and cash equivalents [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	2,619	3,045
Level I [Member] | Short-term investments [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level I [Member] | Short-term investments [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level I [Member] | Short-term investments [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level I [Member] | Short-term investments [Member] | US agency securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level I [Member] | Short-term investments [Member] | Mutual funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	2,006
Level I [Member] | Forward foreign exchange contracts [Member] | Prepaid expenses and other current assets [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Prepaid expenses and other current assets-Forward foreign exchange contracts	'	'
Level II [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	70,493	69,674
Level II [Member] | Cash and cash equivalents [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	10,165	10,107
Level II [Member] | Cash and cash equivalents [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	21,947	17,745
Level II [Member] | Cash and cash equivalents [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	702
Level II [Member] | Cash and cash equivalents [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level II [Member] | Short-term investments [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	10,153	10,057
Level II [Member] | Short-term investments [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	1,000
Level II [Member] | Short-term investments [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	28,228	29,062
Level II [Member] | Short-term investments [Member] | US agency securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	1,001
Level II [Member] | Short-term investments [Member] | Mutual funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level II [Member] | Forward foreign exchange contracts [Member] | Prepaid expenses and other current assets [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Prepaid expenses and other current assets-Forward foreign exchange contracts	'	1,226
Level III [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Cash and cash equivalents [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level III [Member] | Cash and cash equivalents [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level III [Member] | Cash and cash equivalents [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level III [Member] | Cash and cash equivalents [Member] | Money market funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	'	'
Level III [Member] | Short-term investments [Member] | Bank deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Short-term investments [Member] | Commercial paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Short-term investments [Member] | Corporate debt obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Short-term investments [Member] | US agency securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Short-term investments [Member] | Mutual funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	'	'
Level III [Member] | Forward foreign exchange contracts [Member] | Prepaid expenses and other current assets [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Prepaid expenses and other current assets-Forward foreign exchange contracts	'	'

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Fair value transfer between Levels	$0	$0
Level II [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Severance pay assets	$4,100,000	$3,200,000

Fair_Value_of_Financial_Instru4

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level III Financial Liabilities (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2011
Fair Value Disclosures [Abstract]	'
Fair value, Beginning Balance	$69
Change in fair value of convertible preferred stock warrant liability	238
Reclassification to additional paid-in capital upon conversion to common stock warrant	-129
Reclassification to preferred stock upon exercise of warrants	-178
Fair value, Ending Balance	'

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
Forward foreign exchange contracts maturity	'12 months

Derivative_Instruments_Derivat

Derivative Instruments - Derivative Instruments Measured at Fair Value (Detail) (Forward foreign exchange contracts [Member], USD $)	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012
In Thousands, unless otherwise specified	Prepaid expenses and other current assets [Member]	Prepaid expenses and other current assets [Member]	Accrued and other current liabilities [Member]	Accrued and other current liabilities [Member]
	Designated as hedging instrument [Member]	Not designated as hedging instrument [Member]	Designated as hedging instrument [Member]	Not designated as hedging instrument [Member]
Derivatives, Fair Value [Line Items]	'	'	'	'
Derivative Notional Amount, Assets	'	'	$20,513	$2,296
Derivative Fair Value, Assets	'	'	$1,117	$109

Derivative_Instruments_Gains_L

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Designated as hedging instrument [Member]	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'
Gains recognized in OCI	$730	$1,304	'
Losses recognized in OCI	-18	-225	-1,231
Gains recognized from accumulated OCI into net loss	1,829	'	220
Losses recognized from accumulated OCI into net loss	'	-598	'
Losses recognized in net loss	'	-5	-38
Not designated as hedging instrument [Member]	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'
Gains recognized in net loss	71	181	'
Losses recognized in net loss	($60)	($121)	'

Derivative_Instruments_Gains_L1

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Parenthetical) (Detail) (Unrealized gain (loss) on cash flow hedges [Member], Designated as hedging instrument [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating expenses [Member]	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'
Cash flow hedge loss reclassified	$1,712	($553)	$204
Cost of revenue [Member]	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'
Cash flow hedge loss reclassified	$117	($45)	$16

Consolidated_Balance_Sheet_Com2

Consolidated Balance Sheet Components - Allowance for Doubtful Accounts (Detail) (Allowance for doubtful accounts [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for doubtful accounts [Member]	'	'	'
Valuation and Qualifying Accounts Disclosure [Line Items]	'	'	'
Allowance for doubtful accounts, beginning balance	$412	$225	$407
Charged to costs and expenses	46	269	202
Recoveries	'	'	-37
Deductions (write-offs)	-48	-82	-347
Allowance for doubtful accounts, ending balance	$410	$412	$225

Consolidated_Balance_Sheet_Com3

Consolidated Balance Sheet Components - Prepaid and Other Current Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Prepaid Expense And Other Assets Current [Abstract]	'	'
Prepaid expenses	$2,632	$1,646
Derivative asset	'	1,226
Prepaid income taxes	786	631
Interest receivable	268	326
Other	286	527
Total prepaid and other current assets	$3,972	$4,356

Consolidated_Balance_Sheet_Com4

Consolidated Balance Sheet Components - Property and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Total property and equipment	$13,165	$11,196
Less: accumulated depreciation and amortization	-7,690	-5,681
Total property and equipment, net	5,475	5,515
Computers and related equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property and equipment	8,989	7,088
Office furniture and equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property and equipment	1,403	1,438
Leasehold improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property and equipment	$2,773	$2,670

Consolidated_Balance_Sheet_Com5

Consolidated Balance Sheet Components - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property Plant And Equipment [Abstract]	'	'	'
Depreciation and amortization expense	$2.60	$1.80	$1.50

Consolidated_Balance_Sheet_Com6

Consolidated Balance Sheet Components - Accrued Compensation and Benefits (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Employee Related Liabilities Current [Abstract]	'	'
Salary and related benefits	$4,399	$2,761
Accrued vacation	4,122	3,373
Accrued incentive payments	4,409	3,124
Total accrued compensation and benefits	$12,930	$9,258

Consolidated_Balance_Sheet_Com7

Consolidated Balance Sheet Components - Accrued and Other Current Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accrued Liabilities And Other Liabilities [Abstract]	'	'
Accrued expenses	$2,295	$2,602
Income tax payable	325	396
Short-term deferred rent	226	65
Short-term stock repurchase liability	521	801
Other	594	459
Total accrued and other current liabilities	$3,961	$4,323

Consolidated_Balance_Sheet_Com8

Consolidated Balance Sheet Components - Other Long-term Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Other Liabilities Noncurrent [Abstract]	'	'
Stock repurchase liability	$857	$1,377
Long-term deferred rent	725	716
Other	411	545
Total other long-term liabilities	$1,993	$2,638

Other_Income_Expense_Net_Sched

Other Income (Expense), Net - Schedule of Other Income (Expense), Net (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Income:	'	'	'
Interest income	$386	$460	$28
Forward foreign exchange contract gains, net	12	'	'
Foreign currency exchange gains, net	'	'	203
Total	398	460	231
Other Expense:	'	'	'
Convertible preferred stock warrant liability losses	'	'	-238
Forward foreign exchange contract losses, net	'	-19	-39
Foreign currency exchange losses, net	-373	-497	'
Other	-150	-187	-144
Total	-523	-703	-421
Total other income (expense), net	($125)	($243)	($190)

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]	'	'
Maximum borrowing capacity	$6	'
Outstanding credit facility	0	0
Credit facility expiration date	1-May-14	'
Minimum cash and cash equivalents	$3	'
Percentage in payment of unused line fee	0.25%	'
Line of credit [Member]	'	'
Line of Credit Facility [Line Items]	'	'
LIBOR plus interest rate	2.75%	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Loss Contingencies [Line Items]	'	'	'	'
Operating lease expiration year start	'2013	'	'	'
Operating lease expiration year end	'2018	'	'	'
Restricted cash	$1,252,000	$753,000	'	'
Restricted deposits	34,000	591,000	'	'
Operating lease expense [Member]	'	'	'	'
Loss Contingencies [Line Items]	'	'	'	'
Rent expense	3,300,000	2,100,000	1,900,000	'
Tenant improvement allowances	'	336,000	'	639,000
Restricted cash	1,300,000	753,000	666,000	'
Cancelable lease agreement [Member]	'	'	'	'
Loss Contingencies [Line Items]	'	'	'	'
Penalties	80,000	'	'	'
Motor vehicle lease expenses	2,400,000	2,200,000	2,100,000	'
Purchase commitments [Member]	'	'	'	'
Loss Contingencies [Line Items]	'	'	'	'
Commitments purchased	3,200,000	3,200,000	'	'
Period of purchase commitment of inventory from specified date	'6 months	'	'	'
Restricted deposits	$0	$562,000	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Operating Leases	'
2014	$4,693
2015	2,338
2016	2,390
2017	1,917
2018	272
Total	11,610
Estimated Sublease Income	'
2014	578
2015	244
2016	82
2017	'
2018	'
Total	$904

Capital_Stock_Reserved_shares_

Capital Stock - Reserved shares of common stock (Detail)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity [Abstract]	'	'	'	'
Issuance upon exercise of common stock warrant	'	8,333	'	'
Issuance in connection with outstanding stock options	1,675,506	1,989,237	2,871,005	2,763,908
Issuance in connection with restricted stock units outstanding	1,044,651	446,915	'	'
Reserved for future stock option and restricted stock unit grants	1,847,752	1,967,336	'	'
Reserved for future issuance under the employee stock purchase plan	831,271	684,812	'	'
Total	5,399,180	5,096,633	'	'

Capital_Stock_Additional_Infor

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

12 Months Ended

12 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Sep. 09, 2011

Dec. 31, 2013

Feb. 29, 2012

Dec. 31, 2013

Sep. 30, 2012

Jan. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Sep. 09, 2012

Sep. 30, 2012

Dec. 31, 2013

Nov. 30, 2013

Mar. 31, 2010

Dec. 31, 2013

Nov. 30, 2013

Stock options [Member]

Stock options [Member]

Restricted stock units for common stock [Member]

Restricted stock units for common stock [Member]

Restricted stock units for common stock [Member]

Restricted shares of common stock subject to repurchase [Member]

Restricted shares of common stock subject to repurchase [Member]

Restricted shares of common stock subject to repurchase [Member]

Restricted shares of common stock subject to repurchase [Member]

Restricted shares of common stock subject to repurchase [Member]

2003 stock plan [Member]

2003 stock plan [Member]

2003 stock plan [Member]

2011 stock option and incentive plan [Member]

2011 stock option and incentive plan [Member]

2011 stock option and incentive plan [Member]

2011 stock option and incentive plan [Member]

2011 stock option and incentive plan [Member]

2011 stock option and incentive plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

2011 employee stock purchase plan [Member]

Incapsula 2010 share incentive plan [Member]

Incapsula 2010 share incentive plan [Member]

Incapsula 2010 share incentive plan [Member]

Incapsula 2010 share incentive plan [Member]

Director [Member]

Director [Member]

Minimum [Member]

Maximum [Member]

Stock options [Member]

Stock options [Member]

Stock options [Member]

Stock options [Member]

Restricted stock units for common stock [Member]

Restricted stock units for common stock [Member]

Maximum [Member]

Maximum [Member]

Restricted stock units for common stock [Member]

Restricted stock units for common stock [Member]

Minimum [Member]

Maximum [Member]

Incapsula acquisition [Member]

Period

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum percentage of fair value of common stock on grant date

'

'

'

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum percentage of combined voting power

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum percentage of option price of fair value

'

'

'

'

'

'

'

'

'

'

'

'

'

110.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'

'

'

'

'

'

'

'

'

'48 months

'60 months

'

'4 years

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reserve of common stock for future issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

500,000

'

20,000,000

'

4,733,333

'

'

Increase percentage of common stock outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.00%

'

'

'

'

'

'

1.00%

'

'

'

'

'

'

'

'

'

Shares available for grant

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,847,752

'

'

'

'

'

'

'

'

'

'

'

'

10,263,211

'

'

7,095,461

Increase in reserve share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,008,260

971,843

'

'

'

'

'

'

252,065

242,961

'

'

'

'

'

'

'

Maximum percentage of fair value of common stock on grant date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

Expiration period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting period of RSUs

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

'

'

Vesting percentage at each year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

Remaining vesting period of RSUs

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

Performance-based restricted stock units granted

'

'

'

'

'

577,528

458,790

'

0

0

843,819

'

'

'

'

'

'

'

'

'

'

264,878

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15.00%

'

'

'

'

'

'

'

'

'

'

Offering period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'24 months

'

'

'

'

'

'

'

'

'

'

Number of purchase periods for offering

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

Number of years, shares reserved for issuance will increase

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'8 years

'

'

'

'

'

'

'

'

'

Shares expected to vest

1,454,729

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

204,820

'

Weighted-average grant date fair value

$16.48

$14.54

$5.03

'

'

'

'

'

'

'

$1.94

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate grant date fair value, stock options granted

$7,300,000

$10,100,000

$5,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate grant date fair value, stock options vested

4,600,000

2,100,000

1,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Restricted Stock Units Vested in Period

'

'

'

'

'

6,000,000

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Intrinsic value of options exercised

23,200,000

34,600,000

5,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

10,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'2 years 3 months 18 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net cash proceeds from the exercise of stock options

6,300,000

4,200,000

2,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capitalized stock-based compensation cost

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recognized stock-based compensation tax benefits

0

19,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted common stock unvested

'

'

'

'

'

'

'

'

290,062

448,279

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock repurchase liability

857,000

1,377,000

'

1,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested shares

'

'

'

45,000

82,500

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested shares, value

'

'

'

$1,400,000

$2,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital_Stock_Option_and_Perfo

Capital Stock - Option and Performance-Based Restricted Share Unit Activity Under Incapsula Plan (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Number of Stock Options Outstanding, Outstanding- Beginning balance	1,989,237	2,871,005	2,763,908
Number of Stock Options Outstanding, Granted	631,775	698,240	1,067,050
Number of Stock Options Outstanding, Exercised/Released	-687,719	-1,272,941	-563,916
Number of Stock Options Outstanding, Forfeited	-257,787	-307,067	-396,037
Number of Stock Options Outstanding, Outstanding - Ending balance	1,675,506	1,989,237	2,871,005
Weighted-Average Exercise Price of Stock Options Outstanding, Beginning balance	$14.08	$4.15	$1.90
Weighted Average Exercise Price of Stock Options Outstanding, Granted	$36.55	$31.80	$9.74
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released	$6.94	$2.41	$3.73
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited	$25.11	$9.98	$4.02
Weighted Average Exercise Price of Stock Options Outstanding, Ending balance	$23.78	$14.08	$4.15
Incapsula plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Shares Available for Grant, Outstanding - Beginning Balance	2,753,708	2,921,833	3,589,333
Additional shares authorized	5,529,878	'	'
Number of Performance-based Restricted Share Units Outstanding, Outstanding - December 31, 2013	7,095,461	'	'
Shares Available for Grant, Granted	'	-232,500	-1,050,000
Shares Available for Grant, Exercised/Released	'	'	'
Shares Available for Grant, Exercised/Released	'	'	'
Shares Available for Grant, Forfeited	141,562	64,375	382,500
Shares Available for Grant, Outstanding - Ending Balance	89,687	2,753,708	2,921,833
Number of Stock Options Outstanding, Outstanding- Beginning balance	1,836,500	1,774,000	1,144,000
Number of Stock Options Outstanding, Granted	'	232,500	1,050,000
Number of Stock Options Outstanding, Exercised/Released	-1,128,438	-105,625	-37,500
Number of Stock Options Outstanding, Forfeited	-141,562	-64,375	-382,500
Number of Stock Options Outstanding, Outstanding - Ending balance	1,806,500	1,836,500	1,774,000
Weighted-Average Exercise Price of Stock Options Outstanding, Beginning balance	$0.10	$0.08	$0.01
Weighted Average Exercise Price of Stock Options Outstanding, Granted	'	$0.25	$0.18
Weighted Average Exercise Price of Stock Options Outstanding, Exercised/Released	$0.02	$0.15	$0.11
Weighted Average Exercise Price of Stock Options Outstanding, Forfeited	$0.22	$0.18	$0.16
Weighted Average Exercise Price of Stock Options Outstanding, Ending balance	$0.47	$0.10	$0.08
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 Performance-based Restricted Share Units Outstanding, Granted	7,095,461	'	'
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 Stock Options Outstanding, Granted	1,240,000	'	'
Weighted Average Exercise Price of Stock Options Outstanding, Granted	$0.58	'	'

Capital_Stock_Summary_of_Optio

Capital Stock - Summary of Option Activity Under 2003 Plan and 2011 Plan and Related Information (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'	'
Number of Stock Options Outstanding, Outstanding- Beginning balance	1,989,237	2,871,005	2,763,908	'
Number of Stock Options Outstanding, Granted	631,775	698,240	1,067,050	'
Number of Stock Options Outstanding, Exercised	-687,719	-1,272,941	-563,916	'
Number of Stock Options Outstanding, Cancelled or forfeited	-257,787	-307,067	-396,037	'
Number of Stock Options Outstanding, Outstanding - Ending balance	1,675,506	1,989,237	2,871,005	2,763,908
Weighted-Average Exercise Price of Stock Options Outstanding, Beginning balance	$14.08	$4.15	$1.90	'
Vested and expected to vest, Number of Shares	1,454,729	'	'	'
Weighted Average Exercise Price, Granted	$36.55	$31.80	$9.74	'
Number of Shares, Exercisable	512,536	'	'	'
Weighted Average Exercise Price, Exercised	$6.94	$2.41	$3.73	'
Weighted Average Exercise Price, Cancelled or forfeited	$25.11	$9.98	$4.02	'
Weighted Average Exercise Price of Stock Options Outstanding, Ending balance	$23.78	$14.08	$4.15	$1.90
Aggregate Intrinsic Value - Beginning balance	$35,513	$88,012	$4,999	'
Vested and expected to vest, Weighted-Average Exercise Price	$23.08	'	'	'
Aggregate Intrinsic Value - Ending balance	40,813	35,513	88,012	4,999
Weighted Average Exercise Price, Exercisable	$12.87	'	'	'
Vested and expected to vest, Aggregate Intrinsic Value	36,463	'	'	'
Weighted- Average Remaining Contractual Term (in years)	'8 years 4 days	'8 years 1 month 2 days	'7 years 10 months 10 days	'8 years 1 month 2 days
Aggregate Intrinsic Value, Exercisable	$18,074	'	'	'
Vested and expected to vest, Weighted-Average Remaining Contractual Term (in years)	'7 years 11 months 5 days	'	'	'
Weighted Average Remaining Contractual Term (in years), Exercisable	'6 years 10 months 6 days	'	'	'

Capital_Stock_Additional_Infor1

Capital Stock - Additional Information Regarding Company's Stock Options Outstanding and Exercisable (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]	'
Number of Stock Options Outstanding	1,675,506
Weighted Average Remaining Contractual Life (Years)	'8 years 4 days
Weighted Average Exercise Price per Share	$23.78
Shares Subject to Stock Options	512,536
Weighted Average Exercise Price Per Share	$12.87
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	$0.72
Company's stock options outstanding and exercisable, Upper Range	$9.04
Number of Stock Options Outstanding	474,906
Weighted Average Remaining Contractual Life (Years)	'6 years 3 months 4 days
Weighted Average Exercise Price per Share	$3.29
Shares Subject to Stock Options	302,269
Weighted Average Exercise Price Per Share	$2.70
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	$9.05
Company's stock options outstanding and exercisable, Upper Range	$17.35
Number of Stock Options Outstanding	107,947
Weighted Average Remaining Contractual Life (Years)	'7 years 7 months 24 days
Weighted Average Exercise Price per Share	$10.70
Shares Subject to Stock Options	33,116
Weighted Average Exercise Price Per Share	$10.70
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	$17.36
Company's stock options outstanding and exercisable, Upper Range	$25.67
Number of Stock Options Outstanding	44,064
Weighted Average Remaining Contractual Life (Years)	'7 years 11 months 1 day
Weighted Average Exercise Price per Share	$25.61
Shares Subject to Stock Options	18,461
Weighted Average Exercise Price Per Share	$25.61
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	$25.68
Company's stock options outstanding and exercisable, Upper Range	$33.99
Number of Stock Options Outstanding	498,384
Weighted Average Remaining Contractual Life (Years)	'8 years 5 months 12 days
Weighted Average Exercise Price per Share	$31.34
Shares Subject to Stock Options	147,217
Weighted Average Exercise Price Per Share	$30.73
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
Company's stock options outstanding and exercisable, Upper Range	$42.30
Number of Stock Options Outstanding	477,785
Weighted Average Remaining Contractual Life (Years)	'9 years 1 month 13 days
Weighted Average Exercise Price per Share	$35.71
Shares Subject to Stock Options	11,473
Weighted Average Exercise Price Per Share	$37.23
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	$42.31
Company's stock options outstanding and exercisable, Upper Range	$50.62
Number of Stock Options Outstanding	72,420
Weighted Average Remaining Contractual Life (Years)	'9 years 8 months 9 days
Weighted Average Exercise Price per Share	$45.87
Shares Subject to Stock Options	'
Weighted Average Exercise Price Per Share	'

Capital_Stock_Summary_of_RSU_A

Capital Stock - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Restricted stock units for common stock [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	446,915	'
Number of Restricted Stock Units Outstanding, Granted	577,528	458,790
Number of Restricted Stock Units Outstanding, Released	-149,531	'
Number of Restricted Stock Units Outstanding, Cancelled or expired	-95,139	-11,875
Number of Restricted Stock Units Outstanding, Unvested - Ending balance	1,044,651	446,915
Weighted-Average Grant Date Fair Value, Unvested - Beginning Balance	$31.20	'
Weighted-Average Grant Date Fair Value, Granted	$36.94	$31.24
Weighted-Average Grant Date Fair Value, Released	$30.64	'
Weighted-Average Grant Date Fair Value, Cancelled or expired	$34.30	$32.88
Weighted-Average Grant Date Fair Value, Unvested - Ending balance	$31.64	$31.20
Performance RSUs [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Number of Restricted Stock Units Outstanding, Granted	264,878	'
Weighted-Average Grant Date Fair Value, Granted	$20.76	'

Capital_Stock_StockBased_Compe

Capital Stock - Stock-Based Compensation Expense (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	$22,494	$5,968	$1,727
Cost of revenue [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	1,440	469	118
Research and development [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	3,660	1,227	130
Sales and marketing [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	8,537	2,543	412
General and administrative [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total stock-based compensation expense	$8,857	$1,729	$1,067

Capital_Stock_Weighted_Average

Capital Stock - Weighted Average Assumptions for Fair Value of Stock Options Granted to Employees (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee stock purchase plan [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Dividend rate	0.00%	0.00%	'
Risk-free interest rate	0.10%	0.10%	'
Expected term (in years)	'6 months	'6 months	'
Expected volatility	27.00%	39.00%	'
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	1.20%	1.00%	1.70%
Expected term (in years)	'6 years 1 month 6 days	'6 years	'5 years 4 months 24 days
Expected volatility	46.00%	48.00%	49.00%

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) - Changes in Balances of Accumulated Other Comprehensive Income (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	$861	($616)	$452
Other comprehensive income (loss) before reclassifications	746	936	-1,286
Amounts reclassified to net loss	-2,035	541	218
Other comprehensive income (loss)	-1,289	1,477	-1,068
Ending Balance	-428	861	-616
Unrealized gain (loss) on cash flow hedges [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	691	-559	452
Other comprehensive income (loss) before reclassifications	712	652	-1,231
Amounts reclassified to net loss	-1,829	598	220
Other comprehensive income (loss)	-1,117	1,250	-1,011
Ending Balance	-426	691	-559
Unrealized gain (loss) on investments [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning Balance	170	-57	'
Other comprehensive income (loss) before reclassifications	34	284	-55
Amounts reclassified to net loss	-206	-57	-2
Other comprehensive income (loss)	-172	227	-57
Ending Balance	($2)	$170	($57)

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Loss) - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]	'	'	'
Current period unrealized gain (loss) on cash flow hedges, Pre-Tax Amount	$712	$1,079	($1,231)
Reclassification adjustments on cash flow hedges, Pre-Tax Amount	-1,829	598	220
Unrealized gains (losses) on cash flow hedges, net, Pre-Tax Amount	-1,117	1,677	-1,011
Current period unrealized gain (loss) on investments, Pre-Tax Amount	34	291	-55
Reclassification adjustments on investments, Pre-Tax Amount	-206	-57	-2
Unrealized gains (losses) on investments, net, Pre-Tax Amount	-172	234	-57
Other comprehensive income (loss), Pre-Tax Amount	-1,289	1,911	-1,068
Current period unrealized gain (loss) on cash flow hedges, Tax Expense (Benefit)	'	427	'
Reclassification adjustments on cash flow hedges, Tax Expense (Benefit)	'	'	'
Unrealized gains (losses) on cash flow hedges, net, Tax Expense (Benefit)	'	427	'
Current period unrealized gain (loss) on investments, Tax Expense (Benefit)	'	7	'
Reclassification adjustments on investments, Tax Expense (Benefit)	'	'	'
Unrealized gains (losses) on investments, net, Tax Expense (Benefit)	'	7	'
Other comprehensive income (loss), Tax Expense (Benefit)	'	434	'
Current period unrealized gain (loss) on cash flow hedges, After-Tax Amount	712	652	-1,231
Reclassification adjustments on cash flow hedges, After-Tax Amount	-1,829	598	220
Unrealized gains (losses) on cash flow hedges, net, After-Tax Amount	-1,117	1,250	-1,011
Current period unrealized gain (loss) on investments, After-Tax Amount	34	284	-55
Reclassification adjustments on investments, After-Tax Amount	-206	-57	-2
Unrealized gains (losses) on investments, net, After-Tax Amount	-172	227	-57
Other comprehensive income (loss)	($1,289)	$1,477	($1,068)

Income_Taxes_Loss_Before_Provi

Income Taxes - Loss Before Provision for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Domestic	($28,831)	($9,373)	($12,747)
Foreign	3,277	2,026	2,551
Loss before provision for income taxes	($25,554)	($7,347)	($10,196)

Income_Taxes_Provision_for_Inc

Income Taxes - Provision for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current	'	'	'
Federal	'	$51	'
State	127	47	63
Foreign	700	889	618
Total current provision	827	987	681
Deferred	'	'	'
Federal	'	-386	'
State	'	-49	'
Foreign	-50	-7	-19
Total deferred provision	-50	-442	-19
Provision for income taxes	$777	$545	$662

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Provision for Income Taxes at Statutory Rate (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Tax benefit at federal statutory tax rate	($8,688)	($2,497)	($3,465)
Tax benefit at state statutory tax rate	-829	-282	-390
Tax benefit resulting from Beneficiary Enterprise	'	-95	-191
Foreign tax rate differential	-705	-232	-302
Foreign repatriation	'	179	'
Unbenefitted loss of consolidated investment	2,402	1,193	1,026
Change in valuation allowance	7,400	1,373	3,072
Meals and entertainment	197	162	145
Warrants fair value adjustment	'	'	95
Stock compensation	810	497	543
Nondeductible expenses and other	190	247	129
Provision for income taxes	$777	$545	$662
Basic net loss per share amounts of benefits resulting from Beneficiary Enterprise Status	'	'	$0.02

Income_Taxes_Net_Deferred_Tax_

Income Taxes - Net Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred tax assets:	'	'
Reserves and accruals	$1,345	$1,169
Deferred revenue	4,297	5,642
Stock-based compensation	7,042	1,470
Net operating loss carryforwards	20,361	17,530
Other	194	'
Gross deferred tax assets	33,239	25,811
Valuation allowance	-32,656	-24,266
Deferred tax assets	583	1,545
Deferred tax liabilities:	'	'
Stock-based compensation	-166	-314
Depreciation and amortization	-31	-497
Gain on OCI	-2	-435
Total deferred tax liabilities	-200	-1,246
Net deferred tax assets	$383	$299

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail)

1 Months Ended

12 Months Ended

12 Months Ended

Nov. 30, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

ILS

USD ($)

USD ($)

USD ($)

USD ($)

Israeli Tax Authority [Member]

Israeli Tax Authority [Member]

2011 [Member]

2012 [Member]

2013 [Member]

2014 [Member]

2015 and Thereafter [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

USD ($)

State [Member]

Federal [Member]

Israeli Tax Authority [Member]

State [Member]

Federal [Member]

Israeli Tax Authority [Member]

Income Tax Expenses [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Valuation allowance

'

$8,400,000

$1,800,000

$3,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

U.S. federal, net operating loss carryforwards

'

82,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

State net operating loss carryforwards

'

65,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expiration of net operating loss carryforwards

'

'

'

'

'

'

'

'

'

'

'

'

'2033

'2033

'

'2018

'2023

'

Excess tax benefits from stock options included in deferred tax assets for federal net operating losses

'

28,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Excess tax benefits from stock options included in deferred tax assets for state net operating losses

'

21,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accumulated unremitted earnings

'

9,800,000

7,200,000

5,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrecognized tax benefits

'

353,000

239,000

267,000

171,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Accrued interest on income tax expense

'

22,000

7,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax years

'

'

'

'

'

'2006 through 2010

'

'

'

'

'

'

'

'

'

'

'

'

Period for tax exemption

'

'

'

'

'

'2 years

'

'

'

'

'

'

'

'

'

'

'

'

Limitation of tax benefits

'

'

'

'

'

'12 years

'

'

'

'

'

'

'

'

'

'

'

'

Tax rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

10.00%

Additional period for tax exemption

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'8 years

'

'

'5 years

Tax exempted income

'

'

'

'

'

'

2,400,000

'

'

'

'

'

'

'

'

'

'

'

Income tax liabilities

'

'

'

'

'

'

600,000

'

'

'

'

'

'

'

'

'

'

'

Payment to the Israeli Tax Authority

200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of exempt profits

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax rate applicable for R&D activities

'

'

'

'

'

'

'

15.00%

15.00%

12.50%

12.50%

12.00%

'

'

'

'

'

'

Corporate tax rate, previous

'

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Corporate tax rate, current

'

26.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax rate applicable for R&D activities

'

16.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax rate applicable for other activities

'

26.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income_Taxes_Unrecognized_Tax_

Income Taxes - Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Beginning Balance	$239	$267	$171
Additions based on tax positions taken during the current period	134	141	96
Reductions based on tax positions taken during a prior period	-20	-169	'
Ending Balance	$353	$239	$267

Segment_Information_Additional

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2013
	Segment
Segment Reporting [Abstract]	'
Number of operating segments	2

Segment_Information_Summary_of

Segment Information - Summary of Company's Operating Segments (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]	'	'	'
Net revenue	$137,759	$104,235	$78,302
Operating loss	-25,429	-7,104	-10,006
Provision for income tax	777	545	662
Net loss	-25,178	-7,387	-10,269
Depreciation and amortization	2,642	1,841	1,540
Stock-based compensation	22,494	5,968	1,727
Total assets	176,491	153,957	'
Imperva [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net revenue	134,691	103,410	78,214
Operating loss	-18,853	-4,119	-7,436
Provision for income tax	740	527	646
Net loss	-19,874	-4,757	-8,144
Depreciation and amortization	2,298	1,703	1,529
Stock-based compensation	19,559	5,947	1,706
Total assets	174,554	149,998	130,742
Incapsula [Member]	'	'	'
Segment Reporting Information [Line Items]	'	'	'
Net revenue	3,068	825	88
Operating loss	-6,576	-2,985	-2,570
Provision for income tax	37	18	16
Net loss	-6,457	-3,135	-2,714
Depreciation and amortization	344	138	11
Stock-based compensation	2,935	21	21
Total assets	$1,937	$3,959	$2,800

Segment_Information_Components

Segment Information - Components of Net Services Revenue (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net services revenue	$65,606	$44,745	$30,702
Maintenance and support [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net services revenue	44,353	33,647	24,497
Professional services and training [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net services revenue	9,890	6,428	4,730
Subscriptions [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net services revenue	$11,363	$4,670	$1,475

Segment_Information_Companys_N

Segment Information - Company's Net Revenue by Geographic Region, Based on Customer's Location (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net revenue	$137,759	$104,235	$78,302
Americas [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net revenue	83,736	61,588	47,851
EMEA [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net revenue	33,183	24,958	18,464
APAC [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total net revenue	$20,840	$17,689	$11,987

Segment_Information_LongLived_

Segment Information - Long-Lived Assets by Location (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total long-lived assets	$5,475	$5,515	$4,026
United States [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total long-lived assets	3,039	2,851	1,815
Israel [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total long-lived assets	2,422	2,642	2,196
Other [Member]	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'
Total long-lived assets	$14	$22	$15

Net_Loss_per_Share_Computation

Net Loss per Share - Computation of Company's Basic and Diluted Net Loss Per Share of Common Stock (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'
Net loss attributable to Imperva, Inc. stockholders	($25,178)	($7,387)	($10,269)
Shares used in computing net loss per share of common stock, basic and diluted	24,300,198	22,916,426	7,674,554
Net loss per share of common stock, basic and diluted	($1.04)	($0.32)	($1.34)

Net_Loss_per_Share_Antidilutiv

Net Loss per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock options [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share	1,675,506	1,989,237	2,871,005
Restricted stock units for common stock [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share	1,044,651	446,915	'
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 earnings per share	335,062	530,779	733,995
Common stock warrants [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share	'	8,333	8,333

Related_Party_Transaction_Addi

Related Party Transaction - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transactions [Abstract]	'	'	'
Net revenues recorded from indirect sales	$100,000	$400,000	$0
Accounts receivable from the reseller for the indirect sales	$19,000	'	'

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)

Dec. 31, 2013

Jan. 30, 2014

Dec. 31, 2013

Feb. 07, 2014

Dec. 31, 2013

Feb. 07, 2014

Feb. 07, 2014

Feb. 07, 2014

Feb. 11, 2014

Dec. 31, 2013

Feb. 11, 2014

Feb. 11, 2014

Feb. 11, 2014

In Millions, except Share data, unless otherwise specified

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Subsequent Events [Member]

Tomium Software, LLC [Member]

Tomium Software, LLC [Member]

SkyFence Networks, Ltd. [Member]

SkyFence Networks, Ltd. [Member]

SkyFence Networks, Ltd. [Member]

SkyFence Networks, Ltd. [Member]

SkyFence Networks, Ltd. [Member]

Incapsula [Member]

Incapsula [Member]

Incapsula [Member]

Incapsula [Member]

Incapsula [Member]

Stock options [Member]

CEO [Member]

Chief Technology Officer [Member]

Minimum [Member]

Maximum [Member]

Restricted stock units for common stock [Member]

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Business acquisition purchase price, common stock value

'

$3.40

'

$52.30

'

'

'

'

'

'

'

'

'

Date of acquisition

'

'

30-Jan-14

'

'

'

'

'

'

'

'

'

'

Business acquisition purchase price, cash paid

'

4.7

'

16.1

'

'

'

'

'

'

'

'

'

Business acquisition purchase price

'

8.1

'

69.8

'

'

'

'

'

'

'

'

'

Business acquisition purchase price, shares issued

'

60,556

'

884,422

'

24,248

'

'

'

'

'

'

'

Date of acquisition agreement

'

'

'

'

7-Feb-14

'

'

'

'

11-Feb-14

'

'

'

Ownership percentage in acquiree company

'

'

'

'

'

'

42.67%

3.16%

'

'

'

'

'

Exchange for common stock, value

'

'

'

'

'

'

'

'

8.1

'

'

'

'

Collar price of company stock

'

'

'

'

'

'

'

'

'

'

$31.40

$47.10

'

Shares expected to vest

1,454,729

'

'

'

'

'

'

'

'

'

'

'

180,890

Deduction for transaction expenses and cancellation

'

'

'

'

'

'

'

'

$1.10

'

'

'

'