Imperva 10-Q 7 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'IMPV	'
Entity Registrant Name	'IMPERVA INC	'
Entity Central Index Key	'0001364962	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	26,584,517

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
CURRENT ASSETS:	'	'
Cash and cash equivalents	$65,801	$76,704	[1]
Short-term investments	35,395	38,381	[1]
Restricted cash	34	34	[1]
Accounts receivable, net of allowance for doubtful accounts of $410 as of September 30, 2014 and December 31, 2013	35,537	44,446	[1]
Inventory	359	512	[1]
Deferred tax assets	347	341	[1]
Prepaid expenses and other current assets	3,530	3,972	[1]
Total current assets	141,003	164,390	[1]
Property and equipment, net	6,656	5,475	[1]
Goodwill	34,972	0	[1]
Acquired intangible assets, net	9,751	0	[1]
Severance pay fund	4,044	4,140	[1]
Restricted cash	1,575	1,252	[1]
Deferred tax assets	42	42	[1]
Other assets	953	1,192	[1]
TOTAL ASSETS	198,996	176,491	[1]
CURRENT LIABILITIES:	'	'
Accounts payable	3,461	3,948	[1]
Accrued compensation and benefits	13,617	12,930	[1]
Accrued and other current liabilities	5,514	3,961	[1]
Deferred revenue	46,154	40,337	[1]
Total current liabilities	68,746	61,176	[1]
Other liabilities	9,450	1,993	[1]
Deferred revenue	22,793	22,715	[1]
Accrued severance pay	4,331	4,385	[1]
TOTAL LIABILITIES	105,320	90,269	[1]
Commitments and Contingencies (Note 9)	'	'	[1]
STOCKHOLDERS' EQUITY:	'	'
Preferred stock, $0.0001 par value - 5,000,000 shares authorized, no shares issued and outstanding as of September 30, 2014 and December 31, 2013	0	0	[1]
Common stock, $0.0001 par value - 145,000,000 shares authorized, 26,582,777 and 25,206,498 shares issued and outstanding as of September 30, 2014 and December 31, 2013, respectively	2	2	[1]
Additional paid-in capital	239,699	187,957	[1]
Accumulated deficit	-145,162	-98,695	[1]
Accumulated other comprehensive loss	-863	-428	[1]
TOTAL IMPERVA, INC. STOCKHOLDERS' EQUITY	93,676	88,836	[1]
Noncontrolling interest	0	-2,614	[1]
TOTAL STOCKHOLDERS' EQUITY	93,676	86,222	[1]
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$198,996	$176,491	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Allowance for doubtful accounts	$410	$410	[1]
Preferred stock, par value	$0.00	$0.00	[1]
Preferred stock, shares authorized	5,000,000	5,000,000	[1]
Preferred stock, shares issued	0	0	[1]
Preferred stock, shares outstanding	0	0	[1]
Common stock, par value	$0.00	$0.00	[1]
Common stock, shares authorized	145,000,000	145,000,000	[1]
Common stock, shares issued	26,582,777	25,206,498	[1]
Common stock, shares outstanding	26,582,777	25,206,498	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net revenue:	'	'	'	'
Products and license	$19,642	$18,178	$48,199	$48,003
Services	23,033	16,924	64,434	47,023
Total net revenue	42,675	35,102	112,633	95,026
Cost of revenue:	'	'	'	'
Products and license	2,299	1,894	6,106	6,216
Services	7,202	5,396	20,181	14,909
Total cost of revenue	9,501	7,290	26,287	21,125
Gross profit	33,174	27,812	86,346	73,901
Operating expenses:	'	'	'	'
Research and development	10,459	6,725	32,038	19,729
Sales and marketing	26,853	20,135	74,953	55,963
General and administrative	8,987	4,697	25,013	13,677
Amortization of acquired intangible assets	351	'	917	0
Total operating expenses	46,650	31,557	132,921	89,369
Loss from operations	-13,476	-3,745	-46,575	-15,468
Other income (expense), net	48	113	-321	11
Loss before provision (benefit) for income taxes	-13,428	-3,632	-46,896	-15,457
Provision (benefit) for income taxes	190	288	-216	703
Net loss	-13,618	-3,920	-46,680	-16,160
Loss attributable to noncontrolling interest	0	145	213	411
Net loss attributable to Imperva, Inc. stockholders	($13,618)	($3,775)	($46,467)	($15,749)
Net loss per share of common stock attributable to Imperva, Inc. stockholders, basic and diluted	($0.52)	($0.15)	($1.81)	($0.65)
Shares used in computing net loss per share of common stock, basic and diluted	25,967	24,453	25,680	24,174

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net loss	($13,618)	($3,920)	($46,680)	($16,160)
Other comprehensive loss (net of tax):	'	'	'	'
Net change in net unrealized gain (loss) on investments	-30	25	-16	-183
Net change in unrealized gain (loss) on hedging instruments	-500	-328	-419	-425
Other comprehensive income (loss)	-530	-303	-435	-608
Comprehensive loss	-14,148	-4,223	-47,115	-16,768
Comprehensive loss attributable to noncontrolling interest	'	145	213	411
Comprehensive loss attributable to Imperva, Inc. stockholders	($14,148)	($4,078)	($46,902)	($16,357)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (USD $)

Total

Skyfence Networks, Ltd. [Member]

Common Stock [Member]

Common Stock [Member]

Additional Paid-in Capital [Member]

Additional Paid-in Capital [Member]

Additional Paid-in Capital [Member]

Accumulated Deficit [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

In Thousands, except Share data, unless otherwise specified

USD ($)

USD ($)

USD ($)

Incapsula [Member]

USD ($)

Skyfence Networks, Ltd. [Member]

Incapsula [Member]

USD ($)

USD ($)

USD ($)

Incapsula [Member]

USD ($)

USD ($)

USD ($)

Beginning balance at Dec. 31, 2012

$84,231

'

$2

'

$157,989

'

'

($73,517)

$861

($1,104)

'

Beginning balance, shares at Dec. 31, 2012

'

'

24,296,076

'

'

'

'

'

'

'

'

Issuance of common stock related to acquisitions

'

'

'

'

'

'

358

'

'

'

-358

Issuance of common stock, net of repurchases

4,674

'

'

'

4,674

'

'

'

'

'

'

Issuance of common stock, net of repurchases, shares

'

'

655,433

'

'

'

'

'

'

'

'

Vesting of restricted stock

600

'

'

'

600

'

'

'

'

'

'

Stock-based compensation

9,858

'

'

'

9,858

'

'

'

'

'

'

Exercise of warrant

'

'

7,694

'

'

'

'

'

'

'

'

Components of other comprehensive income (loss), net of tax:

'

'

'

'

'

'

'

'

'

'

'

Change in unrealized gain (loss) on investments

-183

'

'

'

'

'

'

'

-183

'

'

Change in unrealized gain (loss) on derivatives

-425

'

'

'

'

'

'

'

-425

'

'

Net loss

-16,160

'

'

'

'

'

'

-15,749

'

-411

'

Comprehensive loss

-16,768

'

'

'

'

'

'

'

'

'

'

Ending balance at Sep. 30, 2013

82,595

'

2

'

173,479

'

'

-89,266

253

-1,873

'

Ending balance, shares at Sep. 30, 2013

'

'

24,959,203

'

'

'

'

'

'

'

'

Beginning balance at Dec. 31, 2013

86,222

[1]

'

2

'

187,957

'

'

-98,695

-428

-2,614

'

Beginning balance, shares at Dec. 31, 2013

'

'

25,206,498

'

'

'

'

'

'

'

'

Issuance of common stock related to acquisitions

24,164

354

'

'

24,164

354

-2,827

'

'

'

2,827

Issuance of common stock related to acquisitions, shares

'

'

738,479

89,603

'

'

'

'

'

'

'

Issuance of common stock, net of repurchases

3,498

'

'

'

3,498

'

'

'

'

'

'

Issuance of common stock, net of repurchases, shares

'

'

548,197

'

'

'

'

'

'

'

'

Vesting of restricted stock

427

'

'

'

427

'

'

'

'

'

'

Stock-based compensation

26,106

'

'

'

26,106

'

'

'

'

'

'

Income tax benefit from employee stock option exercises

20

'

'

'

20

'

'

'

'

'

'

Components of other comprehensive income (loss), net of tax:

'

'

'

'

'

'

'

'

'

'

'

Change in unrealized gain (loss) on investments

-16

'

'

'

'

'

'

'

-16

'

'

Change in unrealized gain (loss) on derivatives

-419

'

'

'

'

'

'

'

-419

'

'

Net loss

-46,680

'

'

'

'

'

'

-46,467

'

-213

'

Comprehensive loss

-47,115

'

'

'

'

'

'

'

'

'

'

Ending balance at Sep. 30, 2014

$93,676

'

$2

'

$239,699

'

'

($145,162)

($863)

'

'

Ending balance, shares at Sep. 30, 2014

'

'

26,582,777

'

'

'

'

'

'

'

'

[1]

The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:	'		'
Net loss	($46,680)		($16,160)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:	'		'
Depreciation and amortization	2,613		1,935
Stock-based compensation	26,106		9,858
Amortization of acquired intangibles	917		0
Amortization of premiums/accretion of discounts on short-term investments	318		547
Excess tax benefits from share-based compensation	-20		0
Changes in operating assets and liabilities:	'		'
Accounts receivable, net	8,909		-1,076
Inventory	153		-213
Prepaid expenses and other assets	713		-654
Accounts payable	-765		-734
Accrued compensation and benefits	498		2,547
Accrued and other liabilities	220		-146
Severance pay (net)	42		16
Deferred revenue	5,895		6,357
Deferred tax assets	-6		-16
Other	0		-12
Net cash provided by (used in) operating activities	-1,087		2,249
CASH FLOWS FROM INVESTING ACTIVITIES:	'		'
Purchase of short-term investments	-26,899		-29,825
Proceeds from sales/maturities of short-term investments	29,821		36,241
Acquisitions, net of cash acquired	-12,083		0
Purchase of property and equipment	-3,694		-1,753
Change in restricted cash	-323		58
Net cash provided by (used in) investing activities	-13,178		4,721
CASH FLOWS FROM FINANCING ACTIVITIES:	'		'
Proceeds from issuance of common stock, net of repurchases	3,342		4,674
Excess tax benefits from share-based compensation	20		0
Net cash provided by financing activities	3,362		4,674
Effect of exchange rate changes on cash and cash equivalents	0		-205
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	-10,903		11,439
CASH AND CASH EQUIVALENTS - Beginning of period	76,704	[1]	59,201
CASH AND CASH EQUIVALENTS - End of period	65,801		70,640
NONCASH INVESTING AND FINANCING ACTIVITIES:	'		'
Vesting of restricted and early exercised stock options	427		600
Common stock issued in connection with acquisitions	$24,164		$0
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Basis_of_Presentation_and_Summ

Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Basis of Presentation and Summary of Significant Accounting Policies	'
	1. Basis of Presentation and Summary of Significant Accounting Policies
	Business
	Imperva, Inc. (together with its subsidiaries, the “Company” or “we”) 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 Company has prepared the accompanying unaudited Condensed Consolidated Financial Statements in accordance with Article 10 of Regulation S-X and pursuant to the rules and regulations for Form 10-Q of the Securities and Exchange Commission (the “SEC”). Pursuant to those rules and regulations, the Company has condensed or omitted certain information and footnote disclosure it normally includes in its annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the Company has made all adjustments (consisting only of normal, recurring adjustments, except as otherwise indicated) necessary to fairly present its consolidated financial position, results of operations, and cash flows. The Company’s interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the consolidated financial statements and notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013, which was filed with the SEC on February 28, 2014 (the “Annual Report”).
	During the three months ended March 31, 2014, we revised our business segments based upon the acquisition of the remaining shares of Incapsula, Inc. that the Company did not already own. As a result, we no longer separately report the Incapsula segment and the Company now operates in one operating, and therefore, reportable segment in order to better align Incapsula with our strategic approach to the markets and customers we serve. The reclassification of historical business segment information had no impact on the Company’s basic financial statements.
	Basis of Consolidation
	The condensed consolidated financial statements include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. On March 20, 2014, the Company acquired the remaining interest it did not previously own in its majority-owned subsidiary, Incapsula, Inc. (“Incapsula”) (Refer to Note 2). The Company separately presented the non-controlling interest on its Condensed Consolidated Balance Sheets in Total Stockholder’s Equity and in its Condensed Consolidated Statements of Operations for periods prior to such date.
	Goodwill and Acquired Intangibles
	Goodwill represents the excess of the aggregate purchase price paid over the fair value of the net tangible assets acquired. Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. In reviewing goodwill, the Company performs a qualitative assessment to test the reporting unit’s goodwill for impairment. Based on the Company’s qualitative assessment, if we determine that the fair value of the reporting unit is more likely than not (i.e. a likelihood of more than 50 percent) to be less than the carrying amount, the two step impairment test will be performed. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value.
	The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the nine months ended September 30, 2014.
	We amortize intangible assets with finite lives over their estimated useful lives and review them for impairment whenever an impairment indicator exists. We continually monitor events and changes in circumstances that could indicate carrying amounts of our intangible assets may not be recoverable. When such events or changes in circumstances occur, we assess recoverability by determining whether the carrying value of such assets will be recovered through the undiscounted expected future cash flows. If the future undiscounted cash flows are less than the carrying amount of these assets, we recognize an impairment loss based on any excess of the carrying amount over the fair value of the assets. We did not recognize any intangible asset impairment charges in the nine months ended September 30, 2014. Our intangible assets are amortized over their estimated useful lives of 7 to 10 years. Amortization is based on a straight-line basis as the consumption pattern of the asset is not apparent. The weighted average useful life of our acquired technology intangible assets was 8 years.
	Concentration of Revenue and Accounts Receivable
	For the nine months ended September 30, 2013, the Company had one customer that represented 10% of the Company’s total revenue. For the three months ended September 30, 2014 and 2013 and for the nine months ended September 30, 2014, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There was one customer that represented 12% of gross accounts receivable as of September 30, 2014. There were no customers who represented greater than 10% of gross accounts receivable as of December 31, 2013.
	Significant Accounting Policies
	Other than the change to our reporting segments and the addition of the Company’s policy for accounting for goodwill and acquired intangibles, there have been no material changes to the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	Recent Accounting Pronouncements
	In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-08, Reporting Discontinued Operations and Disposals of Components of an Entity, which changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. The new guidance is effective for annual and interim periods beginning after December 15, 2014, with early adoption permitted. The new guidance will be applicable for disposal transactions, if any, that we initiate after the adoption date. The adoption of this guidance is not expected to have a material impact on our financial position, results of operations or cash flows.
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, to clarify the principles used to recognize revenue for all entities. The new guidance is effective for annual and interim periods beginning after December 15, 2016 with no early adoption permitted and allows for both retrospective and prospective methods of adoption. We are currently evaluating the impact, if any, the adoption of this guidance will have on our financial position, results of operations or cash flows.
	In June 2014, the FASB issued ASU No. 2014-12, Compensation—Stock Compensation, which provides guidance that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value. Compensation cost for such an award would be recognized over the required service period, if it is probable that the performance condition will be achieved. The updated guidance is effective for annual reporting periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted but we do not anticipate electing early adoption. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, new guidance related to the disclosures around going concern. The new standard provides guidance around management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on our financial statements.

Incapsula

Incapsula	9 Months Ended
	Sep. 30, 2014
Text Block [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.
	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%.
	Under the terms of the agreements between the Company and Incapsula, the Company had the right, but not the obligation, to purchase the remaining ownership interest in Incapsula commencing on November 5, 2013 and ending on November 5, 2018 (the “Purchase Right”). Exercise of the Purchase Right was solely within the Company’s control and the price for the remaining ownership interest was to be based on an Incapsula enterprise valuation calculated as the greater of (i) eight times Incapsula’s prior 12 months trailing revenues or (ii) seven times the aggregate amount Incapsula had raised in connection with its Series A Convertible Preferred Stock financings. On the acquisition date, no value was assigned to this Purchase Right as the option does not meet the definition of a derivative instrument as it does not contain a net settlement feature. Specifically, the Purchase Right could only be gross physically settled as Incapsula was a non-publicly traded company whose stock was not readily convertible to cash.
	In March 2010, the board of directors of Incapsula adopted the Incapsula 2010 Share Incentive Plan pursuant to which Incapsula may grant to its employees options to purchase shares of Incapsula’s common stock or restricted shares. Pursuant to 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 or cashed out, and all outstanding awards and the Incapsula 2010 Share Plan would terminate.
	In March 2014, the Company acquired the remaining outstanding capital stock in exchange for approximately 124,088 shares of Company common stock with an aggregate fair value of $7.7 million, of which 34,485 shares are subject to a 15-month holdback pursuant to the acquisition agreement, and assumed outstanding options to acquire capital stock of Incapsula not already owned by Imperva (the “Incapsula Acquisition”) which are equivalent to 48,359 shares of Company common stock on an as-converted basis. The aggregate consideration for the Incapsula Acquisition is substantially on the same terms of the Purchase Right less the outstanding principal and interest under the Incapsula Loan. In addition, during 2013, the Company issued RSUs for approximately 264,878 shares of Imperva common stock with performance-based vesting tied to 2014 revenue for Incapsula and Incapsula-related products and services (effectively valuing such revenues similarly to the Purchase Right) less the outstanding principal and interest under the Incapsula Loan. At the same time, Incapsula issued similar RSUs for approximately 198,825 shares on an as-converted to Imperva common stock-basis, which the Company assumed in connection with the Incapsula Acquisition, in addition to the consideration for the Incapsula Purchase. These performance-based RSUs granted by Imperva and Incapsula were issued to continuing employees of Incapsula.
	As of the date of the acquisition, the remaining non-controlling interest on the Company’s balance sheet of $2.8 million was reclassified to additional paid-in capital given the Company’s complete ownership of Incapsula.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Acquisitions	'
	3. Acquisitions
	Acquisitions during the first nine months of 2014 were accounted for in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations, and the results of operations of each acquisition have been included in our consolidated results of operations from the respective date of the acquisition. Each of the acquisitions was not material, either individually or in the aggregate to our results of operations in the period of acquisition.
	While we use our best estimates and assumptions as part of the purchase price allocation process to value assets acquired and liabilities assumed at the business combination date, our estimates and assumptions are subject to refinement. As a result, during the preliminary purchase price allocation period, which may be up to one year from the business combination date, we may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. We record adjustments to assets acquired or liabilities assumed subsequent to the purchase price allocation period in our operating results in the period in which the adjustments were determined.
	The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The fair value assigned to identifiable intangible assets acquired is determined using the income approach which discounts expected future cash flows to present value using estimated assumptions determined by management. We believe that these identified intangible assets will have no residual value after their estimated economic useful lives. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets.
	The excess of the purchase price over the identified tangible and intangible assets, less liabilities assumed, is recorded as goodwill and primarily reflects the value of the synergies expected to be generated from combining our and the acquired entities’ technology and operations.
	Acquisition of Skyfence Networks Ltd.
	On February 7, 2014, the Company 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 Software-as-a-Service (“SaaS”) applications, which enforces security policy, protects sensitive data from external and inside threats, as well as ensures compliance with standards.
	Per the terms of the acquisition agreement (as amended) with Skyfence and its security holders, we purchased all of the outstanding shares of capital stock of Skyfence in exchange for (a) approximately $8.6 million in cash, in addition to a holdback payment commitment due 24 months from the date the acquisition closes valued at approximately $7.2 million, and (b) 884,422 shares of Company common stock, of which 532,262 shares are subject to forfeiture based upon time-based vesting and continuing employment, and were therefore excluded from purchase consideration as such amounts will be recorded as compensation expense over the term of the corresponding four-year service period. In addition, 29,871 of the shares are subject to a holdback period of up to 24 months from the date of acquisition. We also assumed stock options outstanding in accordance with the terms of the applicable Skyfence stock option plan and Skyfence stock option agreement relating to that Skyfence stock option. Based on Skyfence’s stock options outstanding at February 7, 2014, Imperva converted options to purchase 164,000 shares of Skyfence stock into options to purchase 24,828 shares of Imperva common stock.
	The fair value of Imperva’s shares issued is based on Imperva’s closing price per share of $59.08 as reported on the New York Stock Exchange at the closing of the Acquisition on February 7, 2014.
	The fair values of the stock option awards assumed were estimated using a Black-Scholes option-pricing model. The estimated fair values of unvested equity awards of $1.1 million will be recorded as operating expense over the remaining requisite service periods as they relate to post-combination services, while the fair values of vested equity based awards of $0.3 million were included in total purchase price as they relate to pre-combination services. The total purchase consideration is as follows (in thousands):
	Cash	$	8,558
	Cash holdback liability		7,157
	Fair value of common stock		20,855
	Estimated fair value of equity awards assumed and replaced		354
		$	36,924
	The acquisition of Skyfence was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. We expensed the related acquisition costs in the amount of $0.9 million in general and administrative expenses. In addition, stock-based compensation expense totaling $5.3 million was recognized from the date of acquisition through September 30, 2014.
	The excess of the consideration for Skyfence over the fair values assigned to the assets acquired and liabilities assumed represents the goodwill resulting from the acquisition. Management believes that the goodwill represents the synergies expected from combining the products and technologies of Imperva with those of Skyfence, which will enhance the Company’s overall product portfolio. The purchased technology will be amortized straight-line over a seven-year preliminary estimated useful life. Also as part of the acquisition, we assumed deferred tax liabilities related to the fair value of the developed technology we obtained in the acquisition. Goodwill recorded in connection with the acquisition is not deductible for income tax purposes. The total purchase price was allocated using the information available at the business combination date. The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands):
	Net tangible assets	$	1,014
	Existing technology		7,965
	Deferred tax liability assumed		(1,528	)
	Goodwill		29,473
	Total purchase price	$	36,924
	The results of operations of Skyfence described above have been included in Imperva’s consolidated financial statements from the date of acquisition. The following table presents pro forma results of operations of the Company and Skyfence as if the companies had been combined as of January 1, 2013, and includes pro forma adjustments related to the amortization of acquired intangible assets and share-based compensation expense and the related income tax effects. Direct transaction costs are excluded from the September 30, 2014 pro forma condensed combined financial information presented below. For pro forma purposes, during the nine months ended September 30, 2014 and 2013, $148,000 and $373,000, respectively, of income tax benefit associated with the deferred tax liability was recognized in earnings. The pro forma condensed combined financial information is presented for informational purposes only. The unaudited pro forma results of operations are not necessarily indicative of results that would have occurred had the acquisition taken place at the beginning of the earliest period presented, or of future results. Included in the pro forma results are fair value adjustments based on the fair values of assets acquired and liabilities assumed as of the acquisition date. Supplemental information on an unaudited pro forma basis, as if the Skyfence acquisition had been consummated on January 1, 2013 is presented as follows (in thousands):
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Pro forma revenue	$	42,675		$	35,102		$	112,633		$	95,026
	Pro forma loss from operations	$	(13,426	)	$	(6,396	)	$	(47,294	)	$	(23,720	)
	Pro forma net loss	$	(13,581	)	$	(6,421	)	$	(47,265	)	$	(23,961	)
	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 $8.3 million includes approximately $4.6 million in cash and assumption of a liability to pay cash of $0.3 million, and also the issuance of 60,556 shares of Company common stock valued at approximately $3.4 million based upon the closing price of the Company’s stock on the acquisition date of $55.45 per share. Imperva acquired certain tangible assets and also assumed a facility lease of Tomium.
	The following table summarizes the preliminary allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands):
	Intangible assets	$	2,704
	Goodwill		5,499
	Total intangible assets acquired		8,203
	Other acquired tangible assets		60
	Fair value of assets acquired	$	8,263
	The total purchase price was allocated using the information available at the business combination date. Goodwill recorded in connection with the acquisition is deductible for U.S. income tax purposes.
	The acquisition of Tomium was accounted for in accordance with the acquisition method of accounting for business combinations with Imperva as the accounting acquirer. We expensed the related acquisition costs, consisting primarily of legal costs in the amount of $0.3 million in general and administrative expenses. Management believes that the goodwill represents the synergies expected from combining the acquired technology and operations with those of Imperva. The intangible assets acquired by Imperva in conjunction with the acquisition of Tomium are being amortized straight-line over a ten-year estimated useful life.
	The results of operations related to the Tomium assets and liabilities have been included in our consolidated statements of operations from the acquisition date. Pro forma results of operations have not been presented because the acquisition was not material to the Company’s results of operations.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents, and Short-Term Investments	9 Months Ended
	Sep. 30, 2014
Cash and Cash Equivalents [Abstract]	'
Cash, Cash Equivalents, and Short-Term Investments	'
	4. Cash, Cash Equivalents, and Short-Term Investments
	The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand, highly liquid investments in commercial paper, money market funds and various deposit accounts.
	The Company considers all high quality investments purchased with original maturities at the date of purchase greater than three months to be short-term investments. Investments are available to be used for current operations and are, therefore, classified as current assets even though maturities may extend beyond one year. Cash equivalents and short-term investments are classified as available-for-sale and are, therefore, recorded at fair value on the condensed consolidated balance sheets, with any unrealized gains and losses reported in accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in its condensed consolidated balance sheets, until realized. The Company uses the specific-identification method to compute gains and losses on the investments. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included as a component of other income (expense), net in the condensed consolidated statements of operations.
	Cash, cash equivalents and short-term investments consist of the following (in thousands):
		As of September 30, 2014
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	18,508	$	—	$	—	$	18,508
	Commercial paper		23,448		—		1		23,447
	Bank deposits		11,017		—		—		11,017
	Money market funds		12,829		—		—		12,829
	Total	$	65,802	$	—	$	1	$	65,801
	Short-term investments:
	Corporate debt obligations	$	25,133	$	16	$	24	$	25,125
	Bank deposits		10,270		—		—		10,270
	Total	$	35,403	$	16	$	24	$	35,395
		As of December 31, 2013
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	41,973	$	—	$	—	$	41,973
	Commercial paper		21,948		—		1		21,947
	Bank deposits		10,165		—		—		10,165
	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
	The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of September 30, 2014 (in thousands):
		As of September 30, 2014
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	22,144	$	22,159
	Due within two years		13,259		13,236
	Total	$	35,403	$	35,395
	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 nine months ended September 30, 2014, the Company did not consider any of its investments to be other-than-temporarily impaired.
	As of September 30, 2014 and December 31, 2013, gross unrealized losses on investments that had been in a continuous loss position for less than12 months were not significant. None of the Company’s investments have been in an unrealized loss position for more than twelve months as of September 30, 2014 and December 31, 2013.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Instruments	'
	5. Fair Value of Financial Instruments
	The Company evaluates assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level to classify them for each reporting period. There have been no transfers between fair value measurement levels during the nine months ended September 30, 2014.
	The Company’s cash equivalents and short-term investment instruments are classified within Level 1 or Level 2 of the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The types of instruments valued based on quoted market prices in active markets include mutual funds and money market securities, and are generally classified within Level 1 of the fair value hierarchy. The types of instruments valued based on quoted prices in less active markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability include U.S. agency securities, investment-grade corporate bonds, bank deposits, and commercial paper. Such instruments are generally classified within Level 2 of the fair value hierarchy.
	The Company executes its foreign currency contracts primarily in the retail market in an over-the-counter environment with a relatively high level of price transparency. The market participants usually are large multi-national and regional banks. The Company’s foreign currency contracts valuation inputs are based on quoted prices and quoted pricing intervals from public data sources and do not involve management judgment. These contracts are typically classified within Level 2 of the fair value hierarchy.
	The following table sets forth the Company’s assets and liabilities that were measured at fair value as of September 30, 2014 and December 31, 2013, by level within the fair value hierarchy (in thousands):
		As of September 30, 2014
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	23,447	$	—	$	23,447
	Bank deposits		—		11,017		—		11,017
	Money market funds		12,829		—		—		12,829
	Short-term investments:
	Corporate debt obligations		—		25,125		—		25,125
	Bank deposits		—		10,270		—		10,270
	Total financial assets	$	12,829	$	69,859	$	—	$	82,688
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	419	$	—	$	419
		As of December 31, 2013
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	21,947	$	—	$	21,947
	Bank deposits		—		10,165		—		10,165
	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
	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 $4.0 million and $4.1 million as of September 30, 2014 and December 31, 2013, respectively.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	6. Derivative Instruments
	The Company’s primary objective for holding derivative instruments is to reduce its exposure to foreign currency rate changes. The Company reduces its exposure by entering into forward foreign exchange contracts with respect to operating expenses that are forecast to be incurred in currencies other than U.S. dollars. Substantially all of the Company’s revenue and capital purchasing activities and a majority of its operating expenditures are transacted in U.S. dollars. However, certain operating expenditures are incurred in or exposed to other currencies, primarily the Israeli shekel and the Euro.
	The Company has established forecasted transaction currency risk management programs to protect against fluctuations in fair value and the volatility of future cash flows caused by changes in exchange rates. The Company’s currency risk management program includes forward foreign exchange contracts designated as cash flow hedges. These forward foreign exchange contracts generally mature within 12 months. The Company does not enter into derivative financial instruments for trading purposes.
	There were no outstanding derivative instruments as of December 31, 2013. Derivative instruments measured at fair value and their classification on the condensed consolidated balance sheet as of September 30, 2014 is presented in the following table (in thousands):
			Liability as of September 30, 2014
			(unaudited)
			Notional			Fair Value
			Amount
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships - included in accrued and other current liabilities		$	7,040		$	419
	Gains (losses) on derivative instruments and their classification on the condensed consolidated statement of operations are presented in the following table (in thousands):
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Gains recognized in OCI(a)		$	52		$	240		$	55		$	726
	Losses recognized in OCI(a)			(620	)		(7	)		(508	)		(7	)
	Gains reclassified from accumulated OCI into net loss(b)			52			561			55			1,144
	Losses reclassified from accumulated OCI into net loss(b)			(73	)		—			(89	)		—
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships:
	Gains recognized in net loss(c)		$	—		$	40		$	—		$	25
	Losses recognized in net loss(c)			—			—			—			(15	)
	(a)	Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”).
	(b)	Effective portion of cash flow hedges reclassified from accumulated other comprehensive income (loss) into net loss, of which $(2) and $(19) were recognized within cost of sales and operating expenses, respectively, for the three months ended September 30, 2014 and $(3) and $(31) were recognized within cost of sales and operating expenses, respectively, for the nine months ended September 30, 2014. $36 and $525 were recognized within cost of sales and operating expenses, respectively for the three months ended September 30, 2013 and $75 and $1,069 were recognized within cost of sales and operating expenses, respectively, for the nine months ended September 30, 2013. All amounts are reflected within the respective condensed consolidated statement of operations.
	(c)	Classified in other income (expense), net.

Acquired_Intangible_Assets

Acquired Intangible Assets	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Acquired Intangible Assets	'
	7. Acquired Intangible Assets
	Acquired technology intangible assets subject to amortization as of September 30, 2014 were as follows (in thousands):
		Cost		Accumulated			Net
				Amortization
	Acquired Technology	$	10,668	$	(917	)	$	9,751
	Acquired intangible assets are amortized over their estimated useful lives of 7 to 10 years. There were no acquired intangible assets prior to January 1, 2014. As of September 30, 2014, we expect amortization expense in future periods to be as follows (in thousands):
	Fiscal Year	Acquired
		Technology
	2014 (remaining 3 months)	$	352
	2015		1,408
	2016		1,408
	2017		1,408
	2018		1,408
	Thereafter		3,767
	Total Expected Amortization Expense	$	9,751

Revolving_Credit_Facility

Revolving Credit Facility	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Revolving Credit Facility	'
	8. Revolving Credit Facility
	In September 2010, the Company entered into a revolving credit facility with a financial institution. The agreement, as amended, provides for a maximum borrowing capacity of up to $6.0 million as of September 30, 2014. As of September 30, 2014 and December 31, 2013, there was no balance outstanding on the credit facility.
	The credit facility expires on May 1, 2015, 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 September 30, 2014 and December 31, 2013, the Company was compliant with the amended covenant of the credit facility.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	9. Commitments and Contingencies
	(a) Operating Leases
	The Company rents its facilities under operating leases with lease periods expiring through 2019. Future minimum payments under these facility operating leases and minimum rentals to be received under non-cancellable subleases are as follows as of September 30, 2014 (in thousands):
	Fiscal Year	Operating		Estimated
		Leases		Sublease
				Income
	2014 (remaining 3 months)	$	1,267	$	138
	2015		5,240		296
	2016		5,429		77
	2017		4,775		—
	2018		3,248		—
	Thereafter		378		—
	Total	$	20,337	$	511
	Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Rent expense for the nine months ended September 30, 2014 and 2013 was $2.9 million and $2.5 million, respectively.
	In connection with a lease of office space, the Company received tenant improvement allowances of $336,000 and $639,000 during the years ended December 31, 2012 and 2010, respectively, from the lessor for certain improvements made to the leased 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 condensed consolidated balance sheets. The deferred rent liability is amortized to rent expense over the term of the lease on a straight-line basis. The leasehold improvements are being amortized to expense over the period from when the improvements were placed into service until the end of their useful life, which is the end of the lease term.
	In addition, certain of the Company’s operating lease agreements for office space also include rent holidays and scheduled rent escalations during the initial lease term. The Company has recorded the rent holidays as a deferred rent within other liabilities on the condensed consolidated balance sheets. The Company recognizes the deferred rent liability and scheduled rent increase on a straight-line basis into rent expense over the lease term commencing on the date the Company takes possession of the lease space.
	As of September 30, 2014 the Company has $1.6 million in restricted deposits to secure bank guarantees provided to its lessors.
	(b) Cancelable Lease Agreement
	The Company leases motor vehicles under a cancelable operating lease agreement. The Company has an option to cancel the lease agreement, which may result in penalties in a maximum amount of $83,000 as of September 30, 2014. Motor vehicle lease expenses for the nine months ended September 30, 2014 and 2013 were $2.0 million and $1.8 million, respectively.
	(c) Purchase Commitments
	As of September 30, 2014 and December 31, 2013, the Company had purchase commitments of $6.3 million and $3.2 million, respectively, to purchase inventory, trial units, and research and development equipment from its vendors. The purchase commitments result from the Company’s contractual obligation to order or build inventory in advance of anticipated sales. According to the Company’s agreements with its vendors, the Company committed to purchase inventory within nine months from the date the inventory arrived at the vendor’s warehouse.
	(d) Litigation
	From time to time, the Company may be subject to other legal proceedings and claims in the ordinary course of business.
	On April 11, 2014, a purported shareholder class action lawsuit was filed in the United States District Court for the Northern District of California against Imperva and certain of its officers. The lawsuit purports to bring suit on behalf of those investors who purchased Imperva’s publicly traded securities between May 2, 2013 and April 9, 2014. Plaintiff alleges that defendants made false and misleading statements, purports to assert claims for violations of the federal securities laws, and seeks unspecified compensatory damages and other relief. On August 7, 2014, the Court entered an order appointing lead plaintiff and counsel for the purported class. Lead plaintiff’s Amended Complaint was filed in October 2014.
	On June 27, 2014, a purported shareholder derivative lawsuit was filed in the Court of Chancery for the State of Delaware against Imperva (as a nominal defendant), and naming certain officers and members of Imperva’s board of directors as individual defendants. The lawsuit relates to the acquisition of Skyfence Networks, Ltd. and the complaint asserts claims for breach of fiduciary duty and unjust enrichment, and seeks to recover unspecified compensatory damages allegedly sustained by Imperva, corporate reforms, the recovery of plaintiffs’ attorney’s fees and other relief. On September 23, 2014, Imperva and the individual defendants moved to dismiss the action. Plaintiffs filed an amended complaint on November 6, 2014. A response to the amended complaint is not yet due.
	In addition, 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. Future litigation may be necessary to defend ourselves, our channel partners and our customers by determining the scope, enforceability and validity of third-party proprietary rights or to establish our proprietary rights.
	Further, the ultimate outcome of any litigation is uncertain and, regardless of outcome, litigation can have an adverse impact on us because of defense costs, potential negative publicity, diversion of management resources and other factors. Accordingly, there can be no assurance that existing or future legal proceedings arising in the ordinary course of business or otherwise will not have a material adverse effect on our business, consolidated financial position, results of operations or cash flows.
	(e) Indemnification
	Under the indemnification provisions of its standard sales contracts, the Company agrees to defend its channel partners and end customers against third-party claims asserting infringement of certain intellectual property rights, which may include patents, copyrights, trademarks, or trade secrets, and to pay judgments and settlements entered on such claims. The Company’s exposure under these indemnifications provisions is generally limited to the total amount paid under the agreement. However, certain agreements included indemnification provisions that could potentially expose the Company to losses in excess of the amount received under the agreement. To date, there have been no claims under such indemnification provisions. Accordingly, the Company has not recorded a liability on its consolidated balance sheets for these indemnification provisions.
	In addition to the foregoing, the Company maintains director and officer insurance, which may cover certain liabilities arising from its obligation to indemnify its directors and officers.

Stock_Plans

Stock Plans	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock Plans	'
	10. Stock Plans
	(a) 2003 Stock Plan
	During 2003, the Board of Directors adopted the 2003 Stock Plan (the “2003 Plan”), which allows for the granting of both incentive stock options and non-qualified stock options and the direct award or sale of shares of the Company’s common stock (including restricted common stock) to officers, employees, directors, consultants and other key persons. Incentive stock options may be granted to employees with exercise prices of no less than the fair value of the common stock on the grant date, and non-qualified options may be granted to employees, directors, or consultants at exercise prices of no less than 85% of the fair value of the common stock on the grant date, as determined by the Board of Directors. If, at the time the Company grants an option, the optionee directly or by attribution owns stock possessing more than 10% of the total combined voting power of all classes of stock of the Company, the option price shall be at least 110% of the fair value. Options granted under the Plan generally expire no later than ten years and, in general, vest four years from the date of grant.
	(b) 2011 Stock Option and Incentive Plan
	In September 2011, the Board of Directors adopted the 2011 Stock Option and Incentive Plan (the “2011 Plan”) which was subsequently approved by the Company’s stockholders. The 2011 Plan replaces the 2003 Plan as the Board has decided not to grant any additional awards under that plan. The Company has reserved a total of 1,000,000 shares of common stock for issuance under the 2011 Plan. In addition, any reserved but unissued shares under the 2003 Stock Plan will be added to the number of shares reserved for issuance under the 2011 Plan. The 2011 Plan also provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning in 2012 and ending in 2015, by 4% of the outstanding number of shares of common stock on the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. As of December 31, 2013, there were 1,847,752 shares available for grant under the 2011 Plan. On January 1, 2014, the share reserve under the 2011 Plan was automatically increased by 1,008,260 shares.
	The 2011 Plan permits the granting of incentive stock options, non-qualified stock options, restricted stock units (RSUs), stock appreciation rights, restricted shares of common stock and performance share awards. The exercise price of stock options may not be less than the 100% of the fair market value of the common stock on the date of grant. Options granted pursuant to the 2011 Plan generally expire in no later than ten years. The Company began granting RSUs in February 2012, which generally vest over either a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter or they completely vest at the end of a three-year period. 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).
	(c) 2011 Employee Stock Purchase Plan
	In September 2011, the Board of Directors adopted the 2011 Employee Stock Purchase Plan (the “ESPP”) which was subsequently approved by the Company’s stockholders. The ESPP took effect on the effective date of the registration statement for the Company’s IPO. The ESPP permits eligible employees to acquire shares of the Company’s common stock by accumulating funds through periodic payroll deductions of up to 15% of base salary. Each offering period may run for no more than 24 months and consist of no more than five purchase periods. The purchase price for shares of the Company’s common stock purchased under the ESPP will be 85% of the lesser of the fair market value of the Company’s common stock on the first day of the offering period or the last trading day of the applicable purchase period within that offering period.
	The Company has initially reserved a total of 500,000 shares of common stock for future issuance under the ESPP. The number of shares reserved for issuance under the ESPP will increase automatically on January 1 of each of the first eight years commencing in 2012 by the number of shares equal to 1% of the Company’s total outstanding shares as of the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. No more than 20,000,000 shares of common stock may be issued under the ESPP and no other shares may be added to the ESPP without the approval of the Company’s stockholders. On January 1, 2014, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 252,065 shares.
	(d) 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 may be granted under the Incapsula Plan shall not exceed 4,733,333 in the aggregate, subject to certain adjustments.
	In November 2013, the board of directors of Incapsula approved the grant of restricted stock units for 7,095,461 shares of Incapsula’s common stock (“Incapsula RSUs”). As part of the Incapsula Acquisition, the Incapsula RSUs were assumed and replaced by RSUs for Company Common Stock issued to continuing employees of Incapsula . The Incapsula RSU’s vest according to performance-based vesting terms tied to 2014 revenue for Incapsula and Incapsula-related products and services, which were converted into approximately 198,825 shares of Company Common Stock at the same exchange ratio applicable to the Incapsula Acquisition. In addition to performance conditions, the awards are dependent on future market price of Imperva’s common stock, which is deemed a market condition under ASC 718. At each reporting date, the Company assesses progress towards the 2014 Incapsula and Incapsula-related product and service revenue performance conditions and adjusts the number of vested fair value of awards and stock-based compensation expense accordingly.
	The following table summarizes option activity under the Incapsula Plan and related information for the nine months ended September 30, 2014:
		Shares			Number of			Number of			Weighted
		Available for			Performance-			Stock Options			Average
		Grant			based			Outstanding			Exercise Price
					Restricted
					Share Units
					Outstanding
	Outstanding - January 1, 2014		89,687			7,095,461			1,806,500		$	0.47
	Granted		(95,000	)		—			95,000			1.25
	Exercised		0			—			—			—
	Forfeited		15,213			(12,713	)		(2,500	)		1.25
	Transferred to Imperva 2011 stock option plan		(9,900	)		(7,082,748	)		(1,899,000	)		0.16
	Outstanding - September 30, 2014		—			—			—		$	—
	The options outstanding and performance restricted share units under the Incapsula 2010 Share Incentive Plan were assumed as part of the Incapsula Acquisition and are equivalent to 247,184 shares of Company common stock on an as-converted basis. The Company does not intend to grant any additional shares under the Incapsula 2010 Share Incentive Plan.
	(e) Stock 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, the Incapsula 2010 Share Incentive Plan, and the Skyfence 2013 Share Incentive Plan (collectively “the Plans”) in the condensed consolidated statements of operations as follows (in thousands):
		For the three months ended						For the nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Cost of revenues	$	569		$	254		$	1,472		$	722
	Research and development		2,353			747			6,335			2,133
	Sales and marketing		3,730			1,620			9,369			4,596
	General and administrative		4,123			792			8,930			2,407
	Total stock-based compensation expense	$	10,775		$	3,413		$	26,106		$	9,858
	The fair value of stock option grants for the three months and nine months ended September 30, 2014 and 2013 was estimated using the following weighted average assumptions:
		For the three months ended						For the nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Stock option grants:
	Dividend rate		0	%		0	%		0	%		0	%
	Risk-free interest rate		2	%		1.8	%		1.9	%		1.2	%
	Expected term (in years)		6.1			6.1			6.1			6.1
	Expected volatility		51	%		47	%		45	%		46	%
	ESPP grants:
	Dividend rate		—			—			0	%		0	%
	Risk-free interest rate		—			—			0.1	%		0.1	%
	Expected term (in years)		—			—			0.5			0.5
	Expected volatility		—			—			57	%		31	%
	The fair value of the RSUs is determined using the closing price of the Company’s common stock on the date of the grant. Compensation is recognized on a straight-line basis over the requisite service period of each grant adjusted for estimated forfeitures.
	The following table summarizes option activity under the Plans and related information:
		Options Outstanding						Weighted Average			Aggregate
								Remaining			Intrinsic Value
								Contractual Life			(in thousands)
		Number of			Weighted			(in years)
		Shares			Average Exercise
					Price
	Balances - January 1, 2014		1,675,506		$	23.78			8.01		$	40,813
	Granted		1,076,327			42.37
	Exercised or released		(311,650	)		10.6
	Cancelled or forfeited		(213,947	)		34.81
	Options assumed in acquisitions		72,607			14.14
Balances - September 30, 2014		2,298,843		$	32.89			8.27		$	11,299
Options exercisable		672,910		$	21.19			6.75		$	6,887
RSU Activity
A summary of RSU activity under the Plans for the nine months ended September 30, 2014, is as follows:
	Number of			Weighted-
	Restricted			Average Grant
	Stock Units			Date Fair Value
	Outstanding
Unvested - January 1, 2014		1,044,651		$	31.64
Granted		1,186,560			42.58
Granted, performance RSUs		96,446			32.07
Released		(187,595	)		34.73
Cancelled or expired		(197,992	)		39.38
RSUs assumed in acquisitions		204,466			61.4
Unvested - September 30, 2014		2,146,536		$	39.56
The aggregate intrinsic value of options exercised under the Plans was $10.7 million for the nine months ended September 30, 2014. The aggregate intrinsic value is calculated as the difference between the per-share exercise price and the market value of the Company’s common stock for each share subject to an option multiplied by the number of shares subject to options. As reported in the Wall Street Journal, the market value as of September 30, 2014 was $28.73 per share. As of September 30, 2014, total compensation cost related to unvested stock-based awards granted to employees under the Plans, but not yet recognized, was $94.3 million, net of estimated forfeitures. As of September 30, 2014, this cost will be amortized to expense over a weighted-average remaining period of 3.1 years, and will be adjusted for subsequent changes in estimated forfeitures. Future stock-based award grants will increase the amount of compensation expense to be recorded in these periods.
There was no capitalized stock-based compensation cost tax benefits during the nine months ended September 30, 2014 and 2013.
(f) Common Stock Subject to Repurchase
Pursuant to restricted stock agreements with the Company’s former 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 condensed consolidated balance sheet and are reclassified to equity as the shares vest. The Company granted 843,819 shares of restricted common stock with a weighted-average grant date fair value per share of $1.94 during the year ended December 31, 2010. There were no grants of shares of restricted common stock during the nine months ended September 30, 2014 and the year ended December 31, 2013. As of September 30, 2014, 210,954 shares of restricted common stock held by the Company’s former CEO were unvested and subject to repurchase by the Company.
In connection with the acquisition of Skyfence in the first quarter of 2014, the Company issued 532,262 shares of the Company’s common stock with a fair value per share of $59.08 which are subject to forfeiture based upon time-based vesting and continuing employment over the term of the corresponding four-year service period. None of these shares were vested as of September 30, 2014.
(g) Early Exercise of Stock Options
In 2010 and 2011, the Company’s board of directors allowed for the early exercise of stock options granted to certain members of the Company’s board of directors. The amounts received in exchange for these shares have been included in other liabilities in the accompanying condensed consolidated balance sheet and are reclassified to equity as the shares vest. As of September 30, 2014, 9,167 shares were unvested.
(h) Equity Awards Issued in Acquisitions
In connection with the Skyfence and Incapsula acquisitions, the Company assumed stock options covering an aggregate of 72,607 shares of its common stock (in addition to the Incapsula RSUs discussed above). At the date of the acquisition, vested stock options and the associated fair value was recorded as part of the purchase consideration. The fair value related to the assumed unvested stock options are recognized as post-combination compensation costs and is being recorded as post-combination compensation expense ratably over the respective remaining service periods.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2014
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):
			For the three months ended									For the three months ended
			September 30, 2014									September 30, 2013
			Unrealized gain			Unrealized gain			Total			Unrealized gain			Unrealized gain			Total
			(loss) on cash			(loss) on						(loss) on cash			(loss) on
			flow hedges			investments						flow hedges			investments
	Balance at July 1		$	(345	)	$	12		$	(333	)	$	593		$	(37	)	$	556
	Other comprehensive income (loss) before reclassifications			(521	)		(41	)		(562	)		233			69			302
	Amounts reclassified to net loss			21			11			32			(561	)		(44	)		(605	)
	Other comprehensive income (loss)			(500	)		(30	)		(530	)		(328	)		25			(303	)
	Balance at September 30		$	(845	)	$	(18	)	$	(863	)	$	265		$	(12	)	$	253
			For the nine months ended									For the nine months ended
			30-Sep-14									30-Sep-13
			Unrealized gain			Unrealized gain			Total			Unrealized gain			Unrealized gain			Total
			(loss) on cash			(loss) on						(loss) on cash			(loss) on
			flow hedges			investments						flow hedges			investments
	Balance at January 1		$	(426	)	$	(2	)	$	(428	)	$	690		$	171		$	861
	Other comprehensive income (loss) before reclassifications			(453	)		(27	)		(480	)		719			23			742
	Amounts reclassified to net loss			34			11			45			(1,144	)		(206	)		(1,350	)
	Other comprehensive income (loss)			(419	)		(16	)		(435	)		(425	)		(183	)		(608	)
	Balance at September 30		$	(845	)	$	(18	)	$	(863	)	$	265		$	(12	)	$	253
	The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the nine months ended September 30, 2014 and 2013 (in thousands):
			For the three months ended									For the three months ended
			September 30, 2014									September 30, 2013
			Pre-Tax			Tax Expense			After-Tax			Pre-Tax			Tax Expense			After-Tax
			Amount			(Benefit)			Amount			Amount			(Benefit)			Amount
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	(567	)	$	46		$	(521	)	$	233		$	—		$	233
	Reclassification adjustments 1			21			—		$	21			(561	)		—			(561	)
	Unrealized gains (losses) on cash flow hedges, net			(546	)		46			(500	)		(328	)		—			(328	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			(51	)		10			(41	)		69			—			69
	Reclassification adjustments 2			11			—			11			(44	)		—			(44	)
	Unrealized gains (losses) on investments			(40	)		10			(30	)		25			—			25
	Other comprehensive income (loss)		$	(586	)	$	56		$	(530	)	$	(303	)	$	—		$	(303	)
			For the nine months ended									For the nine months ended
			30-Sep-14									30-Sep-13
			Pre-Tax			Tax Expense			After-Tax			Pre-Tax			Tax Expense			After-Tax
			Amount			(Benefit)			Amount			Amount			(Benefit)			Amount
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	(452	)	$	(1	)	$	(453	)	$	719		$	—		$	719
	Reclassification adjustments 1			33			1			34			(1,144	)		—			(1,144	)
	Unrealized gains (losses) on cash flow hedges, net			(419	)		—			(419	)		(425	)		—			(425	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			(27	)		—			(27	)		23			—			23
	Reclassification adjustments 2			11			—			11			(206	)		—			(206	)
	Unrealized gains (losses) on investments			(16	)		—			(16	)		(183	)		—			(183	)
	Other comprehensive income (loss)		$	(435	)	$	—		$	(435	)	$	(608	)	$	—		$	(608	)
	1	Refer to note 6 for the affected line items in the condensed consolidated statement of operations
	2	Amount included in other income (expense), net, in the condensed consolidated statement of operations

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	12. Income Taxes
	The Company is subject to income tax in the United States as well as other tax jurisdictions in which it conducts business. Earnings from non-U.S. activities are subject to local country income tax. The Company does not provide for federal income taxes on the undistributed earnings of its foreign subsidiaries as such earnings are to be reinvested indefinitely. The Company recorded income tax expense of $0.2 million and $0.3 million for the three months ended September 30, 2014 and 2013, respectively and $0.7 million for the nine months ended September 30, 2013 and recorded income tax benefit of $0.2 million for the nine months ended September 30, 2014. These income tax expense (benefit) amounts were primarily attributable to foreign taxes.
	Factors that impact the income tax provision include, but are not limited to, stock-based compensation expense, permanent tax adjustments, foreign operations and a valuation allowance against the Company’s deferred tax assets.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	13. Segment Information
	During the three months ended March 31, 2014, we revised our business segments based upon the acquisition of the remaining shares of Incapsula, Inc. that the Company did not already own. As a result, the Company no longer separately reports the Incapsula segment and the Company now operates its business in one operating segment, which is 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. Operating segments are defined as components of an enterprise that engage in business activities for which separate financial information is available and evaluated by the chief operating decision maker in deciding how to allocate resources and assessing performance. The chief operating decision maker is the Company’s Chief Executive Officer.
	The Company’s net services revenue is comprised of the following (in thousands):
		For the three months ended				For the nine months ended
		September 30,				September 30,
		2014		2013		2014		2013
	Maintenance and support	$	13,879	$	11,139	$	40,064	$	31,926
	Professional services and training		2,774		2,724		8,154		7,495
	Subscriptions		6,380		3,061		16,216		7,602
	Total net services revenue	$	23,033	$	16,924	$	64,434	$	47,023
	The Company’s net revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands):
		For the three months ended				For the nine months ended
		September 30,				September 30,
		2014		2013		2014		2013
	Americas	$	22,801	$	19,941	$	63,731	$	58,168
	EMEA		12,929		9,737		30,543		22,239
	APAC		6,945		5,424		18,359		14,619
	Total net revenue	$	42,675	$	35,102	$	112,633	$	95,026
	The following table presents long-lived assets by location (in thousands):
		As of		As of
		September 30,		December 31,
		2014		2013
	United States	$	6,433	$	3,039
	Israel		9,952		2,422
	Other		22		14
	Total long-lived assets	$	16,407	$	5,475

Net_Loss_per_Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Net Loss per Share	'
	14. Net Loss per Share
	Basic and diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding during the period. The computation of net loss per share for each period, including the number of weighted-average shares outstanding, is shown on the face of the condensed consolidated statements of operations.
	We have excluded the impact of common stock equivalents relating to shares underlying outstanding stock options from the calculation of diluted net loss per common share because all such securities are antidilutive for all periods presented.
	The following outstanding shares of common stock and potential common shares were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		For the three months and nine months
		ended September 30,
		2014		2013
	Stock options to purchase common stock		2,298,843		1,826,531
	Restricted stock units for common stock		2,146,536		898,119
	Restricted shares of common stock subject to repurchase		220,121		383,991
	Restricted stock issued in connection with Skyfence acquisition		355,499		—

Basis_of_Presentation_and_Summ1

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Business	'
	Business
	Imperva, Inc. (together with its subsidiaries, the “Company” or “we”) 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 Company has prepared the accompanying unaudited Condensed Consolidated Financial Statements in accordance with Article 10 of Regulation S-X and pursuant to the rules and regulations for Form 10-Q of the Securities and Exchange Commission (the “SEC”). Pursuant to those rules and regulations, the Company has condensed or omitted certain information and footnote disclosure it normally includes in its annual consolidated financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). In management’s opinion, the Company has made all adjustments (consisting only of normal, recurring adjustments, except as otherwise indicated) necessary to fairly present its consolidated financial position, results of operations, and cash flows. The Company’s interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the consolidated financial statements and notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013, which was filed with the SEC on February 28, 2014 (the “Annual Report”).
	During the three months ended March 31, 2014, we revised our business segments based upon the acquisition of the remaining shares of Incapsula, Inc. that the Company did not already own. As a result, we no longer separately report the Incapsula segment and the Company now operates in one operating, and therefore, reportable segment in order to better align Incapsula with our strategic approach to the markets and customers we serve. The reclassification of historical business segment information had no impact on the Company’s basic financial statements.
Basis of Consolidation	'
	Basis of Consolidation
	The condensed consolidated financial statements include the accounts of the Company and its wholly-owned and majority-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. On March 20, 2014, the Company acquired the remaining interest it did not previously own in its majority-owned subsidiary, Incapsula, Inc. (“Incapsula”) (Refer to Note 2). The Company separately presented the non-controlling interest on its Condensed Consolidated Balance Sheets in Total Stockholder’s Equity and in its Condensed Consolidated Statements of Operations for periods prior to such date.
Goodwill and Acquired Intangibles	'
	Goodwill and Acquired Intangibles
	Goodwill represents the excess of the aggregate purchase price paid over the fair value of the net tangible assets acquired. Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. In reviewing goodwill, the Company performs a qualitative assessment to test the reporting unit’s goodwill for impairment. Based on the Company’s qualitative assessment, if we determine that the fair value of the reporting unit is more likely than not (i.e. a likelihood of more than 50 percent) to be less than the carrying amount, the two step impairment test will be performed. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value.
	The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the nine months ended September 30, 2014.
	We amortize intangible assets with finite lives over their estimated useful lives and review them for impairment whenever an impairment indicator exists. We continually monitor events and changes in circumstances that could indicate carrying amounts of our intangible assets may not be recoverable. When such events or changes in circumstances occur, we assess recoverability by determining whether the carrying value of such assets will be recovered through the undiscounted expected future cash flows. If the future undiscounted cash flows are less than the carrying amount of these assets, we recognize an impairment loss based on any excess of the carrying amount over the fair value of the assets. We did not recognize any intangible asset impairment charges in the nine months ended September 30, 2014. Our intangible assets are amortized over their estimated useful lives of 7 to 10 years. Amortization is based on a straight-line basis as the consumption pattern of the asset is not apparent. The weighted average useful life of our acquired technology intangible assets was 8 years.
Concentration of Revenue and Accounts Receivable	'
	Concentration of Revenue and Accounts Receivable
	For the nine months ended September 30, 2013, the Company had one customer that represented 10% of the Company’s total revenue. For the three months ended September 30, 2014 and 2013 and for the nine months ended September 30, 2014, the Company did not have any customers that represented more than 10% of the Company’s total revenue. There was one customer that represented 12% of gross accounts receivable as of September 30, 2014. There were no customers who represented greater than 10% of gross accounts receivable as of December 31, 2013.
Significant Accounting Policies	'
	Significant Accounting Policies
	Other than the change to our reporting segments and the addition of the Company’s policy for accounting for goodwill and acquired intangibles, there have been no material changes to the Company’s significant accounting policies as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-08, Reporting Discontinued Operations and Disposals of Components of an Entity, which changes the criteria for determining which disposals can be presented as discontinued operations and modifies related disclosure requirements. The new guidance is effective for annual and interim periods beginning after December 15, 2014, with early adoption permitted. The new guidance will be applicable for disposal transactions, if any, that we initiate after the adoption date. The adoption of this guidance is not expected to have a material impact on our financial position, results of operations or cash flows.
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, to clarify the principles used to recognize revenue for all entities. The new guidance is effective for annual and interim periods beginning after December 15, 2016 with no early adoption permitted and allows for both retrospective and prospective methods of adoption. We are currently evaluating the impact, if any, the adoption of this guidance will have on our financial position, results of operations or cash flows.
	In June 2014, the FASB issued ASU No. 2014-12, Compensation—Stock Compensation, which provides guidance that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value. Compensation cost for such an award would be recognized over the required service period, if it is probable that the performance condition will be achieved. The updated guidance is effective for annual reporting periods and interim periods within those annual periods beginning after December 15, 2015. Earlier adoption is permitted but we do not anticipate electing early adoption. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.
	In August 2014, the FASB issued ASU No. 2014-15, new guidance related to the disclosures around going concern. The new standard provides guidance around management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on our financial statements.

Acquisitions_Tables

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2014
Skyfence Networks Ltd. [Member]	'
Schedule of Total Purchase Consideration	'
	The total purchase consideration is as follows (in thousands):
	Cash	$	8,558
	Cash holdback liability		7,157
	Fair value of common stock		20,855
	Estimated fair value of equity awards assumed and replaced		354
		$	36,924
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	'
	The following table summarizes the allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date (in thousands):
	Net tangible assets	$	1,014
	Existing technology		7,965
	Deferred tax liability assumed		(1,528	)
	Goodwill		29,473
	Total purchase price	$	36,924
Summary of Supplemental Information on Unaudited Pro Forma Basis	'
	Supplemental information on an unaudited pro forma basis, as if the Skyfence acquisition had been consummated on January 1, 2013 is presented as follows (in thousands):
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Pro forma revenue	$	42,675		$	35,102		$	112,633		$	95,026
	Pro forma loss from operations	$	(13,426	)	$	(6,396	)	$	(47,294	)	$	(23,720	)
	Pro forma net loss	$	(13,581	)	$	(6,421	)	$	(47,265	)	$	(23,961	)
Tomium Software, LLC. [Member]	'
Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed	'
	The following table summarizes the preliminary allocation of the consideration to the fair value of the tangible and intangible assets acquired and liabilities assumed as of the acquisition date based on information available at the business combination date (in thousands):
	Intangible assets	$	2,704
	Goodwill		5,499
	Total intangible assets acquired		8,203
	Other acquired tangible assets		60
	Fair value of assets acquired	$	8,263

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents, and Short-Term Investments (Tables)	9 Months Ended
	Sep. 30, 2014
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 September 30, 2014
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	18,508	$	—	$	—	$	18,508
	Commercial paper		23,448		—		1		23,447
	Bank deposits		11,017		—		—		11,017
	Money market funds		12,829		—		—		12,829
	Total	$	65,802	$	—	$	1	$	65,801
	Short-term investments:
	Corporate debt obligations	$	25,133	$	16	$	24	$	25,125
	Bank deposits		10,270		—		—		10,270
	Total	$	35,403	$	16	$	24	$	35,395
		As of December 31, 2013
		Amortized		Gross		Gross		Fair
		Cost		Unrealized		Unrealized		Value
				Gains		Losses
	Cash and cash equivalents:
	Cash	$	41,973	$	—	$	—	$	41,973
	Commercial paper		21,948		—		1		21,947
	Bank deposits		10,165		—		—		10,165
	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
Summary of Cost and Estimated Fair Value of Short-Term Investments	'
	The following table summarizes the cost and estimated fair value of short-term investments based on stated effective maturities as of September 30, 2014 (in thousands):
		As of September 30, 2014
		Amortized		Estimated
		Cost		Fair
				Value
	Short-term investments:
	Due within one year	$	22,144	$	22,159
	Due within two years		13,259		13,236
	Total	$	35,403	$	35,395

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
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 September 30, 2014 and December 31, 2013, by level within the fair value hierarchy (in thousands):
		As of September 30, 2014
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	23,447	$	—	$	23,447
	Bank deposits		—		11,017		—		11,017
	Money market funds		12,829		—		—		12,829
	Short-term investments:
	Corporate debt obligations		—		25,125		—		25,125
	Bank deposits		—		10,270		—		10,270
	Total financial assets	$	12,829	$	69,859	$	—	$	82,688
	Financial Liability:
	Accrued and other current liabilities - Forward foreign exchange contracts	$	—	$	419	$	—	$	419
		As of December 31, 2013
		Level I		Level II		Level III		Fair Value
	Financial Assets:
	Cash and cash equivalents:
	Commercial paper	$	—	$	21,947	$	—	$	21,947
	Bank deposits		—		10,165		—		10,165
	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

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments Measured at Fair Value	'
	Derivative instruments measured at fair value and their classification on the condensed consolidated balance sheet as of September 30, 2014 is presented in the following table (in thousands):
			Liability as of September 30, 2014
			(unaudited)
			Notional			Fair Value
			Amount
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships - included in accrued and other current liabilities		$	7,040		$	419
Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations	'
	Gains (losses) on derivative instruments and their classification on the condensed consolidated statement of operations are presented in the following table (in thousands):
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
	Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships:
	Gains recognized in OCI(a)		$	52		$	240		$	55		$	726
	Losses recognized in OCI(a)			(620	)		(7	)		(508	)		(7	)
	Gains reclassified from accumulated OCI into net loss(b)			52			561			55			1,144
	Losses reclassified from accumulated OCI into net loss(b)			(73	)		—			(89	)		—
	Foreign Exchange Forward Contract Derivatives not designated as hedging relationships:
	Gains recognized in net loss(c)		$	—		$	40		$	—		$	25
	Losses recognized in net loss(c)			—			—			—			(15	)
	(a)	Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”).
	(b)	Effective portion of cash flow hedges reclassified from accumulated other comprehensive income (loss) into net loss, of which $(2) and $(19) were recognized within cost of sales and operating expenses, respectively, for the three months ended September 30, 2014 and $(3) and $(31) were recognized within cost of sales and operating expenses, respectively, for the nine months ended September 30, 2014. $36 and $525 were recognized within cost of sales and operating expenses, respectively for the three months ended September 30, 2013 and $75 and $1,069 were recognized within cost of sales and operating expenses, respectively, for the nine months ended September 30, 2013. All amounts are reflected within the respective condensed consolidated statement of operations.
	(c)	Classified in other income (expense), net.

Acquired_Intangible_Assets_Tab

Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Summary of Acquired Technology Intangible Assets Subject to Amortization	'
	Acquired technology intangible assets subject to amortization as of September 30, 2014 were as follows (in thousands):
		Cost		Accumulated			Net
				Amortization
	Acquired Technology	$	10,668	$	(917	)	$	9,751
Schedule of Expected Amortization Expense in Future Periods	'
	As of September 30, 2014, we expect amortization expense in future periods to be as follows (in thousands):
	Fiscal Year	Acquired
		Technology
	2014 (remaining 3 months)	$	352
	2015		1,408
	2016		1,408
	2017		1,408
	2018		1,408
	Thereafter		3,767
	Total Expected Amortization Expense	$	9,751

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases	'
	Future minimum payments under these facility operating leases and minimum rentals to be received under non-cancellable subleases are as follows as of September 30, 2014 (in thousands):
	Fiscal Year	Operating		Estimated
		Leases		Sublease
				Income
	2014 (remaining 3 months)	$	1,267	$	138
	2015		5,240		296
	2016		5,429		77
	2017		4,775		—
	2018		3,248		—
	Thereafter		378		—
	Total	$	20,337	$	511

Stock_Plans_Tables

Stock Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Option and Performance-Based Restricted Share Unit Activity Under Incapsula Plan	'
	The following table summarizes option activity under the Incapsula Plan and related information for the nine months ended September 30, 2014:
		Shares			Number of			Number of			Weighted
		Available for			Performance-			Stock Options			Average
		Grant			based			Outstanding			Exercise Price
					Restricted
					Share Units
					Outstanding
	Outstanding - January 1, 2014		89,687			7,095,461			1,806,500		$	0.47
	Granted		(95,000	)		—			95,000			1.25
	Exercised		0			—			—			—
	Forfeited		15,213			(12,713	)		(2,500	)		1.25
	Transferred to Imperva 2011 stock option plan		(9,900	)		(7,082,748	)		(1,899,000	)		0.16
	Outstanding - September 30, 2014		—			—			—		$	—
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, the Incapsula 2010 Share Incentive Plan, and the Skyfence 2013 Share Incentive Plan (collectively “the Plans”) in the condensed consolidated statements of operations as follows (in thousands):
		For the three months ended						For the nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Cost of revenues	$	569		$	254		$	1,472		$	722
	Research and development		2,353			747			6,335			2,133
	Sales and marketing		3,730			1,620			9,369			4,596
	General and administrative		4,123			792			8,930			2,407
	Total stock-based compensation expense	$	10,775		$	3,413		$	26,106		$	9,858
Weighted Average Assumptions for Fair Value of Stock Options Grants	'
	The fair value of stock option grants for the three months and nine months ended September 30, 2014 and 2013 was estimated using the following weighted average assumptions:
		For the three months ended						For the nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Stock option grants:
	Dividend rate		0	%		0	%		0	%		0	%
	Risk-free interest rate		2	%		1.8	%		1.9	%		1.2	%
	Expected term (in years)		6.1			6.1			6.1			6.1
	Expected volatility		51	%		47	%		45	%		46	%
	ESPP grants:
	Dividend rate		—			—			0	%		0	%
	Risk-free interest rate		—			—			0.1	%		0.1	%
	Expected term (in years)		—			—			0.5			0.5
	Expected volatility		—			—			57	%		31	%
Summary of Option Activity under Plans and Related Information	'
	The following table summarizes option activity under the Plans and related information:
		Options Outstanding						Weighted Average			Aggregate
								Remaining			Intrinsic Value
								Contractual Life			(in thousands)
		Number of			Weighted			(in years)
		Shares			Average Exercise
					Price
	Balances - January 1, 2014		1,675,506		$	23.78			8.01		$	40,813
	Granted		1,076,327			42.37
	Exercised or released		(311,650	)		10.6
	Cancelled or forfeited		(213,947	)		34.81
	Options assumed in acquisitions		72,607			14.14
	Balances - September 30, 2014		2,298,843		$	32.89			8.27		$	11,299
	Options exercisable		672,910		$	21.19			6.75		$	6,887
Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value	'
	A summary of RSU activity under the Plans for the nine months ended September 30, 2014, is as follows:
		Number of			Weighted-
		Restricted			Average Grant
		Stock Units			Date Fair Value
		Outstanding
	Unvested - January 1, 2014		1,044,651		$	31.64
	Granted		1,186,560			42.58
	Granted, performance RSUs		96,446			32.07
	Released		(187,595	)		34.73
	Cancelled or expired		(197,992	)		39.38
	RSUs assumed in acquisitions		204,466			61.4
	Unvested - September 30, 2014		2,146,536		$	39.56

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Changes in Balances of Accumulated Other Comprehensive Income (Loss)	'
	The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands):
			For the three months ended									For the three months ended
			September 30, 2014									September 30, 2013
			Unrealized gain			Unrealized gain			Total			Unrealized gain			Unrealized gain			Total
			(loss) on cash			(loss) on						(loss) on cash			(loss) on
			flow hedges			investments						flow hedges			investments
	Balance at July 1		$	(345	)	$	12		$	(333	)	$	593		$	(37	)	$	556
	Other comprehensive income (loss) before reclassifications			(521	)		(41	)		(562	)		233			69			302
	Amounts reclassified to net loss			21			11			32			(561	)		(44	)		(605	)
	Other comprehensive income (loss)			(500	)		(30	)		(530	)		(328	)		25			(303	)
	Balance at September 30		$	(845	)	$	(18	)	$	(863	)	$	265		$	(12	)	$	253
			For the nine months ended									For the nine months ended
			30-Sep-14									30-Sep-13
			Unrealized gain			Unrealized gain			Total			Unrealized gain			Unrealized gain			Total
			(loss) on cash			(loss) on						(loss) on cash			(loss) on
			flow hedges			investments						flow hedges			investments
	Balance at January 1		$	(426	)	$	(2	)	$	(428	)	$	690		$	171		$	861
	Other comprehensive income (loss) before reclassifications			(453	)		(27	)		(480	)		719			23			742
	Amounts reclassified to net loss			34			11			45			(1,144	)		(206	)		(1,350	)
	Other comprehensive income (loss)			(419	)		(16	)		(435	)		(425	)		(183	)		(608	)
	Balance at September 30		$	(845	)	$	(18	)	$	(863	)	$	265		$	(12	)	$	253
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 nine months ended September 30, 2014 and 2013 (in thousands):
			For the three months ended									For the three months ended
			September 30, 2014									September 30, 2013
			Pre-Tax			Tax Expense			After-Tax			Pre-Tax			Tax Expense			After-Tax
			Amount			(Benefit)			Amount			Amount			(Benefit)			Amount
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	(567	)	$	46		$	(521	)	$	233		$	—		$	233
	Reclassification adjustments 1			21			—		$	21			(561	)		—			(561	)
	Unrealized gains (losses) on cash flow hedges, net			(546	)		46			(500	)		(328	)		—			(328	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			(51	)		10			(41	)		69			—			69
	Reclassification adjustments 2			11			—			11			(44	)		—			(44	)
	Unrealized gains (losses) on investments			(40	)		10			(30	)		25			—			25
	Other comprehensive income (loss)		$	(586	)	$	56		$	(530	)	$	(303	)	$	—		$	(303	)
			For the nine months ended									For the nine months ended
			30-Sep-14									30-Sep-13
			Pre-Tax			Tax Expense			After-Tax			Pre-Tax			Tax Expense			After-Tax
			Amount			(Benefit)			Amount			Amount			(Benefit)			Amount
	Unrealized gains (losses) on cash flow hedges:
	Current period unrealized gain (loss)		$	(452	)	$	(1	)	$	(453	)	$	719		$	—		$	719
	Reclassification adjustments 1			33			1			34			(1,144	)		—			(1,144	)
	Unrealized gains (losses) on cash flow hedges, net			(419	)		—			(419	)		(425	)		—			(425	)
	Unrealized gains (losses) on investments:
	Current period unrealized gain (loss)			(27	)		—			(27	)		23			—			23
	Reclassification adjustments 2			11			—			11			(206	)		—			(206	)
	Unrealized gains (losses) on investments			(16	)		—			(16	)		(183	)		—			(183	)
	Other comprehensive income (loss)		$	(435	)	$	—		$	(435	)	$	(608	)	$	—		$	(608	)
	1	Refer to note 6 for the affected line items in the condensed consolidated statement of operations
	2	Amount included in other income (expense), net, in the condensed consolidated statement of operations

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Company's Net Services Revenue	'
	The Company’s net services revenue is comprised of the following (in thousands):
		For the three months ended				For the nine months ended
		September 30,				September 30,
		2014		2013		2014		2013
	Maintenance and support	$	13,879	$	11,139	$	40,064	$	31,926
	Professional services and training		2,774		2,724		8,154		7,495
	Subscriptions		6,380		3,061		16,216		7,602
	Total net services revenue	$	23,033	$	16,924	$	64,434	$	47,023
Company's Net Revenue by Geographic Region, Based on Customer's Location	'
	The Company’s net revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands):
		For the three months ended				For the nine months ended
		September 30,				September 30,
		2014		2013		2014		2013
	Americas	$	22,801	$	19,941	$	63,731	$	58,168
	EMEA		12,929		9,737		30,543		22,239
	APAC		6,945		5,424		18,359		14,619
	Total net revenue	$	42,675	$	35,102	$	112,633	$	95,026
Long-Lived Assets by Location	'
	The following table presents long-lived assets by location (in thousands):
		As of		As of
		September 30,		December 31,
		2014		2013
	United States	$	6,433	$	3,039
	Israel		9,952		2,422
	Other		22		14
	Total long-lived assets	$	16,407	$	5,475

Net_Loss_per_Share_Tables

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock	'
	The following outstanding shares of common stock and potential common shares were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		For the three months and nine months
		ended September 30,
		2014		2013
	Stock options to purchase common stock		2,298,843		1,826,531
	Restricted stock units for common stock		2,146,536		898,119
	Restricted shares of common stock subject to repurchase		220,121		383,991
	Restricted stock issued in connection with Skyfence acquisition		355,499		—

Basis_of_Presentation_and_Summ2

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
	Segment
Revenue, Major Customer [Line Items]	'
Number of operating segments	1
Percentage of likelihood of fair value of reporting unit	50.00%
Impairment of goodwill	$0
Intangible asset impairment charges	$0
Weighted average useful lives of acquired technology intangible assets	'8 years
Minimum [Member]	'
Revenue, Major Customer [Line Items]	'
Estimated useful life	'7 years
Maximum [Member]	'
Revenue, Major Customer [Line Items]	'
Estimated useful life	'10 years

Basis_of_Presentation_and_Summ3

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information - Concentration Risk (Detail)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Revenue [Member]

Revenue [Member]

Revenue [Member]

Revenue [Member]

Revenue [Member]

Revenue [Member]

Revenue [Member]

Revenue [Member]

Accounts Receivable [Member]

Accounts Receivable [Member]

Accounts Receivable [Member]

Accounts Receivable [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Customer Concentration Risk [Member]

Credit Concentration Risk [Member]

Credit Concentration Risk [Member]

Credit Concentration Risk [Member]

Credit Concentration Risk [Member]

Customer

Customer

Customer

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Customer One [Member]

Customer

Minimum [Member]

Minimum [Member]

Customer Two [Member]

Customer

Customer

Concentration Risk [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Number of customers representing more than 10% threshold

0

0

0

'

'

'

'

1

0

'

'

1

Percentage of revenue or gross accounts receivable

'

'

'

10.00%

10.00%

10.00%

10.00%

10.00%

'

10.00%

10.00%

12.00%

Incapsula_Additional_Informati

Incapsula - Additional Information (Detail) (USD $)

1 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

0 Months Ended

1 Months Ended

Mar. 31, 2014

Sep. 30, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 09, 2010

Nov. 05, 2009

Sep. 30, 2014

Mar. 09, 2010

Nov. 05, 2009

Mar. 09, 2010

Mar. 09, 2010

Jan. 31, 2012

Jul. 31, 2011

Incapsula [Member]

Incapsula [Member]

Incapsula [Member]

Incapsula [Member]

Imperva [Member]

Series A Convertible Preferred Stock [Member]

Series A Convertible Preferred Stock [Member]

Series A Convertible Preferred Stock [Member]

Series A Convertible Preferred Stock [Member]

Series A Convertible Preferred Stock [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]

Assumed Outstanding Options [Member]

Restricted Stock Units for Common Stock [Member]

15-Month Holdback [Member]

Restricted Stock Units for Common Stock [Member]

Forward Contract [Member]

Forward Contract [Member]

Subsidiary or Equity Method Investee [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity method investments, shares

'

'

'

'

'

'

'

'

6,666,666

5,000,000

'

'

'

'

'

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

'

34,972,000

0

[1]

'

'

'

'

'

'

'

'

'

0

'

'

'

'

Cash consideration

'

'

'

'

'

'

'

'

3,000,000

'

'

'

'

'

'

3,500,000

3,500,000

Number of shares to be purchased if certain milestones were achieved

'

'

'

'

'

'

'

'

'

'

'

'

'

8,750,000

'

'

'

Cash consideration for milestones achieved

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7,000,000

'

'

Value assigned to forward contract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0

'

'

Purchase Right valuation description

'

'Exercise of the Purchase Right was solely within the Company's control and the price for the remaining ownership interest was to be based on an Incapsula enterprise valuation calculated as the greater of (i) eight times Incapsula's prior 12 months trailing revenues or (ii) seven times the aggregate amount Incapsula had raised in connection with its Series A Convertible Preferred Stock financings.

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Value assigned to Purchase Right

'

'

'

'

'

'

'

'

'

'

0

'

'

'

'

'

'

Amount paid for remaining outstanding capital stock

'

'

'

7,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Business acquisition, shares issued

'

'

'

124,088

48,359

'

'

264,878

'

'

'

'

'

'

'

'

'

Common stock subject to holdback

'

'

'

'

'

'

34,485

'

'

'

'

'

'

'

'

'

'

Common stock subject to holdback, period

'

'

'

'15 months

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares issuable, as-converted to common stock-basis

'

'

'

'

'

198,825

'

'

'

'

'

'

'

'

'

'

'

Non-controlling interest reclassified to additional paid-in capital

$2,827,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

8 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Feb. 07, 2014

Sep. 30, 2014

Sep. 30, 2014

Feb. 07, 2014

Feb. 07, 2014

Sep. 30, 2014

Sep. 30, 2013

Feb. 07, 2014

Jan. 30, 2014

Sep. 30, 2014

Jan. 30, 2014

Maximum [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Tomium Software, LLC. [Member]

Tomium Software, LLC. [Member]

Tomium Software, LLC. [Member]

Maximum [Member]

Pro Forma [Member]

Pro Forma [Member]

Purchased Technology [Member]

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Residual value of intangible assets

$0

'

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

Date of acquisition

'

'

'

'

'

'

'

7-Feb-14

'

'

'

'

'

'

30-Jan-14

'

Business acquisition purchase price, cash paid

'

'

12,083,000

0

'

8,558,000

'

'

'

'

'

'

'

4,600,000

'

'

Holdback payment commitment period

'

'

'

'

'

'24 months

'

'

'

'

'

'

'

'

'

'

Holdback liability

'

'

'

'

'

7,157,000

'

'

'

'

'

'

'

'

'

'

Business acquisition purchase price, shares issued

'

'

'

'

'

884,422

'

'

'

'

'

'

'

60,556

'

'

Compensation expense, service period

'

'

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

Business acquisition, shares for forfeiture

'

'

'

'

'

532,262

'

'

'

'

'

'

'

'

'

'

Options converted to purchase shares

'

'

'

'

'

164,000

'

'

'

'

'

'

'

'

'

'

Options converted, shares issued

'

'

'

'

'

24,828

'

'

'

'

'

'

'

'

'

'

Common stock subject to holdback

'

'

'

'

'

29,871

'

'

'

'

'

'

'

'

'

'

Common stock subject to holdback, period

'

'

'

'

'

'

'

'

'

'24 months

'

'

'

'

'

'

Closing price of stock

'

'

'

'

'

'

'

'

$59.08

'

'

'

'

'

'

$55.45

Unvested equity awards to be recorded as operating expense

'

'

'

'

'

'

'

'

1,100,000

'

'

'

'

'

'

'

Vested equity awards

'

'

'

'

'

354,000

'

'

'

'

'

'

'

'

'

'

Related acquisition costs

'

'

'

'

'

900,000

'

'

'

'

'

'

'

300,000

'

'

Recognized compensation expense

10,775,000

3,413,000

26,106,000

9,858,000

'

'

5,300,000

'

'

'

'

'

'

'

'

'

Estimated useful life

'

'

'

'

'10 years

'

'

'

'

'

'

'

'7 years

'10 years

'

'

Deferred tax liability recognized in earnings

'

'

'

'

'

'

'

'

1,528,000

'

148,000

373,000

'

'

'

'

Total purchase price

'

'

'

'

'

36,924,000

'

'

'

'

'

'

'

8,263,000

'

'

Business acquisition purchase price, assumption of liability to pay cash

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

300,000

Business acquisition purchase price, common stock value

'

'

'

'

'

$20,855,000

'

'

'

'

'

'

'

$3,400,000

'

'

Acquisitions_Schedule_of_Total

Acquisitions - Schedule of Total Purchase Consideration (Detail) (USD $)	9 Months Ended		0 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Feb. 07, 2014
			Skyfence Networks Ltd. [Member]
Business Acquisition [Line Items]	'	'	'
Cash	$12,083	$0	$8,558
Cash holdback liability	'	'	7,157
Fair value of common stock	'	'	20,855
Estimated fair value of equity awards assumed and replaced	'	'	354
Total purchase price	'	'	$36,924

Acquisitions_Summary_of_Alloca

Acquisitions - Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013		Jan. 30, 2014	Jan. 30, 2014	Feb. 07, 2014	Feb. 07, 2014	Feb. 07, 2014
				Tomium Software, LLC. [Member]	Tomium Software, LLC. [Member]	Skyfence Networks Ltd. [Member]	Skyfence Networks Ltd. [Member]	Skyfence Networks Ltd. [Member]
								Existing Technology [Member]
Business Acquisition [Line Items]	'	'		'	'	'	'	'
Intangible assets	'	'		'	$2,704,000	'	'	$7,965,000
Goodwill	34,972,000	0	[1]	'	5,499,000	'	29,473,000	'
Total intangible assets acquired	'	'		'	8,203,000	'	'	'
Other acquired tangible assets	'	'		'	60,000	'	'	'
Total purchase price	'	'		8,263,000	'	36,924,000	'	'
Net tangible assets	'	'		'	'	'	1,014,000	'
Deferred tax liability assumed	'	'		'	'	'	($1,528,000)	'
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquisitions_Summary_of_Supple

Acquisitions - Summary of Supplemental Information on Unaudited Pro Forma Basis (Detail) (Skyfence Networks Ltd. [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Skyfence Networks Ltd. [Member]	'	'	'	'
Business Acquisition [Line Items]	'	'	'	'
Pro forma revenue	$42,675	$35,102	$112,633	$95,026
Pro forma loss from operations	-13,426	-6,396	-47,294	-23,720
Pro forma net loss	($13,581)	($6,421)	($47,265)	($23,961)

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Investments [Line Items]	'	'
Cash and cash equivalents, Amortized Cost	$65,802	$76,705
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	1
Cash and cash equivalents, Fair Value	65,801	76,704
Short-term investments, Amortized Cost	35,403	38,373
Short-term investments, Gross Unrealized Gains	16	22
Short-term investments, Gross Unrealized Losses	24	14
Short-term investments, Estimated Fair Value	35,395	38,381	[1]
Cash [Member]	'	'
Schedule of Investments [Line Items]	'	'
Cash and cash equivalents, Amortized Cost	18,508	41,973
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	18,508	41,973
Commercial Paper [Member]	'	'
Schedule of Investments [Line Items]	'	'
Cash and cash equivalents, Amortized Cost	23,448	21,948
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	1	1
Cash and cash equivalents, Fair Value	23,447	21,947
Corporate Debt Obligations [Member]	'	'
Schedule of Investments [Line Items]	'	'
Short-term investments, Amortized Cost	25,133	28,220
Short-term investments, Gross Unrealized Gains	16	22
Short-term investments, Gross Unrealized Losses	24	14
Short-term investments, Estimated Fair Value	25,125	28,228
Bank Deposits [Member]	'	'
Schedule of Investments [Line Items]	'	'
Cash and cash equivalents, Amortized Cost	11,017	10,165
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	11,017	10,165
Short-term investments, Amortized Cost	10,270	10,153
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Estimated Fair Value	10,270	10,153
Money Market Funds [Member]	'	'
Schedule of Investments [Line Items]	'	'
Cash and cash equivalents, Amortized Cost	12,829	2,619
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	$12,829	$2,619
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Cash_Cash_Equivalents_and_Shor3

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Short-term Investments [Abstract]	'	'
Amortized Cost of short-term investments, Due within one year	$22,144	'
Amortized Cost of short-term investments, Due within two years	13,259	'
Short-term investments, Amortized Cost	35,403	38,373
Estimated fair value of short-term investments, Due within one year	22,159	'
Estimated fair value of short-term investments, Due within two years	13,236	'
Short-term investments, Estimated Fair Value	$35,395	$38,381	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Cash_Cash_Equivalents_and_Shor4

Cash, Cash Equivalents, and Short-Term Investments - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Short-term Investments [Abstract]	'	'
Short-term investments continuous unrealized loss position twelve months or longer value	$0	$0

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Fair value transfers between level 1 to level 2	$0	'
Fair value transfers between level 2 to level 1	0	'
Level II [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Severance pay assets	$4,000,000	$4,100,000

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	$65,801	$76,704
Total financial assets	82,688	73,112
Short-term investments	35,395	38,381	[1]
Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	23,447	21,947
Bank Deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	11,017	10,165
Short-term investments	10,270	10,153
Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	12,829	2,619
Corporate Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	25,125	28,228
Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accrued and other current liabilities - Forward foreign exchange contracts	419	'
Level I [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	12,829	2,619
Level I [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Level I [Member] | Bank Deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Short-term investments	0	0
Level I [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	12,829	2,619
Level I [Member] | Corporate Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	0	0
Level I [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accrued and other current liabilities - Forward foreign exchange contracts	0	'
Level II [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	69,859	70,493
Level II [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	23,447	21,947
Level II [Member] | Bank Deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	11,017	10,165
Short-term investments	10,270	10,153
Level II [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Level II [Member] | Corporate Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	25,125	28,228
Level II [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accrued and other current liabilities - Forward foreign exchange contracts	419	'
Level III [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total financial assets	0	0
Level III [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Level III [Member] | Bank Deposits [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Short-term investments	0	0
Level III [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash and cash equivalents	0	0
Level III [Member] | Corporate Debt Obligations [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	0	0
Level III [Member] | Forward Foreign Exchange Contracts [Member] | Accrued and Other Current Liabilities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Accrued and other current liabilities - Forward foreign exchange contracts	$0	'
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'	'
Forward foreign exchange contracts maturity	'12 months	'
Outstanding derivative instruments	'	$0

Derivative_Instruments_Derivat

Derivative Instruments - Derivative Instruments Measured at Fair Value (Detail) (Forward Foreign Exchange Contracts [Member], Accrued and Other Current Liabilities [Member], USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]	'
Derivative Fair Value	$419
Designated As Hedging Instrument [Member]	'
Derivatives, Fair Value [Line Items]	'
Derivative Notional Amount	7,040
Derivative Fair Value	$419

Derivative_Instruments_Gains_L

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Designated As Hedging Instrument [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Gains recognized in OCI	$52	$240	$55	$726
Losses recognized in OCI	-620	-7	-508	-7
Gains recognized from accumulated OCI into net loss	52	561	55	1,144
Losses recognized from accumulated OCI into net loss	-73	0	-89	0
Not Designated As Hedging Instrument [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Gains recognized in net loss	0	40	0	25
Losses recognized in net loss	$0	$0	$0	($15)

Derivative_Instruments_Gains_L1

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Parenthetical) (Detail) (Designated As Hedging Instrument [Member], Unrealized Gain (Loss) on Cash Flow Hedges [Member], USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating Expenses [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Cash flow hedge loss reclassified	($19)	$525	($31)	$1,069
Cost of Revenues [Member]	'	'	'	'
Derivatives, Fair Value [Line Items]	'	'	'	'
Cash flow hedge loss reclassified	($2)	$36	($3)	$75

Acquired_Intangible_Assets_Sum

Acquired Intangible Assets - Summary of Acquired Technology Intangible Assets Subject to Amortization (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Intangible Assets, Net (Excluding Goodwill) [Abstract]	'	'
Cost	$10,668	'
Accumulated Amortization	-917	'
Acquired intangible assets, net	$9,751	$0	[1]
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquired_Intangible_Assets_Add

Acquired Intangible Assets - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013		Sep. 30, 2014	Sep. 30, 2014
In Thousands, unless otherwise specified				Minimum [Member]	Maximum [Member]
Finite-Lived Intangible Assets [Line Items]	'	'		'	'
Estimated useful life	'	'		'7 years	'10 years
Acquired intangible assets	$9,751	$0	[1]	'	'
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Acquired_Intangible_Assets_Sch

Acquired Intangible Assets - Schedule of Expected Amortization Expense in Future Periods (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Acquired intangible assets, net	$9,751	$0	[1]
Purchased Technology [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
2014 (remaining 3 months)	352	'
2015	1,408	'
2016	1,408	'
2017	1,408	'
2018	1,408	'
Thereafter	3,767	'
Acquired intangible assets, net	$9,751	'
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Revolving_Credit_Facility_Addi

Revolving Credit Facility - Additional Information (Detail) (London Interbank Offered Rate (LIBOR) [Member], Line of Credit [Member], USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
London Interbank Offered Rate (LIBOR) [Member] | Line of Credit [Member]	'	'
Line of Credit Facility [Line Items]	'	'
Maximum borrowing capacity	$6,000,000	'
Outstanding credit facility	0	0
Credit facility expiration date	1-May-15	'
Minimum cash and cash equivalents	$3,000,000	'
Percentage in payment of unused line fee	0.25%	'
LIBOR plus interest rate	2.75%	'
Compliance of credit facility, description	'The Company was compliant with the amended covenant of the credit facility.	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2013
Loss Contingencies [Line Items]	'	'	'	'	'
Operating lease expiration year	'2019	'	'	'	'
Rent expense	$2,900,000	$2,500,000	'	'	'
Tenant improvement allowances	'	'	336,000	639,000	'
Restricted cash	1,575,000	'	'	'	1,252,000	[1]
Commitments purchased	6,300,000	'	'	'	3,200,000
Period of purchase commitment of inventory from specified date	'9 months	'	'	'	'
Cancelable Lease Agreement [Member]	'	'	'	'	'
Loss Contingencies [Line Items]	'	'	'	'	'
Penalties	83,000	'	'	'	'
Motor vehicle lease expenses	$2,000,000	$1,800,000	'	'	'
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) (USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Operating Leases	'
2014 (remaining 3 months)	$1,267
2015	5,240
2016	5,429
2017	4,775
2018	3,248
Thereafter	378
Total	20,337
Estimated Sublease Income	'
2014 (remaining 3 months)	138
2015	296
2016	77
2017	0
2018	0
Thereafter	0
Total	$511

Stock_Plans_Additional_Informa

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

9 Months Ended

0 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

1 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Feb. 07, 2014

Sep. 30, 2014

Feb. 07, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Dec. 31, 2010

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2011

Sep. 30, 2014

Feb. 29, 2012

Sep. 30, 2014

Feb. 29, 2012

Jan. 31, 2012

Sep. 30, 2011

Dec. 31, 2013

Sep. 30, 2011

Mar. 31, 2010

Nov. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Skyfence Networks Ltd. [Member]

Incapsula [Member]

Stock Options [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]

Incapsula 2010 Share Incentive Plan [Member]

Incapsula 2010 Share Incentive Plan [Member]

Incapsula 2010 Share Incentive Plan [Member]

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

Skyfence Networks Ltd. [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]

Restricted Stock Units for Common Stock [Member]

Maximum [Member]

Restricted Stock Units for Common Stock [Member]

Restricted Stock Units for Common Stock [Member]

Minimum [Member]

Maximum [Member]

Incapsula Acquisition [Member]

Share-based Compensation Award, Tranche One [Member]

Period

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum percentage of fair value of common stock on grant date

'

'

'

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum percentage of combined voting power

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum percentage of fair value of common stock on grant date

'

'

'

'

'

'

'

'

'

'

'

'

'

110.00%

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'

'4 years

'

'

'

'

'

'

'

'48 months

'60 months

'

'4 years

'

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

Expiration period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 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

'

'

'

'

'

'

'

'

'

'

'

'

'

Increase in reserve share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,008,260

'

'

'

'

'

'

'

252,065

'

'

'

'

'

Vesting percentage at each year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

'

'

'

'

'

'

Remaining vesting period of RSUs

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'

'

'

'

'

'

'

'

Performance-based restricted stock units granted

1,186,560

'

'

'

'

'

'

'

0

0

843,819

'

'

'

'

'

'

'

'

'

264,878

'

'

'

'

'

'

7,095,461

247,184

'

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

'

'

'

'

Percentage of fair value of common stock on offering period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

85.00%

'

'

'

'

'

'

Number of years, shares reserved for issuance will increase

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'8 years

'

'

'

'

'

'

'

Shares converted into common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

198,825

'

Intrinsic value of options exercised

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$10,700,000

Market value of common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$28.73

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

'

'

'

'

'

1,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

94,300,000

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'3 years 1 month 6 days

Capitalized stock-based compensation cost

$0

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average grant date fair value

'

'

'

'

'

'

'

'

'

'

$1.94

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested shares

2,146,536

'

1,044,651

'

'

'

'

9,167

210,954

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Business Acquisition, shares subject to forfeiture

'

'

'

532,262

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Closing price of stock

'

'

'

'

'

$59.08

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares vested

'

'

'

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Assumed common stock options in acquisitions

72,607

'

'

'

'

'

72,607

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock_Plans_Option_and_Perform

Stock Plans - Option and Performance-Based Restricted Share Unit Activity under Incapsula Plan (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Stock Options Outstanding, - Beginning Balance	1,675,506
Number of Stock Options Outstanding, Granted	1,076,327
Number of Stock Options Outstanding, Exercised	-311,650
Number of Stock Options Outstanding, Forfeited	-213,947
Number of Stock Options Outstanding, - Ending Balance	2,298,843
Options Outstanding, weighted Average Exercise Price - Beginning Balance	$23.78
Weighted Average Exercise Price, Granted	$42.37
Weighted Average Exercise Price, Exercised	$10.60
Weighted Average Exercise Price, Forfeited	$34.81
Options Outstanding, weighted Average Exercise Price - Ending Balance	$32.89
Incapsula Plan [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares Available for Grant, Outstanding - Beginning Balance	89,687
Shares Available for Grant, Granted	-95,000
Shares Available for Grant, Exercised	0
Shares Available for Grant, Forfeited	15,213
Shares Available for Grant, Transferred to Imperva 2011 stock option plan	-9,900
Shares Available for Grant, Outstanding - Ending Balance	0
Number of Performance-based Restricted Share Units Outstanding - Beginning Balance	7,095,461
Number of Performance-based Restricted Share Units Outstanding, Granted	0
Number of Performance-based Restricted Share Units Outstanding, Exercised	0
Number of Performance-based Restricted Share Units Outstanding, Forfeited	-12,713
Number of Performance-based Restricted Share Units Outstanding, Transferred to Imperva 2011 stock option plan	-7,082,748
Number of Performance-based Restricted Share Units Outstanding - Ending Balance	0
Number of Stock Options Outstanding, - Beginning Balance	1,806,500
Number of Stock Options Outstanding, Granted	95,000
Number of Stock Options Outstanding, Exercised	0
Number of Stock Options Outstanding, Forfeited	-2,500
Number of Stock Options Outstanding, Transferred to Imperva 2011 stock option plan	-1,899,000
Number of Stock Options Outstanding, - Ending Balance	0
Options Outstanding, weighted Average Exercise Price - Beginning Balance	$0.47
Weighted Average Exercise Price, Granted	$1.25
Weighted Average Exercise Price, Exercised	$0
Weighted Average Exercise Price, Forfeited	$1.25
Weighted Average Exercise Price, Transferred to Imperva 2011 stock option plan	$0.16
Options Outstanding, weighted Average Exercise Price - Ending Balance	$0

Stock_Plans_StockBased_Compens

Stock Plans - Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock - based compensation expense	$10,775	$3,413	$26,106	$9,858
Cost of Revenues [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock - based compensation expense	569	254	1,472	722
Research and Development [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock - based compensation expense	2,353	747	6,335	2,133
Sales and Marketing [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock - based compensation expense	3,730	1,620	9,369	4,596
General and Administrative [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Total stock - based compensation expense	$4,123	$792	$8,930	$2,407

Stock_Plans_Weighted_Average_A

Stock Plans - Weighted Average Assumptions for Fair Value of Stock Options Grants (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Dividend rate	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	2.00%	1.80%	1.90%	1.20%
Expected term (in years)	'6 years 1 month 6 days	'6 years 1 month 6 days	'6 years 1 month 6 days	'6 years 1 month 6 days
Expected volatility	51.00%	47.00%	45.00%	46.00%
Employee Stock [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Dividend rate	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate	0.00%	0.00%	0.10%	0.10%
Expected term (in years)	'0 years	'0 years	'6 months	'6 months
Expected volatility	0.00%	0.00%	57.00%	31.00%

Stock_Plans_Summary_of_Option_

Stock Plans - Summary of Option Activity Under Plans and Related Information (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Number of Stock Options Outstanding, - Beginning Balance	1,675,506	'
Options Outstanding, Number of Shares, Granted	1,076,327	'
Options Outstanding, Number of Shares, Exercised or released	-311,650	'
Number of Stock Options Outstanding, Cancelled or Forfeited	-213,947	'
Options Outstanding, Number of Shares, Options assumed in acquisitions	72,607	'
Number of Stock Options Outstanding, - Ending Balance	2,298,843	1,675,506
Options Outstanding, Number of Shares, Exercisable	672,910	'
Options Outstanding, weighted Average Exercise Price - Beginning Balance	$23.78	'
Options Outstanding, weighted Average Exercise Price, Granted	$42.37	'
Options Outstanding, weighted Average Exercise Price, Exercised	$10.60	'
Number of Stock Options Outstanding, Cancelled or Forfeited	$34.81	'
Options Outstanding, weighted Average Exercise Price, Options assumed in acquisitions	$14.14	'
Options Outstanding, weighted Average Exercise Price - Ending Balance	$32.89	$23.78
Options Outstanding, weighted Average Exercise Price, Exercisable	$21.19	'
Weighted Average Remaining Contractual Life (in years)	'8 years 3 months 7 days	'8 years 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable	'6 years 9 months	'
Aggregate Intrinsic Value - Beginning Balance	$40,813	'
Aggregate Intrinsic Value - Ending Balance	11,299	40,813
Aggregate Intrinsic Value, Exercisable	$6,887	'

Stock_Plans_Summary_of_RSU_Act

Stock Plans - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	1,044,651
Number of Restricted Stock Units Outstanding, Granted	1,186,560
Number of Restricted Stock Units Outstanding, Granted, performance RSUs	96,446
Number of Restricted Stock Units Outstanding, Released	-187,595
Number of Restricted Stock Units Outstanding, Cancelled or expired	-197,992
Number of Restricted Stock Units Outstanding, RSUs assumed in acquisitions	204,466
Number of Restricted Stock Units Outstanding, Unvested - Ending balance	2,146,536
Weighted-Average Grant Date Fair Value, Unvested - Beginning Balance	$31.64
Weighted-Average Grant Date Fair Value, Granted	$42.58
Weighted-Average Grant Date Fair Value, Granted, performance RSUs	$32.07
Weighted-Average Grant Date Fair Value, Released	$34.73
Weighted-Average Grant Date Fair Value, Cancelled or expired	$39.38
Weighted-Average Grant Date Fair Value, RSUs assumed in acquisitions	$61.40
Weighted-Average Grant Date Fair Value, Unvested - Ending balance	$39.56

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) - Changes in Balances of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning Balance	($333)	$556	($428)	[1]	$861
Other comprehensive income (loss) before reclassifications	-562	302	-480		742
Amounts reclassified to net loss	32	-605	45		-1,350
Other comprehensive income (loss)	-530	-303	-435		-608
Ending Balance	-863	253	-863		253
Unrealized Gain (Loss) on Cash Flow Hedges [Member]	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning Balance	-345	593	-426		690
Other comprehensive income (loss) before reclassifications	-521	233	-453		719
Amounts reclassified to net loss	21	-561	34		-1,144
Other comprehensive income (loss)	-500	-328	-419		-425
Ending Balance	-845	265	-845		265
Unrealized Gain (Loss) on Investments [Member]	'	'	'		'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'		'
Beginning Balance	12	-37	-2		171
Other comprehensive income (loss) before reclassifications	-41	69	-27		23
Amounts reclassified to net loss	11	-44	11		-206
Other comprehensive income (loss)	-30	25	-16		-183
Ending Balance	($18)	($12)	($18)		($12)
[1]	The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Loss) - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]	'	'	'	'
Current period unrealized gain (loss) on cash flow hedges, Pre-Tax Amount	($567)	$233	($452)	$719
Reclassification adjustments on cash flow hedges, Pre-Tax Amount	21	-561	33	-1,144
Unrealized gains (losses) on cash flow hedges, net, Pre-Tax Amount	-546	-328	-419	-425
Current period unrealized gain (loss) on investments, Pre-Tax Amount	-51	69	-27	23
Reclassification adjustments on investments, Pre-Tax Amount	11	-44	11	-206
Unrealized gains (losses) on investments, net, Pre-Tax Amount	-40	25	-16	-183
Other comprehensive income/(loss), Pre-Tax Amount	-586	-303	-435	-608
Current period unrealized gain (loss) on cash flow hedges, Tax Expense (Benefit)	46	0	-1	0
Reclassification adjustments on cash flow hedges, Tax Expense (Benefit)	0	0	1	0
Unrealized gains (losses) on cash flow hedges, net, Tax Expense (Benefit)	46	0	0	0
Current period unrealized gain (loss) on investments, Tax Expense (Benefit)	10	0	0	0
Reclassification adjustments on investments, Tax Expense (Benefit)	0	0	0	0
Unrealized gains (losses) on investments, net, Tax Expense (Benefit)	10	0	0	0
Other Comprehensive income (loss), Tax Expense (Benefit)	56	0	0	0
Current period unrealized gain (loss) on cash flow hedges, After-Tax Amount	-521	233	-453	719
Reclassification adjustments on cash flow hedges, After-Tax Amount	21	-561	34	-1,144
Unrealized gains (losses) on cash flow hedges, net, After-Tax Amount	-500	-328	-419	-425
Current period unrealized gain (loss) on investments, After-Tax Amount	-41	69	-27	23
Reclassification adjustments on investments, After-Tax Amount	11	-44	11	-206
Unrealized gains (losses) on investments, net, After-Tax Amount	-30	25	-16	-183
Other comprehensive income (loss)	($530)	($303)	($435)	($608)

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Income tax expense (benefit)	$190	$288	($216)	$703

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2014
	Segment
Segment Reporting [Abstract]	'
Number of operating segments	1

Segment_Information_Components

Segment Information - Components of Net Services Revenue (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue from External Customer [Line Items]	'	'	'	'
Total net services revenue	$23,033	$16,924	$64,434	$47,023
Maintenance and Support [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total net services revenue	13,879	11,139	40,064	31,926
Professional Services and Training [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total net services revenue	2,774	2,724	8,154	7,495
Subscriptions [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total net services revenue	$6,380	$3,061	$16,216	$7,602

Segment_Information_Companys_N

Segment Information - Company's Net Revenue by Geographic Region, Based on Customer's Location (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total net revenue	$42,675	$35,102	$112,633	$95,026
Americas [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total net revenue	22,801	19,941	63,731	58,168
EMEA [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total net revenue	12,929	9,737	30,543	22,239
APAC [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total net revenue	$6,945	$5,424	$18,359	$14,619

Segment_Information_LongLived_

Segment Information - Long-Lived Assets by Location (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Total long-lived assets	$16,407	$5,475
United States [Member]	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Total long-lived assets	6,433	3,039
Israel [Member]	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Total long-lived assets	9,952	2,422
Other [Member]	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Total long-lived assets	$22	$14

Net_Loss_per_Share_Antidilutiv

Net Loss per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Options [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of diluted net loss per share	2,298,843	1,826,531	2,298,843	1,826,531
Restricted Stock Units for Common Stock [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of diluted net loss per share	2,146,536	898,119	2,146,536	898,119
Restricted Shares of Common Stock Subject to Repurchase [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of diluted net loss per share	220,121	383,991	220,121	383,991
Restricted Stock Issued In Connection with Skyfence Acquisition [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of diluted net loss per share	355,499	0	355,499	0