Imperva 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 14, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	IMPV
Entity Registrant Name	IMPERVA INC
Entity Central Index Key	1,364,962
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		34,565,641
Entity Public Float			$ 1,608

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 192,538	$ 107,343
Short-term investments	166,993	153,749
Restricted cash	52	68
Accounts receivable, net of allowance of $936 and $ 1,784 as of December 31, 2017 and 2016, respectively	75,535	62,571
Inventory	617	590
Prepaid expenses and other current assets	14,894	7,922
Total current assets	450,629	332,243
Property and equipment, net	25,407	21,496
Goodwill	36,389	37,448
Acquired intangible assets, net	3,184	8,393
Severance pay fund	6,554	5,070
Restricted cash	2,284	1,884
Deferred tax assets	2,022	1,220
Other assets	1,593	1,065
TOTAL ASSETS	528,062	408,819
CURRENT LIABILITIES:
Accounts payable	5,869	5,529
Accrued compensation and benefits	22,913	20,840
Accrued and other current liabilities	11,417	7,683
Deferred revenue	126,174	104,042
Total current liabilities	166,373	138,094
Other liabilities	6,253	6,637
Deferred revenue	33,081	26,429
Accrued severance pay	7,238	5,696
TOTAL LIABILITIES	212,945	176,856
Commitments and Contingencies (Note 9)
STOCKHOLDERS' EQUITY:
Preferred stock, $0.0001 par value - 5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2017 and 2016, respectively	0	0
Common stock, $0.0001 par value - 145,000,000 shares authorized, 34,233,888 and 33,088,990 shares issued and outstanding as of December 31, 2017 and 2016, respectively	3	3
Additional paid-in capital	572,106	510,257
Accumulated deficit	(256,537)	(276,819)
Accumulated other comprehensive loss	(455)	(1,478)
TOTAL STOCKHOLDERS' EQUITY	315,117	231,963
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 528,062	$ 408,819

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 936	$ 1,784
Preferred stock, par value, per share	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	34,233,888	33,088,990
Common stock, shares outstanding	34,233,888	33,088,990

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net revenue:
Products and license	$ 97,122	$ 86,798	$ 107,563
Services	224,594	177,657	126,735
Total net revenue	321,716	264,455	234,298
Cost of revenue:
Products and license	7,738	9,525	10,947
Services	56,215	44,307	36,633
Total cost of revenue	63,953	53,832	47,580
Gross profit	257,763	210,623	186,718
Operating expenses:
Research and development	63,452	62,402	53,376
Sales and marketing	152,178	156,465	136,292
General and administrative	54,435	51,260	43,440
Restructuring charges	667	8,118	0
Amortization of acquired intangible assets	714	1,408	1,408
Total operating expenses	271,446	279,653	234,516
Loss from operations	(13,683)	(69,030)	(47,798)
Gain on sale of business	35,871	0	0
Other income (expense), net	1,142	(77)	(402)
Income (loss) before provision for income taxes	23,330	(69,107)	(48,200)
Provision for income taxes	461	1,172	682
Net income (loss)	$ 22,869	$ (70,279)	$ (48,882)
Earnings per share:
Basic	$ 0.68	$ (2.18)	$ (1.64)
Diluted	$ 0.67	$ (2.18)	$ (1.64)
Shares used in computing earnings per share
Basic	33,724	32,284	29,849
Diluted	34,238	32,284	29,849

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 22,869	$ (70,279)	$ (48,882)
Other comprehensive income (loss) (net of tax):
Net change in net unrealized loss on investments	(202)	(103)	(249)
Net change in unrealized gain (loss) on hedging instruments	1,225	(44)	407
Other comprehensive income (loss)	1,023	(147)	158
Comprehensive income (loss)	$ 23,892	$ (70,426)	$ (48,724)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2014	$ 97,243	$ 2	$ 256,388	$ (157,658)	$ (1,489)
Beginning balance, shares at Dec. 31, 2014		26,895,480
Proceeds from follow-on public offering, net of offering costs	127,741	$ 1	127,740
Proceeds from follow-on public offering, net of offering costs, shares		3,450,000
Issuance of common stock, net of repurchases	18,724		18,724
Issuance of common stock, net of repurchases, shares		670,844
Vesting of restricted stock	767		767
Vesting of restricted stock, shares		706,121
Stock-based compensation	50,964		50,964
Issuance of common stock in connection with employee stock purchase plan	4,785		4,785
Issuance of common stock in connection with employee stock purchase plan, shares		114,699
Income tax benefit from employee stock option exercises	165		165
Shares withheld for tax withholding on vesting of restricted stock units	(11,464)		(11,464)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(249)				(249)
Change in unrealized loss on derivatives	407				407
Net income (loss)	(48,882)			(48,882)
Comprehensive income (loss)	(48,724)
Ending balance at Dec. 31, 2015	240,201	$ 3	448,069	(206,540)	(1,331)
Ending balance, shares at Dec. 31, 2015		31,837,144
Issuance of holdback shares in connection with acquisition, shares		206,499
Issuance of common stock, net of repurchases	5,402		5,402
Issuance of common stock, net of repurchases, shares		843,724
Stock-based compensation	59,750		59,750
Issuance of common stock in connection with employee stock purchase plan	5,831		5,831
Issuance of common stock in connection with employee stock purchase plan, shares		201,623
Income tax benefit from employee stock option exercises	36		36
Shares withheld for tax withholding on vesting of restricted stock units	(8,831)		(8,831)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(103)				(103)
Change in unrealized loss on derivatives	(44)				(44)
Net income (loss)	(70,279)			(70,279)
Comprehensive income (loss)	(70,426)
Ending balance at Dec. 31, 2016	231,963	$ 3	510,257	(276,819)	(1,478)
Ending balance, shares at Dec. 31, 2016		33,088,990
Cumulative effect of a change in accounting principle	14		2,601	(2,587)
Issuance of common stock, net of repurchases	15,587		15,587
Issuance of common stock, net of repurchases, shares		951,055
Stock-based compensation	46,670		46,670
Issuance of common stock in connection with employee stock purchase plan	6,633		6,633
Issuance of common stock in connection with employee stock purchase plan, shares		193,843
Shares withheld for tax withholding on vesting of restricted stock units	(9,642)		(9,642)
Components of other comprehensive income (loss), net of tax
Change in unrealized loss on investments	(202)				(202)
Change in unrealized loss on derivatives	1,225				1,225
Net income (loss)	22,869			22,869
Comprehensive income (loss)	23,892
Ending balance at Dec. 31, 2017	$ 315,117	$ 3	$ 572,106	$ (256,537)	$ (455)
Ending balance, shares at Dec. 31, 2017		34,233,888

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 22,869	$ (70,279)	$ (48,882)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	10,857	7,488	4,551
Stock-based compensation	46,670	62,875	50,964
Amortization of acquired intangibles	714	1,408	1,408
Amortization of premiums/accretion of discounts on short-term investments	(25)	238	496
Loss on disposal of equipment	74	267	0
Excess tax benefits from share-based compensation	0	(36)	(165)
Gain on sale of business	(35,871)	0	0
Other	(1,299)	125	0
Changes in operating assets and liabilities:
Accounts receivable, net	(12,964)	(1,520)	(13,605)
Inventory	(93)	(16)	(1,056)
Prepaid expenses and other assets	(1,959)	383	(4,220)
Accounts payable	115	(1,398)	977
Accrued compensation and benefits	5,197	(2,543)	4,510
Accrued and other liabilities	3,378	2,178	3,242
Severance pay, net	58	272	16
Deferred revenue	30,237	23,684	25,482
Deferred tax assets	(802)	(632)	149
Net cash provided by operating activities	67,156	22,494	23,867
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of short-term investments	(130,972)	(129,989)	(89,626)
Proceeds from sales/maturities of short-term investments	117,552	72,453	33,948
Proceeds from sale of business	35,015	0	0
Acquisitions, net of cash acquired	0	(3,914)	0
Net purchases of property and equipment	(13,924)	(16,789)	(8,080)
Change in restricted cash	(384)	(208)	(17)
Net cash provided by (used in) investing activities	7,287	(78,447)	(63,775)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of repurchases	19,095	11,233	23,524
Shares withheld for tax withholding on vesting of restricted stock units	(9,642)	(8,831)	(11,464)
Offering costs relating to follow-on public offering	0	(112)	0
Proceeds from follow-on public offering, net of offering costs	0	0	127,853
Settlement of holdback liability	0	(7,157)	0
Excess tax benefits from share-based compensation	0	36	165
Net cash provided by (used in) financing activities	9,453	(4,831)	140,078
Effect of exchange rate changes on cash and cash equivalents	1,299	(125)	(14)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	85,195	(60,909)	100,156
CASH AND CASH EQUIVALENTS - Beginning of period	107,343	168,252	68,096
CASH AND CASH EQUIVALENTS - End of period	192,538	107,343	168,252
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	1,409	1,480	652
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment incurred but not yet paid	1,645	574	517
Vesting of restricted and early exercised stock options	$ 0	$ 0	$ 767

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	1. The Company and Summary of Significant Accounting Policies Business Imperva, Inc. (together with its subsidiaries, the “Company”) was incorporated in April 2002 in Delaware. The Company is headquartered in Redwood Shores, California and has subsidiaries located throughout the world including Israel, Asia, Europe and North America. The Company is engaged in the development, marketing, sales, service and support of cyber-security solutions that protect data and applications on-premises, in the cloud, and across hybrid environments. Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the fair presentation of the Company’s consolidated financial position, results of operations and cash flows for the periods presented. The consolidated financial statements include the accounts of Imperva Inc., and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company has one operating segment, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications, whether in the cloud or on premises. Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include the fair value of accounts receivable, inventory, intangible assets and goodwill, useful lives of intangible assets and property and equipment, and assumptions used in the calculation of revenue, income taxes and stock-based compensation, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts such estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Concentration of Supply Risk The Company relies on a single third party to manufacture its hardware appliances, and purchases its hardware appliances through such third party’s value-added resellers. Quality or performance failures of the Company’s products or changes in the Company’s suppliers’ financial or business condition could disrupt the Company’s ability to supply quality products to its customers and thereby have a material adverse effect on its business and consolidated financial statements. Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, short-term investments, restricted cash and derivative financial instruments. The Company’s cash, cash equivalents, short-term investments and restricted cash are invested in high-quality instruments with banks and financial institutions located in the United States and Israel. Such deposits may be in excess of insured limits provided on such deposits. The Company uses derivative financial instruments to manage exposures to foreign currency risks. The Company’s derivatives expose it to credit risk to the extent that the counterparty may be unable to meet the terms of the agreement. The Company seeks to mitigate such risk by limiting its counterparties to those with high or investment-grade credit ratings. The Company does not require collateral under these agreements and has not historically experienced any losses due to credit risk or lack of performance by counterparties. Derivative Financial Instruments The Company uses forward foreign currency exchange contracts to reduce its exposure to foreign currency rate changes for operating expenses that are forecasted to be incurred in currencies other than U.S. dollars. The Company records all of its derivative instruments at their gross fair value on the consolidated balance sheets. The Company classifies its cash flows from derivative financial instruments as operating activities. The accounting for changes in the fair value of a derivative instrument depends on whether the instrument has been designated and qualifies as a cash flow hedge for accounting purposes. For forward foreign currency exchange contracts that are designated and qualify as cash flow hedges, the effective portion of the gain or loss resulting from changes in the fair value of the derivative instruments is accounted for in accumulated other comprehensive income (loss) (“AOCI”) in the consolidated statements of stockholders’ equity and reclassified into operating expenses in the consolidated statements of operations in the period or periods during which the hedged transaction affects earnings. As of December 31, 2017, the Company estimated that $0.6 million of net derivative loss included in accumulated other comprehensive income (loss) will be reclassified into earnings within the next 12 months. The ineffective portion of the gain or loss resulting from the change in fair value is recognized in other income (expense), net in the consolidated statements of operations. Cash, Cash Equivalents and Short-Term Investments The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand, highly liquid investments in money market funds and various deposit accounts. The Company considers all high quality investments purchased with original maturities at the date of purchase greater than three months to be short-term investments. Investments are available to be used in current operations and are, therefore, classified as current assets even though maturities may extend beyond one year. Cash equivalents and short-term investments are classified as available-for-sale and are, therefore, recorded at fair value on the consolidated balance sheets, with any unrealized gains and losses reported in the consolidated statements of stockholders’ equity as a component of accumulated other comprehensive income (loss) until realized. The Company uses the specific-identification method to compute gains and losses on the investments. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included as a component of other income (expense), net in the consolidated statements of operations. Restricted Cash The Company has restricted cash pledged as collateral representing a security deposit required for facility leases. As of December 31, 2017 and 2016, the Company has classified $2.3 million and $1.9 million, respectively, of security deposit as non-current assets relating to its facility lease arrangements. Insurance Recoveries Receivable Insurance recoveries receivable consists of amounts receivable by the Company from insurance recoveries in connection with settlement costs and professional fees. Claims for loss recoveries are generally recognized when a loss event has occurred and recovery is considered probable. Inventory Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value where the cost is determined as the lower of an average cost basis or last invoice. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. For the years ended December 31, 2017, 2016 and 2015, the amount of inventory write-downs incurred by the Company were insignificant. Business Combination The Company accounts for its business acquisitions in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations. The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets, generally two to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term or the estimated useful lives of the assets. Upon the retirement or disposition of property and equipment, the related costs and accumulated depreciation is removed and any related gain or loss is recorded in the consolidated statements of operations. Repairs and maintenance that do not extend the life or improve an asset are expensed in the periods incurred. Goodwill and Acquired Intangibles Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The Company operates its business in one operating segment and one reporting unit, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises. In reviewing goodwill, the Company bypasses the qualitative assessment and proceeds directly to performing the quantitative two step impairment test to test the reporting unit’s goodwill for impairment. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill and is used as a screening process for identifying a potential goodwill impairment loss. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value. The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the fiscal year ended December 31, 2017. Intangible assets consist of purchased technology, customer relationships, trade names and domain names which are amortized over the period of estimated benefit using the straight-line method, as the consumption pattern of the asset is not apparent, and estimated useful lives ranging from seven to ten years as of December 31, 2017. No significant residual value is estimated for intangible assets. Impairment of Long-Lived Assets The Company evaluates its long-lived assets, which consist of property and equipment and acquired intangible assets, for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Impairment exists if the carrying amounts of such assets exceed the estimates of future net undiscounted cash flows expected to be generated by such assets. Should impairment exist, the impairment loss would be measured based on the excess carrying value of the asset over the asset’s estimated fair value. As of December 31, 2017 and 2016, the Company has not written down any of its long-lived assets as a result of impairment. Revenue Recognition The Company derives revenue from two sources: (i) products and license revenue, which includes hardware and perpetual software license revenue and (ii) services revenue, which includes maintenance and support, professional services, training and subscription arrangements. Substantially all of product and license sales have been sold in combination with maintenance and support services. Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery or performance has occurred; the sales price is fixed or determinable; and collection is reasonably assured. The Company defines each of the four criteria above as follows: • Persuasive evidence of an arrangement exists: Evidence of an arrangement consists of a purchase order or acknowledgment issued pursuant to the terms and conditions of a direct customer end user or distributor or value-added reseller (VAR) agreement and, in limited cases with both distributor/VAR and an end user agreement and/or purchase order • Delivery or performance has occurred: The Company uses shipping and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance. The Company recognizes product revenue upon transfer of title and risk of loss, which primarily is upon shipment to value-added resellers, distributors or end users. We recognize software license revenue upon transfer of electronic keys to a customer. In most instances, the Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with the Company’s sales. In instances where final acceptance of the product or service is specified by the customer, revenue is deferred until all acceptance criteria have been met • The sales price is fixed or determinable: The Company assesses whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. In the event payment terms are provided that differ from the Company’s standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized when the payments become due, provided the remaining criteria for revenue recognition have been met. • Collection is reasonably assured: The Company assesses probability of collection on a customer-by-customer basis. The Company’s customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. If the Company concludes that collection is not reasonably assured based upon an initial review, the Company does not recognize revenue until payment is received. Maintenance and support and subscription revenue includes arrangements for software maintenance and technical support for the Company’s products and subscription services revenue primarily related to the Company’s cloud-based services. The terms of the Company’s subscription service arrangements do not provide customers the right to take possession of the related software. Maintenance and support is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches and unspecified upgrades on a when-and-if-available basis. Maintenance and support and subscription revenue is initially deferred and recognized ratably over the life of the contract, with the related expenses recognized as incurred. Maintenance and support and subscription contracts usually have a term of one to three years. Unearned maintenance and support and subscription revenue is included in deferred revenue. Professional service revenue primarily consists of the fees the Company earns related to installation and consulting services. The Company recognizes revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 90 days from the start of service. Training services are recognized upon delivery of the training. Multiple Element Arrangements Most of the Company’s products are hardware appliances containing software components that function together to provide the essential functionality of the product. Therefore, the Company’s hardware appliances are considered non-software deliverables and are not subject to industry-specific software revenue recognition guidance. The Company’s product revenue also includes revenue from the sale of stand-alone software products. Stand-alone software may operate on the Company’s hardware appliance, but is not considered essential to the functionality of the hardware and is, therefore, subject to the industry-specific software revenue recognition guidance. Additionally, the Company provides unspecified software upgrades for our products, on a when-and-if available basis, and hardware replacements through maintenance and support contracts. These support arrangements when sold on a stand-alone basis are subject to the industry-specific software revenue recognition guidance. Under the software revenue recognition guidance, the Company uses the residual method to recognize revenue when a product agreement includes one or more elements to be delivered at a future date and Vendor Specific Objective Evidence (“VSOE”) of the fair value of all undelivered elements exists. In the majority of the Company’s contracts, the only element that remains undelivered at the time of delivery of the product is maintenance and support services and subscriptions. Under the residual method, the VSOE of fair value of the undelivered elements is deferred and the remaining portion of the contract fee is recognized as product revenue. If evidence of the VSOE of fair value of one or more undelivered elements does not exist, all revenue is generally deferred and recognized when delivery of those elements occurs or when fair value can be established. For certain arrangements with multiple deliverables, the Company allocates the arrangement fee to the non-software element based upon the relative selling price of such element and, if software and software-related elements (e.g., maintenance and support for the software element) are also included in the arrangement, the Company allocates the arrangement fee to each of those software and software-related elements as a group. After such allocations are made, the amount of the arrangement fee allocated to the software and software-related elements is accounted for using the residual method. When applying the relative selling price method, the Company determines the selling price for each element using VSOE of selling price, if it exists, or if not, Third-Party Evidence (“TPE”) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its Best Estimate of Selling Price (“BESP”) for that element. The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element. The Company limits the amount of revenue recognized for delivered elements to the amount that is not contingent on the future delivery of products or services, or subject to the Company’s future performance obligation. VSOE of fair value for elements of an arrangement is based upon the normal pricing and discounting practices for those services when sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices for a service fall within a reasonably narrow pricing range, evidenced by a substantial majority of such historical stand-alone transactions falling within a reasonably narrow range. In addition, the Company considers major service groups and geographies in determining VSOE. The Company is not able to determine TPE for its products or services. TPE is determined based on competitor prices for similar deliverables when sold separately. Generally, the Company’s go-to-market strategy differs from that of its peers and its offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine what similar competitor products’ selling prices are on a stand-alone basis. When the Company is unable to establish the selling price of its non-software deliverables using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company determines BESP for the purposes of allocating the arrangement by reviewing external and internal market factors including, but not limited to, pricing practices including discounting, the geographies in which the Company offers its products and services, the type of customer (i.e., distributor, value added reseller or direct end user) and competition. Additionally, the Company considers historical transactions, including transactions whereby the deliverable was sold on a stand-alone basis. The determination of BESP is made through consultation with and approval by the Company’s management. Selling prices are analyzed on a quarterly basis to identify if the Company has experienced significant changes in its selling prices that would impact our determination of BESP. For its non-software deliverables the Company allocates the arrangement consideration based on the relative selling price of the deliverables. For its hardware appliances the Company uses BESP as its selling price. For its maintenance and support services, subscriptions and professional services and training, the Company primarily uses VSOE as the selling price and when the Company is unable to establish a selling price using VSOE, it uses BESP. Deferred Revenue Deferred revenue represents amounts invoiced to customers for which the related revenue has not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of the deferred revenues represents the amount that is expected to be recognized as revenue within one year of the consolidated balance sheet date. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. The Company generally does not require collateral from its customers; however, in certain circumstances, may require letters of credit, other collateral, additional guarantees or advance payments. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of its customer accounts. The Company regularly reviews its accounts receivable that remain outstanding past their applicable payment terms and establishes allowance and potential write-offs by considering certain factors such as historical experience, industry data, credit quality, age of balances and current economic conditions that may affect a customers’ ability to pay. Concentration of Revenue and Accounts Receivable Significant customers are those which represent 10% or more of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the year ended December 31, 2017, 2016 and 2015, we had one customer that represented 12%, 13% and 18% of our total revenue, respectively. The same customer represented 18% and 18% of gross accounts receivable as of December 31, 2017 and 2016 respectively. Shipping and Handling Costs Costs related to shipping and handling are included in cost of revenue. Research and Development Costs Research and development costs, including direct and allocated expenses, are expensed as incurred. Software Development Costs The costs to develop software for sale have not been capitalized as the Company believes that the technological feasibility of the related software is not established until substantially all product development is complete. Warranty Costs The Company generally provides a 60-day warranty on hardware appliance products and software from the date of shipment to customers. To date, cost to repair or replace items sold to customers has been insignificant. Advertising Costs The Company expenses advertising costs as incurred. Advertising expense is included within sales and marketing expense in the consolidated statements of operations. For the years ended December 31, 2016, 2015 and 2014, advertising expenses were not material. Retirement Savings Plan The Company maintains a defined contribution 401(k) retirement savings plan for its U.S. employees. Each participant in the 401(k) retirement savings plan may elect to contribute a percentage of his or her annual compensation up to a specified maximum amount allowed under U.S. Internal Revenue Service regulations. There were no employer contributions to the 401(k) retirement savings plan for the years ended December 31, 2017, 2016 and 2015. Severance Pay Asset and Liability The Company has recorded a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. The Company’s liability for severance pay is calculated pursuant to Israeli severance pay law based on the most recent salary for the employees multiplied by the number of years of employment, as of the respective balance sheet date. Employees are entitled to one month salary for each year of employment or a portion thereof. The Company’s liability at each respective balance sheet date for all of its Israeli employees is fully accrued in the accompanying consolidated financial statements and is mainly funded through monthly deposits to the employee’s pension and management insurance policies. The carrying value of these policies is recorded as a severance fund asset in the Company’s consolidated balance sheets. The deposited funds may be withdrawn only upon the fulfillment of the obligation pursuant to Israeli severance pay law. The carrying value of the deposited funds is based on the cash surrender value of these policies and includes profits accumulated through the respective balance sheet date. The Company recognized severance expense related to the Israeli severance pay law during the years ended December 31, 2017, 2016 and 2015 of $1.8 million, $1.6 million, and $1.3 million, respectively. Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes. The Company uses the liability method for accounting for deferred income taxes, which requires recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements, but have not been reflected in its taxable income. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets and liabilities are expected to be realized or settled. The Company regularly assesses the likelihood that its deferred income tax assets will be realized from recoverable income taxes or recovered from future taxable income based on the realization criteria set forth in ASC 740. To the extent that the Company believes any amounts are more likely not to be realized, the Company records a valuation allowance to reduce the deferred income tax assets. In the event the Company determines that all or part of the net deferred tax assets are not realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period such determination is made. Similarly, if the Company subsequently realizes deferred income tax assets that were previously determined to be unrealizable, the respective valuation allowance would be reversed, resulting in an adjustment to earnings in the period such determination is made. In addition, the calculation of the Company’s tax liabilities involves addressing uncertainties in the application of complex tax regulations. The Company recognizes and measures potential liabilities based upon criteria set forth in ASC 740. Based upon these criteria, the Company estimates whether, and the extent to which, additional taxes will be due. If payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities may result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. If the Company’s estimate of tax liabilities is less than the amount ultimately assessed, a further charge to expense would result. Significant judgment is required in determining any valuation allowance recorded against deferred income tax assets. In assessing the need for a valuation allowance, the Company considers all available evidence, including past operating results, estimates of future taxable income, and the feasibility of tax planning strategies. In the event that the Company changes its determination as to the amount of deferred income tax assets that could be realized, it will adjust its valuation allowance with a corresponding effect to the provision for income taxes in the period in which such determination is made. Significant judgment is also required in evaluating the Company’s uncertain tax positions under ASC 740 and determining its provision for income taxes. Although the Company believes its reserves for uncertain tax positions are reasonable, no assurance can be given that the final tax outcome of these matters will not be different from that which is reflected in the Company’s historical income tax provisions and accruals. The Company adjusts these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different from the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the effect of reserves for uncertain tax positions and any changes to the reserves that are considered appropriate, as well as the related net interest and penalties, if applicable. The U.S. Tax Cuts and Jobs Act of 2017 (“Tax Act”) was enacted on December 22, 2017. ASC Topic 740, Accounting for Income Taxes, requires companies to recognize the effect of tax law changes in the period of enactment even though the effective date for most provisions is for tax years beginning after December 31, 2017, or in the case of certain other provisions of the law, January 1, 2018.Given the significance of the legislation, the U.S. Securities and Exchange Commission (the "SEC") staff issued Staff Accounting Bulletin ("SAB") No. 118 (SAB 118), which allows registrants to record provisional amounts during a one year “measurement period” similar to that used when accounting for business combinations. However, the measurement period is deemed to have ended earlier when the registrant has obtained, prepared, and analyzed the information necessary to finalize its accounting. During the measurement period, impacts of the law are expected to be recorded at the time a reasonable estimate for all or a portion of the effects can be made, and provisional amounts can be recognized and adjusted as information becomes available, prepared, or analyzed. The Company is still evaluating the provisions of the Tax Reform and amounts reflected in the financial statements for the year ended December 31, 2017 are provisional. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actio

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition	2. Acquisition On December 15, 2016, the Company acquired certain assets and liabilities of Camouflage Software Inc. (“Camouflage”), a private company based in Newfoundland, Canada. Camouflage is a provider of data management, security and data masking solutions. The Company acquired Camouflage for cash consideration of $4.5 million. Approximately $0.6 million of the consideration is a holdback payment commitment due 24 months from the date the acquisition closes. Imperva acquired certain tangible assets and also assumed liabilities of Camouflage. Substantially all of the consideration was allocated to goodwill and intangible assets, such as developed technology, customer relationships and trade name. The acquisition was accounted for in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations, The purchase consideration allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The Company believes that these identified intangible assets will have no residual value after their estimated economic useful lives. The identifiable intangible assets are subject to amortization on a straight-line basis over a seven-year estimated useful life as this best approximates the benefit period related to these assets. The excess of the purchase consideration over the identified tangible and intangible assets, less liabilities assumed, is recorded as goodwill and primarily reflects the value of the synergies expected to be generated from combining the Company’s and the acquired entities’ technology and operations. 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): Acquired Technology $ 1,050 Customer relationships 480 Trade name and other 280 Goodwill 2,476 Total intangible assets acquired 4,286 Other acquired tangible assets 363 Liability assumed (130 ) Fair value of assets acquired $ 4,519 The total purchase consideration 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 Company expensed the related acquisition costs, consisting primarily of legal costs in the amount of $0.1 million in general and administrative expenses. The Company’s management believes that the goodwill represents the synergies expected from combining the acquired technology and operations with those of Imperva. The results of operations related to the Camouflage assets and liabilities have been included in the Company’s consolidated statements of operations from the acquisition date. Pro forma results of operations have not been presented because the acquisition was not material to the Company’s results of operations.

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-Term Investments	3. Cash, Cash Equivalents and Short-Term Investments Cash, cash equivalents and short-term investments consist of the following (in thousands): As of December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 92,030 $ - $ - $ 92,030 Money market funds 84,144 - - 84,144 US government agencies 16,367 - 3 16,364 Total $ 192,541 $ - $ 3 $ 192,538 Short-term investments: Commercial paper $ 699 $ - $ - $ 699 Corporate debt obligations 123,320 - 488 122,832 US government agencies 43,097 - 114 42,983 Bank deposits 480 - 1 479 Total $ 167,596 $ - $ 603 $ 166,993 As of December 31, 2016 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 63,642 $ - $ - $ 63,642 Commercial paper 6,995 - 2 6,993 Money market funds 36,708 - - 36,708 Total $ 107,345 $ - $ 2 $ 107,343 Short-term investments: Commercial paper $ 14,245 $ - $ 8 $ 14,237 Corporate debt obligations 110,062 - 347 109,715 US government agencies 18,998 2 50 18,950 Bank deposits 10,846 1 - 10,847 Total $ 154,151 $ 3 $ 405 $ 153,749 The following table sets forth the cost and estimated fair value of short-term investments based on stated effective maturities as of December 31, 2017 (in thousands): As of December 31, 2017 Estimated Amortized Fair Cost Value Short-term investments: Due in 2018 $ 94,231 $ 93,980 Due in 2019 73,365 73,013 Total $ 167,596 $ 166,993 The Company reviews its short-term investments on a regular basis to evaluate whether or not any security has experienced an other-than-temporary decline in fair value. The Company considers factors such as the length of time and extent to which the market value has been less than the cost, the financial condition and near-term prospects of the issuer and its intent to sell, or whether it is more likely than not the Company will be required to sell, the investment before recovery of the investment’s amortized cost basis. If the Company believes that an other-than-temporary decline exists in one of these securities, the Company writes down these investments to fair value. For debt securities, the portion of the write-down related to credit loss would be recorded to other income (expense), net, in the Company’s condensed consolidated statements of operations. Any portion not related to credit loss would be recorded to accumulated other comprehensive income (loss), which is reflected as a separate component of stockholders’ equity in the Company’s condensed consolidated balance sheets. During the years ended December 31, 2017 and 2016, the Company did not consider any of its investments to be other-than-temporarily impaired. The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands): As of December 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 699 $ - $ - $ - $ 699 $ - Corporate debt obligations 77,715 377 45,117 111 122,832 488 US government agencies 29,093 76 11,461 38 40,554 114 Bank deposits - - 479 1 479 1 $ 107,507 $ 453 $ 57,057 $ 150 $ 164,564 $ 603 As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 14,237 $ 8 $ - $ - $ 14,237 $ 8 Corporate debt obligations 78,821 323 29,689 24 108,510 347 US government agencies 11,451 46 3,496 4 14,947 50 $ 104,509 $ 377 $ 33,185 $ 28 $ 137,694 $ 405

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	4. Fair Value of Financial Instruments The Company evaluates assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. The following table sets forth the Company’s assets and liabilities that were measured at fair value as of December 31, 2017 and 2016, by level within the fair value hierarchy (in thousands): As of December 31, 2017 Level I Level II Level III Fair Financial Assets: Cash equivalents: Money market funds $ 84,144 $ - $ - $ 84,144 US government agencies - 16,364 - 16,364 Short-term investments: Commercial paper - 699 - 699 Corporate debt obligations - 122,832 - 122,832 US government agencies - 42,983 - 42,983 Bank deposits - 479 - 479 Prepaid expenses and other current assets - Forward foreign exchange contracts - 551 - 551 Total financial assets $ 84,144 $ 183,908 $ - $ 268,052 As of December 31, 2016 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Commercial paper $ - $ 6,993 $ - $ 6,993 Money market funds 36,708 - - 36,708 Short-term investments: Commercial paper - 14,237 - 14,237 Corporate debt obligations - 109,715 - 109,715 US government agencies - 18,950 - 18,950 Bank deposits - 10,847 - 10,847 Total financial assets $ 36,708 $ 160,742 $ - $ 197,450 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ - $ 639 $ - $ 639 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 $6.6 million and $5.1 million as of December 31, 2017 and 2016, respectively. The Company’s cash equivalents and short-term investments are classified within Level 1 or Level 2 of the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The types of instruments valued based on quoted market prices in active markets include mutual funds and money market securities. Such instruments are generally classified within Level 1 of the fair value hierarchy. The types of instruments valued based on quoted prices in less active markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset or liability, include U.S. agency securities, investment-grade corporate bonds, term deposits and commercial paper. Such instruments are generally classified within Level 2 of the fair value hierarchy. There were no transfers between Level 1, Level 2 and Level 3 during the years ended December 31, 2017 and 2016.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments	5. Derivative Instruments The Company’s primary objective for holding derivative instruments is to reduce its exposure to foreign currency rate changes. The Company reduces its exposure by entering into forward foreign exchange contracts with respect to operating expenses that are forecast to be incurred in currencies other than U.S. dollars. Substantially all of the Company’s revenue and capital purchasing activities and a majority of its operating expenditures are transacted in U.S. dollars. However, certain operating expenditures are incurred in or exposed to other currencies, primarily the Israeli shekel, the British Pound and the Euro. The Company has established forecasted transaction currency risk management programs to protect against fluctuations in fair value and the volatility of future cash flows caused by changes in exchange rates. The Company’s currency risk management program includes forward foreign exchange contracts designated as cash flow hedges. These forward foreign exchange contracts generally mature within 12 months. The Company does not enter into derivative financial instruments for trading purposes. Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands): Liability as of December 31, 2017 2016 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in prepaid expenses and other current assets (accrued and other current liabilities) $ 66,560 $ 551 $ 60,756 $ (639 ) Gains (losses) on derivative instruments accounted for as hedges and their classification on the consolidated statement of operations, are presented in the following tables (in thousands): Years ended December 31, 2017 2016 2015 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 5,037 $ 1,775 $ 834 Losses recognized in OCI (a) $ (551 ) $ (1,909 ) $ (1,399 ) Gains recognized from accumulated OCI into net loss (b) $ 3,271 $ 257 $ - Losses recognized from accumulated OCI into net loss (b) $ (10 ) $ (347 ) $ (972 ) (a) Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”). (b) Effective portion of cash flow hedges reclassified from accumulated other income (loss), into net loss, of which $499, $(8) and $(107) were recognized within cost of sales for the years ended December 31, 2017, 2016 and 2015, respectively, and $2,762, $(82), and $(865) were recognized within operating expenses for the year ended December 31, 2017, 2016 and 2015, respectively. All amounts are reflected with the respective consolidated statement of operations.

Consolidated Balance Sheet Comp

Consolidated Balance Sheet Components	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Consolidated Balance Sheet Components	6. Consolidated Balance Sheet Components Allowance for Doubtful Accounts The allowance for doubtful accounts is comprised of the following activity (in thousands): Years Ended December 31, 2017 2016 2015 Allowance for doubtful accounts and sales returns reserve, beginning balance $ 1,784 $ 1,438 $ 215 Allowance for doubtful accounts, beginning balance $ 953 $ 1,115 $ 215 Charged to costs and expenses, net of recoveries (334 ) 315 1,044 Deductions (write-offs) (467 ) (477 ) (144 ) Allowance for doubtful accounts, ending balance 152 953 1,115 Sales returns reserve, beginning balance 831 323 Charged to revenue 1,702 1,560 677 Deductions (write-offs) (1,749 ) (1,052 ) (354 ) Sales returns reserve, ending balance 784 831 323 Total allowance for doubtful accounts and sales returns reserve, ending balance $ 936 $ 1,784 $ 1,438 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, 2017 2016 Prepaid expenses $ 6,001 4,980 Skyfence Escrow Fund Receivable 5,000 - Prepaid income taxes 1,674 1,559 Interest receivable 808 758 Derivative asset 551 - Other 860 625 Total prepaid expenses and other current assets $ 14,894 $ 7,922 Property and Equipment, net Property and equipment, net consist of the following (in thousands): As of December 31, 2017 2016 Computers and related equipment $ 35,885 $ 25,285 Office furniture and equipment 3,371 3,228 Leasehold improvements 13,492 11,947 Total property and equipment 52,748 40,460 Less: accumulated depreciation and amortization (27,341 ) (18,964 ) Total property and equipment, net $ 25,407 $ 21,496 Depreciation and amortization expense totaled $10.9 million, $7.5 million and $4.5 million, for the years ended December 31, 2017, 2016 and 2015, respectively. Accrued Compensation and Benefits Accrued compensation and benefits consist of the following (in thousands): As of December 31, 2017 2016 Salary and related benefits $ 8,824 $ 9,588 Accrued vacation 4,453 4,178 Accrued incentive payments 9,636 5,942 Accrued restructuring - 1,132 Total accrued compensation and benefits $ 22,913 $ 20,840 Accrued and Other Current Liabilities Accrued and other current liabilities consist of the following (in thousands): As of December 31, 2017 2016 Accrued expenses $ 7,516 $ 4,616 Derivative liability - 639 Income tax payable 319 435 Short-term deferred rent 844 461 Sales Taxes Payable 2,098 849 Other 640 683 Total accrued and other current liabilities $ 11,417 $ 7,683 Other Liabilities Other long-term liabilities consist of the following (in thousands): As of December 31, 2017 2016 Long-term deferred rent $ 2,070 $ 2,111 Deferred tax liability 333 1,265 Uncertain Tax Positions 3,615 2,446 Other 235 815 Total other liabilities $ 6,253 $ 6,637

Goodwill and Acquired Intangibl

Goodwill and Acquired Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Intangible Assets	7. Goodwill and Acquired Intangible Assets In February 2017, the Company completed the sale of its assets related to the Skyfence cloud access security broker business (“Skyfence”) to Forcepoint LLC and its Israeli subsidiary. The Company allocated goodwill of $1.1 million to the business being disposed of. Additionally, the acquired intangible assets with the carrying value of $4.5 million were derecognized in connection with this transaction. In December 2016, the Company completed the acquisition of Camouflage Software Inc., which $2.5 million was allocated to goodwill and $1.8 million to acquired intangible assets. The Company did not have any goodwill impairments during 2017, 2016 or 2015. The changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016 were as follows (in thousands): 2017 2016 Balance as of January 1 $ 37,448 $ 34,972 Goodwill with acquisition of Camouflage Software Inc. - 2,476 Goodwill disposed with sale of Skyfence (1,059 ) - Balance as of December 31 $ 36,389 $ 37,448 Acquired intangible assets subject to amortization as of December 31, 2017 and 2016 were as follows (in thousands): As of December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Book Value Acquired Technology $ 3,753 $ (1,216 ) $ 2,537 Customer relationships 480 (71 ) 409 Trade name and other 280 (42 ) 238 Total $ 4,513 $ (1,329 ) $ 3,184 As of December 31, 2016 Gross Carrying Amount Accumulated Amortization Net Book Value Acquired Technology $ 11,718 $ (4,085 ) $ 7,633 Customer relationships 480 - 480 Trade name and other 280 - 280 Total $ 12,478 $ (4,085 ) $ 8,393 Amortization expense related to acquired intangible assets was $0.7 million for the year ended December 31, 2017. Acquired intangible assets are amortized over their estimated useful lives of 7 to 10 years. Acquired technology, customer relationships, and trade names and other have weighted-average remaining useful lives from the date of purchase of 6 years for all three categories. As of December 31, 2017, the Company expects amortization expense in future periods to be as follows (in thousands): Acquired Fiscal Year Intangibles 2018 $ 528 2019 528 2020 528 2021 528 2022 528 Thereafter 544 Total expected amortization expense $ 3,184

Other Income (Expense), net

Other Income (Expense), net	12 Months Ended
	Dec. 31, 2017
Other Income And Expenses [Abstract]
Other Income (Expense), net	8. Other Income (Expense), net Other income (expense), net is comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Other Income: Interest income $ 2,792 $ 1,369 $ 701 Foreign currency forward contract gains, net 27 9 - Foreign currency exchange gains, net 1,227 209 5 Total other income 4,046 1,587 706 Other Expense: Skyfence holdback liability accretion - (6 ) (212 ) Foreign currency exchange losses, net (2,138 ) (708 ) (322 ) Bank charges and Other expenses (766 ) (950 ) (574 ) Total other expense (2,904 ) (1,664 ) (1,108 ) Total other income (expense), net $ 1,142 $ (77 ) $ (402 )

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
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 from 2018 through 2023. Future minimum payments under these facility operating leases are as follows as of December 31, 2017 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2018 $ 8,295 $ 687 2019 4,991 - 2020 4,714 - 2021 557 - 2022 309 - Thereafter 87 - Total $ 18,953 $ 687 Rent expense for the Company’s operating leases is recognized on a straight-line basis over the lease term. Rent expense for the years ended December 31, 2017, 2016 and 2015 was $6.6 million, $6.1 million, and $4.6 million, respectively. In connection with leases for office space, the Company received tenant improvement allowances of $0.7 million, $0.3 million and $0.6 million during the years ended December 31, 2016, 2012 and 2010, respectively. The Company has recorded the tenant improvement allowances as a leasehold improvement within property and equipment, net and as deferred rent within other liabilities on the consolidated balance sheets. The deferred rent liability is amortized to rent expense over the term of the lease on a straight-line basis. The leasehold improvements are being amortized to expense over the period from when the improvements were placed into service until the end of their useful life, which is the end of the respective lease term. In addition, certain of the Company’s operating lease agreements for office space also include rent holidays and scheduled rent escalations during the initial lease term. The Company has recorded the rent holidays as a deferred rent within other liabilities on the consolidated balance sheets. The Company recognizes the deferred rent liability and scheduled rent increase on a straight-line basis into rent expense over the lease term commencing on the date the Company takes possession of the lease space. As of December 31, 2017 and 2016 the Company has $2.3 million and $1.9 million, respectively, in restricted cash to secure bank guarantees provided to the lessor. (b) Cancelable Lease Agreement The Company leases motor vehicles under a cancelable operating lease agreement. The Company has an option to cancel the lease agreement, which may result in penalties in a maximum amount of $0.1 million as of December 31, 2017. Motor vehicle lease expenses for the years ended December 31, 2017, 2016 and 2015 were $4.6 million, $2.7 million and $2.4 million, respectively. (c) Purchase Commitments As of both December 31, 2017 and 2016, the Company had purchase commitments of $2.6 million and $3.8 million, respectively, to purchase inventory, trial units, and research and development equipment from its vendors. The purchase commitments result from the Company’s contractual obligation to order or build inventory in advance of anticipated sales. According to the Company’s agreements with its vendors, the Company committed to purchase inventory within six months from the date the inventory arrived at the vendor’s warehouse. (d) Litigation From time to time, the Company may be subject to other legal proceedings and claims in the ordinary course of business. On April 11, 2014, a purported shareholder class action lawsuit was filed in the United States District Court for the Northern District of California against us and certain of our current and former officers. On August 7, 2014, the Court entered an order appointing lead plaintiff and counsel for the purported class. The lead plaintiff filed an amended complaint on October 10, 2014. The lawsuit named us and certain of our current and former officers and purported to bring suit on behalf of those investors who purchased our publicly traded securities between May 2, 2013 and April 9, 2014. The plaintiff alleged that defendants made false and misleading statements about our operations and business and financial results and purported to assert claims for violations of the federal securities laws. The amended complaint sought unspecified compensatory damages, interest thereon, costs incurred in the action and equitable/injunctive or other relief. On January 6, 2015, defendants filed a motion to dismiss the amended complaint. On September 17, 2015, the Court granted defendants’ motion to dismiss with leave to amend. The lead plaintiff filed an amended complaint on January 13, 2016, again naming the same current and former officers, alleging false and misleading statements about our operations and business and financial results, and seeking the same relief. On February 10, 2016, defendants filed a motion to dismiss the amended complaint. On May 16, 2016, the Court granted the motion in part and denied the motion in part. On September 7, 2016, defendants filed their operative answer to the amended complaint. In July 2017, with the help of a mediator, the parties reached an agreement in principle to settle the action. On October 11, 2017, the Court issued an order granting lead plaintiff’s motion for preliminary approval of the settlement. The Court issued an order granting final approval of the settlement, which was funded entirely by the Company’s insurance carriers, on January 31, 2018. On September 1, 2017, a purported class action lawsuit was filed against us and others, alleging that current, former and prospective employees are entitled to monetary damages for violations of the notice provisions of the Fair Credit Reporting Act and similar California laws governing background checks. The lawsuit was filed in the Superior Court for San Mateo County and on September 29, 2017, we removed the action to the U.S. District Court for the Northern District of California. On November 6, 2017, we filed a motion to dismiss the action. On September 1, 2017, the same plaintiff filed a second purported class action lawsuit against us and others in the Superior Court for San Mateo County, alleging, among other claims, violation of California wage and hour, overtime, meal break and rest break rules and regulations, failure to provide for proper expense reimbursements, failure to maintain accurate and complete payroll records, failure to pay commissions and unfair business practices, and seeking unspecified monetary damages, injunctive relief and attorneys’ fees. We filed an answer to the complaint on September 29, 2017. On November 3, 2017, the plaintiff amended his complaint to assert an additional representative Private Attorney General Act (PAGA) claim against us. On December 6, 2017, we filed an answer to the amended complaint. The plaintiff’s motion for class certification is due on or before September 7, 2018. Our opposition is due on or before November 6, 2018. Any reply is due on or before November 20, 2018. A hearing on the motion for class certification has been set for Friday, December 7, 2018. In addition, the Company has received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of their intellectual property rights. Future litigation may be necessary to defend the Company, its channel partners and its customers by determining the scope, enforceability and validity of third-party proprietary rights or to establish its proprietary rights. In the opinion of management, liabilities associated with these claims, while possible, are not probable at this time, and therefore the Company has not recorded any accrual for them as of December 31, 2017 and 2016. Further, any possible range of loss cannot be reasonably estimated at this time. The ultimate outcome of any litigation is uncertain and, regardless of outcome, litigation can have an adverse impact on the Company because of defense costs, potential negative publicity, diversion of management resources and other factors. Accordingly, there can be no assurance that existing or future legal proceedings arising in the ordinary course of business or otherwise will not have a material adverse effect on the Company’s business, consolidated financial position, results of operations or cash flows. (e) Indemnification Under the indemnification provisions of its standard sales contracts, the Company agrees to defend its channel partners and end customers against third-party claims asserting infringement of certain intellectual property rights, which may include patents, copyrights, trademarks, or trade secrets, and to pay judgments and settlements entered on such claims. The Company’s exposure under these indemnifications provisions is generally limited to the total amount paid under the agreement. However, certain agreements included indemnification provisions that could potentially expose the Company to losses in excess of the amount received under the agreement. To date, there have been no claims under such indemnification provisions. Accordingly, the Company has not recorded a liability on its consolidated balance sheets for these indemnification provisions. In addition to the foregoing, the Company maintains director and officer insurance, which may cover certain liabilities arising from its obligation to indemnify its directors and officers.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Capital Stock	10. Capital Stock Common Stock Reserved for Issuance The Company had reserved shares of common stock, on an as if converted basis, for issuance as follows: As of December 31, 2017 2016 Issuance in connection with outstanding stock options 997,674 1,570,765 Issuance in connection with restricted stock units outstanding 2,353,315 1,994,790 Reserved for future stock option and restricted stock unit grants 2,572,922 2,464,181 Reserved for future issuance under the employee stock purchase plan 1,298,442 1,161,396 7,222,353 7,191,132 Preferred Stock Our board of directors is authorized, subject to any limitations prescribed by law, without stockholder approval, to issue from time to time up to an aggregate of 5,000,000 shares of preferred stock, in one or more series, each series to have such rights and preferences, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences as the Company’s board of directors determines. The rights of the holders of common stock will be subject to, and may be adversely affected by, the rights of holders of any preferred stock that may be issued in the future. The Company currently has no shares of preferred stock outstanding and the Company has no present plans to issue any shares of preferred stock. Stock Plans (a) 2003 Stock Plan During 2003, the Board of Directors adopted the 2003 Stock Plan (the “2003 Plan”), which allowed for the grant of both incentive stock options and non-qualified stock options and the direct award or sale of shares of the Company’s common stock (including restricted common stock) to officers, employees, directors, consultants and other key persons. In connection with the Company’s initial public offering, which was completed in November 2011, the Board of Directors determined not to grant any further awards under the 2003 Plan upon completion of the public offering. The 2011 Stock Option and Incentive Plan (the “2011 Plan”) replaced the 2003 Plan in November 2011. Under the 2003 Plan, incentive stock options could have been granted to employees with exercise prices of no less than the fair value of the common stock on the grant date, and non-qualified options could have been granted to employees, directors, or consultants at exercise prices of no less than 85% of the fair value of the common stock on the grant date, as determined by the Board of Directors. If, at the time the Company granted an option, the optionee directly or by attribution owned stock possessing more than 10% of the total combined voting power of all classes of stock of the Company, the option price had to have been at least 110% of the fair value. Options granted under the 2003 Plan generally expire no later than ten years from the date of grant and, in general, vest four years from the date of grant. (b) 2011 Stock Option and Incentive Plan In September 2011, the Board of Directors adopted the 2011 Plan which was subsequently approved by the Company’s stockholders. The 2011 Plan replaced the 2003 Plan and the Company no longer grants awards under the 2003 Plan. The Company initially reserved a total of 1,000,000 shares of common stock for issuance under the 2011 Plan. In addition, 955,568 reserved but unissued shares under the 2003 Stock Plan were added to the number of shares reserved for issuance under the 2011 Plan. The 2011 Plan also provided that the number of shares reserved and available for issuance under the plan would automatically increase each January 1, beginning in 2012 and ending in 2015, by 4% of the outstanding number of shares of common stock on the immediately preceding December 31. The last automatic increase occurred on January 1, 2015. In April 2017 and May 2016, the Company’s stockholders approved an increase to the share reserve under the 2011 Plan by 850,000 shares and 1,300,000 shares respectively. The 2011 Plan permits the granting of incentive stock options, non-qualified stock options, restricted stock units (“RSUs”), stock appreciation rights, restricted shares of common stock and performance share awards. The exercise price of stock options may not be less than 100% of the fair market value of the common stock on the date of grant. Options granted pursuant to the 2011 Plan generally expire no later than ten years from the date of grant. The Company also grants RSUs. RSUs granted to new hires and merit grants to existing employees generally vest over a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter. Additionally, from time to time, the Company grants performance-based RSUs (“PRSUs”). The PRSUs provide for a target number of shares that generally vest over three years including a one year performance period and two years of service-based vesting. During the quarters ended March 31, 2017 and June 30, 2017, the Company granted PRSUs to its executives to align with the Company’s pay-for-performance philosophy. An aggregate of 46,619 PRSUs were issued to executives during the quarter ended March 31, 2017, based on the Company’s achievement against its annual contract value of subscription bookings target for fiscal 2016 and achieving total operating expenses for 2016 that were 110% or less of the internal operating plan. The PRSUs are subject to vest over a two-year period and vest quarterly through February 15, 2019. For fiscal 2017, the PRSUs vest contingent upon the Company’s achievement of an annual contract value of subscription bookings target for fiscal 2017 and total operating expenses for 2017 that are at 110% or less of the internal operating plan. The amount of PRSUs earned was an aggregate of 74,621 PRSUs to be issued to executives during the quarter ending March 31, 2018. (c) 2011 Employee Stock Purchase Plan In September 2011, the Board of Directors adopted the 2011 Employee Stock Purchase Plan (the “ESPP”) which was subsequently approved by the Company’s stockholders. The ESPP took effect on November 8, 2011, the effective date of the registration statement for the Company’s initial public offering. The ESPP permits eligible employees to acquire shares of the Company’s common stock by accumulating funds through periodic payroll deductions of up to 15% of base salary. Each offering period may run for no more than 24 months and consist of no more than five purchase periods. The purchase price for shares of the Company’s common stock purchased under the ESPP will be 85% of the lesser of the fair market value of the Company’s common stock on the first day of the offering period or the last trading day of the applicable purchase period within that offering period. The Company initially reserved a total of 500,000 shares of common stock for future issuance under the ESPP. The number of shares reserved for issuance under the ESPP increases automatically on January 1 of each of the first eight years commencing in 2012 by the number of shares equal to 1% of the Company’s total outstanding shares as of the immediately preceding December 31. The Board of Directors or compensation committee may reduce the amount of the increase in any particular year. No more than 20,000,000 shares of common stock may be issued under the ESPP and no other shares may be added to the ESPP without the approval of the Company’s stockholders. On January 1, 2017, the share reserve under the 2011 Employee Stock Purchase Plan was automatically increased by 330,889 shares. (d) Inducement Stock Option Plans and Agreement and Inducement Restricted Stock Unit Plans and Agreement In August 2014 and August 2015, the Compensation Committee of the Board of Directors adopted Inducement Stock Option Plans and Agreements (the “Inducement Option Plans”) and Inducement Restricted Stock Unit Plans and Agreements (the “Inducement RSU Plans”), in each case created as employment inducement awards. In accordance with the terms of the Inducement Option Plans, the Company issued options to purchase 290,000 shares of the Company’s common stock at an exercise price equal to the fair market value of a share of the Company’s common stock on the dates of grant of the options. The options, which have a ten-year term, vest at the rate of 25% of the shares on each of the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the option vesting each quarter thereafter so long as the participant has not been terminated. In accordance with the terms of the Inducement RSU Plans, the Company issued RSUs representing an aggregate of 290,000 shares of the Company’s common stock. The RSUs, which expire following settlement, vest at the rate of 25% of the shares on each of the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the RSU vesting each quarter thereafter so long as the participant has not been terminated. (e) 2015 Equity Inducement Plan In October 2015, the Board of Directors adopted the 2015 Equity Inducement Plan, a non-stockholder approved plan that provides for the granting of stock options and RSUs as employment inducement awards and in connection with acquisitions, subject to compliance with applicable securities laws and stock exchange requirements for such plans. The Company has reserved 100,000 shares of common stock for issuance under the 2015 Equity Inducement Plan. No awards have been made under the 2015 Equity Inducement Plan and the entire reserve remains available for grant. Under the terms of the 2015 Equity Inducement Plan, the exercise price of stock options may not be less than 100% of the fair market value of common stock on the date of grant and generally expire no later than ten years from the date of grant. In August 2017 and December 2017, the Board of Directors amended the Equity Inducement Plan to increase the number of shares available for grant by 100,000 shares and 250,000 shares, respectively. (f) Option Activity The following table summarizes option activity under the Plans and related information: Options Outstanding Weighted- Average Remaining Number of Shares Weighted Average Exercis e Contractual Term (in years) Aggregate Intrinsic Value (i n Outstanding - December 31, 2014 2,244,363 $ 33.83 8.27 $ 38,457 Granted 696,971 $ 49.20 Exercised or released (636,424 ) $ 29.44 Cancelled or forfeited (355,821 ) $ 42.00 Outstanding - December 31, 2015 1,949,089 $ 39.27 8.09 $ 47,480 Granted 48,260 $ 53.59 Exercised or released (184,737 ) $ 29.24 Cancelled or forfeited (241,847 ) $ 47.35 Balances - December 31, 2016 1,570,765 $ 39.64 6.90 $ 9,226 Granted - $ - Exercised or released (415,022 ) $ 30.02 Cancelled or forfeited (158,069 ) $ 50.79 Balances - December 31, 2017 997,674 $ 41.87 5.72 $ 5,689 Vested and expected to vest - December 31, 2017 997,674 $ 41.87 5.72 $ 5,689 Exercisable - December 31, 2017 779,746 $ 41.11 5.34 $ 4,958 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $39.70 of the Company’s common stock on December 31, 2017 Additional information regarding the Company’s stock options outstanding and exercisable as of December 31, 2017 is summarized below: Options Outstanding Options Exercisable Exercise Prices Number of Stock Options Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price per Share Shares Subject to Stock Options Weighted Average Exercise Price per Share $0.02 to $10.70 101,276 3.24 $ 8.26 101,276 $ 8.26 $10.71 to $29.10 77,236 5.18 $ 25.30 60,439 $ 24.51 $29.11 to $32.50 93,747 6.53 $ 29.37 42,932 $ 29.50 $32.51 to $35.50 65,474 4.37 $ 34.07 64,499 $ 34.09 $35.51 to $54.50 320,119 6.73 $ 43.20 232,819 $ 43.21 $54.51 to $61.50 209,260 4.92 $ 55.14 190,385 $ 55.02 $61.51 to $69.50 111,802 6.74 $ 65.19 76,855 $ 64.79 $69.51 to $77.50 18,760 7.52 $ 71.72 10,541 $ 71.69 997,674 5.72 $ 41.87 779,746 $ 41.11 (g) RSU Activity A summary of RSU activity for the year ended December 31, 2017, is as follows: Number of Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - December 31, 2015 1,898,025 $ 49.53 Granted 1,160,062 $ 47.42 Granted, performance RSUs 273,900 $ 51.55 Released (884,349 ) $ 43.04 Cancelled or forfeited (452,848 ) $ 49.86 Unvested - December 31, 2016 1,994,790 $ 51.42 Granted 1,489,189 $ 43.36 Granted, performance RSUs 301,900 $ 41.96 Released (749,845 ) $ 47.18 Cancelled or forfeited (682,719 ) $ 48.09 Unvested - December 31, 2017 2,353,315 $ 47.42 (h) Stock-Based Compensation Expense The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2017 2016 2015 Cost of revenue $ 5,290 $ 4,664 $ 3,862 Research and development 12,187 14,711 13,831 Sales and marketing 14,696 20,510 16,717 General and administrative 13,822 17,131 16,554 Restructuring charges 675 5,859 - Total stock-based compensation expense $ 46,670 $ 62,875 $ 50,964 (i) Determining the Fair Value of RSUs, Performance RSUs, Stock Options, and ESPP The fair value of RSUs is determined using the closing price of the Company’s stock on the date of grant. Compensation is recognized on a straight-line basis over the requisite service period of each grant. The fair value of RSUs granted to employees which have multiple performance conditions is determined by the Company using a Monte Carlo simulation model. The key inputs used were the Company’s stock price on the date of grant, the expected volatility, the risk free interest rate and a revenue forecast. The Company updates the estimated expense, at the end of each reporting period. The expense is recognized on an accelerated basis over the requisite service period, which is generally the vesting period of the respective awards. For performance based RSUs granted to employees which only have performance conditions, we recognized expense based on our best estimate of number of awards which are expected to vest upon achievement of performance conditions. We revisit this estimate periodically. The fair value of each stock option and ESPP grant to employees was determined by the Company and its board of directors using the Black-Scholes option-pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment to determine. Expected Term — The expected term represents the period that the Company’s stock-based awards are expected to be outstanding. The expected term is derived from historical data on employee exercises and post-vesting employment termination behavior taking into account the contractual life of the award. For ESPP grants, the expected term is based on the length of the offering period, which is six months. Expected Volatility —The expected volatility was based on our historical volatilities. The volatility is over a period equal to the expected terms of the stock option grants and the offering period for employee stock purchase plan. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero coupon U.S. Treasury notes with maturities approximately equal to the grant’s expected term. Expected Dividend — The Company has never paid dividends and does not expect to pay dividends. A summary of the weighted-average assumptions is as follows: Years Ended December 31 2017 2016 2015 Stock option grants: Dividend rate - 0 % 0 % Risk-free interest rate - 1.4 % 1.8 % Expected term (in years) - 6.0 6.1 Expected volatility - 58 % 49 % ESPP grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 1.3 % 0.5 % 0.4 % Expected term (in years) 0.5 0.5 0.5 Expected volatility 49 % 58 % 65 % The Company did not issue stock option grants for the year ended December 31, 2017. The weighted-average grant date fair value of the Company’s stock options granted during the years ended December 31, 2016 and 2015 was $29.23, and $23.75 per share, respectively. The aggregate grant date fair value of the Company’s stock options granted to employees during the years ended December 31, 2016 and 2015 was $1.4 million, and $16.6 million, respectively. The aggregate grant date fair value of the Company’s stock options vested during the years ended December 31, 2016, and 2015 was $11.9 million, and $11.7 million, respectively. The fair value of the Company’s RSUs vested during the year ended December 31, 2017, 2016 and 2015 was $33.2 million, $38.1 million and $31.4 million, respectively. The aggregate intrinsic value of options exercised under the Plans was $6.2 million, $2.5 million, and $21.6 million for the years ended December 31, 2017, 2016 and 2015, respectively. The aggregate intrinsic value of options exercised is calculated as the difference between the fair market value of the Company’s common stock on the date of the exercise and the exercise price of each option. As of December 31, 2017, total compensation cost related to unvested stock-based awards granted to employees under the Plans, but not yet recognized, was $83.7 million. As of December 31, 2017, this cost will be amortized to expense over a weighted-average remaining period of 2.6 years. Future option grants will increase the amount of compensation expense to be recorded in these periods. Net cash proceeds from the exercise of stock options and the issuance of common stock in connection with the employee stock purchase plan were $9.5 million, $2.4 million, and $12.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. There was no capitalized stock-based compensation cost during the years ended December 31, 2017, 2016 and 2015. Recognized stock-based compensation tax benefits during the year ended December 31, 2016 and 2015 was $0.1 million and $0.2 million, respectively. There was no stock-based compensation tax benefits recognized during the year ended December 31, 2017. (j) Follow-On Public Offering In March 2015, the Company completed a follow-on public offering whereby the Company sold 3,450,000 shares of common stock at a price of $39.00 per share, for aggregate net proceeds of $127.9 million, after deducting underwriting discounts, commissions and other offering costs of approximately $6.7 million.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	11. Accumulated Other Comprehensive Income (Loss) The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands): Years ended December 31, 2017 2016 2015 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,065 ) $ (413 ) $ (1,478 ) $ (1,021 ) $ (310 ) $ (1,331 ) $ (1,428 ) $ (61 ) $ (1,489 ) Other comprehensive income (loss) before reclassifications 4,486 (202 ) 4,284 (134 ) (103 ) (237 ) (565 ) (249 ) (814 ) Amounts reclassified to net loss (3,261 ) - (3,261 ) 90 - 90 972 - 972 Change in other comprehensive income (loss) 1,225 (202 ) 1,023 (44 ) (103 ) (147 ) 407 (249 ) 158 Balance at December 31 $ 160 $ (615 ) $ (455 ) $ (1,065 ) $ (413 ) $ (1,478 ) $ (1,021 ) $ (310 ) $ (1,331 ) The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the years 2017, 2016, and 2015 (in thousands): Year ended December 31, 2017 2016 2015 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ 4,486 $ - $ 4,486 $ (134 ) $ - $ (134 ) $ (565 ) $ - $ (565 ) Reclassification adjustments 1 (3,261 ) - (3,261 ) 90 - 90 972 - $ 972 Unrealized gains (losses) on cash flow hedges, net 1,225 - 1,225 (44 ) - (44 ) 407 - 407 Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ (202 ) - (202 ) $ (103 ) - (103 ) $ (249 ) - (249 ) Unrealized gains (losses) on investments: (202 ) - (202 ) (103 ) - (103 ) (249 ) - (249 ) Other comprehensive income (loss) $ 1,023 $ - $ 1,023 $ (147 ) $ - $ (147 ) $ 158 $ - $ 158 1 Refer to Note 5 for the affected line items in the consolidated statement of operations

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The Company’s geographical breakdown of its loss before provision for income taxes is as follows (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ 20,331 $ (72,139 ) $ (50,892 ) Foreign 2,999 3,032 2,692 Loss before provision for taxes $ 23,330 $ (69,107 ) $ (48,200 ) The components of the provision for income taxes are as follows (in thousands): Years Ended December 31, 2017 2016 2015 Current Federal $ - $ - $ - State 56 62 34 Foreign 2,139 1,654 857 Total current provision 2,195 1,716 891 Deferred Federal 4 130 63 State 13 6 (1 ) Foreign (1,751 ) (680 ) (271 ) Total deferred provision (1,734 ) (544 ) (209 ) Total $ 461 $ 1,172 $ 682 Reconciliation of the provision for income taxes at the statutory rate to the Company’s provision for income tax is as follows (in thousands): Years Ended December 31, 2017 2016 2015 Tax benefit at federal statutory tax rate $ 7,929 $ (23,496 ) $ (16,388 ) Tax benefit at state statutory tax rate 67 (1,008 ) (499 ) Foreign tax rate differential (123 ) 57 (826 ) Change in federal statutory tax rate and valuation allowance under U.S. Tax Reform (185 ) - - Losses not benefitted/(benefitted) (15,440 ) 17,701 9,738 Subsidiary earnings taxed in the US 717 - - Meals and entertainment 309 222 44 Stock compensation 6,006 7,857 8,492 Foreign exchange (gains) and losses, net (776 ) - - Reserve for tax exposure 1,893 - - Nondeductible expenses and other 64 (161 ) 121 Provision for income taxes $ 461 $ 1,172 $ 682 The U.S. Tax Cuts and Jobs Act of 2017 (“Tax Act”) was enacted on December 22, 2017. ASC Topic 740, Accounting for Income Taxes, requires companies to recognize the effect of tax law changes in the period of enactment even though the effective date for most provisions is for tax years beginning after December 31, 2017, or in the case of certain other provisions of the law, January 1, 2018. Given the significance of the legislation, the U.S. Securities and Exchange Commission (the "SEC") staff issued Staff Accounting Bulletin ("SAB") No. 118 (SAB 118), which allows registrants to record provisional amounts during a one year “measurement period” similar to that used when accounting for business combinations. However, the measurement period is deemed to have ended earlier when the registrant has obtained, prepared, and analyzed the information necessary to finalize its accounting. During the measurement period, impacts of the law are expected to be recorded at the time a reasonable estimate for all or a portion of the effects can be made, and provisional amounts can be recognized and adjusted as information becomes available, prepared, or analyzed. The Company is still evaluating the provisions of the Tax Reform and amounts reflected in the financial statements for the year ended December 31, 2017 are provisional. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Reform Act. The accounting is expected to be completed in 2018. The Tax Act reduces the U.S. statutory tax rate from 35% to 21% for years after 2017. Accordingly, we have remeasured our U.S. deferred tax assets and liabilities as of December 31, 2017 to reflect the reduced rate that will apply in future periods when these deferred taxes will reverse, resulting in a reduction of our net deferred tax assets, by approximately $24.9 million, which is offset by the change in valuation allowance by $25.1 million. The net impact of $0.2 million of deferred tax benefit is principally related to the remeasurement of our deferred tax liabilities associated with indefinite-lived intangible assets that are deemed to reverse at the new 21% tax rate. Absent this deferred tax liability, we are in a net deferred tax asset position that is offset by a full valuation allowance. The Tax Act also includes a one-time mandatory repatriation transition tax on the net accumulated earnings and profits of a U.S. taxpayer’s foreign subsidiaries. We have not yet completed the analysis of the earnings and profits of our foreign subsidiaries. However, we estimate that, as a result of foreign tax credits and net operating loss carryforward available to the Company, the impact of the one-time mandatory repatriation tax would not be material. The Tax Act includes numerous provisions, including the repatriation provisions that would have significant impact of our U.S. deferred tax assets, which are generally subject to a full valuation allowance. Although we have made a reasonable estimate of the gross amounts of the deferred tax assets disclosed, a final determination of the Tax Act’s impact on the deferred tax assets and related valuation allowance requirements remain incomplete pending a full analysis of the provisions and their interpretations. Other significant provisions that are not yet effective but may impact income taxes in future years include: an exemption from U.S. tax on dividends of future foreign earnings, a limitation of the utilization of net operating losses generated after fiscal 2018 to 80 percent of taxable income, and a minimum tax on certain foreign earnings in excess of 10 percent of the foreign subsidiaries tangible assets (i.e., global intangible low-taxed income or “GILTI”). We are still evaluating whether to make a policy election to treat the GILTI tax as a period expense or to provide U.S. deferred taxes on foreign temporary differences that are expected to generate GILTI income when they reverse in future years. Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2017 2016 Deferred tax assets: Reserves and accruals $ 2,014 $ 2,817 Deferred revenue 6,466 10,379 Stock-based compensation 3,747 7,361 Net operating loss carryforwards 35,404 47,452 Loss on OCI 231 370 Depreciation and amortization 565 721 Other (3 ) 67 Gross deferred tax assets 48,424 69,167 Valuation allowance (46,125 ) (68,227 ) Total deferred tax assets 2,299 940 Deferred tax liabilities: Stock-based compensation - (21 ) Depreciation and amortization (610 ) (964 ) Total deferred tax liabilities (610 ) (985 ) Net deferred tax liability $ 1,689 $ (45 ) Recognition of deferred tax assets is appropriate when realization of these assets is more likely than not. Based upon the weight of available evidence, which includes the Company’s historical operating performance and the recorded cumulative net losses in all prior fiscal periods, the Company has provided a full valuation allowance against its U.S. deferred tax assets and Imperva Israel net operating loss generated. The Company’s valuation allowance (decreased) increased by ($22.1) million, $14.8 million, and $13.0 million in the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, the Company had U.S. federal and state net operating loss carryforwards of approximately $142.9 million and $70.9 million, respectively. The U.S. federal net operating loss carryforwards will expire at various dates beginning in 2022 through 2037 if not utilized. Most state net operating loss carryforwards will expire at various dates beginning in 2018 through 2037. Net operating loss carryforwards reflected above may be subject to limitations due to ownership changes as provided in the Internal Revenue Code and similar state provisions. The Company has not provided U.S. income tax on certain foreign earnings that are deemed to be indefinitely invested outside the U.S. For fiscal years 2017, 2016, and 2015 the amount of accumulated unremitted earnings from the Company’s foreign subsidiaries is approximately $20.5 million, $9.7 million and $13.6 million, respectively. The amount of taxes attributable to the undistributed earnings is not practicably determinable. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2017 2016 2015 Balance at January 1 $ 2,282 $ 1,154 $ 672 Additions based on tax positions taken during the current period 2,047 761 401 Reductions based on tax positions taken during the prior period (28 ) (42 ) (50 ) Additions based on tax positions taken during a prior period - 409 131 Decrease related to lapse of applicable statute of limitations (181 ) - - Balance at December 31 $ 4,120 $ 2,282 $ 1,154 As of December 31, 2017, 2016 and 2015, the Company had gross unrecognized tax benefits of approximately $4.1 million, $2.3 million and $1.2 million, respectively, all of which would impact the effective tax rate if recognized. While it is often difficult to predict the final outcome of any particular uncertain tax position, the Company does not believe that the amount of unrecognized tax benefits will change significantly in the next twelve months. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in its income tax provision. For the years ended December 31, 2017 and 2016, the Company accrued interest of $0.1 million and $0.2 million in income tax expense, respectively. The Company's material income tax jurisdictions are the United States (federal), California and Israel. The Israeli Tax Authorities have now settled the audit of income tax returns of the Israeli subsidiary for the tax years 2006 through 2010. As a result of net operating loss carryforwards, the Company is subject to audit for tax years 2002 and forward for federal purposes and 2008 and forward for California purposes. The Israeli Tax Authorities have settled the audit of income tax returns of the Israeli subsidiaries for the tax years 2006 through 2010. The Israeli tax authorities issued assessment orders to court for 2011 and 2012 tax years. Tax years 2013 onwards are open for examination. The Company's Israeli subsidiaries ("Israeli subsidiaries") research and development intercompany services activity ("R&D activity") have a "Beneficiary Enterprise" status for a separate investment program that was elected by the Israel subsidiaries starting 2012 under the Law for Encouragement of Capital Investments, 1959 (the "Investments Law), amended from time to time. The entitlement to the above benefits is conditional upon the Israeli subsidiaries fulfilling the conditions stipulated by the Investments Law and regulations published there under.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	13. Segment Information The Company operates its business in one operating segment, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises. Operating segments are defined as components of an enterprise that engage in business activities for which separate financial information is available and evaluated by the chief operating decision maker in deciding how to allocate resources and assessing performance. The chief operating decision maker is the Company’s Chief Executive Officer. The Company’s services revenue was comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Maintenance and support $ 91,300 $ 80,007 $ 66,380 Professional services and training 13,918 13,693 14,084 Subscriptions 119,376 83,957 46,271 Total net services revenue $ 224,594 $ 177,657 $ 126,735 The Company’s revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands): Years Ended December 31, 2017 2016 2015 United States $ 146,215 $ 143,607 $ 141,225 EMEA 63,884 50,838 47,429 APAC 63,959 48,391 30,180 Other 47,658 21,619 15,464 Total net revenue $ 321,716 $ 264,455 $ 234,298 The following table presents long-lived assets by location (in thousands): As of December 31, 2017 2016 2015 United States $ 23,697 $ 20,525 $ 9,913 Israel 4,640 9,344 10,224 Other 254 20 18 Total long-lived assets $ 28,591 $ 29,889 $ 20,155

Net Income (Loss) per Share

Net Income (Loss) per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income (Loss) per Share	14. Net Income (Loss) per Share Basic and diluted net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding during the period. The computation of net income (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. Diluted earnings per share is calculated using our weighted-average outstanding common shares including the dilutive effect of stock awards as determined under the treasury stock method. In periods when the Company recognizes a net loss, the Company excludes the impact of outstanding stock awards from the diluted loss per share calculation as their inclusion would have an antidilutive effect. The table below shows the reconciliation of the basic and diluted shares: Years Ended December 31, 2017 2016 2015 Weighted average number of shares outstanding: Basic 33,724 32,284 29,849 Dilutive effects of: Employee stock options, RSU’s and share based payment awards issued to employees 514 - - Diluted 34,238 32,284 29,849 The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock (in thousands, except per share amounts): Years Ended December 31, 2017 2016 2015 Net income (loss) $ 22,869 $ (70,279 ) $ (48,882 ) Shares used in computing earnings Basic 33,724 32,284 29,849 Diluted 34,238 32,284 29,849 Earnings per share: Basic $ 0.68 $ (2.18 ) $ (1.64 ) Diluted $ 0.67 $ (2.18 ) $ (1.64 ) The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive: Years Ended December 31, 2017 2016 2015 Stock options to purchase common stock 259,744 1,570,765 1,949,089 Restricted stock units for common stock 95,794 1,994,790 1,898,025 Restricted stock issued in connection with Skyfence acquisition - 110,897 118,961

Disposition of Business

Disposition of Business	12 Months Ended
	Dec. 31, 2017
Discontinued Operations And Disposal Groups [Abstract]
Disposition of Business	15. Disposition of Business On February 23, 2017, the Company completed the sale of the assets of its Skyfence cloud access security broker business (“Skyfence”) to Forcepoint LLC and its Israeli subsidiary for consideration of approximately $40 million in cash. Of the total consideration, approximately $5.0 million was remitted directly to escrow to secure the Company’s indemnification obligations. The escrow will be released in June 2018. This escrowed amount is recorded in prepaid expenses and other current assets on our consolidated balance sheet as of December 31, 2017, and represents a noncash item in our consolidated statement of cash flows. As a result of the sale, the Company recognized a gain of $35.9 million during the first quarter of 2017 included in gain on sale of Skyfence in our condensed consolidated statement of operations. The following table presents the carrying amounts of Skyfence immediately preceding the disposition on February 23, 2017: (dollars Assets Prepaid and other current assets 46 Property and equipment, net 219 Goodwill 1,058 Acquired intangible assets, net 4,496 Total assets $ 5,819 Liabilities: Accounts payable $ 104 Accrued and other current liabilities 117 Deferred revenue 1,454 Total liabilities $ 1,675 The Company evaluated the disposition of Skyfence and determined it did not meet the criteria for classification as a discontinued operation and determined that the disposition is not expected to have a material impact to our quarterly consolidated operating loss and net income. However, the Company determined that the disposition does represent an individually significant component of our business. The following table presents certain amounts related to Skyfence in our consolidated results of operations through its disposal on February 23, 2017: Years Ended December 31, 2017 2016 (dollars in thousands) Operating loss $ (3,567 ) $ (24,693 ) Loss before taxes (3,648 ) $ (24,693 ) Net loss (3,659 ) (24,693 )

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	16. Subsequent Event In January 2018, we implemented a restructuring plan to improve customer experiences, fuel product innovation and increase operational effectiveness. We expect to incur restructuring charge during the first quarter of 2018 of $2.3 million to $2.9 million, substantially all of which are for cash severance costs. These actions are expected to be substantially completed by the end of the first quarter of 2018 and we do not expect material costs associated with the activity in future periods.

The Company and Summary of Si24

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Business	Business Imperva, Inc. (together with its subsidiaries, the “Company”) was incorporated in April 2002 in Delaware. The Company is headquartered in Redwood Shores, California and has subsidiaries located throughout the world including Israel, Asia, Europe and North America. The Company is engaged in the development, marketing, sales, service and support of cyber-security solutions that protect data and applications on-premises, in the cloud, and across hybrid environments.
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include all adjustments necessary for the fair presentation of the Company’s consolidated financial position, results of operations and cash flows for the periods presented. The consolidated financial statements include the accounts of Imperva Inc., and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Segment Information	Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company has one operating segment, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications, whether in the cloud or on premises.
Use of Estimates	Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Such management estimates include the fair value of accounts receivable, inventory, intangible assets and goodwill, useful lives of intangible assets and property and equipment, and assumptions used in the calculation of revenue, income taxes and stock-based compensation, among others. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts such estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates.
Concentration of Supply Risk	Concentration of Supply Risk The Company relies on a single third party to manufacture its hardware appliances, and purchases its hardware appliances through such third party’s value-added resellers. Quality or performance failures of the Company’s products or changes in the Company’s suppliers’ financial or business condition could disrupt the Company’s ability to supply quality products to its customers and thereby have a material adverse effect on its business and consolidated financial statements.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash, cash equivalents, short-term investments, restricted cash and derivative financial instruments. The Company’s cash, cash equivalents, short-term investments and restricted cash are invested in high-quality instruments with banks and financial institutions located in the United States and Israel. Such deposits may be in excess of insured limits provided on such deposits. The Company uses derivative financial instruments to manage exposures to foreign currency risks. The Company’s derivatives expose it to credit risk to the extent that the counterparty may be unable to meet the terms of the agreement. The Company seeks to mitigate such risk by limiting its counterparties to those with high or investment-grade credit ratings. The Company does not require collateral under these agreements and has not historically experienced any losses due to credit risk or lack of performance by counterparties.
Derivative Financial Instruments	Derivative Financial Instruments The Company uses forward foreign currency exchange contracts to reduce its exposure to foreign currency rate changes for operating expenses that are forecasted to be incurred in currencies other than U.S. dollars. The Company records all of its derivative instruments at their gross fair value on the consolidated balance sheets. The Company classifies its cash flows from derivative financial instruments as operating activities. The accounting for changes in the fair value of a derivative instrument depends on whether the instrument has been designated and qualifies as a cash flow hedge for accounting purposes. For forward foreign currency exchange contracts that are designated and qualify as cash flow hedges, the effective portion of the gain or loss resulting from changes in the fair value of the derivative instruments is accounted for in accumulated other comprehensive income (loss) (“AOCI”) in the consolidated statements of stockholders’ equity and reclassified into operating expenses in the consolidated statements of operations in the period or periods during which the hedged transaction affects earnings. As of December 31, 2017, the Company estimated that $0.6 million of net derivative loss included in accumulated other comprehensive income (loss) will be reclassified into earnings within the next 12 months. The ineffective portion of the gain or loss resulting from the change in fair value is recognized in other income (expense), net in the consolidated statements of operations.
Cash, Cash Equivalents and Short-Term Investments	Cash, Cash Equivalents and Short-Term Investments The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand, highly liquid investments in money market funds and various deposit accounts. The Company considers all high quality investments purchased with original maturities at the date of purchase greater than three months to be short-term investments. Investments are available to be used in current operations and are, therefore, classified as current assets even though maturities may extend beyond one year. Cash equivalents and short-term investments are classified as available-for-sale and are, therefore, recorded at fair value on the consolidated balance sheets, with any unrealized gains and losses reported in the consolidated statements of stockholders’ equity as a component of accumulated other comprehensive income (loss) until realized. The Company uses the specific-identification method to compute gains and losses on the investments. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included as a component of other income (expense), net in the consolidated statements of operations.
Restricted Cash	Restricted Cash The Company has restricted cash pledged as collateral representing a security deposit required for facility leases. As of December 31, 2017 and 2016, the Company has classified $2.3 million and $1.9 million, respectively, of security deposit as non-current assets relating to its facility lease arrangements.
Insurance Recoveries Receivable	Insurance Recoveries Receivable Insurance recoveries receivable consists of amounts receivable by the Company from insurance recoveries in connection with settlement costs and professional fees. Claims for loss recoveries are generally recognized when a loss event has occurred and recovery is considered probable.
Inventory	Inventory Inventory consists of finished goods hardware appliances and related component parts and is stated at the lower of cost or market value where the cost is determined as the lower of an average cost basis or last invoice. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. For the years ended December 31, 2017, 2016 and 2015, the amount of inventory write-downs incurred by the Company were insignificant.
Business Combination	Business Combination The Company accounts for its business acquisitions in accordance with Accounting Standards Codification (ASC) No. 805, Business Combinations. The total purchase price allocated to the tangible assets acquired is assigned based on the fair values as of the date of the acquisition. The identifiable intangible assets are subject to amortization on a straight-line basis as this best approximates the benefit period related to these assets
Property and Equipment	Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets, generally two to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term or the estimated useful lives of the assets. Upon the retirement or disposition of property and equipment, the related costs and accumulated depreciation is removed and any related gain or loss is recorded in the consolidated statements of operations. Repairs and maintenance that do not extend the life or improve an asset are expensed in the periods incurred.
Goodwill and Acquired Intangibles	Goodwill and Acquired Intangibles Goodwill is not amortized and is reviewed at least annually or whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The Company operates its business in one operating segment and one reporting unit, which is the development, marketing, sales, service and support of cyber-security solutions that protect business-critical data and applications whether in the cloud or on premises. In reviewing goodwill, the Company bypasses the qualitative assessment and proceeds directly to performing the quantitative two step impairment test to test the reporting unit’s goodwill for impairment. The first step of the impairment test involves comparing the fair value of the reporting unit to its net book value, including goodwill and is used as a screening process for identifying a potential goodwill impairment loss. If the net book value exceeds its fair value, then the Company would perform the second step of the goodwill impairment test to determine the amount of the impairment loss. The impairment loss would be calculated by comparing the implied fair value of goodwill of the Company to its net book value. In calculating the implied fair value of the Company’s goodwill, the fair value of the Company would be allocated to all of the other assets and liabilities based on their fair values. The excess of the fair value of the Company over the amount assigned to its other assets and liabilities is the implied fair value of goodwill. An impairment loss would be recognized when the carrying amount of goodwill exceeds its implied fair value. The Company completes its annual impairment test during the fourth quarter of each fiscal year. There was no impairment of goodwill recorded for the fiscal year ended December 31, 2017. Intangible assets consist of purchased technology, customer relationships, trade names and domain names which are amortized over the period of estimated benefit using the straight-line method, as the consumption pattern of the asset is not apparent, and estimated useful lives ranging from seven to ten years as of December 31, 2017. No significant residual value is estimated for intangible assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets, which consist of property and equipment and acquired intangible assets, for indicators of possible impairment when events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Impairment exists if the carrying amounts of such assets exceed the estimates of future net undiscounted cash flows expected to be generated by such assets. Should impairment exist, the impairment loss would be measured based on the excess carrying value of the asset over the asset’s estimated fair value. As of December 31, 2017 and 2016, the Company has not written down any of its long-lived assets as a result of impairment.
Revenue Recognition	Revenue Recognition The Company derives revenue from two sources: (i) products and license revenue, which includes hardware and perpetual software license revenue and (ii) services revenue, which includes maintenance and support, professional services, training and subscription arrangements. Substantially all of product and license sales have been sold in combination with maintenance and support services. Revenue is recognized when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery or performance has occurred; the sales price is fixed or determinable; and collection is reasonably assured. The Company defines each of the four criteria above as follows: • Persuasive evidence of an arrangement exists: Evidence of an arrangement consists of a purchase order or acknowledgment issued pursuant to the terms and conditions of a direct customer end user or distributor or value-added reseller (VAR) agreement and, in limited cases with both distributor/VAR and an end user agreement and/or purchase order • Delivery or performance has occurred: The Company uses shipping and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance. The Company recognizes product revenue upon transfer of title and risk of loss, which primarily is upon shipment to value-added resellers, distributors or end users. We recognize software license revenue upon transfer of electronic keys to a customer. In most instances, the Company does not have significant obligations for future performance, such as customer acceptance provisions, rights of return or pricing credits, associated with the Company’s sales. In instances where final acceptance of the product or service is specified by the customer, revenue is deferred until all acceptance criteria have been met • The sales price is fixed or determinable: The Company assesses whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. In the event payment terms are provided that differ from the Company’s standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized when the payments become due, provided the remaining criteria for revenue recognition have been met. • Collection is reasonably assured: The Company assesses probability of collection on a customer-by-customer basis. The Company’s customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. If the Company concludes that collection is not reasonably assured based upon an initial review, the Company does not recognize revenue until payment is received. Maintenance and support and subscription revenue includes arrangements for software maintenance and technical support for the Company’s products and subscription services revenue primarily related to the Company’s cloud-based services. The terms of the Company’s subscription service arrangements do not provide customers the right to take possession of the related software. Maintenance and support is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches and unspecified upgrades on a when-and-if-available basis. Maintenance and support and subscription revenue is initially deferred and recognized ratably over the life of the contract, with the related expenses recognized as incurred. Maintenance and support and subscription contracts usually have a term of one to three years. Unearned maintenance and support and subscription revenue is included in deferred revenue. Professional service revenue primarily consists of the fees the Company earns related to installation and consulting services. The Company recognizes revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 90 days from the start of service. Training services are recognized upon delivery of the training. Multiple Element Arrangements Most of the Company’s products are hardware appliances containing software components that function together to provide the essential functionality of the product. Therefore, the Company’s hardware appliances are considered non-software deliverables and are not subject to industry-specific software revenue recognition guidance. The Company’s product revenue also includes revenue from the sale of stand-alone software products. Stand-alone software may operate on the Company’s hardware appliance, but is not considered essential to the functionality of the hardware and is, therefore, subject to the industry-specific software revenue recognition guidance. Additionally, the Company provides unspecified software upgrades for our products, on a when-and-if available basis, and hardware replacements through maintenance and support contracts. These support arrangements when sold on a stand-alone basis are subject to the industry-specific software revenue recognition guidance. Under the software revenue recognition guidance, the Company uses the residual method to recognize revenue when a product agreement includes one or more elements to be delivered at a future date and Vendor Specific Objective Evidence (“VSOE”) of the fair value of all undelivered elements exists. In the majority of the Company’s contracts, the only element that remains undelivered at the time of delivery of the product is maintenance and support services and subscriptions. Under the residual method, the VSOE of fair value of the undelivered elements is deferred and the remaining portion of the contract fee is recognized as product revenue. If evidence of the VSOE of fair value of one or more undelivered elements does not exist, all revenue is generally deferred and recognized when delivery of those elements occurs or when fair value can be established. For certain arrangements with multiple deliverables, the Company allocates the arrangement fee to the non-software element based upon the relative selling price of such element and, if software and software-related elements (e.g., maintenance and support for the software element) are also included in the arrangement, the Company allocates the arrangement fee to each of those software and software-related elements as a group. After such allocations are made, the amount of the arrangement fee allocated to the software and software-related elements is accounted for using the residual method. When applying the relative selling price method, the Company determines the selling price for each element using VSOE of selling price, if it exists, or if not, Third-Party Evidence (“TPE”) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for an element, the Company uses its Best Estimate of Selling Price (“BESP”) for that element. The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element. The Company limits the amount of revenue recognized for delivered elements to the amount that is not contingent on the future delivery of products or services, or subject to the Company’s future performance obligation. VSOE of fair value for elements of an arrangement is based upon the normal pricing and discounting practices for those services when sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices for a service fall within a reasonably narrow pricing range, evidenced by a substantial majority of such historical stand-alone transactions falling within a reasonably narrow range. In addition, the Company considers major service groups and geographies in determining VSOE. The Company is not able to determine TPE for its products or services. TPE is determined based on competitor prices for similar deliverables when sold separately. Generally, the Company’s go-to-market strategy differs from that of its peers and its offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine what similar competitor products’ selling prices are on a stand-alone basis. When the Company is unable to establish the selling price of its non-software deliverables using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company determines BESP for the purposes of allocating the arrangement by reviewing external and internal market factors including, but not limited to, pricing practices including discounting, the geographies in which the Company offers its products and services, the type of customer (i.e., distributor, value added reseller or direct end user) and competition. Additionally, the Company considers historical transactions, including transactions whereby the deliverable was sold on a stand-alone basis. The determination of BESP is made through consultation with and approval by the Company’s management. Selling prices are analyzed on a quarterly basis to identify if the Company has experienced significant changes in its selling prices that would impact our determination of BESP. For its non-software deliverables the Company allocates the arrangement consideration based on the relative selling price of the deliverables. For its hardware appliances the Company uses BESP as its selling price. For its maintenance and support services, subscriptions and professional services and training, the Company primarily uses VSOE as the selling price and when the Company is unable to establish a selling price using VSOE, it uses BESP.
Deferred Revenue	Deferred Revenue Deferred revenue represents amounts invoiced to customers for which the related revenue has not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of the deferred revenues represents the amount that is expected to be recognized as revenue within one year of the consolidated balance sheet date.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. The Company generally does not require collateral from its customers; however, in certain circumstances, may require letters of credit, other collateral, additional guarantees or advance payments. The allowance for doubtful accounts is based on the Company’s assessment of the collectability of its customer accounts. The Company regularly reviews its accounts receivable that remain outstanding past their applicable payment terms and establishes allowance and potential write-offs by considering certain factors such as historical experience, industry data, credit quality, age of balances and current economic conditions that may affect a customers’ ability to pay.
Concentration of Revenue and Accounts Receivable	Concentration of Revenue and Accounts Receivable Significant customers are those which represent 10% or more of the Company’s total revenue or gross accounts receivable balance at each respective balance sheet date. For the year ended December 31, 2017, 2016 and 2015, we had one customer that represented 12%, 13% and 18% of our total revenue, respectively. The same customer represented 18% and 18% of gross accounts receivable as of December 31, 2017 and 2016 respectively.
Shipping and Handling Costs	Shipping and Handling Costs Costs related to shipping and handling are included in cost of revenue.
Research and Development Costs	Research and Development Costs Research and development costs, including direct and allocated expenses, are expensed as incurred.
Software Development Costs	Software Development Costs The costs to develop software for sale have not been capitalized as the Company believes that the technological feasibility of the related software is not established until substantially all product development is complete.
Warranty Costs	Warranty Costs The Company generally provides a 60-day warranty on hardware appliance products and software from the date of shipment to customers. To date, cost to repair or replace items sold to customers has been insignificant.
Advertising Costs	Advertising Costs The Company expenses advertising costs as incurred. Advertising expense is included within sales and marketing expense in the consolidated statements of operations. For the years ended December 31, 2016, 2015 and 2014, advertising expenses were not material.
Retirement Savings Plan	Retirement Savings Plan The Company maintains a defined contribution 401(k) retirement savings plan for its U.S. employees. Each participant in the 401(k) retirement savings plan may elect to contribute a percentage of his or her annual compensation up to a specified maximum amount allowed under U.S. Internal Revenue Service regulations. There were no employer contributions to the 401(k) retirement savings plan for the years ended December 31, 2017, 2016 and 2015.
Severance Pay Asset and Liability	Severance Pay Asset and Liability The Company has recorded a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. The Company’s liability for severance pay is calculated pursuant to Israeli severance pay law based on the most recent salary for the employees multiplied by the number of years of employment, as of the respective balance sheet date. Employees are entitled to one month salary for each year of employment or a portion thereof. The Company’s liability at each respective balance sheet date for all of its Israeli employees is fully accrued in the accompanying consolidated financial statements and is mainly funded through monthly deposits to the employee’s pension and management insurance policies. The carrying value of these policies is recorded as a severance fund asset in the Company’s consolidated balance sheets. The deposited funds may be withdrawn only upon the fulfillment of the obligation pursuant to Israeli severance pay law. The carrying value of the deposited funds is based on the cash surrender value of these policies and includes profits accumulated through the respective balance sheet date. The Company recognized severance expense related to the Israeli severance pay law during the years ended December 31, 2017, 2016 and 2015 of $1.8 million, $1.6 million, and $1.3 million, respectively.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification No. 740 (“ASC 740”), Accounting for Income Taxes. The Company uses the liability method for accounting for deferred income taxes, which requires recognition of deferred income tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements, but have not been reflected in its taxable income. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets and liabilities are expected to be realized or settled. The Company regularly assesses the likelihood that its deferred income tax assets will be realized from recoverable income taxes or recovered from future taxable income based on the realization criteria set forth in ASC 740. To the extent that the Company believes any amounts are more likely not to be realized, the Company records a valuation allowance to reduce the deferred income tax assets. In the event the Company determines that all or part of the net deferred tax assets are not realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period such determination is made. Similarly, if the Company subsequently realizes deferred income tax assets that were previously determined to be unrealizable, the respective valuation allowance would be reversed, resulting in an adjustment to earnings in the period such determination is made. In addition, the calculation of the Company’s tax liabilities involves addressing uncertainties in the application of complex tax regulations. The Company recognizes and measures potential liabilities based upon criteria set forth in ASC 740. Based upon these criteria, the Company estimates whether, and the extent to which, additional taxes will be due. If payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities may result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. If the Company’s estimate of tax liabilities is less than the amount ultimately assessed, a further charge to expense would result. Significant judgment is required in determining any valuation allowance recorded against deferred income tax assets. In assessing the need for a valuation allowance, the Company considers all available evidence, including past operating results, estimates of future taxable income, and the feasibility of tax planning strategies. In the event that the Company changes its determination as to the amount of deferred income tax assets that could be realized, it will adjust its valuation allowance with a corresponding effect to the provision for income taxes in the period in which such determination is made. Significant judgment is also required in evaluating the Company’s uncertain tax positions under ASC 740 and determining its provision for income taxes. Although the Company believes its reserves for uncertain tax positions are reasonable, no assurance can be given that the final tax outcome of these matters will not be different from that which is reflected in the Company’s historical income tax provisions and accruals. The Company adjusts these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different from the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the effect of reserves for uncertain tax positions and any changes to the reserves that are considered appropriate, as well as the related net interest and penalties, if applicable. The U.S. Tax Cuts and Jobs Act of 2017 (“Tax Act”) was enacted on December 22, 2017. ASC Topic 740, Accounting for Income Taxes, requires companies to recognize the effect of tax law changes in the period of enactment even though the effective date for most provisions is for tax years beginning after December 31, 2017, or in the case of certain other provisions of the law, January 1, 2018.Given the significance of the legislation, the U.S. Securities and Exchange Commission (the "SEC") staff issued Staff Accounting Bulletin ("SAB") No. 118 (SAB 118), which allows registrants to record provisional amounts during a one year “measurement period” similar to that used when accounting for business combinations. However, the measurement period is deemed to have ended earlier when the registrant has obtained, prepared, and analyzed the information necessary to finalize its accounting. During the measurement period, impacts of the law are expected to be recorded at the time a reasonable estimate for all or a portion of the effects can be made, and provisional amounts can be recognized and adjusted as information becomes available, prepared, or analyzed. The Company is still evaluating the provisions of the Tax Reform and amounts reflected in the financial statements for the year ended December 31, 2017 are provisional. The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Reform Act. The accounting is expected to be completed in 2018.
Stock-Based Compensation	Stock-Based Compensation Compensation costs related to employee restricted stock units (“RSUs”) and stock option grants are based on the fair value of the RSU and options on the date of grant. The Company determines the fair value of RSUs using the closing price of the Company’s stock on the date of grant. The Company determines the grant date fair value of the options using the Black-Scholes option-pricing model and the related stock-based compensation expense is generally recognized on a straight-line basis over the period in which an employee is required to provide service in exchange for the options, or the vesting period of the respective options. The Company adopted the guidance in Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718) - Improvements to Employee Share-Based Payment Accounting, on January 1, 2017. Under this ASU, entities are permitted to make an accounting policy election to either estimate forfeitures on share-based payment awards, as previously required, or to recognize forfeitures as they occur. The Company has elected to recognize forfeitures as they occur and the impact of that change in accounting policy has been recorded as a $2.6 million cumulative effect adjustment to increase our accumulated deficit as of January 1, 2017. Additionally, the Company has elected to use a prospective transition method for presentation of excess tax benefits on the statement of cash flows. The remaining provisions of ASU 2016-09 did not have a material impact on the accompanying condensed consolidated financial statements.
Foreign Currency	Foreign Currency The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are re-measured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are re-measured at historical exchange rates. Gains and losses related to remeasurement are recorded in other income (expense) in the consolidated statements of operations.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company measures and reports its cash equivalents, short-term investments, derivative instruments, and the Israeli severance pay fund assets at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level I—Unadjusted quoted prices in active markets for identical assets or liabilities; Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III—Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level I and Level II assets. Level I securities include highly liquid money market funds and mutual funds. Level II instruments include deposits maintained with financial institutions and derivative instruments.
Net Income (Loss) per Share of Common Stock	Net Income (Loss) per Share of Common Stock The Company’s basic net income (loss) per share of common stock is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period. The weighted-average number of shares of common stock used to calculate the Company’s basic net income (loss) per share of common stock excludes those shares subject to repurchase as these shares are not deemed to be issued for accounting purposes until they vest. The diluted net income (loss) per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, stock options to purchase common stock, common stock subject to repurchase, and warrants to purchase common stock are considered to be common stock equivalents. Basic and diluted net loss per share of common stock was the same during the years ended December 31, 2016 and 2015 as the inclusion of all potential common shares outstanding was anti-dilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2017, the FASB issued ASU 2017-09 Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting, which clarifies which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. Under the new guidance, modification accounting is required if the fair value, vesting conditions or classification (equity or liability) of the new award are different from the original award immediately before the original award is modified. The standard is effective for the Company on January 1, 2018. The new guidance must be applied prospectively to awards modified on or after the adoption date. The future impact of ASU 2017-09 will be dependent on the nature of future stock award modifications. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The new standard requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The standard will be effective for the Company beginning January 1, 2018. The standard will require adoption on a retrospective basis. The new accounting pronouncements will not have a significant impact on the Company’s consolidated financial statements. In August 2016, FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The new standard will make eight targeted changes to how cash receipts and cash payments are presented and classified in the statement of cash flows. The standard will be effective for the Company beginning January 1, 2018. The standard will require adoption on a retrospective basis unless it is impracticable to apply, in which case we would be required to apply the amendments prospectively as of the earliest date practicable. The new accounting pronouncements will not have a significant impact on the Company’s consolidated financial statements. In February 2016, the FASB issued Accounting Standards Update No. 2016-02 regarding ASC Topic 842 "Leases." The amendments in this guidance require balance sheet recognition of lease assets and lease liabilities by lessees for leases classified as operating leases, with an optional policy election to not recognize lease assets and lease liabilities for leases with a term of 12 months or less. The amendments also require new disclosures, including qualitative and quantitative requirements, providing additional information about the amounts recorded in the financial statements. The standard will be effective for the Company beginning January 1, 2019. The amendments require a modified retrospective approach with optional practical expedients. While the Company continues to evaluate the effect of the standard on its ongoing financial reporting, the Company currently believes that the adoption of the ASU may materially affect its Balance Sheet. We are in the process of implementing processes in conjunction with our review of existing lease agreements. We will adopt ASC 842 effective January 1, 2019 and expect to elect certain available transitional practical expedients. In May 2014, the FASB issued ASU 2014-09—Revenue (Topic 606): Revenue from Contracts with Customers. The standard will replace most existing U.S. GAAP guidance on this topic. The standard provides a unified model to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation, among others. The standard also provides guidance on the recognition of costs related to obtaining customer contracts. We will adopt this new standard effective January 1, 2018, and we will use the modified retrospective method of adoption as permitted by the standard. Under that method, the cumulative effect of initially applying the standard is recognized as an adjustment to the opening balance of retained earnings, and revenues reported in the periods prior to the date of adoption are not changed. We are currently developing our revenue disclosures and enhancing our accounting systems to enable the preparation of such disclosures as well as the implementation of our internal controls. Based on our initial assessment the new standard will impact the timing of revenue recognition. In the year of adoption, total revenue will be impacted primarily by (a) acceleration of revenue in certain software arrangements where revenue would be recognized ratably under the current standard, but in 2018 would be recognized at a point in time under the new standard, and (b) reduction in revenue from certain arrangements where revenue was deferred in prior periods and would have been recognized ratably in 2018 but will now be recorded as reduction of deferred revenue and a reduction to accumulated deficit. We expect the net impact to revenue to be immaterial in aggregate, however, the exact impact to revenue of the new standard could vary from quarter to quarter depending upon facts and circumstances of revenue arrangements. We are required to apply the new rules to existing contracts which are not complete as of January 1, 2018, and therefore, upon adoption, we expect to record a cumulative effect adjustment to accumulated deficit as of the adoption date. We are currently in final stages of testing changes to our financial systems to adopt the new standard and quantify this adjustment. We do not expect the cumulative effect adjustment to the deferred revenue balance to be material. In addition to the above revenue recognition timing impacts, the new standard will require incremental contract acquisition costs (such as sales commissions) for customer contracts to be capitalized and amortized over the contract period. Currently, these costs are expensed as incurred. We expect to record an adjustment to establish an asset and a decrease in accumulated deficit related to the requirement to capitalize incremental contract acquisition costs for customer contracts. Based on an initial assessment of the contract cost guidance included in the new standard, we expect to record an asset upon adoption of approximately $16.0 million related to the incremental cost to obtain contracts for contracts which are not complete as of January 1, 2018. This amount is expected to be amortized over its estimated period of benefit, which we currently estimate to be approximately five years.

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2017
Camouflage Software, Inc [Member]
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): Acquired Technology $ 1,050 Customer relationships 480 Trade name and other 280 Goodwill 2,476 Total intangible assets acquired 4,286 Other acquired tangible assets 363 Liability assumed (130 ) Fair value of assets acquired $ 4,519

Cash, Cash Equivalents and Sh26

Cash, Cash Equivalents and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Short-Term Investments	Cash, cash equivalents and short-term investments consist of the following (in thousands): As of December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 92,030 $ - $ - $ 92,030 Money market funds 84,144 - - 84,144 US government agencies 16,367 - 3 16,364 Total $ 192,541 $ - $ 3 $ 192,538 Short-term investments: Commercial paper $ 699 $ - $ - $ 699 Corporate debt obligations 123,320 - 488 122,832 US government agencies 43,097 - 114 42,983 Bank deposits 480 - 1 479 Total $ 167,596 $ - $ 603 $ 166,993 As of December 31, 2016 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents: Cash $ 63,642 $ - $ - $ 63,642 Commercial paper 6,995 - 2 6,993 Money market funds 36,708 - - 36,708 Total $ 107,345 $ - $ 2 $ 107,343 Short-term investments: Commercial paper $ 14,245 $ - $ 8 $ 14,237 Corporate debt obligations 110,062 - 347 109,715 US government agencies 18,998 2 50 18,950 Bank deposits 10,846 1 - 10,847 Total $ 154,151 $ 3 $ 405 $ 153,749
Summary of Cost and Estimated Fair Value of Short-Term Investments	The following table sets forth the cost and estimated fair value of short-term investments based on stated effective maturities as of December 31, 2017 (in thousands): As of December 31, 2017 Estimated Amortized Fair Cost Value Short-term investments: Due in 2018 $ 94,231 $ 93,980 Due in 2019 73,365 73,013 Total $ 167,596 $ 166,993
Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position	The following tables show the short-term investments in an unrealized loss position and the related gross unrealized losses and fair value and length of time that the short-term investments have been in a continuous unrealized loss position (in thousands): As of December 31, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 699 $ - $ - $ - $ 699 $ - Corporate debt obligations 77,715 377 45,117 111 122,832 488 US government agencies 29,093 76 11,461 38 40,554 114 Bank deposits - - 479 1 479 1 $ 107,507 $ 453 $ 57,057 $ 150 $ 164,564 $ 603 As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Commercial paper $ 14,237 $ 8 $ - $ - $ 14,237 $ 8 Corporate debt obligations 78,821 323 29,689 24 108,510 347 US government agencies 11,451 46 3,496 4 14,947 50 $ 104,509 $ 377 $ 33,185 $ 28 $ 137,694 $ 405

Fair Value of Financial Instr27

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis	The following table sets forth the Company’s assets and liabilities that were measured at fair value as of December 31, 2017 and 2016, by level within the fair value hierarchy (in thousands): As of December 31, 2017 Level I Level II Level III Fair Financial Assets: Cash equivalents: Money market funds $ 84,144 $ - $ - $ 84,144 US government agencies - 16,364 - 16,364 Short-term investments: Commercial paper - 699 - 699 Corporate debt obligations - 122,832 - 122,832 US government agencies - 42,983 - 42,983 Bank deposits - 479 - 479 Prepaid expenses and other current assets - Forward foreign exchange contracts - 551 - 551 Total financial assets $ 84,144 $ 183,908 $ - $ 268,052 As of December 31, 2016 Level I Level II Level III Fair Value Financial Assets: Cash equivalents: Commercial paper $ - $ 6,993 $ - $ 6,993 Money market funds 36,708 - - 36,708 Short-term investments: Commercial paper - 14,237 - 14,237 Corporate debt obligations - 109,715 - 109,715 US government agencies - 18,950 - 18,950 Bank deposits - 10,847 - 10,847 Total financial assets $ 36,708 $ 160,742 $ - $ 197,450 Financial Liability: Accrued and other current liabilities - Forward foreign exchange contracts $ - $ 639 $ - $ 639

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments Measured at Fair Value and Classification on Consolidated Balance Sheets	Derivative instruments measured at fair value and their classification on the consolidated balance sheets are presented in the following tables (in thousands): Liability as of December 31, 2017 2016 Notional Amount Fair Value Notional Amount Fair Value Foreign exchange forward contract derivatives in cash flow hedging relationships - included in prepaid expenses and other current assets (accrued and other current liabilities) $ 66,560 $ 551 $ 60,756 $ (639 )
Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations	Gains (losses) on derivative instruments accounted for as hedges and their classification on the consolidated statement of operations, are presented in the following tables (in thousands): Years ended December 31, 2017 2016 2015 Foreign Exchange Forward Contract Derivatives in cash flow hedging relationships: Gains recognized in OCI (a) $ 5,037 $ 1,775 $ 834 Losses recognized in OCI (a) $ (551 ) $ (1,909 ) $ (1,399 ) Gains recognized from accumulated OCI into net loss (b) $ 3,271 $ 257 $ - Losses recognized from accumulated OCI into net loss (b) $ (10 ) $ (347 ) $ (972 ) (a) Net change in the fair value of the effective portion classified in other comprehensive income (loss) (“OCI”). (b) Effective portion of cash flow hedges reclassified from accumulated other income (loss), into net loss, of which $499, $(8) and $(107) were recognized within cost of sales for the years ended December 31, 2017, 2016 and 2015, respectively, and $2,762, $(82), and $(865) were recognized within operating expenses for the year ended December 31, 2017, 2016 and 2015, respectively. All amounts are reflected with the respective consolidated statement of operations.

Consolidated Balance Sheet Co29

Consolidated Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Allowance for Doubtful Accounts	The allowance for doubtful accounts is comprised of the following activity (in thousands): Years Ended December 31, 2017 2016 2015 Allowance for doubtful accounts and sales returns reserve, beginning balance $ 1,784 $ 1,438 $ 215 Allowance for doubtful accounts, beginning balance $ 953 $ 1,115 $ 215 Charged to costs and expenses, net of recoveries (334 ) 315 1,044 Deductions (write-offs) (467 ) (477 ) (144 ) Allowance for doubtful accounts, ending balance 152 953 1,115 Sales returns reserve, beginning balance 831 323 Charged to revenue 1,702 1,560 677 Deductions (write-offs) (1,749 ) (1,052 ) (354 ) Sales returns reserve, ending balance 784 831 323 Total allowance for doubtful accounts and sales returns reserve, ending balance $ 936 $ 1,784 $ 1,438
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): As of December 31, 2017 2016 Prepaid expenses $ 6,001 4,980 Skyfence Escrow Fund Receivable 5,000 - Prepaid income taxes 1,674 1,559 Interest receivable 808 758 Derivative asset 551 - Other 860 625 Total prepaid expenses and other current assets $ 14,894 $ 7,922
Property and Equipment, Net	Property and equipment, net consist of the following (in thousands): As of December 31, 2017 2016 Computers and related equipment $ 35,885 $ 25,285 Office furniture and equipment 3,371 3,228 Leasehold improvements 13,492 11,947 Total property and equipment 52,748 40,460 Less: accumulated depreciation and amortization (27,341 ) (18,964 ) Total property and equipment, net $ 25,407 $ 21,496
Accrued Compensation and Benefits	Accrued compensation and benefits consist of the following (in thousands): As of December 31, 2017 2016 Salary and related benefits $ 8,824 $ 9,588 Accrued vacation 4,453 4,178 Accrued incentive payments 9,636 5,942 Accrued restructuring - 1,132 Total accrued compensation and benefits $ 22,913 $ 20,840
Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following (in thousands): As of December 31, 2017 2016 Accrued expenses $ 7,516 $ 4,616 Derivative liability - 639 Income tax payable 319 435 Short-term deferred rent 844 461 Sales Taxes Payable 2,098 849 Other 640 683 Total accrued and other current liabilities $ 11,417 $ 7,683
Other Long-term Liabilities	Other long-term liabilities consist of the following (in thousands): As of December 31, 2017 2016 Long-term deferred rent $ 2,070 $ 2,111 Deferred tax liability 333 1,265 Uncertain Tax Positions 3,615 2,446 Other 235 815 Total other liabilities $ 6,253 $ 6,637

Goodwill and Acquired Intangi30

Goodwill and Acquired Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Changes in the Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016 were as follows (in thousands): 2017 2016 Balance as of January 1 $ 37,448 $ 34,972 Goodwill with acquisition of Camouflage Software Inc. - 2,476 Goodwill disposed with sale of Skyfence (1,059 ) - Balance as of December 31 $ 36,389 $ 37,448
Summary of Acquired Intangible Assets Subject to Amortization	Acquired intangible assets subject to amortization as of December 31, 2017 and 2016 were as follows (in thousands): As of December 31, 2017 Gross Carrying Amount Accumulated Amortization Net Book Value Acquired Technology $ 3,753 $ (1,216 ) $ 2,537 Customer relationships 480 (71 ) 409 Trade name and other 280 (42 ) 238 Total $ 4,513 $ (1,329 ) $ 3,184 As of December 31, 2016 Gross Carrying Amount Accumulated Amortization Net Book Value Acquired Technology $ 11,718 $ (4,085 ) $ 7,633 Customer relationships 480 - 480 Trade name and other 280 - 280 Total $ 12,478 $ (4,085 ) $ 8,393
Schedule of Expected Amortization Expense in Future Periods	As of December 31, 2017, the Company expects amortization expense in future periods to be as follows (in thousands): Acquired Fiscal Year Intangibles 2018 $ 528 2019 528 2020 528 2021 528 2022 528 Thereafter 544 Total expected amortization expense $ 3,184

Other Income (Expense), net (Ta

Other Income (Expense), net (Tables)	12 Months Ended
	Dec. 31, 2017
Other Income And Expenses [Abstract]
Schedule of Other Income (Expense), Net	Other income (expense), net is comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Other Income: Interest income $ 2,792 $ 1,369 $ 701 Foreign currency forward contract gains, net 27 9 - Foreign currency exchange gains, net 1,227 209 5 Total other income 4,046 1,587 706 Other Expense: Skyfence holdback liability accretion - (6 ) (212 ) Foreign currency exchange losses, net (2,138 ) (708 ) (322 ) Bank charges and Other expenses (766 ) (950 ) (574 ) Total other expense (2,904 ) (1,664 ) (1,108 ) Total other income (expense), net $ 1,142 $ (77 ) $ (402 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Payments Under Operating Leases	Future minimum payments under these facility operating leases are as follows as of December 31, 2017 (in thousands): Operating Leases Estimated Sublease Income Year Ending December 31: 2018 $ 8,295 $ 687 2019 4,991 - 2020 4,714 - 2021 557 - 2022 309 - Thereafter 87 - Total $ 18,953 $ 687

Capital Stock (Tables)

Capital Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Reserved Shares of Common Stock	The Company had reserved shares of common stock, on an as if converted basis, for issuance as follows: As of December 31, 2017 2016 Issuance in connection with outstanding stock options 997,674 1,570,765 Issuance in connection with restricted stock units outstanding 2,353,315 1,994,790 Reserved for future stock option and restricted stock unit grants 2,572,922 2,464,181 Reserved for future issuance under the employee stock purchase plan 1,298,442 1,161,396 7,222,353 7,191,132
Summary of Option Activity under Plans and Related Information	The following table summarizes option activity under the Plans and related information: Options Outstanding Weighted- Average Remaining Number of Shares Weighted Average Exercis e Contractual Term (in years) Aggregate Intrinsic Value (i n Outstanding - December 31, 2014 2,244,363 $ 33.83 8.27 $ 38,457 Granted 696,971 $ 49.20 Exercised or released (636,424 ) $ 29.44 Cancelled or forfeited (355,821 ) $ 42.00 Outstanding - December 31, 2015 1,949,089 $ 39.27 8.09 $ 47,480 Granted 48,260 $ 53.59 Exercised or released (184,737 ) $ 29.24 Cancelled or forfeited (241,847 ) $ 47.35 Balances - December 31, 2016 1,570,765 $ 39.64 6.90 $ 9,226 Granted - $ - Exercised or released (415,022 ) $ 30.02 Cancelled or forfeited (158,069 ) $ 50.79 Balances - December 31, 2017 997,674 $ 41.87 5.72 $ 5,689 Vested and expected to vest - December 31, 2017 997,674 $ 41.87 5.72 $ 5,689 Exercisable - December 31, 2017 779,746 $ 41.11 5.34 $ 4,958 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of $39.70 of the Company’s common stock on December 31, 2017
Additional Information Regarding Company's Stock Options Outstanding and Exercisable	Additional information regarding the Company’s stock options outstanding and exercisable as of December 31, 2017 is summarized below: Options Outstanding Options Exercisable Exercise Prices Number of Stock Options Outstanding Weighted Average Remaining Contractual Life (Years) Weighted Average Exercise Price per Share Shares Subject to Stock Options Weighted Average Exercise Price per Share $0.02 to $10.70 101,276 3.24 $ 8.26 101,276 $ 8.26 $10.71 to $29.10 77,236 5.18 $ 25.30 60,439 $ 24.51 $29.11 to $32.50 93,747 6.53 $ 29.37 42,932 $ 29.50 $32.51 to $35.50 65,474 4.37 $ 34.07 64,499 $ 34.09 $35.51 to $54.50 320,119 6.73 $ 43.20 232,819 $ 43.21 $54.51 to $61.50 209,260 4.92 $ 55.14 190,385 $ 55.02 $61.51 to $69.50 111,802 6.74 $ 65.19 76,855 $ 64.79 $69.51 to $77.50 18,760 7.52 $ 71.72 10,541 $ 71.69 997,674 5.72 $ 41.87 779,746 $ 41.11
Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value	A summary of RSU activity for the year ended December 31, 2017, is as follows: Number of Restricted Stock Units Outstanding Weighted- Average Grant Date Fair Value Unvested - December 31, 2015 1,898,025 $ 49.53 Granted 1,160,062 $ 47.42 Granted, performance RSUs 273,900 $ 51.55 Released (884,349 ) $ 43.04 Cancelled or forfeited (452,848 ) $ 49.86 Unvested - December 31, 2016 1,994,790 $ 51.42 Granted 1,489,189 $ 43.36 Granted, performance RSUs 301,900 $ 41.96 Released (749,845 ) $ 47.18 Cancelled or forfeited (682,719 ) $ 48.09 Unvested - December 31, 2017 2,353,315 $ 47.42
Stock-Based Compensation Expense	The Company recognized stock-based compensation expense under the 2011 Stock Option and Incentive Plan, 2003 Stock Plan, Inducement Plans, 2011 Employee Stock Purchase Plan, and the Incapsula 2010 Share Incentive Plan in the consolidated statements of operations as follows (in thousands): Years Ended December 31, 2017 2016 2015 Cost of revenue $ 5,290 $ 4,664 $ 3,862 Research and development 12,187 14,711 13,831 Sales and marketing 14,696 20,510 16,717 General and administrative 13,822 17,131 16,554 Restructuring charges 675 5,859 - Total stock-based compensation expense $ 46,670 $ 62,875 $ 50,964
Weighted Average Assumptions for Fair Value of Stock Options Grants and ESPP Grants	A summary of the weighted-average assumptions is as follows: Years Ended December 31 2017 2016 2015 Stock option grants: Dividend rate - 0 % 0 % Risk-free interest rate - 1.4 % 1.8 % Expected term (in years) - 6.0 6.1 Expected volatility - 58 % 49 % ESPP grants: Dividend rate 0 % 0 % 0 % Risk-free interest rate 1.3 % 0.5 % 0.4 % Expected term (in years) 0.5 0.5 0.5 Expected volatility 49 % 58 % 65 %

Accumulated Other Comprehensi34

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Changes in Balances of Accumulated Other Comprehensive Income (Loss)	The changes in the balances of accumulated other comprehensive income (loss) by component are as follows (in thousands): Years ended December 31, 2017 2016 2015 Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Unrealized gain (loss) on cash flow hedges Unrealized gain (loss) on investments Total Balance at January 1 $ (1,065 ) $ (413 ) $ (1,478 ) $ (1,021 ) $ (310 ) $ (1,331 ) $ (1,428 ) $ (61 ) $ (1,489 ) Other comprehensive income (loss) before reclassifications 4,486 (202 ) 4,284 (134 ) (103 ) (237 ) (565 ) (249 ) (814 ) Amounts reclassified to net loss (3,261 ) - (3,261 ) 90 - 90 972 - 972 Change in other comprehensive income (loss) 1,225 (202 ) 1,023 (44 ) (103 ) (147 ) 407 (249 ) 158 Balance at December 31 $ 160 $ (615 ) $ (455 ) $ (1,065 ) $ (413 ) $ (1,478 ) $ (1,021 ) $ (310 ) $ (1,331 )
Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following is a summary of reclassifications out of accumulated other comprehensive income (loss) for the years 2017, 2016, and 2015 (in thousands): Year ended December 31, 2017 2016 2015 Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Pre-Tax Amount Tax Expense (Benefit) After-Tax Amount Unrealized gains (losses) on cash flow hedges: Current period unrealized gain (loss) $ 4,486 $ - $ 4,486 $ (134 ) $ - $ (134 ) $ (565 ) $ - $ (565 ) Reclassification adjustments 1 (3,261 ) - (3,261 ) 90 - 90 972 - $ 972 Unrealized gains (losses) on cash flow hedges, net 1,225 - 1,225 (44 ) - (44 ) 407 - 407 Unrealized gains (losses) on investments: Current period unrealized gain (loss) $ (202 ) - (202 ) $ (103 ) - (103 ) $ (249 ) - (249 ) Unrealized gains (losses) on investments: (202 ) - (202 ) (103 ) - (103 ) (249 ) - (249 ) Other comprehensive income (loss) $ 1,023 $ - $ 1,023 $ (147 ) $ - $ (147 ) $ 158 $ - $ 158 1 Refer to Note 5 for the affected line items in the consolidated statement of operations

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Loss Before Provision for Income Taxes	The Company’s geographical breakdown of its loss before provision for income taxes is as follows (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ 20,331 $ (72,139 ) $ (50,892 ) Foreign 2,999 3,032 2,692 Loss before provision for taxes $ 23,330 $ (69,107 ) $ (48,200 )
Provision for Income Taxes	The components of the provision for income taxes are as follows (in thousands): Years Ended December 31, 2017 2016 2015 Current Federal $ - $ - $ - State 56 62 34 Foreign 2,139 1,654 857 Total current provision 2,195 1,716 891 Deferred Federal 4 130 63 State 13 6 (1 ) Foreign (1,751 ) (680 ) (271 ) Total deferred provision (1,734 ) (544 ) (209 ) Total $ 461 $ 1,172 $ 682
Reconciliation of Provision for Income Taxes at Statutory Rate	Reconciliation of the provision for income taxes at the statutory rate to the Company’s provision for income tax is as follows (in thousands): Years Ended December 31, 2017 2016 2015 Tax benefit at federal statutory tax rate $ 7,929 $ (23,496 ) $ (16,388 ) Tax benefit at state statutory tax rate 67 (1,008 ) (499 ) Foreign tax rate differential (123 ) 57 (826 ) Change in federal statutory tax rate and valuation allowance under U.S. Tax Reform (185 ) - - Losses not benefitted/(benefitted) (15,440 ) 17,701 9,738 Subsidiary earnings taxed in the US 717 - - Meals and entertainment 309 222 44 Stock compensation 6,006 7,857 8,492 Foreign exchange (gains) and losses, net (776 ) - - Reserve for tax exposure 1,893 - - Nondeductible expenses and other 64 (161 ) 121 Provision for income taxes $ 461 $ 1,172 $ 682
Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): As of December 31, 2017 2016 Deferred tax assets: Reserves and accruals $ 2,014 $ 2,817 Deferred revenue 6,466 10,379 Stock-based compensation 3,747 7,361 Net operating loss carryforwards 35,404 47,452 Loss on OCI 231 370 Depreciation and amortization 565 721 Other (3 ) 67 Gross deferred tax assets 48,424 69,167 Valuation allowance (46,125 ) (68,227 ) Total deferred tax assets 2,299 940 Deferred tax liabilities: Stock-based compensation - (21 ) Depreciation and amortization (610 ) (964 ) Total deferred tax liabilities (610 ) (985 ) Net deferred tax liability $ 1,689 $ (45 )
Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): 2017 2016 2015 Balance at January 1 $ 2,282 $ 1,154 $ 672 Additions based on tax positions taken during the current period 2,047 761 401 Reductions based on tax positions taken during the prior period (28 ) (42 ) (50 ) Additions based on tax positions taken during a prior period - 409 131 Decrease related to lapse of applicable statute of limitations (181 ) - - Balance at December 31 $ 4,120 $ 2,282 $ 1,154

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Company's Services Revenue	The Company’s services revenue was comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Maintenance and support $ 91,300 $ 80,007 $ 66,380 Professional services and training 13,918 13,693 14,084 Subscriptions 119,376 83,957 46,271 Total net services revenue $ 224,594 $ 177,657 $ 126,735
Company's Revenue by Geographic Region, Based on Customer's Location	The Company’s revenue by geographic region, based on the customer’s location, is summarized as follows (in thousands): Years Ended December 31, 2017 2016 2015 United States $ 146,215 $ 143,607 $ 141,225 EMEA 63,884 50,838 47,429 APAC 63,959 48,391 30,180 Other 47,658 21,619 15,464 Total net revenue $ 321,716 $ 264,455 $ 234,298
Long-Lived Assets by Location	The following table presents long-lived assets by location (in thousands): As of December 31, 2017 2016 2015 United States $ 23,697 $ 20,525 $ 9,913 Israel 4,640 9,344 10,224 Other 254 20 18 Total long-lived assets $ 28,591 $ 29,889 $ 20,155

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Reconciliation of Basic and Diluted Shares	The table below shows the reconciliation of the basic and diluted shares: Years Ended December 31, 2017 2016 2015 Weighted average number of shares outstanding: Basic 33,724 32,284 29,849 Dilutive effects of: Employee stock options, RSU’s and share based payment awards issued to employees 514 - - Diluted 34,238 32,284 29,849
Antidilutive Securities Excluded from Computation of Diluted Net Income (Loss) Per Share of Common Stock	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive: Years Ended December 31, 2017 2016 2015 Stock options to purchase common stock 259,744 1,570,765 1,949,089 Restricted stock units for common stock 95,794 1,994,790 1,898,025 Restricted stock issued in connection with Skyfence acquisition - 110,897 118,961
Common Stock [Member]
Reconciliation of Basic and Diluted Shares	The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock (in thousands, except per share amounts): Years Ended December 31, 2017 2016 2015 Net income (loss) $ 22,869 $ (70,279 ) $ (48,882 ) Shares used in computing earnings Basic 33,724 32,284 29,849 Diluted 34,238 32,284 29,849 Earnings per share: Basic $ 0.68 $ (2.18 ) $ (1.64 ) Diluted $ 0.67 $ (2.18 ) $ (1.64 )

Disposition of Business (Tables

Disposition of Business (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations And Disposal Groups [Abstract]
Schedule of Carrying Amounts Immediately Preceding Disposition and Consolidated Results of Operations Through Disposal	The following table presents the carrying amounts of Skyfence immediately preceding the disposition on February 23, 2017: (dollars Assets Prepaid and other current assets 46 Property and equipment, net 219 Goodwill 1,058 Acquired intangible assets, net 4,496 Total assets $ 5,819 Liabilities: Accounts payable $ 104 Accrued and other current liabilities 117 Deferred revenue 1,454 Total liabilities $ 1,675 The following table presents certain amounts related to Skyfence in our consolidated results of operations through its disposal on February 23, 2017: Years Ended December 31, 2017 2016 (dollars in thousands) Operating loss $ (3,567 ) $ (24,693 ) Loss before taxes (3,648 ) $ (24,693 ) Net loss (3,659 ) (24,693 )

The Company and Summary of Si39

The Company and Summary of Significant Accounting Policies - Additional Information (Detail)	Jan. 01, 2017USD ($)	Dec. 31, 2017USD ($)SegmentPartyCustomer	Dec. 31, 2016USD ($)Customer	Dec. 31, 2015USD ($)	Jan. 01, 2018USD ($)
Revenue, Major Customer [Line Items]
Number of operating segments | Segment		1
Number of third party | Party		1
Net derivative loss included in AOCI to be reclassified into earnings		$ 600,000
Security deposit as non-current assets		2,284,000	$ 1,884,000
Impairment of goodwill		$ 0
Period to complete Professional service arrangements		90 days
Warranty period		60 days
Employer contributions to the 401(k) retirement savings plan		$ 0	0	$ 0
Salary in calculation for severance pay by severance pay law		1 month
Severance expense for employees in Israel		$ 1,800,000	$ 1,600,000	$ 1,300,000
ASU 2016-09 [Member]
Revenue, Major Customer [Line Items]
Cumulative effect adjustment to accumulated deficit	$ 2,600,000
ASU 2014-09 [Member]
Revenue, Major Customer [Line Items]
Incremental cost amortization expected period		5 years
ASU 2014-09 [Member] | Subsequent Event [Member]
Revenue, Major Customer [Line Items]
Incremental cost					$ 16,000,000
Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Number of customers representing 18% or more of gross accounts receivable | Customer		1	1
Revenue [Member] | Customer Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers		12.00%	13.00%	18.00%
Number of customers representing 10% or more of revenue | Customer		1
Accounts Receivable | Credit Concentration Risk [Member]
Revenue, Major Customer [Line Items]
Minimum percentage of revenue or gross accounts receivable balance required to be significant customers		18.00%	18.00%
Minimum [Member]
Revenue, Major Customer [Line Items]
Estimated useful lives		2 years
Estimated useful life		7 years
Standard payment terms to customers range		30 days
Term of maintenance and support and subscription contracts		1 year
Maximum [Member]
Revenue, Major Customer [Line Items]
Estimated useful lives		7 years
Estimated useful life		10 years
Standard payment terms to customers range		90 days
Term of maintenance and support and subscription contracts		3 years

Acquisition - Additional Inform

Acquisition - Additional Information (Detail) - USD ($)	Dec. 15, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Business acquisition purchase price, cash paid		$ 0	$ 3,914,000	$ 0
Camouflage Software, Inc [Member]
Business Acquisition [Line Items]
Business acquisition purchase price, cash paid	$ 4,500,000
Holdback payment commitment period	24 months
Holdback liability	$ 600,000
Residual value of intangible assets	$ 0
Estimated useful life	7 years
Related acquisition costs	$ 100,000

Acquisition - Summary of Alloca

Acquisition - Summary of Allocation of Consideration to Fair Value of Tangible and Intangible Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 15, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 36,389	$ 37,448		$ 34,972
Camouflage Software, Inc [Member]
Business Acquisition [Line Items]
Goodwill			$ 2,476
Total intangible assets acquired			4,286
Other acquired tangible assets			363
Liability assumed			(130)
Fair value of assets acquired			4,519
Camouflage Software, Inc [Member] | Acquired Technology [Member]
Business Acquisition [Line Items]
Intangible assets acquired other than goodwill			1,050
Camouflage Software, Inc [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets acquired other than goodwill			480
Camouflage Software, Inc [Member] | Trade Name and Other [Member]
Business Acquisition [Line Items]
Intangible assets acquired other than goodwill			$ 280

Cash, Cash Equivalents and Sh42

Cash, Cash Equivalents and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 192,541	$ 107,345
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	3	2
Cash and cash equivalents, Fair Value	192,538	107,343
Short-term investments, Amortized Cost	167,596	154,151
Short-term investments, Gross Unrealized Gains	0	3
Short-term investments, Gross Unrealized Losses	603	405
Short-term investments, Estimated Fair Value	166,993	153,749
Cash [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	92,030	63,642
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	92,030	63,642
US Government Agencies [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	16,367
Cash and cash equivalents, Gross Unrealized Gains	0
Cash and cash equivalents, Gross Unrealized Losses	3
Cash and cash equivalents, Fair Value	16,364
Short-term investments, Amortized Cost	43,097	18,998
Short-term investments, Gross Unrealized Gains	0	2
Short-term investments, Gross Unrealized Losses	114	50
Short-term investments, Estimated Fair Value	42,983	18,950
Money Market Funds [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost	84,144	36,708
Cash and cash equivalents, Gross Unrealized Gains	0	0
Cash and cash equivalents, Gross Unrealized Losses	0	0
Cash and cash equivalents, Fair Value	84,144	36,708
Corporate Debt Obligations [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	123,320	110,062
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	488	347
Short-term investments, Estimated Fair Value	122,832	109,715
Commercial Paper [Member]
Schedule of Investments [Line Items]
Cash and cash equivalents, Amortized Cost		6,995
Cash and cash equivalents, Gross Unrealized Gains		0
Cash and cash equivalents, Gross Unrealized Losses		2
Cash and cash equivalents, Fair Value		6,993
Short-term investments, Amortized Cost	699	14,245
Short-term investments, Gross Unrealized Gains	0	0
Short-term investments, Gross Unrealized Losses	0	8
Short-term investments, Estimated Fair Value	699	14,237
Bank Deposits [Member]
Schedule of Investments [Line Items]
Short-term investments, Amortized Cost	480	10,846
Short-term investments, Gross Unrealized Gains	0	1
Short-term investments, Gross Unrealized Losses	1	0
Short-term investments, Estimated Fair Value	$ 479	$ 10,847

Cash, Cash Equivalents and Sh43

Cash, Cash Equivalents and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short Term Investments [Abstract]
Amortized Cost of short-term investments, Due in 2018	$ 94,231
Amortized Cost of short-term investments, Due in 2019	73,365
Short-term investments, Amortized Cost	167,596	$ 154,151
Estimated fair value of short-term investments, Due in 2018	93,980
Estimated fair value of short-term investments, Due in 2019	73,013
Short-term investments, Estimated Fair Value	$ 166,993	$ 153,749

Cash, Cash Equivalents and Sh44

Cash, Cash Equivalents and Short-Term Investments - Schedule of Short-Term Investments at Fair Value and Length of Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 107,507	$ 104,509
Less than 12 Months, Unrealized Losses	453	377
12 Months or Greater, Fair Value	57,057	33,185
12 Months or Greater, Unrealized Losses	150	28
Total, Fair Value	164,564	137,694
Total, Unrealized Losses	603	405
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	699	14,237
Less than 12 Months, Unrealized Losses	0	8
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	699	14,237
Total, Unrealized Losses	0	8
Corporate Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	77,715	78,821
Less than 12 Months, Unrealized Losses	377	323
12 Months or Greater, Fair Value	45,117	29,689
12 Months or Greater, Unrealized Losses	111	24
Total, Fair Value	122,832	108,510
Total, Unrealized Losses	488	347
US Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	29,093	11,451
Less than 12 Months, Unrealized Losses	76	46
12 Months or Greater, Fair Value	11,461	3,496
12 Months or Greater, Unrealized Losses	38	4
Total, Fair Value	40,554	14,947
Total, Unrealized Losses	114	$ 50
Bank Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Fair Value	479
12 Months or Greater, Unrealized Losses	1
Total, Fair Value	479
Total, Unrealized Losses	$ 1

Fair Value of Financial Instr45

Fair Value of Financial Instruments - Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 192,538	$ 107,343
Short-term investments	166,993	153,749
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	84,144	36,708
US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	16,364
Short-term investments	42,983	18,950
Corporate Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	122,832	109,715
Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		6,993
Short-term investments	699	14,237
Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	479	10,847
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	268,052	197,450
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	84,144	36,708
Fair Value, Measurements, Recurring [Member] | US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	16,364
Short-term investments	42,983	18,950
Fair Value, Measurements, Recurring [Member] | Corporate Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	122,832	109,715
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		6,993
Short-term investments	699	14,237
Fair Value, Measurements, Recurring [Member] | Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	479	10,847
Fair Value, Measurements, Recurring [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	84,144	36,708
Fair Value, Measurements, Recurring [Member] | Level I [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	84,144	36,708
Fair Value, Measurements, Recurring [Member] | Level I [Member] | US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Level I [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level I [Member] | Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	183,908	160,742
Fair Value, Measurements, Recurring [Member] | Level II [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level II [Member] | US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	16,364
Short-term investments	42,983	18,950
Fair Value, Measurements, Recurring [Member] | Level II [Member] | Corporate Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	122,832	109,715
Fair Value, Measurements, Recurring [Member] | Level II [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		6,993
Short-term investments	699	14,237
Fair Value, Measurements, Recurring [Member] | Level II [Member] | Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	479	10,847
Fair Value, Measurements, Recurring [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	0	0
Fair Value, Measurements, Recurring [Member] | Level III [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level III [Member] | US Government Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | 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
Fair Value, Measurements, Recurring [Member] | Level III [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Short-term investments	0	0
Fair Value, Measurements, Recurring [Member] | Level III [Member] | Bank Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	0	0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Prepaid Expenses and Other Current Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	551
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Prepaid Expenses and Other Current Assets [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Prepaid Expenses and Other Current Assets [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	551
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Prepaid Expenses and Other Current Assets [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Prepaid expenses and other current assets - Forward foreign exchange contracts	$ 0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [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		639
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level I [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		0
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		639
Forward Foreign Exchange Contracts [Member] | Fair Value, Measurements, Recurring [Member] | Accrued and Other Current Liabilities [Member] | Level III [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Accrued and other current liabilities - Forward foreign exchange contracts		$ 0

Fair Value of Financial Instr46

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value transfers between level 1 to level 2	$ 0	$ 0
Fair value transfers between level 2 to level 1	0	0
Fair value transfers into level 3	0	0
Fair value transfers out of level 3	0	0
Level II [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Severance pay assets	$ 6,600,000	$ 5,100,000

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
Forward Foreign Exchange Contracts [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative contracts maturity	12 months

Derivative Instruments - Deriva

Derivative Instruments - Derivative Instruments Measured at Fair Value and Classification on Consolidated Balance Sheets (Detail) - Forward Foreign Exchange Contracts [Member] - Designated As Hedging Instrument [Member] - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$ 66,560,000	$ 60,756,000
Derivative Fair Value	$ 551,000
Accrued and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Fair Value		$ (639,000)

Derivative Instruments - Gains

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Detail) - Designated As Hedging Instrument [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Gains recognized in OCI	$ 5,037	$ 1,775	$ 834
Losses recognized in OCI	(551)	(1,909)	(1,399)
Gains recognized from accumulated OCI into net loss	3,271	257	0
Losses recognized from accumulated OCI into net loss	$ (10)	$ (347)	$ (972)

Derivative Instruments - Gain50

Derivative Instruments - Gains (Losses) on Derivative Instruments and Classification on Consolidated Statement of Operations (Parenthetical) (Detail) - Designated As Hedging Instrument [Member] - Unrealized Gain (Loss) on Cash Flow Hedges [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cost of Sales [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ 499	$ (8)	$ (107)
Operating Expenses [Member]
Derivatives, Fair Value [Line Items]
Cash flow hedge Gain (loss) reclassified	$ 2,762	$ (82)	$ (865)

Consolidated Balance Sheet Co51

Consolidated Balance Sheet Components - Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts and sales returns reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	$ 1,784	$ 1,438	$ 215
Allowance for doubtful accounts, ending balance	936	1,784	1,438
Allowance for doubtful accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	953	1,115	215
Charged to costs and expenses, net of recoveries	(334)	315	1,044
Deductions (write-offs)	(467)	(477)	(144)
Allowance for doubtful accounts, ending balance	152	953	1,115
Sales returns reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts, beginning balance	831	323
Charged to revenue	1,702	1,560	677
Deductions (write-offs)	(1,749)	(1,052)	(354)
Allowance for doubtful accounts, ending balance	$ 784	$ 831	$ 323

Consolidated Balance Sheet Co52

Consolidated Balance Sheet Components - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Prepaid Expense And Other Assets Current [Abstract]
Prepaid expenses	$ 6,001	$ 4,980
Skyfence Escrow Fund Receivable	5,000	0
Prepaid income taxes	1,674	1,559
Interest receivable	808	758
Derivative asset	551	0
Other	860	625
Total prepaid expenses and other current assets	$ 14,894	$ 7,922

Consolidated Balance Sheet Co53

Consolidated Balance Sheet Components - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 52,748	$ 40,460
Less: accumulated depreciation and amortization	(27,341)	(18,964)
Total property and equipment, net	25,407	21,496
Computers and related equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	35,885	25,285
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	3,371	3,228
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 13,492	$ 11,947

Consolidated Balance Sheet Co54

Consolidated Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 10,857	$ 7,488	$ 4,551

Consolidated Balance Sheet Co55

Consolidated Balance Sheet Components - Accrued Compensation and Benefits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Employee Related Liabilities Current [Abstract]
Salary and related benefits	$ 8,824	$ 9,588
Accrued vacation	4,453	4,178
Accrued incentive payments	9,636	5,942
Accrued restructuring	0	1,132
Total accrued compensation and benefits	$ 22,913	$ 20,840

Consolidated Balance Sheet Co56

Consolidated Balance Sheet Components - Accrued and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities And Other Liabilities [Abstract]
Accrued expenses	$ 7,516	$ 4,616
Derivative liability	0	639
Income tax payable	319	435
Short-term deferred rent	844	461
Sales Taxes Payable	2,098	849
Other	640	683
Total accrued and other current liabilities	$ 11,417	$ 7,683

Consolidated Balance Sheet Co57

Consolidated Balance Sheet Components - Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Noncurrent [Abstract]
Long-term deferred rent	$ 2,070	$ 2,111
Deferred tax liability	333	1,265
Uncertain Tax Positions	3,615	2,446
Other	235	815
Total other liabilities	$ 6,253	$ 6,637

Goodwill and Acquired Intangi58

Goodwill and Acquired Intangible Assets - Additional Information (Detail) - USD ($)	Dec. 15, 2016	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Goodwill allocated to disposal of assets			$ 1,059,000	$ 0
Goodwill acquired			0	2,476,000
Intangible assets acquired			4,513,000	12,478,000
Goodwill impairments			0
Amortization of acquired intangibles			$ 714,000	1,408,000	$ 1,408,000
Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated useful life			7 years
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated useful life			10 years
Acquired Technology [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired			$ 3,753,000	11,718,000
Weighted average remaining useful life			6 years
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired			$ 480,000	480,000
Weighted average remaining useful life			6 years
Trade Name and Other [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired			$ 280,000	280,000
Weighted average remaining useful life			6 years
Camouflage Software, Inc [Member]
Finite Lived Intangible Assets [Line Items]
Goodwill acquired				2,500,000
Intangible assets acquired				1,800,000
Goodwill impairments			$ 0	$ 0	$ 0
Estimated useful life	7 years
Skyfence Cloud Access Security Broker Business [Member]
Finite Lived Intangible Assets [Line Items]
Goodwill allocated to disposal of assets		$ 1,100,000
Intangible assets derecognized in connection with disposal of assets		$ 4,500,000

Goodwill and Acquired Intangi59

Goodwill and Acquired Intangible Assets - Changes in the Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Balance as of January 1	$ 37,448	$ 34,972
Goodwill acquired	0	2,476
Goodwill disposed with sale of Skyfence	(1,059)	0
Balance as of December 31	$ 36,389	$ 37,448

Goodwill and Acquired Intangi60

Goodwill and Acquired Intangible Assets - Summary of Acquired Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,513	$ 12,478
Accumulated Amortization	(1,329)	(4,085)
Net Book Value	3,184	8,393
Acquired Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,753	11,718
Accumulated Amortization	(1,216)	(4,085)
Net Book Value	2,537	7,633
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	480	480
Accumulated Amortization	(71)	0
Net Book Value	409	480
Trade Name and Other [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	280	280
Accumulated Amortization	(42)	0
Net Book Value	$ 238	$ 280

Goodwill and Acquired Intangi61

Goodwill and Acquired Intangible Assets - Schedule of Expected Amortization Expense in Future Periods (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
2,018	$ 528
2,019	528
2,020	528
2,021	528
2,022	528
Thereafter	544
Net Book Value	$ 3,184	$ 8,393

Other Income (Expense), Net - S

Other Income (Expense), Net - Schedule of Other Income (Expense), Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income:
Interest income	$ 2,792	$ 1,369	$ 701
Foreign currency forward contract gains, net	27	9	0
Foreign currency exchange gains, net	1,227	209	5
Total other income	4,046	1,587	706
Other Expense:
Skyfence holdback liability accretion	0	(6)	(212)
Foreign currency exchange losses, net	(2,138)	(708)	(322)
Bank charges and Other expenses	(766)	(950)	(574)
Total other expense	(2,904)	(1,664)	(1,108)
Total other income (expense), net	$ 1,142	$ (77)	$ (402)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Dec. 31, 2010
Loss Contingencies [Line Items]
Rent expense	$ 6,600,000	$ 6,100,000	$ 4,600,000
Tenant improvement allowances		700,000		$ 300,000	$ 600,000
Restricted cash	2,284,000	1,884,000
Purchase commitments	$ 2,600,000	3,800,000
Period of purchase commitment of inventory from specified date	6 months
Loss contingency accrual	$ 0	0
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Motor vehicle lease expenses	$ 4,600,000	$ 2,700,000	$ 2,400,000
Minimum [Member]
Loss Contingencies [Line Items]
Operating lease expiration year	2,018
Maximum [Member]
Loss Contingencies [Line Items]
Operating lease expiration year	2,023
Maximum [Member] | Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	$ 100,000

Commitments and Contingencies64

Commitments and Contingencies - Future Minimum Payments Under Operating Leases and Minimum Rentals to be Received Under Non-Cancellable Subleases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases
2,018	$ 8,295
2,019	4,991
2,020	4,714
2,021	557
2,022	309
Thereafter	87
Total	18,953
Estimated Sublease Income
2,018	687
2,019	0
2,020	0
2,021	0
2,022	0
Thereafter	0
Total	$ 687

Capital Stock - Reserved Shares

Capital Stock - Reserved Shares of Common Stock (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Issuance in connection with outstanding stock options	997,674	1,570,765	1,949,089	2,244,363
Issuance in connection with restricted stock units outstanding	2,353,315	1,994,790	1,898,025
Reserved for future stock option and restricted stock unit grants	2,572,922	2,464,181
Reserved for future issuance under the employee stock purchase plan	1,298,442	1,161,396
Total	7,222,353	7,191,132

Capital Stock - Additional Info

Capital Stock - Additional Information (Detail)

Jan. 01, 2017shares

Dec. 31, 2017shares

Aug. 31, 2017shares

Apr. 30, 2017shares

May 31, 2016shares

Oct. 31, 2015shares

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

Aug. 31, 2014shares

Jan. 31, 2012

Sep. 30, 2011Periodshares

Mar. 31, 2018shares

Mar. 31, 2017shares

Dec. 31, 2017USD ($)shares

Dec. 31, 2016USD ($)$ / sharesshares

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

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

Preferred stock, shares authorized

5,000,000

5,000,000

5,000,000

Preferred stock, shares outstanding

0

0

0

Preferred stock, shares issued

0

0

0

Reserve of common stock for future issuance

7,222,353

7,222,353

7,191,132

Performance-based restricted stock units granted

1,489,189

1,160,062

Number of stock option outstanding, granted

0

48,260

696,971

Weighted-average grant date fair value | $ / shares

$ 29.23

$ 23.75

Aggregate grant date fair value, stock options granted | $

$ 1,400,000

$ 16,600,000

Aggregate grant date fair value, stock options vested | $

11,900,000

11,700,000

Intrinsic value of options exercised | $

$ 6,200,000

2,500,000

21,600,000

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

83,700,000

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

2 years 7 months 6 days

Net cash proceeds from the exercise of stock options | $

$ 9,500,000

2,400,000

12,100,000

Capitalized stock-based compensation cost | $

0

0

0

Recognized stock-based compensation tax benefits | $

0

100,000

200,000

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

19,095,000

11,233,000

23,524,000

Underwriting discounts, commissions and other offering expenses | $

0

112,000

0

Follow-On Public Offering [Member]

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

Issuance of common stock, shares

3,450,000

Sale of common stock, price per share | $ / shares

$ 39

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

$ 127,900,000

Underwriting discounts, commissions and other offering expenses | $

$ 6,700,000

Restricted Stock Units for Common Stock [Member]

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

Number of Restricted Stock Units Vested in Period | $

$ 33,200,000

$ 38,100,000

$ 31,400,000

2003 Stock Plan [Member]

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

Reserve of common stock for future issuance

955,568

955,568

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

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

Maximum percentage of fair value of common stock on grant date

85.00%

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

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

Expiration period

10 years

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

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

Vesting period

4 years

2011 Stock Option and Incentive Plan [Member]

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

Reserve of common stock for future issuance

1,000,000

Increase percentage of common stock outstanding

4.00%

Increase in reserve share

850,000

1,300,000

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

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

Maximum percentage of fair value of common stock on grant date

100.00%

Expiration period

10 years

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

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

Vesting period

4 years

Description of vesting terms

The Company also grants RSUs. RSUs granted to new hires and merit grants to existing employees generally vest over a four-year period with 25% vesting at the end of one year and the remainder vesting quarterly thereafter.

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

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

Vesting percentage at the end of period

25.00%

2011 Stock Option and Incentive Plan [Member] | Performance-based RSUs [Member]

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

Vesting period

3 years

Description of vesting terms

For fiscal 2017, the PRSUs vest contingent upon the Company’s achievement of an annual contract value of subscription bookings target for fiscal 2017 and total operating expenses for 2017 that are at 110% or less of the internal operating plan.

Vesting performance period

1 year

Vesting service period

2 years

Vest contingent upon the company’s achievement of total operating expenses at the internal operating plan, percentage

110.00%

Award expiration date

Feb. 15, 2019

2011 Stock Option and Incentive Plan [Member] | Performance-based RSUs [Member] | Executives [Member]

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

Performance-based restricted stock units granted

46,619

2011 Stock Option and Incentive Plan [Member] | Performance-based RSUs [Member] | Scenario, Forecast [Member] | Executives [Member]

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

Performance-based restricted stock units granted

74,621

2011 Employee Stock Purchase Plan [Member]

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

Reserve of common stock for future issuance

500,000

Increase percentage of common stock outstanding

1.00%

Increase in reserve share

330,889

Program effective date

Nov. 8, 2011

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

15.00%

Offering period

24 months

Percentage of fair value of common stock on offering period

85.00%

Number of years, shares reserved for issuance increase

8 years

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

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

Reserve of common stock for future issuance

20,000,000

Number of purchase periods for offering | Period

5

Inducement Stock Option Plans And Agreement [Member]

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

Expiration period

10 years

Description of vesting terms

In accordance with the terms of the Inducement Option Plans, the Company issued options to purchase 290,000 shares of the Company’s common stock at an exercise price equal to the fair market value of a share of the Company’s common stock on the dates of grant of the options. The options, which have a ten-year term, vest at the rate of 25% of the shares on each of the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the option vesting each quarter thereafter so long as the participant has not been terminated.

Number of stock option outstanding, granted

290,000

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

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

Vesting percentage at the end of period

25.00%

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

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

Vesting percentage at the end of period

6.25%

Inducement Restricted Stock Unit Plans and Agreement [Member]

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

Description of vesting terms

In accordance with the terms of the Inducement RSU Plans, the Company issued RSUs representing an aggregate of 290,000 shares of the Company’s common stock. The RSUs, which expire following settlement, vest at the rate of 25% of the shares on each of the first anniversary of the vesting commencement date with an additional 6.25% of the shares subject to the RSU vesting each quarter thereafter so long as the participant has not been terminated.

Shares available for grant

290,000

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

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

Vesting percentage at the end of period

25.00%

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

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

Vesting percentage at the end of period

6.25%

2015 Equity Inducement Plan [Member]

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

Reserve of common stock for future issuance

100,000

2015 Equity Inducement Plan [Member] | Stock options [Member]

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

Maximum percentage of fair value of common stock on grant date

100.00%

Expiration period

10 years

Increase in reserve share

250,000

100,000

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

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

Maximum percentage of fair value of common stock on grant date

110.00%

Minimum percentage of combined voting power

10.00%

Capital Stock - Summary of Opti

Capital Stock - Summary of Option Activity under Plans and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options Outstanding, Beginning balance	1,570,765	1,949,089	2,244,363
Number of Stock Options Outstanding, Granted	0	48,260	696,971
Number of Stock Options Outstanding, Exercised or released	(415,022)	(184,737)	(636,424)
Number of Stock Options Outstanding, Cancelled or forfeited	(158,069)	(241,847)	(355,821)
Number of Stock Options Outstanding, Ending balance	997,674	1,570,765	1,949,089	2,244,363
Number of Shares, Vested and expected to vest	997,674
Number of Shares, Exercisable	779,746
Weighted Average Exercise Price of Stock Options Outstanding	$ 39.64	$ 39.27	$ 33.83
Weighted Average Exercise Price, Granted	0	53.59	49.20
Weighted Average Exercise Price, Exercised or released	30.02	29.24	29.44
Weighted Average Exercise Price, Cancelled or forfeited	50.79	47.35	42
Weighted Average Exercise Price of Stock Options Outstanding	41.87	$ 39.64	$ 39.27	$ 33.83
Weighted-Average Exercise Price, Vested and expected to vest	41.87
Weighted Average Exercise Price, Exercisable	$ 41.11
Weighted-Average Remaining Contractual Term (in years)	5 years 8 months 19 days	6 years 10 months 24 days	8 years 1 month 2 days	8 years 3 months 7 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	5 years 8 months 19 days
Weighted Average Remaining Contractual Term (in years), Exercisable	5 years 4 months 2 days
Aggregate Intrinsic Value	$ 5,689	$ 9,226	$ 47,480	$ 38,457
Aggregate Intrinsic Value, Vested and expected to vest	5,689
Aggregate Intrinsic Value, Exercisable	$ 4,958

Capital Stock - Summary of Op68

Capital Stock - Summary of Option Activity under Plans and Related Information (Parenthetical) (Detail)	Dec. 31, 2017$ / shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Closing stock price	$ 39.70

Capital Stock - Additional In69

Capital Stock - Additional Information Regarding Company's Stock Options Outstanding and Exercisable (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Stock Options Outstanding	997,674
Weighted Average Remaining Contractual Life (Years)	5 years 8 months 19 days
Weighted Average Exercise Price per Share	$ 41.87	$ 39.64	$ 39.27	$ 33.83
Shares Subject to Stock Options	779,746
Weighted Average Exercise Price per Share	$ 41.11
Exercise price range one [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	0.02
Company's stock options outstanding and exercisable, Upper Range	$ 10.70
Number of Stock Options Outstanding	101,276
Weighted Average Remaining Contractual Life (Years)	3 years 2 months 26 days
Weighted Average Exercise Price per Share	$ 8.26
Shares Subject to Stock Options	101,276
Weighted Average Exercise Price per Share	$ 8.26
Exercise price range two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	10.71
Company's stock options outstanding and exercisable, Upper Range	$ 29.10
Number of Stock Options Outstanding	77,236
Weighted Average Remaining Contractual Life (Years)	5 years 2 months 4 days
Weighted Average Exercise Price per Share	$ 25.30
Shares Subject to Stock Options	60,439
Weighted Average Exercise Price per Share	$ 24.51
Exercise price range three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	29.11
Company's stock options outstanding and exercisable, Upper Range	$ 32.50
Number of Stock Options Outstanding	93,747
Weighted Average Remaining Contractual Life (Years)	6 years 6 months 10 days
Weighted Average Exercise Price per Share	$ 29.37
Shares Subject to Stock Options	42,932
Weighted Average Exercise Price per Share	$ 29.50
Exercise price range four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	32.51
Company's stock options outstanding and exercisable, Upper Range	$ 35.50
Number of Stock Options Outstanding	65,474
Weighted Average Remaining Contractual Life (Years)	4 years 4 months 13 days
Weighted Average Exercise Price per Share	$ 34.07
Shares Subject to Stock Options	64,499
Weighted Average Exercise Price per Share	$ 34.09
Exercise price range five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	35.51
Company's stock options outstanding and exercisable, Upper Range	$ 54.50
Number of Stock Options Outstanding	320,119
Weighted Average Remaining Contractual Life (Years)	6 years 8 months 23 days
Weighted Average Exercise Price per Share	$ 43.20
Shares Subject to Stock Options	232,819
Weighted Average Exercise Price per Share	$ 43.21
Exercise price range six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	54.51
Company's stock options outstanding and exercisable, Upper Range	$ 61.50
Number of Stock Options Outstanding	209,260
Weighted Average Remaining Contractual Life (Years)	4 years 11 months 1 day
Weighted Average Exercise Price per Share	$ 55.14
Shares Subject to Stock Options	190,385
Weighted Average Exercise Price per Share	$ 55.02
Exercise price range seven [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	61.51
Company's stock options outstanding and exercisable, Upper Range	$ 69.50
Number of Stock Options Outstanding	111,802
Weighted Average Remaining Contractual Life (Years)	6 years 8 months 26 days
Weighted Average Exercise Price per Share	$ 65.19
Shares Subject to Stock Options	76,855
Weighted Average Exercise Price per Share	$ 64.79
Exercise price range eight [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Company's stock options outstanding and exercisable, Lower Range	69.51
Company's stock options outstanding and exercisable, Upper Range	$ 77.50
Number of Stock Options Outstanding	18,760
Weighted Average Remaining Contractual Life (Years)	7 years 6 months 7 days
Weighted Average Exercise Price per Share	$ 71.72
Shares Subject to Stock Options	10,541
Weighted Average Exercise Price per Share	$ 71.69

Capital Stock - Summary of RSU

Capital Stock - Summary of RSU Activity Outstanding and Weighted Average Grant Date Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Restricted Stock Units Outstanding, Unvested - Beginning Balance	1,994,790	1,898,025
Number of Restricted Stock Units Outstanding, Granted	1,489,189	1,160,062
Number of Restricted Stock Units Outstanding, Granted, performance RSUs	301,900	273,900
Number of Restricted Stock Units Outstanding, Released	(749,845)	(884,349)
Number of Restricted Stock Units Outstanding, Cancelled or forfeited	(682,719)	(452,848)
Number of Restricted Stock Units Outstanding, Unvested - Ending Balance	2,353,315	1,994,790
Weighted-Average Grant Date Fair Value, Unvested	$ 51.42	$ 49.53
Weighted-Average Grant Date Fair Value, Granted	43.36	47.42
Weighted-Average Grant Date Fair Value, Granted, performance RSUs	41.96	51.55
Weighted-Average Grant Date Fair Value, Released	47.18	43.04
Weighted-Average Grant Date Fair Value, Cancelled or forfeited	48.09	49.86
Weighted-Average Grant Date Fair Value, Unvested	$ 47.42	$ 51.42

Capital Stock - Stock-Based Com

Capital Stock - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 46,670	$ 62,875	$ 50,964
Cost of revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,290	4,664	3,862
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	12,187	14,711	13,831
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	14,696	20,510	16,717
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	13,822	17,131	16,554
Restructuring Charges [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 675	$ 5,859	$ 0

Capital Stock - Weighted Averag

Capital Stock - Weighted Average Assumptions for Fair Value of Stock Options Grants and ESPP Grants (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%	0.00%
Risk-free interest rate	0.00%	1.40%	1.80%
Expected term (in years)	0 years	6 years	6 years 1 month 6 days
Expected volatility	0.00%	58.00%	49.00%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend rate	0.00%	0.00%	0.00%
Risk-free interest rate	1.30%	0.50%	0.40%
Expected term (in years)	6 months	6 months	6 months
Expected volatility	49.00%	58.00%	65.00%

Accumulated Other Comprehensi73

Accumulated Other Comprehensive Income (Loss) - Changes in Balances of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 231,963	$ 240,201	$ 97,243
Other comprehensive income (loss) before reclassifications	4,284	(237)	(814)
Amounts reclassified to net loss	(3,261)	90	972
Other comprehensive income (loss)	1,023	(147)	158
Ending balance	315,117	231,963	240,201
Unrealized Gain (Loss) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,065)	(1,021)	(1,428)
Other comprehensive income (loss) before reclassifications	4,486	(134)	(565)
Amounts reclassified to net loss	(3,261)	90	972
Other comprehensive income (loss)	1,225	(44)	407
Ending balance	160	(1,065)	(1,021)
Unrealized Gain (Loss) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(413)	(310)	(61)
Other comprehensive income (loss) before reclassifications	(202)	(103)	(249)
Amounts reclassified to net loss	0	0	0
Other comprehensive income (loss)	(202)	(103)	(249)
Ending balance	(615)	(413)	(310)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,478)	(1,331)	(1,489)
Ending balance	$ (455)	$ (1,478)	$ (1,331)

Accumulated Other Comprehensi74

Accumulated Other Comprehensive Income (Loss) - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), Pre-Tax Amount	$ 1,023	$ (147)	$ 158
Other comprehensive income (loss), Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss) before reclassification adjustments, After-Tax Amount	4,284	(237)	(814)
Other comprehensive income (loss), Reclassification adjustments, After-Tax Amount	(3,261)	90	972
Other comprehensive income (loss)	1,023	(147)	158
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassification adjustments, Pre-Tax Amount	4,486	(134)	(565)
Other comprehensive income (loss), Reclassification adjustments, Pre-Tax Amount	(3,261)	90	972
Other comprehensive income (loss), Pre-Tax Amount	1,225	(44)	407
Other comprehensive income (loss) before reclassification adjustments, Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss), Reclassification adjustments, Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss), Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss) before reclassification adjustments, After-Tax Amount	4,486	(134)	(565)
Other comprehensive income (loss), Reclassification adjustments, After-Tax Amount	(3,261)	90	972
Other comprehensive income (loss)	1,225	(44)	407
Unrealized Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassification adjustments, Pre-Tax Amount	(202)	(103)	(249)
Other comprehensive income (loss), Pre-Tax Amount	(202)	(103)	(249)
Other comprehensive income (loss) before reclassification adjustments, Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss), Tax Expense (Benefit)	0	0	0
Other comprehensive income (loss) before reclassification adjustments, After-Tax Amount	(202)	(103)	(249)
Other comprehensive income (loss), Reclassification adjustments, After-Tax Amount	0	0	0
Other comprehensive income (loss)	$ (202)	$ (103)	$ (249)

Income Taxes - Loss Before Prov

Income Taxes - Loss Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 20,331	$ (72,139)	$ (50,892)
Foreign	2,999	3,032	2,692
Income (loss) before provision for income taxes	$ 23,330	$ (69,107)	$ (48,200)

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 0	$ 0	$ 0
State	56	62	34
Foreign	2,139	1,654	857
Total current provision	2,195	1,716	891
Deferred
Federal	4	130	63
State	13	6	(1)
Foreign	(1,751)	(680)	(271)
Total deferred provision	(1,734)	(544)	(209)
Provision for income taxes	$ 461	$ 1,172	$ 682

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Provision for Income Taxes at Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory tax rate	$ 7,929	$ (23,496)	$ (16,388)
Tax benefit at state statutory tax rate	67	(1,008)	(499)
Foreign tax rate differential	(123)	57	(826)
Change in federal statutory tax rate and valuation allowance under U.S. Tax Reform	(185)	0	0
Losses not benefitted/(benefitted)	(15,440)	17,701	9,738
Subsidiary earnings taxed in the US	717	0	0
Meals and entertainment	309	222	44
Stock compensation	6,006	7,857	8,492
Foreign exchange (gains) and losses, net	(776)	0	0
Reserve for tax exposure	1,893	0	0
Nondeductible expenses and other	64	(161)	121
Provision for income taxes	$ 461	$ 1,172	$ 682

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Expenses [Line Items]
U.S. statutory tax rate		35.00%
Reduction in net deferred tax assets		$ 24,900
Change in valuation allowance		25,100
Deferred tax benefit related to remeasurement of deferred tax liabilities associated with indefinite-lived intangible assets		$ 200
Maximum percentage of net operating losses allowed as a percent of taxable income		80.00%
Minimum tax on certain foreign earnings in excess of foreign subsidiaries tangible assets		10.00%
Valuation allowance		$ (22,100)	$ 14,800	$ 13,000
U.S. federal, net operating loss carryforwards		142,900
State net operating loss carryforwards		70,900
Accumulated unremitted earnings		20,500	9,700	13,600
Unrecognized tax benefits		4,120	2,282	$ 1,154	$ 672
Accrued interest on income tax expense		$ 100	$ 200
Tax years, subject to audit		2,013
Earliest Tax Year [Member] | Israeli Tax Authorities [Member]
Income Tax Expenses [Line Items]
Income tax returns, audit settled year		2,006
Tax years, currently under examination		2,011
Earliest Tax Year [Member] | Federal Purposes [Member]
Income Tax Expenses [Line Items]
Tax years, subject to audit		2,002
Earliest Tax Year [Member] | California Purposes [Member]
Income Tax Expenses [Line Items]
Tax years, subject to audit		2,008
Latest Tax Year [Member] | Israeli Tax Authorities [Member]
Income Tax Expenses [Line Items]
Income tax returns, audit settled year		2,010
Tax years, currently under examination		2,012
Maximum [Member] | State [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,037
Maximum [Member] | Federal [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,037
Minimum [Member] | State [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,018
Minimum [Member] | Federal [Member]
Income Tax Expenses [Line Items]
Expiration of net operating loss carryforwards		2,022
Scenario, Forecast [Member]
Income Tax Expenses [Line Items]
U.S. statutory tax rate	21.00%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Reserves and accruals	$ 2,014	$ 2,817
Deferred revenue	6,466	10,379
Stock-based compensation	3,747	7,361
Net operating loss carryforwards	35,404	47,452
Loss on OCI	231	370
Depreciation and amortization	565	721
Other	(3)	67
Gross deferred tax assets	48,424	69,167
Valuation allowance	(46,125)	(68,227)
Total deferred tax assets	2,299	940
Deferred tax liabilities:
Stock-based compensation	0	(21)
Depreciation and amortization	(610)	(964)
Total deferred tax liabilities	(610)	(985)
Net deferred tax asset	$ 1,689
Net deferred tax liability		$ (45)

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Beginning Balance	$ 2,282	$ 1,154	$ 672
Additions based on tax positions taken during the current period	2,047	761	401
Reductions based on tax positions taken during the prior period	(28)	(42)	(50)
Additions based on tax positions taken during a prior period	0	409	131
Decrease related to lapse of applicable statute of limitations	(181)	0	0
Ending Balance	$ 4,120	$ 2,282	$ 1,154

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting [Abstract]
Number of operating segments	1

Segment Information - Company's

Segment Information - Company's of Services Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Total net services revenue	$ 224,594	$ 177,657	$ 126,735
Maintenance and Support [Member]
Revenue from External Customer [Line Items]
Total net services revenue	91,300	80,007	66,380
Professional Services and Training [Member]
Revenue from External Customer [Line Items]
Total net services revenue	13,918	13,693	14,084
Subscriptions [Member]
Revenue from External Customer [Line Items]
Total net services revenue	$ 119,376	$ 83,957	$ 46,271

Segment Information - Company83

Segment Information - Company's Revenue by Geographic Region, Based on Customer's Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 321,716	$ 264,455	$ 234,298
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	146,215	143,607	141,225
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	63,884	50,838	47,429
APAC [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	63,959	48,391	30,180
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenue	$ 47,658	$ 21,619	$ 15,464

Segment Information - Long-Live

Segment Information - Long-Lived Assets by Location (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 28,591	$ 29,889	$ 20,155
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	23,697	20,525	9,913
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	4,640	9,344	10,224
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 254	$ 20	$ 18

Net Income (Loss) per Share - R

Net Income (Loss) per Share - Reconciliation of Basic and Diluted Shares (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted average number of shares outstanding:
Basic	33,724	32,284	29,849
Dilutive effects of:
Employee stock options, RSU’s and share based payment awards issued to employees	514	0	0
Diluted	34,238	32,284	29,849

Net Income (Loss) per Share - C

Net Income (Loss) per Share - Computation of Company's Basic and Diluted Net Loss Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ 22,869	$ (70,279)	$ (48,882)
Shares used in computing earnings per share
Basic	33,724	32,284	29,849
Diluted	34,238	32,284	29,849
Earnings per share:
Basic	$ 0.68	$ (2.18)	$ (1.64)
Diluted	$ 0.67	$ (2.18)	$ (1.64)

Net Income (Loss) per Share - A

Net Income (Loss) per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share of Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	259,744	1,570,765	1,949,089
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	95,794	1,994,790	1,898,025
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	0	110,897	118,961

Disposition of Business - Addit

Disposition of Business - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 23, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Escrow to secure indemnification obligations		$ 5,000	$ 0
Recognized gain on sale of Skyfence		$ 35,871	$ 0	$ 0
Skyfence Cloud Access Security Broker Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Cash consideration on sale of assets					$ 40,000
Escrow to secure indemnification obligations					$ 5,000
Recognized gain on sale of Skyfence	$ 35,900

Disposition of Business - Sched

Disposition of Business - Schedule of Carrying Amounts Immediately Preceding Disposition (Detail) - Skyfence Networks Ltd. [Member] $ in Thousands	Feb. 23, 2017USD ($)
Assets
Prepaid and other current assets	$ 46
Property and equipment, net	219
Goodwill	1,058
Acquired intangible assets, net	4,496
Total assets	5,819
Liabilities:
Accounts payable	104
Accrued and other current liabilities	117
Deferred revenue	1,454
Total liabilities	$ 1,675

Disposition of Business - Sch90

Disposition of Business - Schedule of Consolidated Results of Operations Through Disposal (Detail) - Skyfence Cloud Access Security Broker Business [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Operating loss	$ (3,567)	$ (24,693)
Loss before taxes	(3,648)	(24,693)
Net loss	$ (3,659)	$ (24,693)

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Restructuring charge		$ 667	$ 8,118	$ 0
Scenario, Forecast [Member] | Minimum [Member]
Subsequent Event [Line Items]
Restructuring charge	$ 2,300
Scenario, Forecast [Member] | Maximum [Member]
Subsequent Event [Line Items]
Restructuring charge	$ 2,900