Proofpoint (PFPT) 10-K 23 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 03, 2017	Jun. 30, 2016
Document Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Entity Registrant Name	PROOFPOINT INC
Entity Central Index Key	1,212,458
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		43,296,403
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,571

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 345,426	$ 346,205
Short-term investments	51,325	60,032
Accounts receivable, net of allowance for doubtful accounts of $216 and $199 at December 31, 2016 and 2015, respectively	72,951	54,522
Inventory	598	485
Deferred product costs	1,829	2,228
Deferred commissions	21,168	19,314
Prepaid expenses and other current assets	17,498	5,695
Total current assets	510,795	488,481
Property and equipment, net	52,523	34,501
Deferred product costs	310	314
Goodwill	167,270	133,769
Intangible assets, net	61,708	41,330
Long-term deferred commissions	4,496	3,488
Other assets	4,558	3,733
Total assets	801,660	705,616
Current liabilities:
Accounts payable	15,297	14,081
Accrued liabilities	50,765	35,053
Capital lease obligations	32	32
Deferred rent	409	496
Deferred revenue	259,109	182,195
Total current liabilities	325,612	231,857
Convertible senior notes	366,541	345,699
Long-term capital lease obligations	91	123
Long-term deferred rent	2,413	2,033
Other long-term liabilities	9,008	1,188
Long-term deferred revenue	53,072	41,531
Total liabilities	756,737	622,431
Commitments and contingencies (Note 7)
Stockholders' equity:
Convertible preferred stock, $0.0001 par value; 5,000 shares authorized; no shares issued and outstanding as of December 31, 2016 and 2015	0	0
Common stock, $0.0001 par value; 200,000 shares authorized; 43,015 and 40,840 shares issued and outstanding at December 31, 2016 and 2015, respectively	4	4
Additional paid-in capital	514,034	441,104
Accumulated other comprehensive loss	(7)	(23)
Accumulated deficit	(469,108)	(357,900)
Total stockholders' equity	44,923	83,185
Total liabilities and stockholders' equity	$ 801,660	$ 705,616

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts	$ 216	$ 199
Number of shares of common stock reserved for future issuance
Par value of common stock (USD per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	200,000,000	200,000,000
Common stock issued (in shares)	43,015,000	40,840,000
Common stock outstanding (in shares)	43,015,000	40,840,000
Convertible preferred stock [Member]
Preferred stock:
Par value of preferred stock (USD per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Subscription		$ 365,960	$ 257,329	$ 187,527
Hardware and services		9,536	8,068	8,080
Total revenue		375,496	265,397	195,607
Cost of revenue:
Subscription	[1],[2]	94,716	71,746	53,136
Hardware and services	[1],[2]	13,877	12,312	12,543
Total cost of revenue	[1],[2]	108,593	84,058	65,679
Gross profit		266,903	181,339	129,928
Operating expense:
Research and development	[1],[2]	98,506	74,459	51,903
Sales and marketing	[1],[2]	201,204	148,414	98,333
General and administrative	[1],[2]	52,774	36,616	26,679
Total operating expense	[1],[2]	352,484	259,489	176,915
Operating loss		(85,581)	(78,150)	(46,987)
Interest expense		(23,538)	(18,000)	(11,213)
Other expense, net		(1,103)	(1,927)	(2,230)
Loss before (provision for) benefit from income taxes		(110,222)	(98,077)	(60,430)
(Provision for) benefit from income taxes		(986)	(635)	313
Net loss		$ (111,208)	$ (98,712)	$ (60,117)
Net loss per share, basic and diluted (in dollars per share)		$ (2.66)	$ (2.48)	$ (1.61)
Weighted average shares outstanding, basic and diluted (in shares)		41,859	39,787	37,381
Intangible amortization expense		$ 14,421	$ 12,256	$ 8,790
Cost of subscription revenue
Operating expense:
Stock-based compensation expense		7,427	5,028	2,404
Intangible amortization expense		9,423	7,079	4,157
Cost of hardware and services revenue
Operating expense:
Stock-based compensation expense		1,494	1,098	604
Research and development
Operating expense:
Stock-based compensation expense		24,342	20,672	10,204
Intangible amortization expense		60	91	93
Sales and marketing
Operating expense:
Stock-based compensation expense		28,607	21,511	10,795
Intangible amortization expense		4,938	5,074	4,494
General and administrative
Operating expense:
Stock-based compensation expense		16,826	11,785	6,997
Intangible amortization expense		$ 0	$ 12	$ 46
[1]	Includes intangible amortization expense as follows: Cost of subscription revenue $9,423, research and development $60, sales and marketing $4,938 and general and administrative $0 for the year ended December 31, 2016. Cost of subscription revenue $7,079, research and development $91, sales and marketing $5,074 and general and administrative $12 for the year ended December 31, 2015. Cost of subscription revenue $4,157, research and development $93, sales and marketing $4,494 and general and administrative $46 for the year ended December 31, 2014.
[2]	Includes stock-based compensation expenses as follows:Cost of subscription $7,427, cost of hardware and service revenue $1,494, research and development $24,342, sales and marketing $28,607 and general and administrative $16,826 for the year ended December 31, 2016. Cost of subscription $5,028, cost of hardware and service revenue $1,098, research and development $20,672, sales and marketing $21,511 and general and administrative $11,785 for the year ended December 31, 2015. Cost of subscription $2,404, cost of hardware and service revenue $604, research and development $10,204, sales and marketing $10,795 and general and administrative $6,997 for the year ended December 31, 2014

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (111,208)	$ (98,712)	$ (60,117)
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on investments, net	16	4	(27)
Comprehensive loss	$ (111,192)	$ (98,708)	$ (60,144)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2013	$ 88,098	$ 4	$ 287,165	$ 0	$ (199,071)
Beginning balance (shares) at Dec. 31, 2013		36,140
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(60,117)				(60,117)
Unrealized gains (losses) on investments, net	(27)			(27)
Stock-based compensation expense	29,233		29,233
Common stock issued	18,513		18,513
Common stock issued (shares)		2,574
Tax withholding upon vesting of restricted stock awards	(4,170)		(4,170)
Tax withholding upon vesting of restricted stock awards (shares)		(105)
Exercise of warrants (shares)		2
Issuance of restricted stock (shares)		54
Vesting of early exercise options	3		3
Ending balance at Dec. 31, 2014	71,533	$ 4	330,744	(27)	(259,188)
Ending balance (shares) at Dec. 31, 2014		38,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(98,712)				(98,712)
Unrealized gains (losses) on investments, net	4			4
Embedded conversion feature on Convertible Senior Notes	54,049		54,049
Stock-based compensation expense	54,418		54,418
Common stock issued	20,292		20,292
Common stock issued (shares)		2,486
Tax withholding upon vesting of restricted stock awards	(18,400)		(18,400)
Tax withholding upon vesting of restricted stock awards (shares)		(311)
Vesting of early exercise options	1		1
Ending balance at Dec. 31, 2015	83,185	$ 4	441,104	(23)	(357,900)
Ending balance (shares) at Dec. 31, 2015		40,840
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(111,208)				(111,208)
Unrealized gains (losses) on investments, net	16			16
Stock-based compensation expense	70,560		70,560
Acquisition of FireLayers, Ltd. (Note 2)	176		176
Acquisition of FireLayers, Ltd. (Note 2) (shares)		111
Common stock issued	27,799		27,799
Common stock issued (shares)		2,474
Tax withholding upon vesting of restricted stock awards	(25,605)		(25,605)
Tax withholding upon vesting of restricted stock awards (shares)		(410)
Ending balance at Dec. 31, 2016	$ 44,923	$ 4	$ 514,034	$ (7)	$ (469,108)
Ending balance (shares) at Dec. 31, 2016		43,015

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (111,208)	$ (98,712)	$ (60,117)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	31,552	24,900	17,823
Loss on disposal of property and equipment	434	162	2
Amortization of investment premiums, net of accretion of purchase discounts	4	103	312
Foreign currency transaction loss	852	1,657	2,182
Provision for (recovery of) allowance for doubtful accounts	17	(231)	175
Stock-based compensation	78,696	60,094	31,004
Change in fair value of contingent consideration	(669)	0	5
Amortization of debt issuance costs and accretion of debt discount	20,842	14,933	8,753
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	(18,754)	(12,811)	(15,510)
Inventory	(113)	14	328
Deferred product costs	402	(388)	(791)
Deferred commissions	(2,862)	(7,742)	(4,122)
Prepaid expenses	(2,660)	(1,829)	(945)
Other current assets	(1,472)	104	(351)
Deferred income taxes	(1)	509	(691)
Long-term assets	959	47	(23)
Accounts payable	4,271	2,460	189
Accrued liabilities	6,398	4,448	3,995
Earn-out payment	0	0	(13)
Deferred rent	292	(165)	2,315
Deferred revenue	87,255	58,951	38,093
Net cash provided by operating activities	94,235	46,504	22,613
Cash flows from investing activities
Proceeds from sales and maturities of short-term investments	123,405	39,056	11,353
Purchase of short-term investments	(114,686)	(64,537)	(37,805)
Purchase of property and equipment	(34,407)	(25,827)	(14,988)
Payments to escrow account	(9,645)	0	0
Receipts from escrow account	260	0	0
Acquisitions of business, net of cash acquired	(54,158)	(51,553)	(53,680)
Net cash used in investing activities	(89,231)	(102,861)	(95,120)
Cash flows from financing activities
Proceeds from issuance of common stock, net of repurchases	21,779	18,583	17,640
Withholding taxes related to restricted stock net share settlement	(25,588)	(18,108)	(4,170)
Proceeds from issuance of convertible senior notes, net of discount	0	223,790	0
Payments of debt issuance costs	0	(371)	(191)
Repayments of notes payable and loans	(32)	(706)	(1,655)
Holdback payments for prior acquisitions	(1,397)	0	(741)
Payment of contingent earn-outs	0	0	(487)
Net cash (used in) provided by financing activities	(5,238)	223,188	10,396
Effect of exchange rate changes on cash and cash equivalents	(545)	(963)	(1,338)
Net (decrease) increase in cash and cash equivalents	(779)	165,868	(63,449)
Cash and cash equivalents
Beginning of period	346,205	180,337	243,786
End of period	345,426	346,205	180,337
Supplemental disclosures of cash flow information
Cash paid for interest	4,250	3,381	2,582
Cash paid for taxes	893	672	491
Supplemental disclosure of noncash investing and financing activities
Unpaid purchases of property and equipment and asset retirement obligations	6,035	4,906	2,576
Liability awards converted to equity	$ 6,059	$ 1,745	$ 0

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	The Company and Summary of Significant Accounting Policies The Company Proofpoint, Inc. (the "Company") was incorporated in Delaware in June 2002 and is headquartered in California. Proofpoint, Inc. is a leading security-as-a-service provider that enables large and mid-sized organizations worldwide to defend, protect, archive and govern their most sensitive data. The Company's security-as-a-service platform is comprised of an integrated suite of on-demand data protection solutions, including threat protection, incident response, regulatory compliance, archiving, governance, eDiscovery, and secure communication. Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP"). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Starting January 1, 2016, the Company began separately presenting the effect of exchange rate changes on cash and cash equivalents in its consolidated statements of cash flows due to growing operations in foreign currency environments. Amounts in the comparable prior periods have been reclassified to conform to the current period presentation. Refer to "Sales Commissions" below regarding the Company's change in accounting policy for sales commissions effective January 1, 2016. During the reporting periods, the Company completed a number of acquisitions which are more fully described in Note 2, "Acquisitions". The consolidated financial statements include the results of operations from these business combinations from their date of acquisition. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. Actual results could differ materially from those estimates. Significant items subject to such estimates and assumptions include those related to revenue recognition, deferred commissions, stock-based compensation expense, fair value of assets acquired and liabilities assumed in business combinations, impairment assessments of goodwill, intangible assets and other long-lived assets, loss contingencies, and the recognition and measurement of current and deferred income taxes. Foreign Currency Remeasurement and Transactions The functional currency of the Company's wholly-owned foreign subsidiaries is the U.S. dollar. Accordingly, the subsidiaries remeasure monetary assets and liabilities at period-end exchange rates, while nonmonetary items are remeasured at historical rates. Income and expense accounts are remeasured at the average exchange rates in effect during the year. Remeasurement adjustments are recognized in the consolidated statements of operations as transaction gains or losses within other income (expense), net, in the period of occurrence. Aggregate transaction losses included in determining net loss were $852 , $1,657 and $2,182 for the years ended December 31, 2016, 2015 and 2014, respectively. Cash and Cash Equivalents The Company considers currency on hand, demand deposits, time deposits, money market funds and all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash and cash equivalents. Cash and cash equivalents are held in various financial institutions in the United States and internationally. Investments The Company classifies all its investments as available-for-sale at the time of purchase since it is management's intent that these investments be available for current operations, and as such, includes these investments as short-term investments on its balance sheets. These investments consist of money market funds, corporate debt securities, commercial papers, U.S. agency and Treasury securities, and certificates of deposit with original maturities longer than three months. Short-term investments classified as available-for-sale are recorded at fair value with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of stockholders' equity. Realized gains and losses are recorded in the consolidated statements of operations and comprehensive loss based on specific identification. Inventories Inventories are stated at lower of cost or market value, with costs computed on a first-in, first-out basis. The Company periodically reviews its inventories for excess and obsolete items and adjusts carrying costs to estimated net realizable values when they are determined to be less than cost. Inventories held at December 31, 2016 and 2015 consist primarily of finished goods. Revenue Recognition The Company derives its revenue primarily from two sources: (1) subscription revenue for rights related to the use of the security-as-a-service platform and (2) hardware, training and professional services revenue provided to customers related to their use of the platform. The Company records its revenues net of any value added or sales tax. Subscription revenue is derived from a subscription‑based enterprise licensing model with contract terms typically ranging from one to three years, and consists of (i) subscription fees from the licensing of the security-as-a-service platform, (ii) subscription fees for access to the on-demand elements of the platform and (iii) subscription fees for the right to access the Company’s customer support services. Revenue is recognized when all of the following criteria have been met: • Persuasive evidence of an arrangement exists; • Delivery has occurred or services have been rendered; • Sales price is fixed or determinable; and • Collectability is reasonably assured. The Company generates sales directly through its sales team and, to a growing extent, through its channel partners. Sales to channel partners are made at a discount and revenues are recorded at this discounted price once all revenue recognition criteria are met. Channel partners generally receive an order from an end-customer prior to placing an order with the Company, and these partners do not carry any inventory of the Company's products or solutions. Payment from channel partners is not contingent on the partner’s success in sales to end-customers. In the event that the Company offers rebates, joint marketing funds, or other incentive programs to a partner, recorded revenues are reduced by these amounts accordingly. From time to time, certain third parties that the Company has an arrangement with provide the Company with referrals for which the Company pays a referral fee. The referral fee paid could vary depending on the level of effort. These fees are recorded in sales and marketing expense in proportion to the related revenue streams consistent with the sales commissions accounting. The Company did not incur any material referral fee expenses during the years ended December 31, 2016, 2015 and 2014. The Company applies industry-specific software revenue recognition guidance to transactions involving the licensing of software, as well as related support, training, and other professional services. The Company has analyzed all of the elements included in its multiple element software arrangements and has determined that it does not have sufficient VSOE of fair value to allocate revenue to its subscription and software license agreements, support, training and professional services. The Company defers all revenue under the software arrangement until the commencement of the subscription services and any associated professional services. Once the subscription services and the associated professional services have commenced, the entire fee from the arrangement is recognized ratably over the remaining period of the arrangement. If the professional services are essential to the functionality of the subscription, then the revenue recognition does not commence until such services are completed. The Company's revenue arrangements typically include subscription services to its security-as-a-service platform. These hosted on demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Certain arrangements also include the sale of hardware appliances. Revenue from hardware appliances containing software components and hardware components that function together to deliver the hardware appliance's essential functionality is excluded from the scope of the industry specific revenue recognition guidance. The Company recognizes revenue from its hosted on demand services in accordance with general revenue recognition accounting guidance. Only revenue derived from the licensing of the software is recognized in accordance with the industry specific revenue guidance. When a sales arrangement contains multiple elements, such as hardware appliances, subscription services, customer support services, and/or professional services, the Company allocates revenue to each unit of accounting or element based on a selling price hierarchy. An element constitutes a separate unit of accounting when the delivered item has standalone value and delivery of the undelivered element is probable and within the Company's control. When applying the relative selling price method, the Company determines the selling price for each deliverable using vendor-specific objective evidence (“VSOE”) of selling price. If VSOE does not exist, the Company uses third-party evidence (“TPE”) of selling price. If neither VSOE nor TPE of selling price exist for a deliverable, the Company uses its best estimate of selling price ("BESP") for that deliverable. Revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for each element. The Company determines BESP for an individual element within a multiple element revenue arrangement using the same methods utilized to determine the selling price of an element sold on a standalone basis. The Company estimates the selling price for its subscription solutions by considering internal factors such as historical pricing practices and it estimates the selling price of hardware and other services using a cost plus model. Hardware appliance revenue is recognized upon shipment. Subscription and support revenue are recognized over the contract period commencing on the start date of the contract. Professional services and training, when sold with hardware appliances or subscription and support services, are accounted for separately when those services have standalone value. In determining whether professional services and training services can be accounted for separately from subscription and support services, the Company considers the following factors: availability of the services from other vendors, the nature of the services, and the dependence of the subscription services on the customer’s decision to buy the professional services. If professional services and training do not qualify for separate accounting, the Company recognizes the professional services and training ratably over the contract term of the subscription services. Delivery generally occurs when the hardware appliance is delivered to a common carrier freight on board shipping point by the Company or the hosted service has been activated and communicated to the customer accordingly. The Company’s fees are typically considered to be fixed or determinable at the inception of an arrangement and are negotiated at the outset of an arrangement, generally based on specific products and quantities to be delivered. In the event payment terms are provided that differ significantly from the Company's standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized as the fees become paid. The Company assesses collectability based on a number of factors, including credit worthiness of the customer and past transaction history of the customer. Through December 31, 2016 , the Company has not experienced material credit losses. Deferred Revenue Deferred revenue primarily consists of billings or payments received in advance of revenue recognition from the sale of the Company’s subscription fees, training and professional services. Once the revenue recognition criteria are met, this revenue is recognized ratably over the term of the associated contract. Deferred Product Costs Deferred product costs are the incremental costs that are directly associated with each noncancellable customer contract or hosting agreement and primarily consist of cost of appliances and royalty payments made to third parties, from whom the Company has obtained licenses to integrate certain software into its products. The costs are deferred and amortized over the noncancellable term of the related customer contract or hosting agreement, which typically range from 12 to 36 months. Property and Equipment Property and equipment are stated at cost. Depreciation is computed using the straight-line method over the estimated useful life of the related asset. Amortization of leasehold improvements is computed using the straight-line method over the shorter of the lease term or the estimated useful life of the asset or improvement. Cost of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. When property and equipment are retired or otherwise disposed of, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is included in other (expense) income, net. Impairment of Intangible Assets and Other Long-Lived Assets The Company evaluates long-lived assets, including property, equipment and definitive-lived intangible assets, for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of such assets (or asset group) to the future undiscounted cash flows the assets (or asset group) is expected to generate. If the assets are considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired assets. The Company also evaluates the estimated remaining useful lives of intangible assets and other long-lived assets to assess whether a revision to the remaining periods of amortization is required. No assets were determined to be impaired to date. Software Development Costs Internally developed software includes security software developed to meet the Company's internal needs to provide cloud-based subscription services to its end-customers and business software that the Company customizes to meet its operating needs. These capitalized costs consist of internal compensation related costs and external direct costs incurred during the application development stage. The costs capitalized were not material in the years ended December 31, 2016 and 2015. The costs to develop software that is marketed externally have not been capitalized as the current software development process is essentially completed concurrently with the establishment of technological feasibility. As such, all related software development costs are expensed as incurred and included in research and development expense in the consolidated statements of operations. Internally and externally developed software is amortized over the software’s estimated useful life of three to five years. Advertising and Promotion Costs Expenses related to advertising and promotion of solutions is charged to sales and marketing expense as incurred. The Company did not incur any material advertising and promotion expenses during the years ended December 31, 2016, 2015 and 2014 . Goodwill and Intangible Assets Goodwill represents the excess of the purchase price of the acquired enterprise over the fair value of identifiable assets acquired and liabilities assumed. The Company performs an annual goodwill impairment test during the fourth quarter of the calendar year and more frequently if an event or circumstances indicates that impairment may have occurred. For the purposes of impairment testing, the Company has determined that it has one operating segment and one reporting unit. The Company performs a two-step impairment test of goodwill whereby the fair value of the reporting unit is compared to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net assets assigned to that unit, goodwill is not considered impaired and further testing is not required. If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of the reporting unit, then the Company must perform the second step of the impairment test in order to determine the implied fair value of the reporting unit’s goodwill. If the carrying value of a reporting unit’s goodwill exceeds its implied fair value, then impairment loss equal to the difference is recorded. The identification and measurement of goodwill impairment involves the estimation of the fair value of the Company. The estimate of fair value of the Company, based on the best information available as of the date of the assessment, is subjective and requires judgment, including management assumptions about expected future revenue forecasts and discount rates, changes in the overall economy, trends in the stock price and other factors. No impairment was identified by the Company as of December 31, 2016 . Intangible assets consist of developed technology, customer relationships, non-compete arrangements, trademarks and patents, and order backlog. The values assigned to intangibles are based on estimates and judgments regarding expectations for success and life cycle of solutions and technologies acquired. Intangible assets are amortized on a straight-line basis over their estimated lives, which approximate the pattern in which the economic benefits of the intangible assets are consumed, as follows (in years): Low High Patents 4 5 Developed technology 3 7 Customer relationships 2 7 Non-compete agreements 2 4 Order backlog 1 3 Tradenames and trademarks 1 5 Warranty The Company provides limited warranties on all sales and provides for the estimated cost of the warranties at the date of sale, to the extent not already provided by its own vendors. The estimated cost of warranties not provided by vendors has not been material to date. Income Taxes The Company accounts for income taxes in accordance with authoritative guidance, which requires use of the asset and liability method. Under this method, deferred income tax assets and liabilities are determined based on the difference between the consolidated financial statements carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rates expected to apply to taxable income in the years in which the differences are expected to be reversed. The Company records net deferred tax assets to the extent the Company believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operations. The Company has elected to use the "with and without" approach as described in ASC 740-20, "Intraperiod Tax Allocation" in determining the order in which tax attributes are utilized. As a result, the Company will only recognize a tax benefit from stock-based awards in additional paid-in capital if an incremental tax benefit is realized after all other tax attributes currently available to the Company have been utilized. In addition, the Company has elected to account for the impact of stock-based awards on other tax attributes, such as the research tax credit, within the consolidated statements of operations. The Company recognizes interest and penalties related to uncertain tax positions within the income tax expense line in the consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line on the consolidated balance sheets. Employee Benefit Plans The Company sponsors a 401(k) defined contribution plan covering all employees. The Company may make discretionary contributions to the 401(k). To date, no contributions have been made by the Company. Stock-Based Compensation The Company issues stock-based compensation awards to employees and directors in the form of stock options, restricted stock units ("RSUs"), performance stock units ("PSUs"), employee stock purchase plan ("ESPP") and stock bonus and other liability awards (collectively, "awards"). The Company measures and recognizes compensation expense for all stock-based awards based on the awards' fair value. Stock-based compensation for RSUs and PSUs is measured based on the value of the Company's common stock on the grant date. Stock-based compensation for employee stock options and ESPP awards are measured on the date of grant using a Black-Scholes option pricing model. Stock bonus and other liability awards are accounted for as liability-classified awards, because the obligations are based predominantly on fixed monetary amounts that are generally known at the inception of the obligation, to be settled with a variable number of shares of the Company's common stock. Awards vest either on a graded schedule or in a lump sum. The Company determines the fair value of each award as a single award and recognizes the expense on a straight-line basis over the service period of the award, which is generally the vesting period. The exercise price of stock options granted is equal to the fair value of the Company's common stock on the date of grant. Stock options expire ten years from the date of grant. Stock-based compensation expense is based on awards ultimately expected to vest, and the expense is recorded net of estimated forfeitures. Comprehensive Income (Loss) Comprehensive income (loss) includes all changes in equity that are not the result of transactions with stockholders. The Company’s comprehensive income (loss) consists of its net loss and changes in unrealized gains (losses) on its available-for-sale investments. Loss Contingencies The Company may be involved in various lawsuits, claims and proceedings that arise in the ordinary course of business. The Company records a provision for a liability when it believes that it is both probable that a liability has been incurred and the amount can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. The Company reviews these provisions at least quarterly and adjusts these provisions to reflect the impact of negotiations, settlements, rulings, and updated information. Sales Commissions Effective January 1, 2016, the Company changed its accounting policy for sales commissions that are incremental and directly related to its customer sales contracts in which revenue is deferred. These commission costs are accrued and capitalized upon execution of a non-cancelable customer contract, and subsequently expensed over the term of such contract in proportion to the related future revenue streams. For commission costs where revenue is recognized, the related commission costs are recorded in the period of revenue recognition. Prior to this change in accounting policy, commission costs were expensed in the period in which they were incurred. The adoption of this accounting policy change has been applied retrospectively to all periods presented in this Annual Report on Form 10-K, in which the cumulative effect of the change has been reflected as of the beginning of the first period presented. Deferred commissions as of December 31, 2016 and December 31, 2015 were $25,664 and $22,802 , respectively. During the years ended December 31, 2016, 2015 and 2014, the Company deferred $36,009 , $29,642 and $19,107 of commission costs and amortized $33,147 , $21,900 and $14,985 within sales and marketing expense, respectively. The Company believes this change in accounting policy is preferable as the direct and incremental commission costs are closely related to the revenue, and therefore they should be recorded as an asset and recognized as an expense over the same period that the related revenue is recognized. The cumulative effect of the change on accumulated deficit was $10,938 as of December 31, 2013. The following tables present the changes to the financial statement lines as a result of the accounting change for the periods presented in the accompanying Consolidated Financial Statements: Consolidated Balance Sheet As of December 31, 2015 As reported Adjustment As adjusted Short-term deferred commissions $ — $ 19,314 $ 19,314 Long-term deferred commissions $ — $ 3,488 $ 3,488 Accumulated deficit $ (380,702 ) $ 22,802 $ (357,900 ) Consolidated Statements of Operations Year ended December 31, 2015 Year ended December 31, 2014 As reported Adjustment As adjusted As reported Adjustment As adjusted Operating expenses: Sales and marketing $ 156,156 $ (7,742 ) $ 148,414 $ 102,455 $ (4,122 ) $ 98,333 Net loss $ (106,454 ) $ 7,742 $ (98,712 ) $ (64,239 ) $ 4,122 $ (60,117 ) Net loss per share, basic and diluted $ (2.68 ) $ 0.20 $ (2.48 ) $ (1.72 ) $ 0.11 $ (1.61 ) Weighted average shares outstanding, basic and diluted 39,787 — 39,787 37,381 — 37,381 Consolidated Statements of Comprehensive Loss Year ended December 31, 2015 Year ended December 31, 2014 As reported Adjustment As adjusted As reported Adjustment As adjusted Net loss $ (106,454 ) $ 7,742 $ (98,712 ) $ (64,239 ) $ 4,122 $ (60,117 ) Unrealized gains on short-term investments, net $ 4 $ — $ 4 $ (27 ) $ — $ (27 ) Comprehensive loss $ (106,450 ) $ 7,742 $ (98,708 ) $ (64,266 ) $ 4,122 $ (60,144 ) Recent Accounting Policies In January 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to perform a hypothetical purchase price allocation to measure goodwill impairment. A goodwill impairment will be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The update to the standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, and applied prospectively. The Company does not expect ASU 2017-04 to have a material impact on its financial statements. In January 2017, FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805) Clarifying the Definition of Business (ASU 2017-01). ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The update to the standard is effective for interim and annual periods beginning after December 15, 2017, and applied prospectively. The Company is currently evaluating the impact of the adoption of ASU 2017-01 on its consolidated financial statements. In October 2016, FASB issued Accounting Standards Update No. 2016-16, Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16). ASU 2016-16 eliminates the requirement to defer the recognition of current and deferred income taxes for intra-entity asset transfer until the asset has been sold to an outside party. Therefore, an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 is effective for interim and annual reporting periods beginning after December 15, 2017. Early adoption is permitted as of the first interim period and the amendments should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently evaluating the impact of the adoption of ASU 2016-16 on its consolidated financial statements. In August 2016, FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 makes eight targeted changes how cash receipts and cash payments are presented and classified in the statement of cash flows. The update to the standard is effective for interim and annual periods beginning after December 15, 2017, and requires adoption on a retrospective transition method unless it is impracticable to apply. The Company is currently evaluating the impact of the adoption of ASU 2016-15 on its consolidated financial statements. In June 2016, FASB issued an Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 changes the impairment model for most financial assets, and will require the use of an expected loss model in place of the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The update to the standard is effective for interim and annual periods beginning after December 15, 2019. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial statements. In March 2016, FASB issued Accounting Standards Update No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). ASU 2016-09 changes how companies account for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The update to the standard is effective for interim and annual periods beginning after December 15, 2016. The Company does not expect ASU 2016-09 to have a material impact on its financial statements. In February 2016, FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (ASU 2016-02), which requires lessees to put most leases on their balance sheets but recognize the expenses on their statements of operations in a manner similar to current practice. ASU 2016-02 states that a lessee would recognize a lease liability for the obligation to make lease payments and a right-to-use asset for the right to use the underlying asset for the lease term. The new standard is effective for interim and annual periods beginning after December 15, 2018 and early adoption is permitted. While the Company is currently assessing the impact ASU 2016-02 will have on the Company's consolidated financial statements, the Company expects the primary impact to its consolidated financial position upon adoption will be the recognition, on a discounted basis, of the Company's minimum commitments under noncancelable operating leases on our consolidated balance sheets resulting in the recording of right of use assets and lease obligations. In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers: Topic 606 (ASU 2014-09), to supersede nearly all existing revenue recognition guidance under U.S. GAAP. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 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 required under existing U.S. 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. Originally, ASU 2014-09 would be effective for t

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Acquisitions	Acquisitions Acquisitions are accounted for under the purchase method of accounting in which the tangible and identifiable intangible assets and liabilities of each acquired company are recorded at their respective fair values as of each acquisition date, including an amount for goodwill representing the difference between the respective acquisition consideration and fair values of identifiable net assets. The Company believes that for each acquisition, the combined entities will achieve savings in corporate overhead costs and opportunities for growth through expanded geographic and customer segment diversity with the ability to leverage additional products and capabilities. These factors, among others, contributed to a purchase price in excess of the estimated fair value of each acquired company's net identifiable assets acquired and, as a result, goodwill was recorded in connection with each acquisition. Goodwill related to each acquisition, other than FireLayers, Ltd., Return Path, Inc., Marble Security, Inc., Emerging Threats Pro, LLC and one of the acquisitions made in the fourth quarter of 2015, is not deductible for tax purposes. While the Company uses its best estimates and assumptions as part of the purchase price allocation process to value assets acquired and liabilities assumed at the acquisition date, these estimates and assumptions are subject to refinement. When additional information becomes available, such as finalization of negotiations of working capital adjustments and tax related matters, the Company may revise its preliminary purchase price allocation. As a result, during the preliminary purchase price allocation period, which may be up to one year from the acquisition date, the Company may record adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Subsequent to the purchase price allocation period, adjustments to assets acquired or liabilities assumed are recognized in the operating results. 2016 Acquisitions FireLayers On October 24, 2016 (the "FireLayers Acquisition Date"), pursuant to the terms of share purchase agreement, the Company acquired all shares of FireLayers, Ltd. ("FireLayers"), a provider of solutions for organizations to control and protect their cloud applications. With this acquisition, the Company will extend Targeted Attack Protection to SaaS applications, enabling customers to protect their employees using SaaS applications from advanced malware. The Company has provisionally estimated fair values of acquired tangible assets, intangible assets and liabilities at the FireLayers Acquisition Date. The amounts reported are considered provisional as the Company is completing the valuation work to determine the fair value of certain assets and liabilities acquired, largely with respect to working capital adjustments. The results of operations and the provisional fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the FireLayers Acquisition Date. Revenue from FireLayers was not material for the year ended December 31, 2016, and due to the continued integration of the combined businesses, it was impractical to determine the earnings. The total purchase price was $45,616 , net of cash acquired of $210 . Of the cash consideration paid, $7,740 was held in escrow to secure indemnification obligations, which has not been released as of the filing date of this Annual Report on Form 10-K. The Company incurred $827 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2016. Per the terms of the share purchase agreement, unvested stock options held by FireLayers employees were canceled and exchanged for unvested stock options to purchase shares of the Company's common stock. The fair value of $1,326 of these unvested options, which are subject to the recipient's continued service with the Company and thus excluded from the purchase price, will be recognized ratably as stock-based compensation expense over the required service period. Also, as part of the share purchase agreement, 111 shares of restricted stock were issued to certain key employees with the total fair value of $8,669 (see Note 9), which was not included in the purchase price. The shares of restricted stock are subject to forfeiture if employment terminates prior to the lapse of the restrictions, and their fair value is expensed as stock-based compensation expense over the vesting period. Fair value of acquired assets and liabilities assumed The following table summarizes the estimated fair values of acquired assets and liabilities: Estimated Estimated Current assets acquired $ 432 N/A Developed technology 22,600 5 Fixed assets 52 N/A Deferred tax liability, net (3,530 ) N/A Other liabilities assumed (540 ) N/A Additional-paid-in-capital (176 ) N/A Goodwill 26,988 Indefinite $ 45,826 Return Path On August 24, 2016 (the "Return Path Acquisition Date"), pursuant to the terms of an asset purchase agreement, the Company acquired Return Path, Inc.'s ("Return Path") Email Fraud Protection ("EFP") business unit. Return Path's EFP business, which provides standards-based DMARC authentication and proprietary sender-analysis capabilities, will be integrated into the Company's suite of email protection solutions to further enhance its business email compromise capabilities. The Company has provisionally estimated fair values of acquired tangible assets, intangible assets and liabilities at the Return Path Acquisition Date. The amounts reported are considered provisional as the Company is completing the valuation work to determine the fair value of certain assets and liabilities acquired, largely with respect to working capital adjustments. The results of operations and the provisional fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Return Path Acquisition Date. The Company recorded $1,025 revenue from Return Path for the year ended December 31, 2016, and due to the continued integration of the combined businesses, it was impractical to determine the earnings. Pro forma results of operations have not been presented because the acquisition was not material to the Company's results of operations. The total purchase price was $17,513 , of which $9,162 was classified and recorded as contingent consideration on the balance sheet as of the Return Path Acquisition Date. The Company expects to pay the contingent consideration within two years depending on the timing of contract assignments following the Return Path acquisition date and the maximum potential payment amount could be up to $9,644 . The Company incurred $406 in acquisition related costs which were recorded within operating expenses for the year ended December 31, 2016. The fair value of the contingent consideration liability was determined as of the acquisition date using unobservable inputs. These inputs include the estimated amount and timing of future contract assignments, the probability of success and a risk-adjusted discount rate to adjust the probability-weighted cash flows to present value. Fair value of acquired assets and liabilities assumed The following table summarizes the estimated fair values of acquired assets and liabilities: Estimated Estimated Customer relationships $ 7,600 6 Developed technology 3,900 4 Order Backlog 700 1 Deferred revenue assumed (1,200 ) N/A Goodwill 6,513 Indefinite $ 17,513 2015 Acquisitions In the fourth quarter of the year ended December 31, 2015, the Company made two acquisitions that were accounted for as business combinations. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements from the respective date of each acquisition. Pro forma results of operations for these acquisitions have not been presented because the Company does not consider these acquisitions to be material, individually or in the aggregate, to the Company's consolidated financial statements. The aggregate purchase price was $11,568 . The Company incurred $355 in acquisition related costs which were recorded within operating expenses for the year ended December 31, 2015. The following table summarizes the fair values of acquired tangible and intangible assets, liabilities and goodwill: Fair Value Estimated Current assets acquired $ 414 N/A Fixed assets acquired 73 N/A Liabilities assumed (234 ) N/A Deferred revenue assumed (1,400 ) N/A Deferred tax liability, net (45 ) N/A Customer relationships 2,800 7 Order Backlog 900 3 Developed technology 3,000 4 Goodwill 6,060 Indefinite $ 11,568 Marble Security, Inc. On July 22, 2015 (the "Marble Acquisition Date"), pursuant to the terms of an asset purchase agreement, the Company acquired certain assets of Marble Security, Inc. ("Marble"). The Marble mobile security technology proactively removes malicious mobile applications by leveraging its tight integration with the leading enterprise mobility management platforms, including MobileIron and AirWatch by VMware. The acquisition extends the Company’s threat intelligence and advanced threat protection for email and social media security into the realm of mobile devices. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Marble Acquisition Date. Revenue from Marble was not material for the year ended December 31, 2015, and due to the continued integration of the combined businesses, it was impractical to determine the earnings. Pro forma results of operations have not been presented because the acquisition was not material to the Company's results of operations. The total purchase price was $8,500 . Of the cash consideration paid, $1,700 was held in escrow, to secure indemnification obligations, which has not been released as of the filing date of this Annual Report on Form 10-K. The Company incurred $277 in acquisition related costs which were recorded within operating expenses for the year ended December 31, 2015. Fair value of acquired assets The following table summarizes the fair values of acquired tangible, intangible assets and goodwill: Fair Value Estimated Fixed assets acquired $ 25 N/A Developed technology 7,300 4 Goodwill 1,175 Indefinite $ 8,500 Emerging Threats Pro, LLC On March 6, 2015 (the "Emerging Threats Acquisition Date"), pursuant to the terms of a purchase agreement, the Company acquired 100% of membership interests in Emerging Threats Pro, LLC ("Emerging Threats"). Based in Indianapolis, Indiana, Emerging Threats provides threat intelligence solutions to help protect networks from known or potentially malicious threats. With this acquisition, the Company integrated Emerging Threat's advanced threat intelligence solutions with its existing Targeted Attack Protection and Threat Response security solutions to advance threat detection and response across the completed attack chain. The combined technology provides customers with deeper insight into cyberthreats, enabling them to react faster to inbound cyberattacks, and to identify, block, and disable previously undetected malware already embedded in their organizations. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Emerging Threat Acquisition Date. Revenue from Emerging Threats was $2,477 for the year ended December 31, 2015, and due to the continued integration of the combined businesses, it was impractical to determine the earnings. The total purchase price was $31,803 , net of cash acquired of $52 , of which $3,662 was paid in the second quarter of 2015. Of the cash consideration paid, $6,000 was held in escrow, to secure indemnification obligations, which has not been released as of the filing date of this Annual Report on Form 10-K. The Company incurred $277 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2015. Fair value of acquired assets and liabilities assumed The determination of the fair values of the assets acquired and liabilities assumed has been prepared on a provisional basis and changes to that determination may occur as additional information becomes available. The following table summarizes the fair values of tangible and intangible assets acquired, liabilities assumed and goodwill: Fair Value Estimated Current assets acquired $ 1,275 N/A Fixed assets acquired 174 N/A Liabilities assumed (448 ) N/A Deferred revenue assumed (700 ) N/A Holdback liability to the sellers (3,662 ) N/A Trade names 200 2 Customer relationships 4,200 7 Order Backlog 200 1 Developed technology 7,900 7 Goodwill 19,054 Indefinite $ 28,193 2014 Acquisitions Nexgate, Inc. On October 31, 2014 (the "Nexgate Acquisition Date"), pursuant to the terms of an agreement and plan of merger, a wholly-owned subsidiary of the Company merged with and into Nexgate, Inc. ("Nexgate"), with Nexgate surviving as a wholly-owned subsidiary of the Company. Formerly based in Burlingame, California, Nexgate provides cloud-based brand protection and compliance for enterprise social media accounts. With this acquisition, the Company's customers can effectively protect their online brand presence and social media communication infrastructure. Nexgate technology identifies and remediates fraudulent social media accounts, account hacks, and content that contains malware, spam and abusive language. In addition, the Nexgate solution enforces policy on authorized accounts and posts for compliance with a wide-range of social media regulatory requirements. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the Nexgate Acquisition Date. Revenue from Nexgate was not material for the year ended December 31, 2014. At the Nexgate Acquisition Date, the Company paid $31,771 in cash consideration, net of cash acquired of $1,032 . The Company incurred $231 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2014. Fair value of acquired assets and liabilities assumed The following table summarizes the fair values of tangible assets acquired, liabilities assumed, intangible assets and goodwill: Fair Value Estimated Current assets acquired $ 1,340 N/A Fixed assets acquired 15 N/A Liabilities assumed (64 ) N/A Deferred revenue assumed (600 ) N/A Customer relationships 3,000 7 Order backlog 200 2 Core/developed technology 3,200 4 In-process research and development 900 N/A Deferred tax liability, net (792 ) N/A Goodwill 25,604 Indefinite $ 32,803 NetCitadel, Inc. On May 13, 2014 (the "NetCitadel Acquisition Date"), pursuant to the terms of an agreement and plan of merger, a wholly-owned subsidiary of the Company merged with and into NetCitadel, Inc. ("NetCitadel"), with NetCitadel surviving as a wholly-owned subsidiary of the Company. Formerly based in Mountain View, California, NetCitadel is a pioneer in the field of automated security incident response. The acquisition extends the reach and capabilities of the Company's existing advanced threat solutions, adding additional threat verification and containment capabilities via an open platform that unifies products from the Company and other vendors. The results of operations and the fair values of the acquired assets and liabilities assumed have been included in the accompanying consolidated financial statements since the NetCitadel Acquisition Date. Revenue from NetCitadel was not material for the year ended December 31, 2014. At the NetCitadel Acquisition Date, the Company paid $22,731 . The Company incurred $345 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2014. Fair value of acquired assets and liabilities assumed The following table summarizes the fair values of tangible assets acquired, liabilities assumed, intangible assets and goodwill: Fair Value Estimated Tangible assets acquired $ 14 N/A Liabilities assumed (1,267 ) N/A Customer relationships 100 5 Core/developed technology 5,500 5 Goodwill 18,384 Indefinite $ 22,731 Pro Forma Financial Information (unaudited) The following unaudited pro forma financial information presents the combined results of operations for the years ended December 31, 2016, 2015 and 2014 as though the acquisitions that occurred during the reporting periods had occurred as of the beginning of the comparable prior annual reporting periods, with adjustments to give effect to pro forma events that are directly attributable to the acquisitions such as amortization expense of acquired intangible assets, stock-based compensation directly attributable to the acquisitions and acquisition-related transaction costs. The unaudited pro forma results do not include immaterial acquisitions made in the fourth quarter of 2015 and the acquisitions of Return Path and Marble, and do not reflect any operating efficiencies or potential cost savings which may result from the consolidation of the operations of the Company and acquisitions. Accordingly, these unaudited pro forma results are presented for informational purposes only and are not necessarily indicative of what the actual results of operations of the combined company would have been if the acquisitions had occurred at the beginning of the period presented, nor are they indicative of future results of operations: Year Ended December 31, 2016 2015 2014 Total revenue $ 375,515 $ 264,904 $ 200,124 Net loss $ (119,531 ) $ (111,440 ) $ (75,066 ) Basic and diluted net loss per share $ (2.86 ) $ (2.80 ) $ (2.01 ) The unaudited pro forma financial information includes acquisition-related transaction costs of $827 for the year ended December 31, 2016 .

Concentration of Risks

Concentration of Risks	12 Months Ended
	Dec. 31, 2016
Risks and Uncertainties [Abstract]
Concentration of Risks	Concentration of Risks Financial instruments that potentially subject the Company to credit risk consist principally of cash and cash equivalents, short-term investments and accounts receivable. The Company limits its concentration of risk in cash equivalents and short-term investments by diversifying its investments among a variety of industries and issuers and by limiting the average maturity to one year or less. The Company's professional portfolio managers adhere to this investment policy as approved by the Company's Board of Directors. The Company's investment policy is to invest only in fixed income investments denominated and payable in U.S. dollars. Investment in obligations of the U.S. government and its agencies, money market instruments, commercial paper, certificates of deposit, bankers' acceptances, corporate bonds of U.S. companies, municipal securities and asset backed securities are allowed. The Company does not invest in auction rate securities, futures contracts, or hedging instruments. The Company's accounts receivables are derived from revenue earned from customers primarily located in the United States of America. The Company performs periodic evaluations of its customers' financial condition and generally does not require its customers to provide collateral or other security to support accounts receivable, and maintains an allowance for doubtful accounts. Credit losses historically have not been material. During the years ended December 31, 2016 and 2015, no individual customers accounted for more than 10% of total revenue. One customer accounted for 12% of total revenue in the year ended December 31, 2014. One customer accounted for 21% and 16% of total accounts receivable as of December 31, 2016 and 2015, respectively.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Allowance for doubtful accounts activity and balances are presented below: Balance at Beginning of Period Additions (Reversals) to Costs and Expenses Write Offs Balance at End of Period Year ended December 31, 2014 $ 276 $ 158 $ (5 ) $ 429 Year ended December 31, 2015 $ 429 $ (169 ) $ (61 ) $ 199 Year ended December 31, 2016 $ 199 $ 156 $ (139 ) $ 216 Property and equipment at December 31, 2016 and 2015 consist of the following: Useful Life (in years) December 31, 2016 2015 Computer equipment 2 to 4 $ 92,462 $ 63,867 Software 2 to 5 2,266 1,684 Furniture 5 1,532 1,074 Office equipment 2 to 5 467 347 Leasehold improvements 5 years, or lease term, if shorter 6,198 4,728 Other 2 59 59 Construction in progress 1,483 934 104,467 72,693 Less: Accumulated depreciation (51,944 ) (38,192 ) $ 52,523 $ 34,501 Property and equipment acquired under capital leases: December 31, 2016 2015 Computer equipment $ 453 $ 453 Less: Accumulated depreciation (341 ) (310 ) $ 112 $ 143 Depreciation expense for the years ended December 31, 2016, 2015 and 2014 , was approximately $17,131 , $12,644 , and $9,033 , respectively. This included depreciation expense for assets under capital leases of $31 , $23 and $19 for the years ended December 31, 2016, 2015 and 2014 , respectively. Accrued liabilities at December 31, 2016 and 2015 consisted of the following: December 31, 2016 2015 Accrued compensation $ 30,295 $ 21,994 Customer deposits 173 1,384 Accrued royalties 754 509 Acquisition-related contingent consideration 7,629 — Other 11,914 11,166 $ 50,765 $ 35,053

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The goodwill activity and balances are presented below: December 31, 2016 2015 Opening balance $ 133,769 $ 107,504 Add: Goodwill from acquisitions 33,501 26,289 Less: Other adjustments to Goodwill — (24 ) Closing balance $ 167,270 $ 133,769 The goodwill balance as of December 31, 2016 and 2015 was the result of the acquired businesses (see Note 2). Intangible Assets Intangible assets consisted of the following: December 31, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technology $ 83,769 $ (38,042 ) $ 45,727 $ 57,268 $ (28,618 ) $ 28,650 Customer relationships 17,943 (3,228 ) 14,715 23,382 (12,291 ) 11,091 Non-compete agreements — — — 804 (691 ) 113 Trademark and patents 930 (667 ) 263 1,006 (502 ) 504 Order backlog 1,600 (597 ) 1,003 1,300 (328 ) 972 $ 104,242 $ (42,534 ) $ 61,708 $ 83,760 $ (42,430 ) $ 41,330 Amortization expense of intangibles totaled $14,421 , $12,256 and $8,790 during the years ended December 31, 2016, 2015 and 2014 , respectively. Future estimated amortization costs of intangible assets as of December 31, 2016 are presented below: Year Ended December 31, 2017 $ 16,381 2018 15,291 2019 11,926 2020 9,221 2021 7,422 Thereafter 1,467 $ 61,708

Fair Value Measurements and Inv

Fair Value Measurements and Investments	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements and Investments	Fair Value Measurements and Investments Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., the “exit price”) in an orderly transaction between market participants at the measurement date. A hierarchy for inputs used in measuring fair value has been defined to minimize the use of unobservable inputs by requiring the use of observable market data when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on active market data. Unobservable inputs are inputs that reflect the Company’s assumptions about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances. The fair value hierarchy prioritizes the inputs into three broad levels: • Level 1: Quoted (unadjusted) prices in active markets for identical assets or liabilities. The Company’s Level 1 assets generally consist of money market funds. • Level 2: Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities 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 asset or liability. The Company’s Level 2 assets and liabilities consist of corporate debt securities, commercial papers, U.S. agency and Treasury securities and convertible senior notes. • Level 3: Unobservable inputs to the valuation methodology that are supported by little or no market activity and that are significant to the measurement of the fair value of the assets or liabilities. Level 3 assets and liabilities include those whose fair value measurements are determined using pricing models, discounted cash flow methodologies or similar valuation techniques, as well as significant management judgment or estimation. In connection with the acquisition of Return Path, a liability was recognized on Return Path Acquisition Date for the estimate of the fair value of the Company's contingent payment. The Company determined the fair value of the Acquisition-related contingent liability based on the estimated amount and timing of future contract assignments, and the probability of success. This fair value measurement is based on significant inputs not observable in the market and thus represent Level 3 measurement. The following tables summarize, for each category of assets or liabilities carried at fair value, the respective fair value as of December 31, 2016 and 2015 and the classification by level of input within the fair value hierarchy: Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 304,020 $ 304,020 $ — $ — Corporate debt securities 2,139 — 2,139 — Commercial papers 13,243 — 13,243 — Short-term investments: Corporate debt securities 24,450 — 24,450 — Commercial papers 22,979 — 22,979 — U.S. agency securities 1,946 — 1,946 — U.S. Treasury securities 1,950 — 1,950 — Total financial assets $ 370,727 $ 304,020 $ 66,707 $ — Liabilities Acquisition-related contingent consideration $ 8,233 $ — $ — $ 8,233 Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 306,983 $ 306,983 $ — $ — Corporate debt securities 3,178 — 3,178 — Commercial papers 8,996 — 8,996 — Short-term investments: Corporate debt securities 36,527 — 36,527 — Commercial papers 16,290 — 16,290 — U.S. agency securities 5,414 — 5,414 — U.S. Treasury securities 1,801 — 1,801 — Total financial assets $ 379,189 $ 306,983 $ 72,206 $ — Based on quoted market prices as of December 31, 2016 , the fair value of the 0.75% and 1.25% Convertible Senior Notes (Note 8) were approximately $257,600 and $364,389 , respectively, determined using Level 2 inputs as they are not actively traded in markets. The following table represents a reconciliation of the Acquisition-related contingent consideration liability measured at fair value on a recurring basis, using significant unobservable inputs (Level 3): Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Balance as of December 31, 2015 $ — Additions during the period 9,162 Payments during the period (260 ) Adjustments to fair value during the period recorded in General and Administrative expenses (669 ) Balance as of December 31, 2016 $ 8,233 The carrying amounts of the Company's cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to their short maturities. Investments The cost and fair value of the Company’s cash and available-for-sale investments as of December 31, 2016 and 2015 were as follows: December 31, 2016 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 26,024 $ — $ — $ 26,024 Money market funds 304,020 — — 304,020 Corporate debt securities 2,140 — (1 ) 2,139 Commercial papers 13,243 — — 13,243 Total $ 345,427 $ — $ (1 ) $ 345,426 Short-term investments: Corporate debt securities $ 24,458 $ — $ (8 ) $ 24,450 Commercial papers 22,979 — — 22,979 U.S. agency securities 1,945 1 — 1,946 U.S. Treasury securities 1,950 — — 1,950 Total $ 51,332 $ 1 $ (8 ) $ 51,325 December 31, 2015 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 27,048 $ — $ — $ 27,048 Money market funds 306,983 — — 306,983 Corporate debt securities 3,178 — — 3,178 Commercial papers 8,996 — — 8,996 Total $ 346,205 $ — $ — $ 346,205 Short-term investments: Corporate debt securities $ 36,549 $ — $ (22 ) $ 36,527 Commercial papers 16,290 — — 16,290 U.S. agency securities 5,415 — (1 ) 5,414 U.S. Treasury securities 1,801 — — 1,801 Total $ 60,055 $ — $ (23 ) $ 60,032 As of December 31, 2016 and 2015 , all investments mature in less than one year . Fair values for marketable securities are based on quoted market prices for the same or similar instruments. The Company reviews its investments on a quarterly basis to identify and evaluate investments that have an indication of possible impairment and has determined that no other-than-temporary impairments were required to be recognized during the years ended December 31, 2016, 2015 and 2014.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases The Company leases certain of its facilities under noncancellable operating leases with various expiration dates through 2024. Premises rent expense was $5,054 , $3,831 and $3,283 for the years ended December 31, 2016, 2015 and 2014 , respectively. Capital Leases In July 2012, the Company entered into two lease agreements to lease certain office equipment with expiration dates in July and October 2015. The leases bear an annual interest rate of 4.50% and were secured by fixed assets used in the Company's office locations. Also, in July 2015, the Company entered into a new lease agreement (the "July 2015 Lease") to lease certain office equipment with expiration in August 2020. The July 2015 Lease bears an annual interest rate of 6.5% . All leases are secured by fixed assets used in the Company's office locations. At December 31, 2016 , future annual minimum lease payments under noncancellable operating and capital leases were as follows: Capital Operating 2017 $ 41 $ 13,911 2018 39 13,337 2019 37 11,095 2020 22 5,027 2021 — 2,220 Thereafter — 5,616 Total minimum lease payments 139 $ 51,206 Less: Amount representing interest (16 ) Present value of capital lease obligations 123 Less: Current portion (32 ) Long-term portion of capital lease obligations $ 91 Contingencies Under the indemnification provisions of the Company's customer agreements, the Company agrees to indemnify and defend and hold harmless its customers against, among other things, infringement of any patent, trademark or copyright under any country's laws or the misappropriation of any trade secret arising from the customers' legal use of the Company's solutions. The exposure to the Company under these indemnification provisions is generally limited to the total amount paid by the customers under the applicable customer agreement. However, certain indemnification provisions potentially expose the Company to losses in excess of the aggregate amount paid to the Company by the customer under the applicable customer agreement. To date, there have been no claims against the Company or its customers pursuant to these indemnification provisions. Legal Contingencies From time to time, the Company may be involved in legal proceedings and subject to claims in the ordinary course of business. On December 16, 2013, Finjan, Inc. sued the Company and its wholly-owned subsidiary, Armorize Technologies, Inc., in the United States District Court, Northern District of California for alleged patent infringement of a variety of its patents, demanding preliminary and permanent injunctive relief, and unspecified damages. On June 3, 2016, the Company executed a Confidential Patent License, Settlement and Release Agreement with Finjan, Inc. The Company evaluated the transaction as a multiple-element arrangement and allocated the payment of $10,900 to each identifiable element using its relative fair value. Based on estimates of fair value, the Company determined that the primary benefit of the arrangement is avoided litigation cost and the release of any potential past claims, with no material value attributable to future use or benefit. Accordingly, the Company recorded a $10,900 settlement charge within general and administrative expense in its consolidated statement of operations for the year ended December 31, 2016. The settlement charge was reduced by $1,938 received from escrow as part of the Armorize Technologies, Inc. Acquisition Agreement. The Company paid $4,300 to Finjan, Inc. in June 2016, $3,300 in December 2016, and will pay $3,300 on or before January 3, 2018. The remaining $3,300 payable was recorded in other-long term liabilities on the balance sheet as of December 31, 2016.

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2016
Senior Notes [Abstract]
Convertible Senior Notes	Convertible Senior Notes 0.75% Convertible Senior Notes due June 2020 On June 17, 2015 , the Company issued $200,000 principal amount of 0.75% Convertible Senior Notes (the " 0.75% Notes") due 2020 in a private offering to qualified institutional buyers ("Holders") pursuant to Rule 144A under the Securities Act of 1934, as amended (the "Securities Act"). The initial Holders of the 0.75% Notes also had an option to purchase an additional $30,000 in principal amount which was exercised in full. The net proceeds after the agent's discount and issuance costs of $6,581 from the 0.75% Notes offering were approximately $223,419 . The Company uses the net proceeds for working capital and general corporate purposes, which may include funding the Company's operations, capital expenditures, and potential acquisitions of businesses, products or technologies believed to be of strategic importance. The 0.75% Notes bear interest at 0.75% per year, payable semi-annually in arrears every June 15 and December 15, beginning on December 15, 2015. The 0.75% Notes are unsecured and rank senior in right of payment to any indebtedness expressly subordinated in right of payment to the 0.75% Notes. They rank equally with the Company's other existing and future unsecured indebtedness that is not subordinated and are structurally subordinated to any current or future secured indebtedness to the extent of the value of the assets securing the indebtedness and other liabilities of the Company's subsidiaries. The initial conversion rate is 12.3108 shares of the Company’s common stock per $1 principal amount of notes which equates to 2,831 shares of common stock, or a conversion price equivalent of $81.23 per share of common stock. Throughout the term of the 0.75% Notes, the conversion rate may be adjusted upon the occurrence of certain events, such as the payment of cash dividends or issuance of stock warrants. The 0.75% Notes mature on June 15, 2020 , unless repurchased, redeemed or converted in accordance with their terms prior to such date. At the Company's option, on or after June 20, 2018 , the Company will be able to redeem all or a portion of the 0.75% Notes at 100% of the principal amount, plus any accrued and unpaid interest, under certain conditions. The Company may redeem the 0.75% Notes in shares of the Company’s common stock, cash, or some combination of each. Prior to December 15, 2019 , the 0.75% Notes will be convertible at the option of the Holders only upon the satisfaction of certain conditions and during certain periods if any of the following events occur: • during the calendar quarter commencing after September 30, 2015, if the last reported sale price of the Company's common stock is greater than or equal to 130% of the applicable conversion price on each such trading day for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the preceding calendar quarter; • during the 5 business day period after any 5 consecutive trading day period in which the trading price, as defined, per $1 principal amount of the 0.75% Notes for each trading day of such measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the applicable conversion rate on each such trading day; • upon a notice of redemption by the Company; or • upon the occurrence of specified corporate transactions. Subsequent to December 15, 2019 , Holders may convert their 0.75% Notes at the applicable conversion rate at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date. Holders of the 0.75% Notes also have the right to require the Company to repurchase all or a portion of the 0.75% Notes at 100% of the principal amount, plus accrued and unpaid special interest, if any, upon the occurrence of certain fundamental changes to the Company. In accordance with the authoritative accounting guidance, the Company allocated the total amount of the 0.75% Notes into liability and equity components. The carrying value of the liability component at issuance was calculated as the present value of its cash flows using a discount rate of 6.50% based on the a blended rate between the yield rate for a Moody's B1 rating and the average debt rate for comparable convertible transactions from similar companies. The difference between the 0.75% Notes principal and the carrying value of the liability component, representing the value of conversion premium assigned to the equity component, was recorded as an increase to additional paid in capital and as a debt discount on the issuance date. The equity component is being accreted using the effective interest rate method over the period from the issuance date through June 15, 2020 as a non-cash charge to interest expense. The amount recorded to additional paid in capital is not remeasured as long as it continues to meet the conditions for equity classification. Upon issuance of the 0.75% Notes, the Company recorded $174,359 as debt and $55,641 as additional paid in capital within stockholders' equity. Additionally, the debt discount and issuance costs were allocated based on the total amount incurred to the liability and equity components using the same proportions as the proceeds from the 0.75% Notes. The equity issuance costs of $1,592 were recorded as a decrease to additional paid-in capital at the issuance date. 1.25% Convertible Senior Notes due December 2018 On December 11, 2013 , the Company issued $175,000 principal amount of 1.25% Convertible Senior Notes (the " 1.25% Notes," and together with the 0.75% Notes, the “Notes”) due 2018 in a private offering to Holders pursuant to Rule 144A under the Exchange Act. The initial Holders of the 1.25% Notes also had an option to purchase an additional $26,250 in principal amount which was exercised in full. The net proceeds after the agent's discount and issuance costs of $5,803 from the 1.25% Notes offering were approximately $195,446 . The Company uses the net proceeds for working capital and general corporate purposes, which may include funding the Company's operations, capital expenditures, potential acquisitions of businesses, products or technologies believed to be of strategic importance. The 1.25% Notes bear interest at 1.25% per year, payable semi-annually in arrears every June 15 and December 15, beginning on June 15, 2014. On July 5, 2016, the Company and the Trustee executed a supplemental indenture to address an administrative issue with the timing of a redemption notice. The amendment did not adversely affect the right of any holder and therefore did not require their consent. There were no other changes to terms of the Notes. The 1.25% Notes are unsecured and rank senior in right of payment to any indebtedness expressly subordinated in right of payment to the 1.25% Notes. They rank equally with the Company's other existing and future unsecured indebtedness that is not subordinated and are structurally subordinated to any current or future secured indebtedness to the extent of the value of the assets securing the indebtedness and other liabilities of the Company's subsidiaries. The initial conversion rate is 25.6271 shares of the Company’s common stock per $1 principal amount of the 1.25% Notes which equates to 5,158 shares of common stock, or a conversion price equivalent of $39.02 per share of common stock. Throughout the term of the 1.25% Notes, the conversion rate may be adjusted upon the occurrence of certain events, such as the payment of cash dividends or issuance of stock warrants. The 1.25% Notes mature on December 15, 2018 , unless repurchased, redeemed or converted in accordance with their terms prior to such date. At the Company's option, on or after December 20, 2016 , the Company will be able redeem all or a portion of the 1.25% Notes at 100% of the principal amount, plus any accrued and unpaid interest, under certain conditions. The Company may redeem the 1.25% Notes in shares of the Company’s common stock, cash, or some combination of each. Prior to June 15, 2018 , the 1.25% Notes will be convertible at the option of the Holders only upon the satisfaction of certain conditions and during certain periods if any of the following events occur: • during the calendar quarter commencing after March 31, 2014, if the last reported sale price of the Company's common stock is greater than or equal to 130% of the applicable conversion price on each such trading day for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the preceding calendar quarter; • during the 5 business day period after any 5 consecutive trading day period in which the trading price, as defined, per $1 principal amount of the 1.25% Notes for each trading day of such measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the applicable conversion rate on each such trading day; • upon a notice of redemption by the Company; or • upon the occurrence of specified corporate transactions. Subsequent to June 15, 2018 , Holders may convert their 1.25% Notes at the applicable conversion rate at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date. Holders of the 1.25% Notes also have the right to require the Company to repurchase all or a portion of the 1.25% Notes at 100% of the principal amount, plus accrued and unpaid special interest, if any, upon the occurrence of certain fundamental changes to the Company. In accordance with the authoritative accounting guidance, the Company allocated the total amount of the 1.25% Notes into liability and equity components. The carrying value of the liability component at issuance was calculated as the present value of its cash flows using a discount rate of 6.5% based on the a blended rate between the yield rate for a Moody's B1-rating and the average debt rate for comparable convertible transactions from similar companies. The difference between the 1.25% Notes principal and the carrying value of the liability component, representing the value of conversion premium assigned to the equity component, was recorded as an increase to additional paid in capital and as a debt discount on the issuance date. The equity component is being accreted using the effective interest rate method over the period from the issuance date through December 15, 2018 as a non-cash charge to interest expense. The amount recorded to additional paid in capital is not remeasured as long as it continues to meet the conditions for equity classification. Upon issuance of the Notes, the Company recorded $156,672 as debt and $44,578 as additional paid in capital within stockholders' equity. Additionally, the debt discount and issuance costs were allocated based on the total amount incurred to the liability and equity components using the same proportions as the proceeds from the 1.25% Notes. The equity issuance costs of $1,285 were recorded as a decrease to additional paid-in capital at the issuance date. The following tables represent the carrying values of all Notes as of December 31, 2016 and 2015 : December 31, 2016 0.75% Notes 1.25% Notes TOTAL Liability component: Principal $ 230,000 $ 201,250 $ 431,250 Less: debt discount and issuance costs, net of amortization (43,896 ) (20,813 ) (64,709 ) Net carrying amount $ 186,104 $ 180,437 $ 366,541 Equity component (1) $ 54,049 $ 43,293 $ 97,342 December 31, 2015 0.75% Notes 1.25% Notes TOTAL Liability component: Principal $ 230,000 $ 201,250 $ 431,250 Less: debt discount and issuance costs, net of amortization (54,952 ) (30,599 ) (85,551 ) Net carrying amount $ 175,048 $ 170,651 $ 345,699 Equity component (1) $ 54,049 $ 43,293 $ 97,342 (1) Recorded on the consolidated balance sheets as additional paid-in capital, net of the $2,877 issuance costs in equity For the years ended December 31, 2016, 2015 and 2014 , the Company incurred the following interest expense related to the Notes: 2016 2015 2014 Interest expense related to contractual interest coupon $ 4,240 $ 3,441 $ 2,511 Amortization of debt discount and issuance costs 20,842 14,933 8,753 Total $ 25,082 $ 18,374 $ 11,264

Equity Award Plans

Equity Award Plans	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Award Plans	Equity Award Plans Stock-Based Compensation Plans On March 30, 2012, the Board of Directors and the Company’s stockholders approved the 2012 Equity Incentive Plan (the "2012 Plan"), which became effective in April 2012. The Company has four equity incentive plans: the Company’s 2002 stock option plan (the “2002 Plan”), the 2012 Plan, and two FireLayers Plans assumed by the Company upon the acquisition of FireLayers in 2016. Upon the Company's initial public offering, all shares that were reserved under the 2002 Plan but not issued, and shares issued but subsequently returned to the plan through forfeitures, cancellations and repurchases became part of the 2012 Plan and no further shares will be granted pursuant to the 2002 Plan. No further shares will be granted pursuant to both FireLayers plans. All outstanding stock awards under the 2002 Plan, the two FireLayers plans and 2012 Plan will continue to be governed by their existing terms. Under the 2012 Plan, the Company has the ability to issue incentive stock options (“ISOs”), nonstatutory stock options (“NSOs”), restricted stock awards, stock bonus awards, stock appreciation rights ("SARs"), restricted stock units ("RSUs"), and performance stock units ("PSUs"). The 2012 Plan also allows direct issuance of common stock to employees, outside directors and consultants at prices equal to the fair market value at the date of grant of options or issuance of common stock. Additionally, the 2012 Plan provides for the grant of performance cash awards to employees, directors and consultants. The Company has the right to repurchase any unvested shares (at the option exercise price) of common stock issued directly or under option exercises. The right of repurchase generally expires over the vesting period. Stock bonus and other liability awards are accounted for as liability-classified awards, because the obligations are based predominantly on fixed monetary amounts that are generally known at the inception of the obligation, to be settled with a variable number of shares of the Company's common stock. Under the equity incentive plans, the term of an option grant shall not exceed ten years from the date of its grant and options generally vest over a three to four -year period, with vesting on a monthly or annual interval. Under the 2012 Plan, 20,316 shares of common stock are reserved for issuance to eligible participants. As of December 31, 2016 , 6,139 shares were available for future grant. Restricted stock awards generally vest over a four -year period. Stock Options The fair value of options granted is estimated on the grant date using the Black-Scholes option valuation model. This valuation model for stock-based compensation expense requires the Company to make assumptions and judgments about the variables used in the calculation, including the expected term (weighted-average period of time that the options granted are expected to be outstanding), the volatility of the common stock price and the assumed risk-free interest rate. The Company recognizes stock-based compensation expense for only those shares expected to vest over the requisite service period of the award. The Company determines its estimated forfeiture rate based on an analysis of its actual forfeitures and will continue to evaluate the appropriateness of the forfeiture rate based on recent forfeiture activity and expected future employee turnover, if any. Changes in the estimated forfeiture rate can have a significant effect on reported stock-based compensation expense, as the cumulative effect of adjusting the rate for all expense is recognized in the period the forfeiture estimate is changed. No compensation cost is recorded for options that do not vest and the compensation cost from vested options, whether forfeited or not, is not reversed. The weighted average fair value of stock options granted to employees during the years ended December 31, 2016, 2015 and 2014 , was $24.04 , $28.20 and $20.25 , respectively. The fair values were estimated on the grant dates using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2016 2015 2014 Expected life (in years) 5.31 - 6.08 5.31 - 6.08 5.31 - 6.08 Volatility 45% 50% - 52% 54% - 58% Risk-free interest rate 1.3% - 1.4% 1.6% - 1.8% 1.8% - 1.9% Dividend yield —% —% —% The estimate for expected life of options granted reflects the midpoint of the vesting term and the contractual life computed utilizing the simplified method as allowed by the SEC staff. The Company does not have significant historical share option exercise experience and hence considers the expected term assumption calculated using the simplified method to be reasonable. Starting January 1, 2016, the expected volatility of the Company's common stock is based on the Company's historical volatility. Prior to January 1, 2016, the common stock price volatility was determined based on the historical average volatilities of the common stock of a group of publicly-traded peer companies that operate in a similar industry as the Company did not have sufficient trading history for its common stock. The risk-free interest rate used was the Federal Reserve Bank's constant maturities interest rate commensurate with the expected life of the options in effect at the time of the grant. The expected dividend yield was zero , as the Company does not anticipate paying a dividend within the relevant time frame. The Company realized no income tax benefit from stock option exercises in each of the periods presented due to recurring losses and valuation allowances. Stock option activity under the Plan is as follows: Shares subject to Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Balance at December 31, 2013 7,223 $ 8.17 6.82 $ 180,543 Options granted 563 36.91 Options exercised (1,984 ) 6.56 Options forfeited and canceled (514 ) 16.25 Balance at December 31, 2014 5,288 11.06 6.31 $ 196,608 Options granted 284 57.47 Options exercised (1,429 ) 8.31 Options forfeited and canceled (101 ) 19.11 Balance at December 31, 2015 4,042 15.10 5.77 $ 201,736 Options assumed per FireLayers acquisition 20 4.33 Options granted 237 54.11 Options exercised (1,089 ) 11.59 Options forfeited and canceled (27 ) 43.15 Balance at December 31, 2016 3,183 $ 18.91 5.39 $ 164,842 Exercisable, December 31, 2016 2,590 $ 12.68 4.73 $ 150,144 Vested and expected to vest, December 31, 2016 3,124 $ 18.31 5.33 $ 163,622 The total intrinsic value of options exercised was $58,061 , $72,993 and $64,455 , for the years ended December 31, 2016, 2015 and 2014 , respectively. Total cash proceeds from such option exercises were $12,620 , $11,868 and $13,007 for the years ended December 31, 2016, 2015 and 2014 , respectively. The grant date fair value of options that vested was $9,106 , $9,520 and $10,755 during the years ended December 31, 2016, 2015 and 2014 , respectively. As of December 31, 2016, the Company had unrecognized stock-based compensation expense of $11,800 related to stock options that will be recognized, net of forfeitures, over the average remaining vesting term of the options of 2.09 years. Restricted Stock Units A following table summarized the activity of RSUs, PSUs and stock-bonus awards: RSUs and PSUs Outstanding Number of Shares Granted Fair Value Per Unit Awarded and unvested at December 31, 2013 1,214 $ 29.57 Awards granted 2,362 39.77 Awards vested (396 ) 30.79 Awards forfeited (246 ) 31.59 Awarded and unvested at December 31, 2014 2,934 37.45 Awards granted 1,541 61.48 Awards vested (897 ) 38.70 Awards forfeited (267 ) 41.89 Awarded and unvested at December 31, 2015 3,311 47.94 Awards granted 1,605 64.08 Awards vested (1,116 ) 44.73 Awards forfeited (335 ) 51.40 Awarded and unvested at December 31, 2016 3,465 $ 56.11 As of December 31, 2016 , there was $118,420 of unamortized stock-based compensation expense related to unvested RSUs, which are expected to be recognized over a weighted average period of 2.97 years. The Company granted 146 and 189 PSUs in the years ended December 31, 2016 and 2015, respectively. The PSU vesting conditions were based on individual performance targets. Unamortized expense was $9,660 as of December 31, 2016, net of estimated forfeitures. Stock Bonus Awards and Other Liability Awards The total accrued liability for the stock bonus awards and other liability awards was $7,855 and $5,676 as of December 31, 2016 and 2015, respectively. 93 and 30 shares of common stock earned under the stock bonus program were issued during the years ended December 31, 2016 and 2015, respectively. Stock based compensation expense related to stock bonus program were $5,288 , $3,792 and $1,771 for the years ended December 31, 2016, 2015 and 2014. In March 2015, the Company issued liability awards with a fair value of $6,885 , which vest over three years period and are subject to continuous service and other conditions. The liability awards will be settled with a variable number of shares of the Company's common stock. During the year ended December 31, 2016, 45 shares were vested and issued. The Company recognized $2,299 and $1,884 of stock-based compensation expense related to these liability awards in the years ended December 31, 2016 and 2015. Employee Stock Purchase Plan On March 30, 2012, the Board of Directors and the Company’s stockholders approved the 2012 Employee Stock Purchase Plan (the "ESPP"), which became effective in April 2012. A total of 745 shares of the Company's common stock was initially reserved for future issuance under the ESPP. The number of shares reserved for issuance under the ESPP will increase automatically on January 1 of each of the first eight years commencing with 2013 by the number of shares equal to 1% of the Company's shares outstanding on the immediately preceding December 31, but not to exceed 1,490 shares, unless the Board of Directors, in its discretion, determines to make a smaller increase. As of December 31, 2016 , there were 1,360 shares of the Company's common stock available for future issuance under the ESPP. The fair value of the option component of the ESPP shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Year ended December 31, 2016 2015 2014 Expected life (in years) 0.5 0.5 0.5 Volatility 37% - 48% 42% - 47% 45% - 52% Risk-free interest rate 0.38% - 0.45% 0.08% - 0.33% 0.05% - 0.07% Dividend yield —% —% —% The Company issued 200 shares and 161 shares under the ESPP in 2016 and 2015, respectively, at a weighted average exercise price per share of $45.65 and $41.84 , respectively. As of December 31, 2016 , the Company expects to recognize $1,510 of the total unamortized compensation cost related to employee purchases under the ESPP over a weighted average period of 0.37 years. Restricted Stock The Company granted 54 shares of restricted stock in the fourth quarter of 2014 to certain key employees with a total fair value of $2,357 and two -year cliff vesting in 2016. The shares fully vested in 2016. The Company granted 111 shares of restricted stock in the fourth quarter of 2016 to certain key employees with a total fair value of $8,669 and three -year annual vesting. As of December 31, 2016, there was $8,123 of unamortized stock-based compensation expense related to the unvested shares of restricted stock. The shares of restricted stock are subject to forfeiture if employment terminates prior to the lapse of the restrictions, and are expensed over the vesting period. They are considered issued and outstanding shares of the Company at the grant date and have the same rights as other shares of common stock.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share of common stock is calculated by dividing the net loss 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 basic net loss per share of common stock excludes those shares subject to repurchase related to stock options or restricted stock that were exercised or issued prior to vesting as these shares are not deemed to be issued for accounting purposes until they vest. Diluted net loss per share of common stock is computed by dividing the net loss using the weighted‑average number of shares of common stock, excluding common stock subject to repurchase, and, if dilutive, potential shares of common stock outstanding during the period. Basic and diluted net loss per common share was the same for all periods presented as the impact of all potentially dilutive securities outstanding was anti-dilutive. The following table presents the potentially dilutive common shares outstanding that were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been anti-dilutive: December 31, 2016 2015 2014 Stock options to purchase common stock 3,183 4,042 5,288 Restricted stock units 3,465 3,311 2,934 Employee stock purchase plan 92 81 90 Common stock subject to repurchase 135 54 54 Bonus shares 159 174 37 1.25% Convertible senior notes 5,158 5,158 5,158 0.75% Convertible senior notes 2,831 2,831 — Total 15,023 15,651 13,561

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting Operating segments are reported in a manner consistent with the internal reporting supported and defined by the components of an enterprise about which separate financial information is available, provided and is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is its Chief Executive Officer. The Company’s Chief Executive Officer reviews financial information presented on a consolidated basis. The Company has one business activity, and there are no segment managers who are held accountable for operations, operating results and plans for levels or components below the consolidated unit level. Accordingly, the Company determined that it has one operating and reportable segment. Starting January 1, 2016, the Company included privacy solutions into the "Archiving, Privacy and Governance" group. Amounts in the comparable prior period have been reclassified to conform to the current presentation. The following sets forth total revenue by solutions offered by the Company and by geographic area. Revenue by geographic area is based upon the billing address of the customer: Year Ended December 31, 2016 2015 2014 Total revenue by solution: Protection and Advanced Threat $ 272,621 $ 183,050 $ 126,812 Archiving, Privacy and Governance 102,875 82,347 68,795 Total revenue $ 375,496 $ 265,397 $ 195,607 Year Ended December 31, 2016 2015 2014 Total revenue by geographic area: United States $ 312,601 $ 218,424 $ 157,593 Rest of world 62,895 46,973 38,014 Total revenue $ 375,496 $ 265,397 $ 195,607 The following sets forth long-lived tangible assets by geographic area: December 31, 2016 2015 Long-lived assets: United States $ 43,789 $ 29,514 Rest of world 8,734 4,987 Total long-lived assets $ 52,523 $ 34,501

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The domestic and foreign components of loss before (provision for) benefit from income taxes were as follows for the years ended December 31, 2016, 2015 and 2014 : Year Ended December 31, 2016 2015 2014 Domestic $ (112,904 ) $ (101,453 ) $ (65,433 ) Foreign 2,682 3,376 5,003 Loss before (provision for) benefit from income taxes $ (110,222 ) $ (98,077 ) $ (60,430 ) The (provision for) benefit from income taxes is comprised of: Year Ended December 31, 2016 2015 2014 Current tax expense: Federal $ — $ — $ — State 72 54 121 Foreign 795 514 530 Total current 867 568 651 Deferred tax expense: Federal 411 105 (792 ) State — (45 ) — Foreign (292 ) 7 (172 ) Total deferred 119 67 (964 ) Provision for (benefit from) income taxes $ 986 $ 635 $ (313 ) The reconciliation of income tax expense (benefit) at the statutory federal income tax rate of 34% to the income tax provision (benefit) included in the consolidated statements of operations for the years ended December 31, 2016, 2015 and 2014 is as follows: Year Ended December 31, 2016 2015 2014 Tax at federal statutory rate $ (37,476 ) $ (33,346 ) $ (20,546 ) Foreign income tax rate differential (187 ) (270 ) (600 ) State, net of federal benefit (3,478 ) (2,952 ) (1,585 ) Stock compensation charges 3,517 2,393 1,304 SubPart F and other permanent items 1,422 1,434 2,579 Provision to return and other 1,419 749 3,621 Research and development credits (4,464 ) (2,920 ) (2,052 ) Uncertain tax positions 749 561 391 Valuation allowance 39,484 34,986 16,575 Provision (benefit from) for income taxes $ 986 $ 635 $ (313 ) Deferred tax assets and liabilities reflect the net tax effects of net operating loss and tax credit carryovers and the temporary differences between the carrying amount of assets and liabilities for financial reporting and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets were as follows at December 31, 2016 and 2015: At December 31, 2016 2015 Deferred tax assets: Net operating loss carryforwards $ 119,168 $ 98,882 Tax credit carryforwards 13,966 10,856 Research expenditures 2,401 2,301 Deferred revenue 13,698 12,165 Stock compensation 18,509 13,289 Fixed assets 207 1,426 Accruals and other 11,554 8,997 Gross deferred tax assets 179,503 147,916 Valuation allowance (141,398 ) (101,909 ) Total deferred tax assets 38,105 46,007 Deferred tax liabilities: Intangible assets and other (8,793 ) (7,547 ) Deferred commissions (9,545 ) (8,438 ) Convertible senior notes (21,541 ) (28,267 ) Total deferred tax liabilities (39,879 ) (44,252 ) Total net deferred tax assets $ (1,774 ) $ 1,755 Non-current deferred income tax assets (included in other long-term assets) $ 2,121 $ 2,116 Non-current deferred income tax liabilities (included in long-term liabilities) $ 3,895 $ 411 The Company records net deferred tax assets to the extent that Company believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operations. Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. The valuation allowance increased by approximately $39,489 and $10,980 during the years ended years ended December 31, 2016 and 2015 , respectively. Effective January 1, 2016, the Company changed its accounting policy for sales commissions that are incremental and directly related to customer sales contracts in which revenue is deferred (see Note 1), as a result of the accounting policy change, the valuation allowance as of December 31, 2015 has been retrospectively reduced by $8,438 . As of December 31, 2016 and 2015 , the Company had net operating loss carry-forwards for federal income tax purposes of $533,825 and $425,640 , respectively. The amount of federal net-operating loss carry-forwards at December 31, 2016 and 2015 for which a benefit will be recorded in APIC when realized is approximately $214,229 and $158,246 , respectively. The federal net operating losses will begin to expire in 2018. As of December 31, 2016 and 2015 , the Company had federal research credit carry-forwards of $9,231 and $6,642 respectively. The federal research and development credits will begin to expire in 2022. As of December 31, 2016 and 2015 , the Company had net operating loss carry-forwards for state income tax purposes of approximately $305,493 and $253,460 , respectively. The amount of state net-operating loss carry-forwards at December 31, 2016 and 2015 for which a benefit will be recorded in APIC when realized is approximately $125,497 and $90,849 , respectively. The state net operating losses expire between 2017 and 2036. As of December 31, 2016 and 2015 , the Company had research and development credit carry-forwards for state income tax purpose of $11,195 and $8,734 , respectively. The state research and development credits have no expiration period. The operating losses carry-forwards in non-U.S. locations were $7,045 as of December 31, 2016, there were no operating losses carry-forwards as of December 31, 2015. The non-US operating losses carry-forwards have no expiration period. In addition, as of December 31, 2016 and 2015 , the Company had research and development credit carry-forwards in its non-U.S. locations of approximately $2,010 and $2,058 , respectively. The non-U.S. research and development credits will begin to expire in 2031. Utilization of the federal and state net operating losses may be subject to substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. Analyses have been conducted to determine whether an ownership change had occurred since inception. The analyses have indicated that although ownership changes have occurred in prior years, the net operating losses and research and development credits would not expire before utilization as a result of the ownership change. In the event the Company has subsequent changes in ownership, net operating losses and research and development credit carryovers could be limited and may expire unutilized as a result of the subsequent ownership change. The Company recognizes interest and penalties related to uncertain tax positions within the income tax expense line in the consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets. During the year ended December 31, 2016 , the Company reduced income tax expense by $45 from interest and penalties related to tax contingencies and has $182 of interest and penalties recorded as a long-term income tax liability as of December 31, 2016 . During the year ended December 31, 2015 , the Company reduced income tax expense by $15 from interest and penalties related to tax contingencies and had $227 of interest and penalties recorded as a long-term income tax liability. As of December 31, 2016 , the Company had recorded unrecognized tax benefits of $922 that if recognized, would benefit the Company's effective tax rate. As of December 31, 2015 , the Company had recorded unrecognized tax benefits of $1,202 that if recognized, would benefit the Company's effective tax rate. The Company does not anticipate that the amount of unrecognized tax benefits relating to tax positions existing at December 31, 2016 will significantly increase or decrease within the next twelve months. Because of net operating loss and credit carry-forwards, all of the Company's tax years dating to inception in 2002 remain open to tax examination in U.S. and certain state tax jurisdictions. For other major non-U.S. jurisdictions, tax years from 2009 to present remain open to tax examination. The Company is not currently under audit in any material jurisdictions. The aggregate changes in the balance of gross unrecognized tax benefits were as follows: Ending balance as of December 31, 2013 $ 3,823 Increase in balances related to tax positions taken during the current period 524 Increase in balances related to tax positions taken during the prior period — Decrease in balances related to tax positions taken during the prior period (87 ) Decrease in balances related to statute expirations during the current period (31 ) Ending balance as of December 31, 2014 4,229 Increase in balances related to tax positions taken during the current period 806 Increase in balances related to tax positions taken during the prior period — Decrease in balances related to tax positions taken during the prior period (130 ) Decrease in balances related to statute expirations during the current period (85 ) Ending balance as of December 31, 2015 4,820 Increase in balances related to tax positions taken during the current period 1,262 Increase in balances related to tax positions taken during the prior period 20 Decrease in balances related to tax positions taken during the prior period (17 ) Decrease in balances related to statute expirations during the current period (239 ) Ending balance as of December 31, 2016 $ 5,846 As of December 31, 2016 , $206 of foreign withholding taxes associated with the repatriation of earning of foreign subsidiaries had been provided on $4,120 of undistributed earnings for certain foreign subsidiaries. The Company intends to reinvest the remainder of its undistributed earnings indefinitely outside the United States. As of December 31, 2016 , the Company estimated that no material additional U.S. income taxes would have to be provided if all of the undistributed earnings of the foreign subsidiaries were repatriated back to the United States as substantially all earnings from its foreign subsidiaries are previously taxed income. As of December 31, 2016 , the Company estimated that approximately $600 of additional foreign withholding tax would have to be provided if all of the undistributed earnings of the Company's foreign subsidiaries were repatriated back to the United States.

The Company and Summary of Si20

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles ("GAAP"). The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Starting January 1, 2016, the Company began separately presenting the effect of exchange rate changes on cash and cash equivalents in its consolidated statements of cash flows due to growing operations in foreign currency environments. Amounts in the comparable prior periods have been reclassified to conform to the current period presentation. Refer to "Sales Commissions" below regarding the Company's change in accounting policy for sales commissions effective January 1, 2016. During the reporting periods, the Company completed a number of acquisitions which are more fully described in Note 2, "Acquisitions". The consolidated financial statements include the results of operations from these business combinations from their date of acquisition.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting period. Actual results could differ materially from those estimates. Significant items subject to such estimates and assumptions include those related to revenue recognition, deferred commissions, stock-based compensation expense, fair value of assets acquired and liabilities assumed in business combinations, impairment assessments of goodwill, intangible assets and other long-lived assets, loss contingencies, and the recognition and measurement of current and deferred income taxes.
Foreign Currency Remeasurement and Transactions	Foreign Currency Remeasurement and Transactions The functional currency of the Company's wholly-owned foreign subsidiaries is the U.S. dollar. Accordingly, the subsidiaries remeasure monetary assets and liabilities at period-end exchange rates, while nonmonetary items are remeasured at historical rates. Income and expense accounts are remeasured at the average exchange rates in effect during the year. Remeasurement adjustments are recognized in the consolidated statements of operations as transaction gains or losses within other income (expense), net, in the period of occurrence.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers currency on hand, demand deposits, time deposits, money market funds and all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash and cash equivalents. Cash and cash equivalents are held in various financial institutions in the United States and internationally.
Investments	Investments The Company classifies all its investments as available-for-sale at the time of purchase since it is management's intent that these investments be available for current operations, and as such, includes these investments as short-term investments on its balance sheets. These investments consist of money market funds, corporate debt securities, commercial papers, U.S. agency and Treasury securities, and certificates of deposit with original maturities longer than three months. Short-term investments classified as available-for-sale are recorded at fair value with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of stockholders' equity. Realized gains and losses are recorded in the consolidated statements of operations and comprehensive loss based on specific identification.
Inventories	Inventories Inventories are stated at lower of cost or market value, with costs computed on a first-in, first-out basis. The Company periodically reviews its inventories for excess and obsolete items and adjusts carrying costs to estimated net realizable values when they are determined to be less than cost.
Revenue Recognition	Revenue Recognition The Company derives its revenue primarily from two sources: (1) subscription revenue for rights related to the use of the security-as-a-service platform and (2) hardware, training and professional services revenue provided to customers related to their use of the platform. The Company records its revenues net of any value added or sales tax. Subscription revenue is derived from a subscription‑based enterprise licensing model with contract terms typically ranging from one to three years, and consists of (i) subscription fees from the licensing of the security-as-a-service platform, (ii) subscription fees for access to the on-demand elements of the platform and (iii) subscription fees for the right to access the Company’s customer support services. Revenue is recognized when all of the following criteria have been met: • Persuasive evidence of an arrangement exists; • Delivery has occurred or services have been rendered; • Sales price is fixed or determinable; and • Collectability is reasonably assured. The Company generates sales directly through its sales team and, to a growing extent, through its channel partners. Sales to channel partners are made at a discount and revenues are recorded at this discounted price once all revenue recognition criteria are met. Channel partners generally receive an order from an end-customer prior to placing an order with the Company, and these partners do not carry any inventory of the Company's products or solutions. Payment from channel partners is not contingent on the partner’s success in sales to end-customers. In the event that the Company offers rebates, joint marketing funds, or other incentive programs to a partner, recorded revenues are reduced by these amounts accordingly. From time to time, certain third parties that the Company has an arrangement with provide the Company with referrals for which the Company pays a referral fee. The referral fee paid could vary depending on the level of effort. These fees are recorded in sales and marketing expense in proportion to the related revenue streams consistent with the sales commissions accounting. The Company did not incur any material referral fee expenses during the years ended December 31, 2016, 2015 and 2014. The Company applies industry-specific software revenue recognition guidance to transactions involving the licensing of software, as well as related support, training, and other professional services. The Company has analyzed all of the elements included in its multiple element software arrangements and has determined that it does not have sufficient VSOE of fair value to allocate revenue to its subscription and software license agreements, support, training and professional services. The Company defers all revenue under the software arrangement until the commencement of the subscription services and any associated professional services. Once the subscription services and the associated professional services have commenced, the entire fee from the arrangement is recognized ratably over the remaining period of the arrangement. If the professional services are essential to the functionality of the subscription, then the revenue recognition does not commence until such services are completed. The Company's revenue arrangements typically include subscription services to its security-as-a-service platform. These hosted on demand service arrangements do not provide customers with the right to take possession of the software supporting the hosted services. Certain arrangements also include the sale of hardware appliances. Revenue from hardware appliances containing software components and hardware components that function together to deliver the hardware appliance's essential functionality is excluded from the scope of the industry specific revenue recognition guidance. The Company recognizes revenue from its hosted on demand services in accordance with general revenue recognition accounting guidance. Only revenue derived from the licensing of the software is recognized in accordance with the industry specific revenue guidance. When a sales arrangement contains multiple elements, such as hardware appliances, subscription services, customer support services, and/or professional services, the Company allocates revenue to each unit of accounting or element based on a selling price hierarchy. An element constitutes a separate unit of accounting when the delivered item has standalone value and delivery of the undelivered element is probable and within the Company's control. When applying the relative selling price method, the Company determines the selling price for each deliverable using vendor-specific objective evidence (“VSOE”) of selling price. If VSOE does not exist, the Company uses third-party evidence (“TPE”) of selling price. If neither VSOE nor TPE of selling price exist for a deliverable, the Company uses its best estimate of selling price ("BESP") for that deliverable. Revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for each element. The Company determines BESP for an individual element within a multiple element revenue arrangement using the same methods utilized to determine the selling price of an element sold on a standalone basis. The Company estimates the selling price for its subscription solutions by considering internal factors such as historical pricing practices and it estimates the selling price of hardware and other services using a cost plus model. Hardware appliance revenue is recognized upon shipment. Subscription and support revenue are recognized over the contract period commencing on the start date of the contract. Professional services and training, when sold with hardware appliances or subscription and support services, are accounted for separately when those services have standalone value. In determining whether professional services and training services can be accounted for separately from subscription and support services, the Company considers the following factors: availability of the services from other vendors, the nature of the services, and the dependence of the subscription services on the customer’s decision to buy the professional services. If professional services and training do not qualify for separate accounting, the Company recognizes the professional services and training ratably over the contract term of the subscription services. Delivery generally occurs when the hardware appliance is delivered to a common carrier freight on board shipping point by the Company or the hosted service has been activated and communicated to the customer accordingly. The Company’s fees are typically considered to be fixed or determinable at the inception of an arrangement and are negotiated at the outset of an arrangement, generally based on specific products and quantities to be delivered. In the event payment terms are provided that differ significantly from the Company's standard business practices, the fees are deemed to not be fixed or determinable and revenue is recognized as the fees become paid. The Company assesses collectability based on a number of factors, including credit worthiness of the customer and past transaction history of the customer.
Deferred Revenue	Deferred Revenue Deferred revenue primarily consists of billings or payments received in advance of revenue recognition from the sale of the Company’s subscription fees, training and professional services. Once the revenue recognition criteria are met, this revenue is recognized ratably over the term of the associated contract.
Deferred Product Costs	Deferred Product Costs Deferred product costs are the incremental costs that are directly associated with each noncancellable customer contract or hosting agreement and primarily consist of cost of appliances and royalty payments made to third parties, from whom the Company has obtained licenses to integrate certain software into its products. The costs are deferred and amortized over the noncancellable term of the related customer contract or hosting agreement, which typically range from 12 to 36 months.
Property and Equipment	Property and Equipment Property and equipment are stated at cost. Depreciation is computed using the straight-line method over the estimated useful life of the related asset. Amortization of leasehold improvements is computed using the straight-line method over the shorter of the lease term or the estimated useful life of the asset or improvement. Cost of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. When property and equipment are retired or otherwise disposed of, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is included in other (expense) income, net.
Impairment of Intangible Assets and Other Long-Lived Assets	Impairment of Intangible Assets and Other Long-Lived Assets The Company evaluates long-lived assets, including property, equipment and definitive-lived intangible assets, for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of such assets (or asset group) to the future undiscounted cash flows the assets (or asset group) is expected to generate. If the assets are considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired assets. The Company also evaluates the estimated remaining useful lives of intangible assets and other long-lived assets to assess whether a revision to the remaining periods of amortization is required.
Software Development Costs	Software Development Costs Internally developed software includes security software developed to meet the Company's internal needs to provide cloud-based subscription services to its end-customers and business software that the Company customizes to meet its operating needs. These capitalized costs consist of internal compensation related costs and external direct costs incurred during the application development stage. The costs capitalized were not material in the years ended December 31, 2016 and 2015. The costs to develop software that is marketed externally have not been capitalized as the current software development process is essentially completed concurrently with the establishment of technological feasibility. As such, all related software development costs are expensed as incurred and included in research and development expense in the consolidated statements of operations. Internally and externally developed software is amortized over the software’s estimated useful life of three to five years.
Advertising and Promotion Costs	Advertising and Promotion Costs Expenses related to advertising and promotion of solutions is charged to sales and marketing expense as incurred.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of the purchase price of the acquired enterprise over the fair value of identifiable assets acquired and liabilities assumed. The Company performs an annual goodwill impairment test during the fourth quarter of the calendar year and more frequently if an event or circumstances indicates that impairment may have occurred. For the purposes of impairment testing, the Company has determined that it has one operating segment and one reporting unit. The Company performs a two-step impairment test of goodwill whereby the fair value of the reporting unit is compared to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net assets assigned to that unit, goodwill is not considered impaired and further testing is not required. If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of the reporting unit, then the Company must perform the second step of the impairment test in order to determine the implied fair value of the reporting unit’s goodwill. If the carrying value of a reporting unit’s goodwill exceeds its implied fair value, then impairment loss equal to the difference is recorded. The identification and measurement of goodwill impairment involves the estimation of the fair value of the Company. The estimate of fair value of the Company, based on the best information available as of the date of the assessment, is subjective and requires judgment, including management assumptions about expected future revenue forecasts and discount rates, changes in the overall economy, trends in the stock price and other factors. No impairment was identified by the Company as of December 31, 2016 . Intangible assets consist of developed technology, customer relationships, non-compete arrangements, trademarks and patents, and order backlog. The values assigned to intangibles are based on estimates and judgments regarding expectations for success and life cycle of solutions and technologies acquired.
Warranty	Warranty The Company provides limited warranties on all sales and provides for the estimated cost of the warranties at the date of sale, to the extent not already provided by its own vendors.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with authoritative guidance, which requires use of the asset and liability method. Under this method, deferred income tax assets and liabilities are determined based on the difference between the consolidated financial statements carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rates expected to apply to taxable income in the years in which the differences are expected to be reversed. The Company records net deferred tax assets to the extent the Company believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax planning strategies and recent financial operations. The Company has elected to use the "with and without" approach as described in ASC 740-20, "Intraperiod Tax Allocation" in determining the order in which tax attributes are utilized. As a result, the Company will only recognize a tax benefit from stock-based awards in additional paid-in capital if an incremental tax benefit is realized after all other tax attributes currently available to the Company have been utilized. In addition, the Company has elected to account for the impact of stock-based awards on other tax attributes, such as the research tax credit, within the consolidated statements of operations. The Company recognizes interest and penalties related to uncertain tax positions within the income tax expense line in the consolidated statements of operations. Accrued interest and penalties are included within the related tax liability line on the consolidated balance sheets.
Employee Benefit Plans	Employee Benefit Plans The Company sponsors a 401(k) defined contribution plan covering all employees. The Company may make discretionary contributions to the 401(k).
Stock-Based Compensation	Stock-Based Compensation The Company issues stock-based compensation awards to employees and directors in the form of stock options, restricted stock units ("RSUs"), performance stock units ("PSUs"), employee stock purchase plan ("ESPP") and stock bonus and other liability awards (collectively, "awards"). The Company measures and recognizes compensation expense for all stock-based awards based on the awards' fair value. Stock-based compensation for RSUs and PSUs is measured based on the value of the Company's common stock on the grant date. Stock-based compensation for employee stock options and ESPP awards are measured on the date of grant using a Black-Scholes option pricing model. Stock bonus and other liability awards are accounted for as liability-classified awards, because the obligations are based predominantly on fixed monetary amounts that are generally known at the inception of the obligation, to be settled with a variable number of shares of the Company's common stock. Awards vest either on a graded schedule or in a lump sum. The Company determines the fair value of each award as a single award and recognizes the expense on a straight-line basis over the service period of the award, which is generally the vesting period. The exercise price of stock options granted is equal to the fair value of the Company's common stock on the date of grant. Stock options expire ten years from the date of grant. Stock-based compensation expense is based on awards ultimately expected to vest, and the expense is recorded net of estimated forfeitures.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes all changes in equity that are not the result of transactions with stockholders. The Company’s comprehensive income (loss) consists of its net loss and changes in unrealized gains (losses) on its available-for-sale investments.
Loss Contingencies	Loss Contingencies The Company may be involved in various lawsuits, claims and proceedings that arise in the ordinary course of business. The Company records a provision for a liability when it believes that it is both probable that a liability has been incurred and the amount can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. The Company reviews these provisions at least quarterly and adjusts these provisions to reflect the impact of negotiations, settlements, rulings, and updated information.
Sales Commissions	Sales Commissions Effective January 1, 2016, the Company changed its accounting policy for sales commissions that are incremental and directly related to its customer sales contracts in which revenue is deferred. These commission costs are accrued and capitalized upon execution of a non-cancelable customer contract, and subsequently expensed over the term of such contract in proportion to the related future revenue streams. For commission costs where revenue is recognized, the related commission costs are recorded in the period of revenue recognition. Prior to this change in accounting policy, commission costs were expensed in the period in which they were incurred. The adoption of this accounting policy change has been applied retrospectively to all periods presented in this Annual Report on Form 10-K, in which the cumulative effect of the change has been reflected as of the beginning of the first period presented.
Recent Accounting Pronouncements	Recent Accounting Policies In January 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment (ASU 2017-04). ASU 2017-04 removes the requirement to perform a hypothetical purchase price allocation to measure goodwill impairment. A goodwill impairment will be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The update to the standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, and applied prospectively. The Company does not expect ASU 2017-04 to have a material impact on its financial statements. In January 2017, FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805) Clarifying the Definition of Business (ASU 2017-01). ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The update to the standard is effective for interim and annual periods beginning after December 15, 2017, and applied prospectively. The Company is currently evaluating the impact of the adoption of ASU 2017-01 on its consolidated financial statements. In October 2016, FASB issued Accounting Standards Update No. 2016-16, Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16). ASU 2016-16 eliminates the requirement to defer the recognition of current and deferred income taxes for intra-entity asset transfer until the asset has been sold to an outside party. Therefore, an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 is effective for interim and annual reporting periods beginning after December 15, 2017. Early adoption is permitted as of the first interim period and the amendments should be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently evaluating the impact of the adoption of ASU 2016-16 on its consolidated financial statements. In August 2016, FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 makes eight targeted changes how cash receipts and cash payments are presented and classified in the statement of cash flows. The update to the standard is effective for interim and annual periods beginning after December 15, 2017, and requires adoption on a retrospective transition method unless it is impracticable to apply. The Company is currently evaluating the impact of the adoption of ASU 2016-15 on its consolidated financial statements. In June 2016, FASB issued an Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 changes the impairment model for most financial assets, and will require the use of an expected loss model in place of the currently used incurred loss method. Under this model, entities will be required to estimate the lifetime expected credit loss on such instruments and record an allowance to offset the amortized cost basis of the financial asset, resulting in a net presentation of the amount expected to be collected on the financial asset. The update to the standard is effective for interim and annual periods beginning after December 15, 2019. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial statements. In March 2016, FASB issued Accounting Standards Update No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). ASU 2016-09 changes how companies account for certain aspects of share-based payment awards to employees, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The update to the standard is effective for interim and annual periods beginning after December 15, 2016. The Company does not expect ASU 2016-09 to have a material impact on its financial statements. In February 2016, FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (ASU 2016-02), which requires lessees to put most leases on their balance sheets but recognize the expenses on their statements of operations in a manner similar to current practice. ASU 2016-02 states that a lessee would recognize a lease liability for the obligation to make lease payments and a right-to-use asset for the right to use the underlying asset for the lease term. The new standard is effective for interim and annual periods beginning after December 15, 2018 and early adoption is permitted. While the Company is currently assessing the impact ASU 2016-02 will have on the Company's consolidated financial statements, the Company expects the primary impact to its consolidated financial position upon adoption will be the recognition, on a discounted basis, of the Company's minimum commitments under noncancelable operating leases on our consolidated balance sheets resulting in the recording of right of use assets and lease obligations. In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers: Topic 606 (ASU 2014-09), to supersede nearly all existing revenue recognition guidance under U.S. GAAP. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASU 2014-09 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 required under existing U.S. 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. Originally, ASU 2014-09 would be effective for the Company starting January 1, 2017 using either of two methods: (i) retrospective to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-09; or (ii) retrospective with the cumulative effect of initially applying ASU 2014-09 recognized at the date of initial application and providing certain additional disclosures as defined per ASU 2014-09. In July 2015, the FASB voted to amend ASU 2014-09 by approving a one-year deferral of the effective date as well as providing the option to early adopt the standard on the original effective date. The FASB has issued several updates to the standard which i) clarify the application of the principal versus agent guidance (ASU 2016-08); ii) clarify the guidance on inconsequential and perfunctory promises and licensing (ASU 2016-10) and iii) narrow-scope improvements and practical expedients (ASU 2016-12). The Company is currently evaluating the impact of the adoption of ASU 2014-09 on its consolidated financial statements.

The Company and Summary of Si21

The Company and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of useful lives intangible assets	Intangible assets are amortized on a straight-line basis over their estimated lives, which approximate the pattern in which the economic benefits of the intangible assets are consumed, as follows (in years): Low High Patents 4 5 Developed technology 3 7 Customer relationships 2 7 Non-compete agreements 2 4 Order backlog 1 3 Tradenames and trademarks 1 5
Schedule of changes to financial statements resulting from accounting change	The following tables present the changes to the financial statement lines as a result of the accounting change for the periods presented in the accompanying Consolidated Financial Statements: Consolidated Balance Sheet As of December 31, 2015 As reported Adjustment As adjusted Short-term deferred commissions $ — $ 19,314 $ 19,314 Long-term deferred commissions $ — $ 3,488 $ 3,488 Accumulated deficit $ (380,702 ) $ 22,802 $ (357,900 ) Consolidated Statements of Operations Year ended December 31, 2015 Year ended December 31, 2014 As reported Adjustment As adjusted As reported Adjustment As adjusted Operating expenses: Sales and marketing $ 156,156 $ (7,742 ) $ 148,414 $ 102,455 $ (4,122 ) $ 98,333 Net loss $ (106,454 ) $ 7,742 $ (98,712 ) $ (64,239 ) $ 4,122 $ (60,117 ) Net loss per share, basic and diluted $ (2.68 ) $ 0.20 $ (2.48 ) $ (1.72 ) $ 0.11 $ (1.61 ) Weighted average shares outstanding, basic and diluted 39,787 — 39,787 37,381 — 37,381 Consolidated Statements of Comprehensive Loss Year ended December 31, 2015 Year ended December 31, 2014 As reported Adjustment As adjusted As reported Adjustment As adjusted Net loss $ (106,454 ) $ 7,742 $ (98,712 ) $ (64,239 ) $ 4,122 $ (60,117 ) Unrealized gains on short-term investments, net $ 4 $ — $ 4 $ (27 ) $ — $ (27 ) Comprehensive loss $ (106,450 ) $ 7,742 $ (98,708 ) $ (64,266 ) $ 4,122 $ (60,144 )

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2016
Business Acquisition [Line Items]
Schedule of pro forma information	Accordingly, these unaudited pro forma results are presented for informational purposes only and are not necessarily indicative of what the actual results of operations of the combined company would have been if the acquisitions had occurred at the beginning of the period presented, nor are they indicative of future results of operations: Year Ended December 31, 2016 2015 2014 Total revenue $ 375,515 $ 264,904 $ 200,124 Net loss $ (119,531 ) $ (111,440 ) $ (75,066 ) Basic and diluted net loss per share $ (2.86 ) $ (2.80 ) $ (2.01 )
FireLayers [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the estimated fair values of acquired assets and liabilities: Estimated Estimated Current assets acquired $ 432 N/A Developed technology 22,600 5 Fixed assets 52 N/A Deferred tax liability, net (3,530 ) N/A Other liabilities assumed (540 ) N/A Additional-paid-in-capital (176 ) N/A Goodwill 26,988 Indefinite $ 45,826
Return Path [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the estimated fair values of acquired assets and liabilities: Estimated Estimated Customer relationships $ 7,600 6 Developed technology 3,900 4 Order Backlog 700 1 Deferred revenue assumed (1,200 ) N/A Goodwill 6,513 Indefinite $ 17,513
Acquisition in 4th Quarter of 2015 [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of acquired tangible and intangible assets, liabilities and goodwill: Fair Value Estimated Current assets acquired $ 414 N/A Fixed assets acquired 73 N/A Liabilities assumed (234 ) N/A Deferred revenue assumed (1,400 ) N/A Deferred tax liability, net (45 ) N/A Customer relationships 2,800 7 Order Backlog 900 3 Developed technology 3,000 4 Goodwill 6,060 Indefinite $ 11,568
Marble Security [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of acquired tangible, intangible assets and goodwill: Fair Value Estimated Fixed assets acquired $ 25 N/A Developed technology 7,300 4 Goodwill 1,175 Indefinite $ 8,500
Emerging Threats [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of tangible and intangible assets acquired, liabilities assumed and goodwill: Fair Value Estimated Current assets acquired $ 1,275 N/A Fixed assets acquired 174 N/A Liabilities assumed (448 ) N/A Deferred revenue assumed (700 ) N/A Holdback liability to the sellers (3,662 ) N/A Trade names 200 2 Customer relationships 4,200 7 Order Backlog 200 1 Developed technology 7,900 7 Goodwill 19,054 Indefinite $ 28,193
Nexgate [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of tangible assets acquired, liabilities assumed, intangible assets and goodwill: Fair Value Estimated Current assets acquired $ 1,340 N/A Fixed assets acquired 15 N/A Liabilities assumed (64 ) N/A Deferred revenue assumed (600 ) N/A Customer relationships 3,000 7 Order backlog 200 2 Core/developed technology 3,200 4 In-process research and development 900 N/A Deferred tax liability, net (792 ) N/A Goodwill 25,604 Indefinite $ 32,803
NetCitadel [Member]
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of tangible assets acquired, liabilities assumed, intangible assets and goodwill: Fair Value Estimated Tangible assets acquired $ 14 N/A Liabilities assumed (1,267 ) N/A Customer relationships 100 5 Core/developed technology 5,500 5 Goodwill 18,384 Indefinite $ 22,731

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of allowance for doubtful accounts	Allowance for doubtful accounts activity and balances are presented below: Balance at Beginning of Period Additions (Reversals) to Costs and Expenses Write Offs Balance at End of Period Year ended December 31, 2014 $ 276 $ 158 $ (5 ) $ 429 Year ended December 31, 2015 $ 429 $ (169 ) $ (61 ) $ 199 Year ended December 31, 2016 $ 199 $ 156 $ (139 ) $ 216
Schedule of property and equipment	Property and equipment at December 31, 2016 and 2015 consist of the following: Useful Life (in years) December 31, 2016 2015 Computer equipment 2 to 4 $ 92,462 $ 63,867 Software 2 to 5 2,266 1,684 Furniture 5 1,532 1,074 Office equipment 2 to 5 467 347 Leasehold improvements 5 years, or lease term, if shorter 6,198 4,728 Other 2 59 59 Construction in progress 1,483 934 104,467 72,693 Less: Accumulated depreciation (51,944 ) (38,192 ) $ 52,523 $ 34,501
Schedule of property and equipment acquired under capital leases	Property and equipment acquired under capital leases: December 31, 2016 2015 Computer equipment $ 453 $ 453 Less: Accumulated depreciation (341 ) (310 ) $ 112 $ 143
Schedule of accrued liabilities	Accrued liabilities at December 31, 2016 and 2015 consisted of the following: December 31, 2016 2015 Accrued compensation $ 30,295 $ 21,994 Customer deposits 173 1,384 Accrued royalties 754 509 Acquisition-related contingent consideration 7,629 — Other 11,914 11,166 $ 50,765 $ 35,053

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill	The goodwill activity and balances are presented below: December 31, 2016 2015 Opening balance $ 133,769 $ 107,504 Add: Goodwill from acquisitions 33,501 26,289 Less: Other adjustments to Goodwill — (24 ) Closing balance $ 167,270 $ 133,769
Intangible assets excluding goodwill	Intangible assets consisted of the following: December 31, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technology $ 83,769 $ (38,042 ) $ 45,727 $ 57,268 $ (28,618 ) $ 28,650 Customer relationships 17,943 (3,228 ) 14,715 23,382 (12,291 ) 11,091 Non-compete agreements — — — 804 (691 ) 113 Trademark and patents 930 (667 ) 263 1,006 (502 ) 504 Order backlog 1,600 (597 ) 1,003 1,300 (328 ) 972 $ 104,242 $ (42,534 ) $ 61,708 $ 83,760 $ (42,430 ) $ 41,330
Future estimated amortization costs of intangible assets	Future estimated amortization costs of intangible assets as of December 31, 2016 are presented below: Year Ended December 31, 2017 $ 16,381 2018 15,291 2019 11,926 2020 9,221 2021 7,422 Thereafter 1,467 $ 61,708

Fair Value Measurements and I25

Fair Value Measurements and Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair value, by balance sheet grouping	The following tables summarize, for each category of assets or liabilities carried at fair value, the respective fair value as of December 31, 2016 and 2015 and the classification by level of input within the fair value hierarchy: Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 304,020 $ 304,020 $ — $ — Corporate debt securities 2,139 — 2,139 — Commercial papers 13,243 — 13,243 — Short-term investments: Corporate debt securities 24,450 — 24,450 — Commercial papers 22,979 — 22,979 — U.S. agency securities 1,946 — 1,946 — U.S. Treasury securities 1,950 — 1,950 — Total financial assets $ 370,727 $ 304,020 $ 66,707 $ — Liabilities Acquisition-related contingent consideration $ 8,233 $ — $ — $ 8,233 Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 306,983 $ 306,983 $ — $ — Corporate debt securities 3,178 — 3,178 — Commercial papers 8,996 — 8,996 — Short-term investments: Corporate debt securities 36,527 — 36,527 — Commercial papers 16,290 — 16,290 — U.S. agency securities 5,414 — 5,414 — U.S. Treasury securities 1,801 — 1,801 — Total financial assets $ 379,189 $ 306,983 $ 72,206 $ —
Reconciliation of the acquisition-related contingent consideration liability measured at fair value	The following table represents a reconciliation of the Acquisition-related contingent consideration liability measured at fair value on a recurring basis, using significant unobservable inputs (Level 3): Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Balance as of December 31, 2015 $ — Additions during the period 9,162 Payments during the period (260 ) Adjustments to fair value during the period recorded in General and Administrative expenses (669 ) Balance as of December 31, 2016 $ 8,233
Fair value of cash and cash equivalents, and investments	The cost and fair value of the Company’s cash and available-for-sale investments as of December 31, 2016 and 2015 were as follows: December 31, 2016 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 26,024 $ — $ — $ 26,024 Money market funds 304,020 — — 304,020 Corporate debt securities 2,140 — (1 ) 2,139 Commercial papers 13,243 — — 13,243 Total $ 345,427 $ — $ (1 ) $ 345,426 Short-term investments: Corporate debt securities $ 24,458 $ — $ (8 ) $ 24,450 Commercial papers 22,979 — — 22,979 U.S. agency securities 1,945 1 — 1,946 U.S. Treasury securities 1,950 — — 1,950 Total $ 51,332 $ 1 $ (8 ) $ 51,325 December 31, 2015 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 27,048 $ — $ — $ 27,048 Money market funds 306,983 — — 306,983 Corporate debt securities 3,178 — — 3,178 Commercial papers 8,996 — — 8,996 Total $ 346,205 $ — $ — $ 346,205 Short-term investments: Corporate debt securities $ 36,549 $ — $ (22 ) $ 36,527 Commercial papers 16,290 — — 16,290 U.S. agency securities 5,415 — (1 ) 5,414 U.S. Treasury securities 1,801 — — 1,801 Total $ 60,055 $ — $ (23 ) $ 60,032

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Future annual minimum lease payments under noncancellable operating and capital leases	At December 31, 2016 , future annual minimum lease payments under noncancellable operating and capital leases were as follows: Capital Operating 2017 $ 41 $ 13,911 2018 39 13,337 2019 37 11,095 2020 22 5,027 2021 — 2,220 Thereafter — 5,616 Total minimum lease payments 139 $ 51,206 Less: Amount representing interest (16 ) Present value of capital lease obligations 123 Less: Current portion (32 ) Long-term portion of capital lease obligations $ 91

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2016
Senior Notes [Abstract]
Schedule of liability and equity components of convertible debt	The following tables represent the carrying values of all Notes as of December 31, 2016 and 2015 : December 31, 2016 0.75% Notes 1.25% Notes TOTAL Liability component: Principal $ 230,000 $ 201,250 $ 431,250 Less: debt discount and issuance costs, net of amortization (43,896 ) (20,813 ) (64,709 ) Net carrying amount $ 186,104 $ 180,437 $ 366,541 Equity component (1) $ 54,049 $ 43,293 $ 97,342 December 31, 2015 0.75% Notes 1.25% Notes TOTAL Liability component: Principal $ 230,000 $ 201,250 $ 431,250 Less: debt discount and issuance costs, net of amortization (54,952 ) (30,599 ) (85,551 ) Net carrying amount $ 175,048 $ 170,651 $ 345,699 Equity component (1) $ 54,049 $ 43,293 $ 97,342 (1) Recorded on the consolidated balance sheets as additional paid-in capital, net of the $2,877 issuance costs in equity
Schedule of convertible senior notes interest and accretion	For the years ended December 31, 2016, 2015 and 2014 , the Company incurred the following interest expense related to the Notes: 2016 2015 2014 Interest expense related to contractual interest coupon $ 4,240 $ 3,441 $ 2,511 Amortization of debt discount and issuance costs 20,842 14,933 8,753 Total $ 25,082 $ 18,374 $ 11,264

Equity Award Plans (Tables)

Equity Award Plans (Tables)	12 Months Ended
	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Valuation assumptions	The fair values were estimated on the grant dates using the Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2016 2015 2014 Expected life (in years) 5.31 - 6.08 5.31 - 6.08 5.31 - 6.08 Volatility 45% 50% - 52% 54% - 58% Risk-free interest rate 1.3% - 1.4% 1.6% - 1.8% 1.8% - 1.9% Dividend yield —% —% —%
Activity under stock option plan	Stock option activity under the Plan is as follows: Shares subject to Options Outstanding Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Balance at December 31, 2013 7,223 $ 8.17 6.82 $ 180,543 Options granted 563 36.91 Options exercised (1,984 ) 6.56 Options forfeited and canceled (514 ) 16.25 Balance at December 31, 2014 5,288 11.06 6.31 $ 196,608 Options granted 284 57.47 Options exercised (1,429 ) 8.31 Options forfeited and canceled (101 ) 19.11 Balance at December 31, 2015 4,042 15.10 5.77 $ 201,736 Options assumed per FireLayers acquisition 20 4.33 Options granted 237 54.11 Options exercised (1,089 ) 11.59 Options forfeited and canceled (27 ) 43.15 Balance at December 31, 2016 3,183 $ 18.91 5.39 $ 164,842 Exercisable, December 31, 2016 2,590 $ 12.68 4.73 $ 150,144 Vested and expected to vest, December 31, 2016 3,124 $ 18.31 5.33 $ 163,622
Summary of RSUs awarded and unvested under stock option plan	A following table summarized the activity of RSUs, PSUs and stock-bonus awards: RSUs and PSUs Outstanding Number of Shares Granted Fair Value Per Unit Awarded and unvested at December 31, 2013 1,214 $ 29.57 Awards granted 2,362 39.77 Awards vested (396 ) 30.79 Awards forfeited (246 ) 31.59 Awarded and unvested at December 31, 2014 2,934 37.45 Awards granted 1,541 61.48 Awards vested (897 ) 38.70 Awards forfeited (267 ) 41.89 Awarded and unvested at December 31, 2015 3,311 47.94 Awards granted 1,605 64.08 Awards vested (1,116 ) 44.73 Awards forfeited (335 ) 51.40 Awarded and unvested at December 31, 2016 3,465 $ 56.11
ESPP 2012 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Valuation assumptions	The fair value of the option component of the ESPP shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Year ended December 31, 2016 2015 2014 Expected life (in years) 0.5 0.5 0.5 Volatility 37% - 48% 42% - 47% 45% - 52% Risk-free interest rate 0.38% - 0.45% 0.08% - 0.33% 0.05% - 0.07% Dividend yield —% —% —%

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of antidilutive securities excluded from computation of earnings per share	The following table presents the potentially dilutive common shares outstanding that were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been anti-dilutive: December 31, 2016 2015 2014 Stock options to purchase common stock 3,183 4,042 5,288 Restricted stock units 3,465 3,311 2,934 Employee stock purchase plan 92 81 90 Common stock subject to repurchase 135 54 54 Bonus shares 159 174 37 1.25% Convertible senior notes 5,158 5,158 5,158 0.75% Convertible senior notes 2,831 2,831 — Total 15,023 15,651 13,561

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Revenue from external customers by products and services	Revenue by geographic area is based upon the billing address of the customer: Year Ended December 31, 2016 2015 2014 Total revenue by solution: Protection and Advanced Threat $ 272,621 $ 183,050 $ 126,812 Archiving, Privacy and Governance 102,875 82,347 68,795 Total revenue $ 375,496 $ 265,397 $ 195,607
Revenue from external customers by geographic areas	Year Ended December 31, 2016 2015 2014 Total revenue by geographic area: United States $ 312,601 $ 218,424 $ 157,593 Rest of world 62,895 46,973 38,014 Total revenue $ 375,496 $ 265,397 $ 195,607
Long-lived assets by geographic area	The following sets forth long-lived tangible assets by geographic area: December 31, 2016 2015 Long-lived assets: United States $ 43,789 $ 29,514 Rest of world 8,734 4,987 Total long-lived assets $ 52,523 $ 34,501

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of domestic and foreign components of loss before benefit from (provision for) income taxes	The domestic and foreign components of loss before (provision for) benefit from income taxes were as follows for the years ended December 31, 2016, 2015 and 2014 : Year Ended December 31, 2016 2015 2014 Domestic $ (112,904 ) $ (101,453 ) $ (65,433 ) Foreign 2,682 3,376 5,003 Loss before (provision for) benefit from income taxes $ (110,222 ) $ (98,077 ) $ (60,430 )
Schedule of components of income tax expense	The (provision for) benefit from income taxes is comprised of: Year Ended December 31, 2016 2015 2014 Current tax expense: Federal $ — $ — $ — State 72 54 121 Foreign 795 514 530 Total current 867 568 651 Deferred tax expense: Federal 411 105 (792 ) State — (45 ) — Foreign (292 ) 7 (172 ) Total deferred 119 67 (964 ) Provision for (benefit from) income taxes $ 986 $ 635 $ (313 )
Schedule of reconciliation of income tax expense	The reconciliation of income tax expense (benefit) at the statutory federal income tax rate of 34% to the income tax provision (benefit) included in the consolidated statements of operations for the years ended December 31, 2016, 2015 and 2014 is as follows: Year Ended December 31, 2016 2015 2014 Tax at federal statutory rate $ (37,476 ) $ (33,346 ) $ (20,546 ) Foreign income tax rate differential (187 ) (270 ) (600 ) State, net of federal benefit (3,478 ) (2,952 ) (1,585 ) Stock compensation charges 3,517 2,393 1,304 SubPart F and other permanent items 1,422 1,434 2,579 Provision to return and other 1,419 749 3,621 Research and development credits (4,464 ) (2,920 ) (2,052 ) Uncertain tax positions 749 561 391 Valuation allowance 39,484 34,986 16,575 Provision (benefit from) for income taxes $ 986 $ 635 $ (313 )
Schedule of deferred tax assets and liabilities	Significant components of the Company's deferred tax assets were as follows at December 31, 2016 and 2015: At December 31, 2016 2015 Deferred tax assets: Net operating loss carryforwards $ 119,168 $ 98,882 Tax credit carryforwards 13,966 10,856 Research expenditures 2,401 2,301 Deferred revenue 13,698 12,165 Stock compensation 18,509 13,289 Fixed assets 207 1,426 Accruals and other 11,554 8,997 Gross deferred tax assets 179,503 147,916 Valuation allowance (141,398 ) (101,909 ) Total deferred tax assets 38,105 46,007 Deferred tax liabilities: Intangible assets and other (8,793 ) (7,547 ) Deferred commissions (9,545 ) (8,438 ) Convertible senior notes (21,541 ) (28,267 ) Total deferred tax liabilities (39,879 ) (44,252 ) Total net deferred tax assets $ (1,774 ) $ 1,755 Non-current deferred income tax assets (included in other long-term assets) $ 2,121 $ 2,116 Non-current deferred income tax liabilities (included in long-term liabilities) $ 3,895 $ 411
Schedule of unrecognized tax benefits	The aggregate changes in the balance of gross unrecognized tax benefits were as follows: Ending balance as of December 31, 2013 $ 3,823 Increase in balances related to tax positions taken during the current period 524 Increase in balances related to tax positions taken during the prior period — Decrease in balances related to tax positions taken during the prior period (87 ) Decrease in balances related to statute expirations during the current period (31 ) Ending balance as of December 31, 2014 4,229 Increase in balances related to tax positions taken during the current period 806 Increase in balances related to tax positions taken during the prior period — Decrease in balances related to tax positions taken during the prior period (130 ) Decrease in balances related to statute expirations during the current period (85 ) Ending balance as of December 31, 2015 4,820 Increase in balances related to tax positions taken during the current period 1,262 Increase in balances related to tax positions taken during the prior period 20 Decrease in balances related to tax positions taken during the prior period (17 ) Decrease in balances related to statute expirations during the current period (239 ) Ending balance as of December 31, 2016 $ 5,846

The Company and Summary of Si32

The Company and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Foreign currency remeasurement and transactions:
Foreign currency transaction loss	$ 852	$ 1,657	$ 2,182
Deferred product costs:
Advertising expense	0	0	$ 0
Software development costs capitalized	$ 0	$ 0
Minimum [Member]
Revenue Recognition
Contract term	1 year
Deferred product costs:
Number of months deferred product costs are recognized	12 months
Maximum [Member]
Revenue Recognition
Contract term	3 years
Deferred product costs:
Number of months deferred product costs are recognized	36 months
Software [Member] | Minimum [Member]
Deferred product costs:
Estimated life of intangible assets	3 years
Software [Member] | Maximum [Member]
Deferred product costs:
Estimated life of intangible assets	5 years
Employee stock option [Member]
Deferred product costs:
Term until award expiration	10 years

The Company and Summary of Si33

The Company and Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2016USD ($)segment
Intangible assets:
Number of segments	1
Number of reporting units	1
Goodwill, impairment loss | $	$ 0
Minimum [Member] | Patents [Member]
Intangible assets:
Estimated life of intangible assets	4 years
Minimum [Member] | Developed technology [Member]
Intangible assets:
Estimated life of intangible assets	3 years
Minimum [Member] | Customer relationships [Member]
Intangible assets:
Estimated life of intangible assets	2 years
Minimum [Member] | Non-compete agreements [Member]
Intangible assets:
Estimated life of intangible assets	2 years
Minimum [Member] | Order Backlog [Member]
Intangible assets:
Estimated life of intangible assets	1 year
Minimum [Member] | Trademarks and trademarks [Member]
Intangible assets:
Estimated life of intangible assets	1 year
Maximum [Member] | Patents [Member]
Intangible assets:
Estimated life of intangible assets	5 years
Maximum [Member] | Developed technology [Member]
Intangible assets:
Estimated life of intangible assets	7 years
Maximum [Member] | Customer relationships [Member]
Intangible assets:
Estimated life of intangible assets	7 years
Maximum [Member] | Non-compete agreements [Member]
Intangible assets:
Estimated life of intangible assets	4 years
Maximum [Member] | Order Backlog [Member]
Intangible assets:
Estimated life of intangible assets	3 years
Maximum [Member] | Trademarks and trademarks [Member]
Intangible assets:
Estimated life of intangible assets	5 years

The Company and Summary of Si34

The Company and Summary of Significant Accounting Policies - Sales Commissions, Change in Accounting Policy (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Deferred commissions		$ 25,664	$ 22,802
Deferred commission costs		36,009	29,642	$ 19,107
Amortization of commission costs		33,147	21,900	14,985
Short-term deferred commissions, adjustment			19,314
Short-term deferred commissions, as adjusted		21,168	19,314
Long-term deferred commissions, adjustment			3,488
Long-term deferred commissions, as adjusted		4,496	3,488
Accumulated deficit, as reported			(380,702)
Accumulated deficit, adjustment			22,802		$ 10,938
Accumulated deficit, as adjusted		(469,108)	(357,900)
Operating expenses: Sales and marketing, as reported			156,156	102,455
Operating expenses: Sales and marketing, adjustment			(7,742)	(4,122)
Operating expenses: Sales and marketing, as adjusted	[1],[2]	201,204	148,414	98,333
Net loss, as reported			(106,454)	(64,239)
Net loss, adjustment			7,742	4,122
Net loss		$ (111,208)	$ (98,712)	$ (60,117)
Net loss per share, basic and diluted, as reported (in dollars per share)			$ (2.68)	$ (1.72)
Net loss per share, basic and diluted, adjustment (in dollars per share)			0.20	0.11
Net loss per share, basic and diluted (in dollars per share)		$ (2.66)	$ (2.48)	$ (1.61)
Weighted average shares outstanding, basic and diluted (in shares)		41,859	39,787	37,381
Unrealized gains on short-term investments		$ 16	$ 4	$ (27)
Comprehensive loss, as reported			(106,450)	(64,266)
Comprehensive loss		$ (111,192)	$ (98,708)	$ (60,144)
[1]	Includes intangible amortization expense as follows: Cost of subscription revenue $9,423, research and development $60, sales and marketing $4,938 and general and administrative $0 for the year ended December 31, 2016. Cost of subscription revenue $7,079, research and development $91, sales and marketing $5,074 and general and administrative $12 for the year ended December 31, 2015. Cost of subscription revenue $4,157, research and development $93, sales and marketing $4,494 and general and administrative $46 for the year ended December 31, 2014.
[2]	Includes stock-based compensation expenses as follows:Cost of subscription $7,427, cost of hardware and service revenue $1,494, research and development $24,342, sales and marketing $28,607 and general and administrative $16,826 for the year ended December 31, 2016. Cost of subscription $5,028, cost of hardware and service revenue $1,098, research and development $20,672, sales and marketing $21,511 and general and administrative $11,785 for the year ended December 31, 2015. Cost of subscription $2,404, cost of hardware and service revenue $604, research and development $10,204, sales and marketing $10,795 and general and administrative $6,997 for the year ended December 31, 2014

Acquisitions - 2016 Acquisition

Acquisitions - 2016 Acquisitions (Details) - USD ($) shares in Thousands, $ in Thousands	Oct. 24, 2016	Aug. 24, 2016	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired					$ 54,158	$ 51,553	$ 53,680
Acquisition-related costs					827
Revenue					375,496	265,397	195,607
Fair value of assets acquired and liabilities assumed
Goodwill			$ 167,270	$ 107,504	167,270	$ 133,769	$ 107,504
FireLayers [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired	$ 45,616
Cash acquired from acquisitions	210
Escrow	7,740
Acquisition-related costs					827
Fair value of unvested options	1,326
Fair value of assets acquired and liabilities assumed
Current assets acquired	432
Finite lived intangible assets	$ 22,600
Acquired finite-lived intangible assets, weighted average useful life (in years)	5 years
Fixed assets	$ 52
Deferred tax liability, net	(3,530)
Other liabilities assumed	(540)
Additional-paid-in-capital	(176)
Goodwill	26,988
Recognized identifiable assets acquired and liabilities assumed, net	$ 45,826
Return Path [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 17,513
Escrow		9,644
Acquisition-related costs					406
Revenue					$ 1,025
Acquisition-related contingent consideration		9,162
Fair value of assets acquired and liabilities assumed
Deferred revenue assumed		(1,200)
Goodwill		6,513
Recognized identifiable assets acquired and liabilities assumed, net		17,513
Customer relationships [Member] | Return Path [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 7,600
Acquired finite-lived intangible assets, weighted average useful life (in years)		6 years
Core/developed technology [Member] | Return Path [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 3,900
Acquired finite-lived intangible assets, weighted average useful life (in years)		4 years
Order Backlog [Member] | Return Path [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 700
Acquired finite-lived intangible assets, weighted average useful life (in years)		1 year
Restricted Stock [Member]
Business Acquisition [Line Items]
Shares granted in period				54
Restricted Stock [Member] | FireLayers [Member]
Business Acquisition [Line Items]
Shares granted in period			111
Fair value of shares granted			$ 8,669

Acquisitions - 2015 Acquisition

Acquisitions - 2015 Acquisitions (Details) $ in Thousands	Jul. 22, 2015USD ($)	Mar. 06, 2015USD ($)	Dec. 31, 2015USD ($)business	Jun. 30, 2015USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Business Acquisition [Line Items]
Acquisition-related costs					$ 827
Holdback payments for prior acquisitions					1,397	$ 0	$ 741
Revenue					375,496	265,397	195,607
Fair value of assets acquired and liabilities assumed
Goodwill			$ 133,769		$ 167,270	133,769	$ 107,504
Acquisition in 4th Quarter of 2015 [Member]
Business Acquisition [Line Items]
Number of businesses acquired | business			2
Purchase price			$ 11,568
Acquisition-related costs						355
Fair value of assets acquired and liabilities assumed
Current assets acquired			414			414
Fixed assets acquired			73			73
Liabilities assumed			(234)			(234)
Deferred revenue assumed			(1,400)			(1,400)
Deferred tax liability, net			(45)			(45)
Goodwill			6,060			6,060
Recognized identifiable assets acquired and liabilities assumed, net			11,568			11,568
Marble Security [Member]
Business Acquisition [Line Items]
Purchase price	$ 8,500
Acquisition-related costs						277
Escrow	1,700
Fair value of assets acquired and liabilities assumed
Fixed assets acquired	25
Goodwill	1,175
Recognized identifiable assets acquired and liabilities assumed, net	8,500
Emerging Threats [Member]
Business Acquisition [Line Items]
Purchase price		$ 31,803
Acquisition-related costs						277
Escrow		$ 6,000
Percentage of voting interests acquired		100.00%
Cash acquired from acquisitions		$ 52
Holdback payments for prior acquisitions				$ 3,662
Revenue						2,477
Fair value of assets acquired and liabilities assumed
Current assets acquired		1,275
Fixed assets acquired		174
Liabilities assumed		(448)
Deferred revenue assumed		(700)
Goodwill		19,054
Holdback liability to the sellers		(3,662)
Recognized identifiable assets acquired and liabilities assumed, net		28,193
Trade names [Member] | Emerging Threats [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 200
Acquired finite-lived intangible assets, weighted average useful life (in years)		2 years
Customer relationships [Member] | Acquisition in 4th Quarter of 2015 [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets			$ 2,800			2,800
Acquired finite-lived intangible assets, weighted average useful life (in years)			7 years
Customer relationships [Member] | Emerging Threats [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 4,200
Acquired finite-lived intangible assets, weighted average useful life (in years)		7 years
Order Backlog [Member] | Acquisition in 4th Quarter of 2015 [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets			$ 900			900
Acquired finite-lived intangible assets, weighted average useful life (in years)			3 years
Order Backlog [Member] | Emerging Threats [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 200
Acquired finite-lived intangible assets, weighted average useful life (in years)		1 year
Developed technology [Member] | Acquisition in 4th Quarter of 2015 [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets			$ 3,000			$ 3,000
Acquired finite-lived intangible assets, weighted average useful life (in years)			4 years
Developed technology [Member] | Marble Security [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 7,300
Acquired finite-lived intangible assets, weighted average useful life (in years)	4 years
Developed technology [Member] | Emerging Threats [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 7,900
Acquired finite-lived intangible assets, weighted average useful life (in years)		7 years

Acquisitions - 2014 Acquisition

Acquisitions - 2014 Acquisitions (Details) - USD ($) $ in Thousands	Oct. 31, 2014	May 13, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired			$ 54,158	$ 51,553	$ 53,680
Acquisition-related costs			827
Fair value of assets acquired and liabilities assumed
Goodwill			$ 167,270	$ 133,769	107,504
Nexgate [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired	$ 31,771
Cash acquired from acquisitions	1,032
Acquisition-related costs					231
Fair value of assets acquired and liabilities assumed
Current assets acquired	1,340
Fixed assets acquired	15
Liabilities assumed	(64)
Deferred revenue assumed	(600)
Deferred tax liability, net	(792)
Goodwill	25,604
Recognized identifiable assets acquired and liabilities assumed, net	32,803
Nexgate [Member] | Customer relationships [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 3,000
Acquired finite-lived intangible assets, weighted average useful life (in years)	7 years
Nexgate [Member] | Order Backlog [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 200
Acquired finite-lived intangible assets, weighted average useful life (in years)	2 years
Nexgate [Member] | Core/developed technology [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 3,200
Acquired finite-lived intangible assets, weighted average useful life (in years)	4 years
Nexgate [Member] | In Process Research and Development [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 900
NetCitadel [Member]
Business Acquisition [Line Items]
Acquisition-related costs					$ 345
Cash consideration for acquisition		$ 22,731
Fair value of assets acquired and liabilities assumed
Fixed assets acquired		14
Liabilities assumed		(1,267)
Goodwill		18,384
Recognized identifiable assets acquired and liabilities assumed, net		22,731
NetCitadel [Member] | Customer relationships [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 100
Acquired finite-lived intangible assets, weighted average useful life (in years)		5 years
NetCitadel [Member] | Core/developed technology [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 5,500
Acquired finite-lived intangible assets, weighted average useful life (in years)		5 years

Acquisitions - Pro Forma Financ

Acquisitions - Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Total revenue	$ 375,515	$ 264,904	$ 200,124
Net loss	$ (119,531)	$ (111,440)	$ (75,066)
Basic and diluted net loss per share (in dollars per share)	$ (2.86)	$ (2.80)	$ (2.01)
Acquisition-related costs	$ 827

Concentration of Risks (Details

Concentration of Risks (Details) - customer	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Total revenue [Member]
Concentration Risk [Line Items]
Number of customers	0	0
Major Customer 1 [Member] | Total revenue [Member]
Concentration Risk [Line Items]
Number of customers			1
Concentration risk percentage			12.00%
Major Customer 1 [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of customers	1	1
Concentration risk percentage	21.00%	16.00%

Balance Sheet Components - Allo

Balance Sheet Components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Period	$ 199	$ 429	$ 276
Additions to Costs and Expenses	156	(169)	158
Write Offs	(139)	(61)	(5)
Balance at End of Period	$ 216	$ 199	$ 429

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Property and equipment, gross	$ 104,467	$ 72,693
Less: Accumulated depreciation	(51,944)	(38,192)
Property and equipment, net	52,523	34,501
Computer equipment [Member]
Property and Equipment
Property and equipment, gross	$ 92,462	63,867
Computer equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	2 years
Computer equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	4 years
Software [Member]
Property and Equipment
Property and equipment, gross	$ 2,266	1,684
Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	2 years
Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Furniture [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Property and Equipment
Property and equipment, gross	$ 1,532	1,074
Office equipment [Member]
Property and Equipment
Property and equipment, gross	$ 467	347
Office equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life	2 years
Office equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Leasehold improvements [Member]
Property and Equipment
Property and equipment, gross	$ 6,198	4,728
Leasehold improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life	5 years
Other [Member]
Property, Plant and Equipment [Line Items]
Useful life	2 years
Property and Equipment
Property and equipment, gross	$ 59	59
Construction in progress [Member]
Property and Equipment
Property and equipment, gross	$ 1,483	$ 934

Balance Sheet Components - Pr42

Balance Sheet Components - Property and Equipment, Other Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and equipment acquired under capital leases
Depreciation expense	$ 17,131	$ 12,644	$ 9,033
Computer equipment [Member]
Property and equipment acquired under capital leases
Capital leased assets, gross	453	453
Less: Accumulated depreciation	(341)	(310)
Capital leased assets, net	112	143
Capital leases [Member]
Property and equipment acquired under capital leases
Depreciation expense	$ 31	$ 23	$ 19

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued compensation	$ 30,295	$ 21,994
Customer deposits	173	1,384
Accrued royalties	754	509
Business Combination, Contingent Consideration, Liability, Current	7,629	0
Other	11,914	11,166
Total accrued liabilities	$ 50,765	$ 35,053

Goodwill and Intangible Asset44

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill activity and balances
Opening balance	$ 133,769	$ 107,504
Add: Goodwill from acquisitions	33,501	26,289
Less: Other adjustments to Goodwill	0	(24)
Closing balance	$ 167,270	$ 133,769

Goodwill and Intangible Asset45

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Intangible assets excluding goodwill:
Gross Carrying Amount	$ 104,242	$ 83,760
Accumulated Amortization	(42,534)	(42,430)
Net Carrying Amount	61,708	41,330
Intangible amortization expense	14,421	12,256	$ 8,790
Developed technology [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	83,769	57,268
Accumulated Amortization	(38,042)	(28,618)
Net Carrying Amount	45,727	28,650
Customer relationships [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	17,943	23,382
Accumulated Amortization	(3,228)	(12,291)
Net Carrying Amount	14,715	11,091
Non-compete agreements [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	0	804
Accumulated Amortization	0	(691)
Net Carrying Amount	0	113
Trademark and patents [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	930	1,006
Accumulated Amortization	(667)	(502)
Net Carrying Amount	263	504
Order Backlog [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	1,600	1,300
Accumulated Amortization	(597)	(328)
Net Carrying Amount	$ 1,003	$ 972

Goodwill and Intangible Asset46

Goodwill and Intangible Assets - Future Estimated Amortization Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
2,017	$ 16,381
2,018	15,291
2,019	11,926
2,020	9,221
2,021	7,422
Thereafter	1,467
Net Carrying Amount	$ 61,708	$ 41,330

Fair Value Measurements and I47

Fair Value Measurements and Investments - Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and cash equivalents, fair value disclosure	$ 345,426	$ 346,205
Short-term investments, fair value disclosure	51,325	60,032
Total financial assets	370,727	379,189
Liabilities
Acquisition-related contingent consideration	8,233
Money market funds
Assets
Cash and cash equivalents, fair value disclosure	304,020	306,983
Corporate debt securities
Assets
Cash and cash equivalents, fair value disclosure	2,139	3,178
Short-term investments, fair value disclosure	24,450	36,527
Commercial papers
Assets
Cash and cash equivalents, fair value disclosure	13,243	8,996
Short-term investments, fair value disclosure	22,979	16,290
U.S. agency securities
Assets
Short-term investments, fair value disclosure	1,946	5,414
U.S. Treasury securities
Assets
Short-term investments, fair value disclosure	1,950	1,801
Quoted prices in active markets for indentical assets (Level 1)
Assets
Total financial assets	304,020	306,983
Quoted prices in active markets for indentical assets (Level 1) | Money market funds
Assets
Cash and cash equivalents, fair value disclosure	304,020	306,983
Significant other observable inputs (Level 2)
Assets
Total financial assets	66,707	72,206
Significant other observable inputs (Level 2) | Corporate debt securities
Assets
Cash and cash equivalents, fair value disclosure	2,139	3,178
Short-term investments, fair value disclosure	24,450	36,527
Significant other observable inputs (Level 2) | Commercial papers
Assets
Cash and cash equivalents, fair value disclosure	13,243	8,996
Short-term investments, fair value disclosure	22,979	16,290
Significant other observable inputs (Level 2) | U.S. agency securities
Assets
Short-term investments, fair value disclosure	1,946	5,414
Significant other observable inputs (Level 2) | U.S. Treasury securities
Assets
Short-term investments, fair value disclosure	1,950	$ 1,801
Unobservable Inputs (Level 3)
Liabilities
Acquisition-related contingent consideration	$ 8,233
Convertible Senior Notes 0.75% [Member] | Convertible Notes Payable [Member] | Significant other observable inputs (Level 2)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Interest rate, stated percentage	0.75%
Convertible debt, fair value disclosures	$ 257,600
Convertible Senior Notes 1.25% [Member] | Convertible Notes Payable [Member] | Significant other observable inputs (Level 2)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Interest rate, stated percentage	1.25%
Convertible debt, fair value disclosures	$ 364,389

Fair Value Measurements and I48

Fair Value Measurements and Investments - Reconciliation of Acquisition-related Contingent Consideration Liability (Details) - Contingent Consideration $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 0
Additions during the period	9,162
Payments during the period	(260)
Adjustments to fair value during the period recorded in General and Administrative expenses	(669)
Ending balance	$ 8,233

Fair Value Measurements and I49

Fair Value Measurements and Investments - Investments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, amortized cost	$ 345,427,000	$ 346,205,000
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	(1,000)	0
Cash and cash equivalents, fair value	345,426,000	346,205,000
Short-term investments, amortized cost	51,332,000	60,055,000
Short-term investments, unrealized gains	1,000	0
Short-term investments, unrealized losses	(8,000)	(23,000)
Short-term investments, fair value	$ 51,325,000	$ 60,032,000
Maximum investment maturity term	1 year	1 year
Other-than-temporary impairments	$ 0	$ 0	$ 0
Cash
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, amortized cost	26,024,000	27,048,000
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	0	0
Cash and cash equivalents, fair value	26,024,000	27,048,000
Money market funds
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, amortized cost	304,020,000	306,983,000
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	0	0
Cash and cash equivalents, fair value	304,020,000	306,983,000
Corporate debt securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, amortized cost	2,140,000	3,178,000
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	(1,000)	0
Cash and cash equivalents, fair value	2,139,000	3,178,000
Short-term investments, amortized cost	24,458,000	36,549,000
Short-term investments, unrealized gains	0	0
Short-term investments, unrealized losses	(8,000)	(22,000)
Short-term investments, fair value	24,450,000	36,527,000
Commercial papers
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, amortized cost	13,243,000	8,996,000
Cash and cash equivalents, unrealized gains	0	0
Cash and cash equivalents, unrealized losses	0	0
Cash and cash equivalents, fair value	13,243,000	8,996,000
Short-term investments, amortized cost	22,979,000	16,290,000
Short-term investments, unrealized gains	0	0
Short-term investments, unrealized losses	0	0
Short-term investments, fair value	22,979,000	16,290,000
U.S. agency securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Short-term investments, amortized cost	1,945,000	5,415,000
Short-term investments, unrealized gains	1,000	0
Short-term investments, unrealized losses	0	(1,000)
Short-term investments, fair value	1,946,000	5,414,000
U.S. Treasury securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Short-term investments, amortized cost	1,950,000	1,801,000
Short-term investments, unrealized gains	0	0
Short-term investments, unrealized losses	0	0
Short-term investments, fair value	$ 1,950,000	$ 1,801,000

Commitments and Contingencies50

Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jul. 31, 2015	Jul. 31, 2012lease_agreement
Commitments and Contingencies Disclosure [Abstract]
Operating leases rent expense	$ 5,054	$ 3,831	$ 3,283
Capital Leases
2,017	41
2,018	39
2,019	37
2,020	22
2,021	0
Thereafter	0
Total minimum capital lease payments	139
Less: Amount representing interest	(16)
Present value of capital lease obligations	123
Less: Current portion	(32)	$ (32)
Long-term portion of capital lease obligations	91
Operating Leases
2,017	13,911
2,018	13,337
2,019	11,095
2,020	5,027
2,021	2,220
Thereafter	5,616
Total minimum operating lease payments	$ 51,206
Capital leases
Commitments and contingencies:
Number of lease agreement | lease_agreement					2
Interest rate, stated percentage				6.50%	4.50%

Commitments and Contingencies -

Commitments and Contingencies - Legal Contingencies (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Loss contingency, loss in period			$ 10,900
Reduction in settlement charge			1,938
Loss contingency, damages paid	$ 3,300	$ 4,300
Settlement payable	$ 3,300		$ 3,300

Convertible Senior Notes (Detai

Convertible Senior Notes (Details) $ / shares in Units, shares in Thousands	Jun. 17, 2015USD ($)sharesd$ / shares	Dec. 11, 2013USD ($)sharesd$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Debt:
Proceeds from issuance of convertible senior notes, net of discount			$ 0	$ 223,790,000	$ 0
Convertible senior notes			366,541,000	345,699,000
Senior Notes [Member]
Debt:
Face amount			431,250,000	431,250,000
Convertible senior notes			366,541,000	345,699,000
Carrying amount of the equity component net			97,342,000	97,342,000
Issuance cost			2,877,000
0.75% Convertible Senior Notes, Due June 2020 [Member] | Senior Notes [Member]
Debt:
Face amount	$ 200,000,000		$ 230,000,000	230,000,000
Option to purchase additional principal amount	30,000,000
Issuance costs	6,581,000
Proceeds from issuance of convertible senior notes, net of discount	$ 223,419,000
Debt interest rate	0.75%
Conversion ratio, initial	12.3108
Number of shares convertible, initial rate | shares	2,831
Conversion price per share, initial (in dollars per share) | $ / shares	$ 81.23
Percentage of principal amount redeemed			100.00%
Threshold percentage of stock price trigger	130.00%
Threshold trading days | d	20
Number of threshold consecutive trading days	30 days
Number of consecutive business days following consecutive trading day period	5 days
Number of consecutive trading days	5 days
Trading price as percentage of closing price of common stock	98.00%
Effective rate used to amortization debt discount	6.50%
Convertible senior notes	$ 174,359,000		$ 186,104,000	175,048,000
Carrying amount of the equity component net	55,641,000		54,049,000	54,049,000
Issuance cost	$ 1,592,000
Convertible Senior Notes 1.25% [Member] | Senior Notes [Member]
Debt:
Face amount		$ 175,000,000	$ 201,250,000	201,250,000
Option to purchase additional principal amount		26,250,000
Issuance costs		5,803,000
Proceeds from issuance of convertible senior notes, net of discount		$ 195,446,000
Debt interest rate		1.25%
Conversion ratio, initial		25.6271
Number of shares convertible, initial rate | shares		5,158
Conversion price per share, initial (in dollars per share) | $ / shares		$ 39.02
Percentage of principal amount redeemed			100.00%
Threshold percentage of stock price trigger		130.00%
Threshold trading days | d		20
Number of threshold consecutive trading days		30 days
Number of consecutive business days following consecutive trading day period		5 days
Number of consecutive trading days		5 days
Trading price as percentage of closing price of common stock		98.00%
Effective rate used to amortization debt discount		6.50%
Convertible senior notes		$ 156,672,000	$ 180,437,000	170,651,000
Carrying amount of the equity component net		44,578,000	$ 43,293,000	$ 43,293,000
Issuance cost		$ 1,285,000
On Or After June 2018 [Member] | 0.75% Convertible Senior Notes, Due June 2020 [Member] | Senior Notes [Member]
Debt:
Percentage of principal amount redeemed			100.00%
On Or After December 20, 2016 [Member] | Convertible Senior Notes 1.25% [Member] | Senior Notes [Member]
Debt:
Percentage of principal amount redeemed		100.00%

Convertible Senior Notes (Liabi

Convertible Senior Notes (Liability Component of Notes) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 17, 2015	Dec. 11, 2013
Liability component:
Convertible senior notes	$ 366,541,000	$ 345,699,000
Interest Expense, Debt
Interest expense, 1.25% coupon	4,240,000	3,441,000	$ 2,511,000
Amortization of debt issuance costs and accretion of debt discount	20,842,000	14,933,000	8,753,000
Interest expense, total	25,082,000	18,374,000	$ 11,264,000
Senior Notes [Member]
Liability component:
Principal	431,250,000	431,250,000
Less: debt discount, net of amortization	(64,709,000)	(85,551,000)
Convertible senior notes	366,541,000	345,699,000
Carrying amount of the equity component net	97,342,000	97,342,000
Issuance cost	2,877,000
Senior Notes [Member] | 0.75% Convertible Senior Notes, Due June 2020 [Member]
Liability component:
Principal	230,000,000	230,000,000		$ 200,000,000
Less: debt discount, net of amortization	(43,896,000)	(54,952,000)
Convertible senior notes	186,104,000	175,048,000		174,359,000
Carrying amount of the equity component net	54,049,000	54,049,000		55,641,000
Issuance cost				$ 1,592,000
Senior Notes [Member] | Convertible Senior Notes 1.25% [Member]
Liability component:
Principal	201,250,000	201,250,000			$ 175,000,000
Less: debt discount, net of amortization	(20,813,000)	(30,599,000)
Convertible senior notes	180,437,000	170,651,000			156,672,000
Carrying amount of the equity component net	$ 43,293,000	$ 43,293,000			44,578,000
Issuance cost					$ 1,285,000

Equity Award Plans - Stock-Base

Equity Award Plans - Stock-Based Compensation Plans (Details) shares in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016shares	Dec. 31, 2016planshares
Stock-based compensation:
Equity incentive plans held by the Company (number of plans) | plan		4
Employee stock option [Member]
Stock-based compensation:
Term until award expiration		10 years
2012 Equity Incentive Plan [Member]
Stock-based compensation:
Shares authorized for issuance (in shares) | shares	20,316	20,316
Options available for future grant under the stock plans | shares	6,139	6,139
2012 Equity Incentive Plan [Member] | Employee stock option [Member] | Minimum [Member]
Stock-based compensation:
Award vesting period		3 years
2012 Equity Incentive Plan [Member] | Employee stock option [Member] | Maximum [Member]
Stock-based compensation:
Term until award expiration		10 years
Award vesting period		4 years
2012 Equity Incentive Plan [Member] | Restricted Stock [Member]
Stock-based compensation:
Award vesting period		4 years
FireLayers [Member]
Stock-based compensation:
Equity incentive plans held by the Company (number of plans) | plan		2
FireLayers [Member] | Restricted Stock [Member]
Stock-based compensation:
Award vesting period	3 years

Equity Award Plans - Stock Opti

Equity Award Plans - Stock Option Activity (Details) - Employee stock option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation:
Weighted-average fair value of stock options granted (in dollars per share)	$ 24.04	$ 28.20	$ 20.25
Fair value assumptions:
Volatility	45.00%
Dividend yield	0.00%	0.00%	0.00%
Shares subject to options outstanding, weighted average exercise price:
Total intrinsic value of options exercised	$ 58,061	$ 72,993	$ 64,455
Total proceeds from option exercises	12,620	11,868	13,007
Fair value of option grants that vested	$ 9,106	$ 9,520	$ 10,755
2012 Equity Incentive Plan [Member]
Stock option activity under the Plan:
Outstanding, beginning of period (in shares)	4,042	5,288	7,223
Options assumed per FireLayers acquisition (in shares)	20
Options granted (in shares)	237	284	563
Options exercised (in shares)	(1,089)	(1,429)	(1,984)
Options forfeited and canceled (in shares)	(27)	(101)	(514)
Outstanding, end of period (in shares)	3,183	4,042	5,288	7,223
Exercisable (in shares)	2,590
Vested and expected to vest (in shares)	3,124
Shares subject to options outstanding, weighted average exercise price:
Balance at beginning of period (USD per share)	$ 15.10	$ 11.06	$ 8.17
Options assumed per FireLayers acquisition (USD per share)	4.33
Options granted (USD per share)	54.11	57.47	36.91
Options exercised (USD per share)	11.59	8.31	6.56
Options forfeited and canceled (USD per share)	43.15	19.11	16.25
Balance at end of period (USD per share)	18.91	$ 15.10	$ 11.06	$ 8.17
Exercisable (in USD per share)	12.68
Vested and expected to vest (in USD per share)	$ 18.31
Weighted average remaining contractual term	5 years 4 months 21 days	5 years 9 months 7 days	6 years 3 months 22 days	6 years 9 months 26 days
Weighted average remaining contractual term, Exercisable	4 years 8 months 22 days
Weighted average remaining contractual term, Vested and expected to vest	5 years 3 months 31 days
Aggregate intrinsic value	$ 164,842	$ 201,736	$ 196,608	$ 180,543
Aggregate intrinsic value, exercisable	150,144
Aggregate intrinsic value, vested and expected to vest	163,622
Unrecognized stock-based compensation expense	$ 11,800
Average remaining vesting term	2 years 1 month 3 days
Minimum [Member]
Fair value assumptions:
Expected life (in years)	5 years 3 months 22 days	5 years 3 months 22 days	5 years 3 months 22 days
Volatility		50.00%	54.00%
Risk-free interest rate	1.30%	1.60%	1.80%
Maximum [Member]
Fair value assumptions:
Expected life (in years)	6 years 29 days	6 years 29 days	6 years 29 days
Volatility		52.00%	58.00%
Risk-free interest rate	1.40%	1.80%	1.90%

Equity Award Plans - Restricted

Equity Award Plans - Restricted Stock Units (Details) - 2012 Equity Incentive Plan [Member] - Restricted stock units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
RSU's Outstanding, Number of Shares:
Awarded at beginning of period (in shares)	3,311	2,934	1,214
Awards granted (in shares)	1,605	1,541	2,362
Awards vested (in shares)	(1,116)	(897)	(396)
Awards forfeited (in shares)	(335)	(267)	(246)
Awarded at end of period (in shares)	3,465	3,311	2,934
RSUs Outstanding, Granted Fair Value Per Unit:
Awarded at beginning of period (USD per share)	$ 47.94	$ 37.45	$ 29.57
Awards granted (USD per share)	64.08	61.48	39.77
Awards vested (USD per share)	44.73	38.70	30.79
Awards forfeited (USD per share)	51.40	41.89	31.59
Awarded at end of period (USD per share)	$ 56.11	$ 47.94	$ 37.45
Unamortized stock-based compensation expense	$ 118,420
Average remaining vesting term	2 years 11 months 21 days

Equity Award Plans - Performanc

Equity Award Plans - Performance Stock Units (Details) - Performance Shares [Member] - 2012 Equity Incentive Plan [Member] - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	146	189
Unamortized stock-based compensation expense	$ 9,660

Equity Award Plans - Stock Bonu

Equity Award Plans - Stock Bonus Awards (Details) - USD ($) shares in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 2,299	$ 1,884
Fair value of liability awards issued	$ 6,885
Award vesting period	3 years
Common stock issued (shares)		45
2012 Equity Incentive Plan [Member] | Stock Bonus Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total accrued liability		$ 7,855	$ 5,676
Shares of common stock issued		93	30
Stock-based compensation expense		$ 5,288	$ 3,792	$ 1,771

Equity Award Plans - Employee S

Equity Award Plans - Employee Stock Purchase Plan (Details) - ESPP 2012 Plan [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Mar. 30, 2012	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation:
Shares authorized for issuance (in shares)	745
Period for annual increase	8 years
Percent increase of outstanding shares	1.00%
Maximum number of additional shares to be authorized (in shares)	1,490
Increase in common stock reserved and available for issuance ESPP (in shares)		1,360
Fair value assumptions:
Expected life (in years)		6 months	6 months	6 months
Dividend yield		0.00%	0.00%	0.00%
Shares issued (in shares)		200	161
Weighted average price per share (USD per share)		$ 45.65	$ 41.84
Unamortized stock-based compensation expense		$ 1,510
Average remaining vesting term		4 months 13 days
Minimum [Member]
Fair value assumptions:
Volatility		37.00%	42.00%	45.00%
Risk-free interest rate		0.38%	0.08%	0.05%
Maximum [Member]
Fair value assumptions:
Volatility		48.00%	47.00%	52.00%
Risk-free interest rate		0.45%	0.33%	0.07%

Equity Award Plans - Restrict60

Equity Award Plans - Restricted Stock (Details) - Restricted Stock [Member] - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted in period		54
Fair value of shares granted		$ 2,357
Cliff Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		2 years
FireLayers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted in period	111
Fair value of shares granted	$ 8,669
Award vesting period	3 years
Unrecognized stock-based compensation expense	$ 8,123

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Common Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	15,023	15,651	13,561
Stock options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	3,183	4,042	5,288
Restricted stock units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	3,465	3,311	2,934
Employee stock purchase plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	92	81	90
Common stock subject to repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	135	54	54
Bonus shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	159	174	37
Convertible Senior Notes 1.25% [Member] | Convertible senior notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	5,158	5,158	5,158
Convertible Senior Notes 0.75% [Member] | Convertible senior notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	2,831	2,831	0

Segment Reporting - Revenue by

Segment Reporting - Revenue by Solution (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Revenue from External Customer [Line Items]
Number of segments | segment	1
Revenue	$ 375,496	$ 265,397	$ 195,607
Protection and Advanced Threat [Member]
Revenue from External Customer [Line Items]
Revenue	272,621	183,050	126,812
Archiving, Privacy and Governance [Member]
Revenue from External Customer [Line Items]
Revenue	$ 102,875	$ 82,347	$ 68,795

Segment Reporting - by Geograph

Segment Reporting - by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment reporting:
Revenue	$ 375,496	$ 265,397	$ 195,607
Long-lived assets	52,523	34,501
United States [Member]
Segment reporting:
Revenue	312,601	218,424	157,593
Long-lived assets	43,789	29,514
Rest of world [Member]
Segment reporting:
Revenue	62,895	46,973	$ 38,014
Long-lived assets	$ 8,734	$ 4,987

Income Taxes - Domestic and For

Income Taxes - Domestic and Foreign Components of Loss Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
Domestic	$ (112,904)	$ (101,453)	$ (65,433)
Foreign	2,682	3,376	5,003
Loss before (provision for) benefit from income taxes	$ (110,222)	$ (98,077)	$ (60,430)

Income Taxes - Expense for Inco

Income Taxes - Expense for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax expense:
Federal	$ 0	$ 0	$ 0
State	72	54	121
Foreign	795	514	530
Total current	867	568	651
Deferred tax expense:
Federal	411	105	(792)
State	0	(45)	0
Foreign	(292)	7	(172)
Total deferred	119	67	(964)
Provision for (benefit from) income taxes	$ 986	$ 635	$ (313)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Federal statutory income tax rate	34.00%	34.00%	34.00%
Valuation allowance increase (decrease)	$ 39,489	$ 10,980
Accrued interest and penalties	45	15
Liability recorded on interest and penalties	182	227
Uncertain tax benefits that would affect effective tax rate if recognized	922	1,202
Foreign withholdings	206
Undistributed earnings of foreign subsidiaries	4,120
Estimated additional tax liability if foreign undistributed earnings were repatriated	600
Federal [Member]
Income Tax [Line Items]
Operating loss carryforwards	533,825	425,640
Operating loss carryforwards, benefit recognized	214,229	158,246
State [Member]
Income Tax [Line Items]
Operating loss carryforwards	305,493	253,460
Operating loss carryforwards, benefit recognized	125,497	90,849
Foreign [Member]
Income Tax [Line Items]
Operating loss carryforwards	7,045	0
Research tax credit carryforward [Member] | Federal [Member]
Income Tax [Line Items]
Tax credit carryforward	9,231	6,642
Research tax credit carryforward [Member] | State [Member]
Income Tax [Line Items]
Tax credit carryforward	11,195	8,734
Research tax credit carryforward [Member] | Foreign [Member]
Income Tax [Line Items]
Tax credit carryforward	$ 2,010	2,058
Change in Sales Commissions [Member]
Income Tax [Line Items]
Valuation allowance increase (decrease)		$ (8,438)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at federal statutory rate	$ (37,476)	$ (33,346)	$ (20,546)
Foreign income tax rate differential	(187)	(270)	(600)
State, net of federal benefit	(3,478)	(2,952)	(1,585)
Stock compensation charges	3,517	2,393	1,304
SubPart F and other permanent items	1,422	1,434	2,579
Provision to return and other	1,419	749	3,621
Research and development credits	(4,464)	(2,920)	(2,052)
Uncertain tax positions	749	561	391
Valuation allowance	39,484	34,986	16,575
Provision for (benefit from) income taxes	$ 986	$ 635	$ (313)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$ 119,168	$ 98,882
Tax credit carryforwards	13,966	10,856
Research expenditures	2,401	2,301
Deferred revenue	13,698	12,165
Stock compensation	18,509	13,289
Fixed assets	207	1,426
Accruals and other	11,554	8,997
Gross deferred tax assets	179,503	147,916
Valuation allowance	(141,398)	(101,909)
Total deferred tax assets	38,105	46,007
Deferred tax liabilities:
Intangible assets and other	(8,793)	(7,547)
Deferred commissions	(9,545)	(8,438)
Convertible senior notes	(21,541)	(28,267)
Total deferred tax liabilities	(39,879)	(44,252)
Total net deferred tax liabilities	(1,774)
Total net deferred tax assets		1,755
Non-current deferred income tax assets (included in other long-term assets)	2,121	2,116
Non-current deferred income tax liabilities (included in long-term liabilities)	$ 3,895	$ 411

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 4,820	$ 4,229	$ 3,823
Increase in balances related to tax positions taken during the current period	1,262	806	524
Increase in balances related to tax positions taken during the prior period	20	0	0
Decrease in balances related to tax positions taken during the prior period	(17)	(130)	(87)
Decrease in balances related to statute expirations during the current period	(239)	(85)	(31)
Ending balance	$ 5,846	$ 4,820	$ 4,229