Proofpoint (PFPT) 10-K 25 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 12, 2016	Jun. 30, 2015
Document Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
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		41,163,655
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,435

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 346,205	$ 180,337
Short-term investments	60,032	34,649
Accounts receivable, net of allowance for doubtful accounts of $199 and $429 at December 31, 2015 and 2014, respectively	54,522	40,912
Inventory	485	499
Deferred product costs	2,228	1,847
Prepaid expenses and other current assets	5,695	7,994
Total current assets	469,167	266,238
Property and equipment, net	34,501	18,718
Deferred product costs	314	307
Goodwill	133,769	107,504
Intangible assets, net	41,330	27,086
Other assets	3,733	4,163
Total assets	682,814	424,016
Current liabilities:
Accounts payable	14,081	9,249
Accrued liabilities	35,053	24,220
Equipment loans and capital lease obligations	32	695
Deferred rent	496	569
Deferred revenue	182,195	123,550
Total current liabilities	231,857	158,283
Convertible senior notes	345,699	161,396
Long-term capital lease obligations	123	0
Long-term deferred rent	2,033	2,099
Other long-term liabilities	1,188	6,640
Long-term deferred revenue	41,531	39,125
Total liabilities	$ 622,431	$ 367,543
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, 2015 and 2014	$ 0	$ 0
Common stock, $0.0001 par value; 200,000 shares authorized at December 31, 2015 and 2014; 40,840 and 38,665 shares issued and outstanding at December 31, 2015 and 2014, respectively	4	4
Additional paid-in capital	441,104	330,744
Accumulated other comprehensive loss	(23)	(27)
Accumulated deficit	(380,702)	(274,248)
Total stockholders' equity	60,383	56,473
Total liabilities and stockholders' equity	$ 682,814	$ 424,016

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$ 199	$ 429
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)	40,840,000	38,665,000
Common stock outstanding (in shares)	40,840,000	38,665,000
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, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Subscription		$ 257,329	$ 187,527	$ 132,062
Hardware and services		8,068	8,080	5,869
Total revenue		265,397	195,607	137,931
Cost of revenue:
Subscription		71,746	53,136	35,438
Hardware and services		12,312	12,543	6,124
Total cost of revenue	[1],[2]	84,058	65,679	41,562
Gross profit		181,339	129,928	96,369
Operating expense:
Research and development		74,459	51,903	34,449
Sales and marketing		156,156	102,455	71,781
General and administrative		36,616	26,679	19,622
Total operating expense	[1],[2]	267,231	181,037	125,852
Operating loss		(85,892)	(51,109)	(29,483)
Interest expense		(18,000)	(11,213)	(641)
Other expense, net		(1,927)	(2,230)	(215)
Loss before (provision for) benefit from income taxes		(105,819)	(64,552)	(30,339)
(Provision for) benefit from income taxes		(635)	313	2,808
Net loss		$ (106,454)	$ (64,239)	$ (27,531)
Net loss per share, basic and diluted (in dollars per share)		$ (2.68)	$ (1.72)	$ (0.79)
Weighted average shares outstanding, basic and diluted (in shares)		39,787	37,381	34,874
Stock-based compensation expense		$ 2,000
Intangible amortization expense		12,256	$ 8,790	$ 4,044
Cost of subscription revenue
Operating expense:
Stock-based compensation expense		5,028	2,404	1,007
Intangible amortization expense		7,079	4,157	2,220
Cost of hardware and services revenue
Operating expense:
Stock-based compensation expense		1,098	604	196
Research and development
Operating expense:
Stock-based compensation expense		20,672	10,204	3,608
Intangible amortization expense		91	93	47
Sales and marketing
Operating expense:
Stock-based compensation expense		21,511	10,795	4,270
Intangible amortization expense		5,074	4,494	1,743
General and administrative
Operating expense:
Stock-based compensation expense		11,785	6,997	3,002
Intangible amortization expense		$ 12	$ 46	$ 34
[1]	Includes intangible amortization expense as follows: 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. Cost of subscription revenue $2,220, research and development $47, sales and marketing $1,743 and general and administrative $34 for the year ended December 31, 2013.
[2]	Includes stock-based compensation expenses as follows: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. Cost of subscription $1,007, cost of hardware and service revenue $196, research and development $3,608, sales and marketing $4,270 and general and administrative $3,002 for the year ended December 31, 2013

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (106,454)	$ (64,239)	$ (27,531)
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on investments, net	4	(27)	(3)
Comprehensive loss	$ (106,450)	$ (64,266)	$ (27,534)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2012	$ 33,808	$ 3	$ 216,280	$ 3	$ (182,478)
Beginning balance (shares) at Dec. 31, 2012		33,044
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(27,531)				(27,531)
Unrealized gain (loss) on short-term investments	(3)			(3)
Embedded conversion feature on Convertible Senior Notes	43,293		43,293
Stock-based compensation expense	11,231		11,231
Stock options exercised	13,510	$ 1	13,509
Stock options exercised (shares)		2,879
Issuance of common stock under employee stock purchase plan	2,839		2,839
Issuance of common stock under employee stock purchase plan (shares)		217
Vesting of early exercise options	13		13
Ending balance at Dec. 31, 2013	77,160	$ 4	287,165	0	(210,009)
Ending balance (shares) at Dec. 31, 2013		36,140
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(64,239)				(64,239)
Unrealized gain (loss) on short-term investments	(27)			(27)
Stock-based compensation expense	29,233		29,233
Common stock issued under stock-based compensation plans	18,513		18,513
Common stock issued under stock-based compensation plans (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		2
Issuance of restricted stock (shares)		54
Vesting of early exercise options	3		3
Ending balance at Dec. 31, 2014	56,473	$ 4	330,744	(27)	(274,248)
Ending balance (shares) at Dec. 31, 2014		38,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(106,454)				(106,454)
Unrealized gain (loss) on short-term investments	4			4
Embedded conversion feature on Convertible Senior Notes	54,049		54,049
Stock-based compensation expense	54,418		54,418
Common stock issued under stock-based compensation plans	20,292		20,292
Common stock issued under stock-based compensation plans (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	$ 60,383	$ 4	$ 441,104	$ (23)	$ (380,702)
Ending balance (shares) at Dec. 31, 2015		40,840

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (106,454)	$ (64,239)	$ (27,531)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	24,900	17,823	9,967
Loss on disposal of property and equipment	162	2	2
Amortization of investment premiums, net of accretion of purchase discounts	103	312	575
Provision for (recovery of) allowance for doubtful accounts	(231)	175	40
Stock-based compensation	60,094	31,004	12,083
Change in fair value of contingent earn-outs	0	5	9
Amortization of debt issuance costs and accretion of debt discount	14,933	8,753	489
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	(12,117)	(14,666)	(4,500)
Inventory	14	328	(223)
Deferred product costs	(388)	(791)	149
Prepaid expenses	(1,829)	(945)	636
Other current assets	104	(351)	(248)
Deferred income taxes	509	(691)	(3,458)
Long-term assets	47	(23)	(316)
Accounts payable	2,460	189	931
Accrued liabilities	4,448	3,995	1,883
Earn-out payment	0	(13)	(1)
Deferred rent	(165)	2,315	(438)
Deferred revenue	58,951	38,093	22,575
Net cash provided by operating activities	45,541	21,275	12,624
Cash flows from investing activities
Proceeds from sales and maturities of short-term investments	39,056	11,353	59,046
Purchase of short-term investments	(64,537)	(37,805)	(20,376)
Purchase of property and equipment	(25,827)	(14,988)	(7,666)
Acquisitions of business, net of cash acquired	(51,553)	(53,680)	(40,972)
Net cash used in investing activities	(102,861)	(95,120)	(9,968)
Cash flows from financing activities
Proceeds from issuance of common stock, net of repurchases	18,583	17,640	16,367
Withholding taxes related to restricted stock net share settlement	(18,108)	(4,170)	0
Proceeds from convertible debt	223,790	0	195,641
Payments of debt issuance costs	(371)	(191)	0
Repayments of notes payable and loans	(706)	(1,655)	(10,033)
Holdback payments for prior acquisitions	0	(741)	0
Payment of contingent earn-outs	0	(487)	(99)
Net cash provided by financing activities	223,188	10,396	201,876
Net increase (decrease) in cash and cash equivalents	165,868	(63,449)	204,532
Cash and cash equivalents
Beginning of period	180,337	243,786	39,254
End of period	346,205	180,337	243,786
Supplemental disclosures of cash flow information
Cash paid for interest	3,381	2,582	148
Cash paid for taxes	672	491	385
Supplemental disclosure of noncash investing and financing activities
Unpaid deferred offering costs	0	0	195
Unpaid purchases of property and equipment	$ 4,906	$ 2,576	$ 1,039

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	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 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. Principles of Consolidation 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. 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 accounting principles generally accepted in the United States of America (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, 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 $1,657 , $2,182 and $180 for the years ended December 31, 2015, 2014 and 2013, 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, 2015 and 2014 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 probable. 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. 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, 2015 , 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, such as property and equipment, including intangible assets other than goodwill, 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. 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, 2015, 2014 and 2013 . 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, 2015 . Intangible assets consist of developed technology, customer relationships, non-compete arrangements, trademarks and patents, order backlog and in-process research and development asset. 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 In-process research and development asset is not amortized until the associated project is completed. 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. Recent Accounting Policies In November 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (ASU 2015-17). ASU 2015-17 requires that deferred tax assets and liabilities be classified as noncurrent in the balance sheet. ASU 2015-17 is effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, with early adoption permitted. The Company early adopted this ASU on a prospective basis in the fourth quarter of 2015 and, as a result, classified $5,879 of current deferred tax assets within other long-term liabilities on the accompanying consolidated balance sheet as of December 31, 2015, and the prior periods were not retrospectively adjusted. In September 2015, FASB issued Accounting Standards Update No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 eliminates the requirement for an acquirer to retrospectively adjust provisional amounts recorded in a business combination to reflect new information about the facts and circumstances that existed as of the acquisition date and that, if known, would have affected measurement or recognition of amounts initially recognized. As an alternative, the amendment requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The amendments require that the acquirer record, in the financial statements of the period in which adjustments to provisional amounts are determined, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. The new standard is effective prospectively for fiscal years beginning after December 15, 2015, including interim periods within those fiscal years, with early adoption permitted. The Company does not expect any impact of ASU 2015-16 on its consolidated financial statements. In April 2015, FASB issued Accounting Standards Update No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015-03), which requires the Company to present such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs will continue to be reported as interest expense. ASU 2015-03 is effective for fiscal years beginning after December 15, 2015 and interim periods within those fiscal years, with early adoption permitted. The Company early adopted this ASU effective during the second quarter of 2015 and has applied it retrospectively to all prior periods presented. Consequently, other long-term assets and convertible senior notes liabilities as of December 31, 2014 included on the consolidated balance sheet herein were reduced by $234 . There was no impact on the Company's results of operations or cash flows due to the adoption of this guidance. 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 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 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 Company is currently evaluating the timing and impact of the adoption of ASU 2014-09 on its consolidated financial statements.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
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 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. 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 Company has provisionally estimated fair values of acquired tangible and intangible assets at each Acquisition Date. The amounts reported were considered provisional as the Company was completing the valuation work to determine the fair value of certain assets acquired. 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 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: Estimated 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 Company has provisionally estimated fair values of acquired tangible and intangible assets at the Marble Acquisition Date. The amounts reported were considered provisional as the Company was completing the valuation work to determine the fair value of certain assets acquired. The results of operations and the provisional fair values of the acquired assets and liabilities assumed have been included in the accompanying condensed 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 Quarterly 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 determination of the fair values of the assets acquired 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 acquired tangible, intangible assets and goodwill: Estimated 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 Company has provisionally estimated the fair values for the acquired tangible and identifiable intangible assets and liabilities assumed at the Emerging Threats Acquisition Date. The amounts reported were considered provisional as the Company was completing the valuation work to determine the fair value of certain assets acquired and liabilities assumed. 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 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: Estimated 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 in USD 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 in USD 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 2013 Acquisitions Sendmail, Inc. On October 1, 2013 (the "Sendmail Acquisition Date"), pursuant to the terms of an Agreement and Plan of Merger, a wholly-owned subsidiary of the Company merged with and into Sendmail, Inc. ("Sendmail"), with Sendmail surviving as a wholly-owned subsidiary of the Company. Formerly based in Emeryville, California, Sendmail is a leading provider of messaging infrastructure solutions to enterprises whose solutions ensure global email connectivity, routing and message delivery between people, systems and applications located on-premise, in-cloud or on mobile devices. The acquisition of Sendmail allows the Company access to its Sentrion Email Platform business, customers, core engineering and professional teams which have demonstrated a sustained level of expertise in messaging infrastructure. During the quarter ended December 31, 2013, the Company completed the valuation of the estimated fair values of the acquired tangible and identifiable intangible assets and liabilities assumed at the Sendmail Acquisition Date, and the results of operations and the fair values of the acquired assets and liabilities assumed have been included in the consolidated financial statements since the Sendmail Acquisition Date. The Company recorded 2,975 in revenue from Sendmail for the year ended December 31, 2013 . At the Sendmail Acquisition Date, the Company paid $12,463 in cash consideration, net of cash acquired of $1,117 . Of the cash consideration paid, $3,422 was held in escrow to secure indemnification obligations, of which $ 719 was recovered from indemnification claims in 2014. As part of the acquisition, the Company assumed and paid off $7,933 in long-term debt on the Sendmail Acquisition Date. The Company incurred $1,877 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2013 . 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 in USD Estimated Tangible assets acquired $ 5,202 N/A Liabilities assumed (5,162 ) N/A Deferred revenue assumed (14,549 ) N/A Long-term debt assumed (7,933 ) N/A Trade name 400 5 Customer relationships 8,000 3 Patents 300 5 Core/developed technology 3,000 3 Goodwill 24,322 Indefinite $ 13,580 Armorize Technologies, Inc. On September 5, 2013 (the "Armorize Acquisition Date"), pursuant to the terms of an Agreement and Plan of Merger, a wholly-owned subsidiary of the Company merged with and into Armorize Technologies, Inc. ("Armorize"), with Armorize surviving as a wholly-owned subsidiary of the Company. Based in Taiwan, Armorize develops and markets leading cloud-based SaaS anti-malware products and will add real-time dynamic detection of next generation threats and malware to the Company's existing capabilities. During the quarter ended September 30, 2013, the Company completed the valuation of the estimated fair values of the acquired tangible and identifiable intangible assets and liabilities assumed at the Armorize Acquisition Date, and the results of operations and the fair values of the acquired assets and liabilities assumed have been included in the consolidated financial statements since the Armorize Acquisition Date. The Company recorded $ 781 in revenue from Armorize for the year ended December 31, 2013 . At the Armorize Acquisition Date, the Company paid $24,215 in cash consideration, net of cash acquired of $1,746 . The Company incurred $747 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2013 . 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 in USD Estimated Tangible assets acquired $ 2,754 N/A Liabilities assumed (1,234 ) N/A Customer relationships 1,300 2 Non-compete agreements 500 3 Core/developed technology 3,850 5 Goodwill 18,791 Indefinite $ 25,961 Abaca Technology Corporation On July 19, 2013 (the "Abaca Technology Acquisition Date"), pursuant to the terms of an Agreement and Plan of Merger, a wholly-owned subsidiary of the Company merged with and into Abaca Technology Corporation ("Abaca Technology"), with Abaca Technology surviving as a wholly-owned subsidiary of the Company. Abaca Technology specializes in email filtering and protection algorithms and their cloud-based, in-memory threat scoring technologies are expected to complement the Company's continued investment in anti-spam and threat detection capabilities. During the quarter ended September 30, 2013, the Company completed the valuation of the estimated fair values of the acquired tangible and identifiable intangible assets and liabilities at the Abaca Technology Acquisition Date, and the results of operations and the fair values of the acquired assets and liabilities assumed have been included in the consolidated financial statements since the Abaca Technology Acquisition Date. The Company recorded $311 in revenue from Abaca Technology for the year ended December 31, 2013 . At the Abaca Technology Acquisition Date, the Company paid $23 in cash consideration, net of cash acquired of $3 . The purchase consideration included an additional amount of $1,520 which was held back to secure contingent liabilities related to indemnification obligations. The initial fair values of the contingent liabilities of $1,397 were recorded in other long-term liabilities in the consolidated balance sheet. The indemnification obligations have not been released as of the filing date of this Annual Report on Form 10-K. The Company incurred $218 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2013 . 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 in USD Estimated Tangible assets acquired $ 311 N/A Liabilities assumed (962 ) N/A Customer relationships 40 3 Core/developed technology 1,770 5 Goodwill 264 Indefinite $ 1,423 eDynamics, LLC On July 10, 2013 (the "eDynamics Acquisition Date"), pursuant to the terms of an Asset Purchase Agreement. the Company purchased substantially all of the business intellectual property and assumed certain liabilities of eDynamics, LLC ("eDynamics"). eDynamics is a social media archiving company and is expected to be an integral part of the Company's broader effort in rolling out a comprehensive social media archiving platform for customers. During the quarter ended September 30, 2013, the Company completed the valuation of the estimated fair values of the acquired tangible and identifiable intangible assets and liabilities assumed at the eDynamics Acquisition Date, and the results of operations and the fair values of the acquired assets and liabilities assumed have been included in the consolidated financial statements since the eDynamics Acquisition Date. Revenue from eDynamics was not material for the year ended December 31, 2013 . At the eDynamics Acquisition Date, the Company paid $500 in cash consideration. The Company also agreed to pay earn-out consideration ("Acquisition-related contingent earn-out liability") of up to $600 through April 2014, such liability being contingent upon the achievement of specified product development milestones. The initial fair value of the contingent earn-out liability of $586 was recorded as part of the purchase consideration. The purchase consideration also included an additional amount of $100 , which was held back to secure any claims that may arise in the 12-month period after the eDynamics Acquisition Date. The initial fair value of such amount withheld of $72 as well as the Acquisition-related contingent earn-out liability were recorded in accrued liabilities on the consolidated balance sheet. The Company paid $100 of the contingent earn-out liability during the year ended December 31, 2013, the remaining earn-out consideration and holdback amount were paid in full in year ended December 31, 2014 . The Company incurred $6 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2013 . 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 in USD Estimated Customer relationships $ 243 3.5 Non-compete agreements 75 2 Core/developed technology 733 3.5 Goodwill 107 Indefinite $ 1,158 Mail Distiller Limited On April 5, 2013 (the "Mail Distiller Acquisition Date"), pursuant to the terms of a share transfer agreement, the Company purchased all of the outstanding share capital of Mail Distiller Limited, a Northern Ireland Company ("Mail Distiller"). Mail Distiller is a European-based provider of the SaaS email security solutions. Mail Distiller allowed the Company to create the Proofpoint Essentials product line, a suite of SaaS security and compliance solutions specifically designed for distribution across managed service providers and dedicated security resellers. During the quarter ended June 30, 2013, the Company completed the valuation of the estimated fair values of the acquired tangible and identifiable intangible assets and liabilities assumed at the Mail Distiller Acquisition Date, and the results of operations and the fair values of the acquired assets and liabilities assumed have been included in the consolidated financial statements since the Mail Distiller Acquisition Date. The Company recognized $216 in revenue from Mail Distiller for the year ended December 31, 2013 . At the Mail Distiller Acquisition Date, the Company paid $3,771 in cash consideration, net of cash acquired of $60 . The purchase consideration included an additional amount of $669 held back to secure indemnification obligations, which was recorded in accrued liabilities on the consolidated balance sheet as of December 31, 2013 . The indemnification obligations has been released in year ended December 31, 2014 . The Company incurred $258 in acquisition-related costs which were recorded within operating expenses for the year ended December 31, 2013 . 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 in USD Estimated Tangible assets acquired $ 204 N/A Liabilities assumed (1,052 ) N/A Trade name 7 1 Customer relationships 1,291 2 Non-compete agreements 123 2 Core/developed technology 2,475 7 Goodwill 1,452 Indefinite $ 4,500 Pro Forma Financial Information The following unaudited pro forma financial information presents the combined results of operations for the years ended December 31, 2015, 2014 and 2013 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 acquisition of 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, 2015 2014 2013 Total revenue $ 264,904 $ 200,124 $ 166,577 Net loss (108,398 ) (75,066 ) (46,090 ) Basic and diluted net loss per share $ (2.72 ) $ (2.01 ) $ (1.32 ) The unaudited pro forma financial information includes acquisition-related transaction costs of $277 for the year ended year ended December 31, 2015 .

Concentration of Risks

Concentration of Risks	12 Months Ended
	Dec. 31, 2015
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 year ended December 31, 2015 , no individual customers accounted for more than 10% of total revenue. One customer accounted for 12% and 14% of total revenue in the years ended December 31, 2014 and 2013, respectively. One customer accounted for 16% of total accounts receivable as of December 31, 2015 . No customers accounted for more than 10% of total accounts receivable as of December 31, 2014 .

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2015
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, 2013 $ 187 $ 91 $ (2 ) $ 276 Year ended December 31, 2014 $ 276 $ 158 $ (5 ) $ 429 Year ended December 31, 2015 $ 429 $ (169 ) $ (61 ) $ 199 Property and equipment at December 31, 2015 and 2014 consist of the following: Useful Life (in years) December 31, 2015 2014 Computer equipment 2 to 4 $ 63,867 $ 42,933 Software 2 to 5 1,684 1,850 Furniture 5 1,074 170 Office equipment 2 to 5 347 582 Leasehold improvements 5 years, or lease term, if shorter 4,728 4,341 Other 2 59 59 Construction in progress 934 643 72,693 50,578 Less: Accumulated depreciation (38,192 ) (31,860 ) $ 34,501 $ 18,718 Property and equipment acquired under capital leases: December 31, 2015 2014 Computer equipment $ 453 $ 346 Less: Accumulated depreciation (310 ) (336 ) $ 143 $ 10 Depreciation expense for the years ended December 31, 2015, 2014 and 2013 , was approximately $12,644 , $9,033 , and $5,923 , respectively. This included depreciation expense for assets under capital leases of $23 , $19 and $48 for the years ended December 31, 2015, 2014 and 2013 , respectively. Construction in progress as of December 31, 2015 includes capitalized software development costs of $203 , which was incurred in 2015 and the asset was not placed in service as of December 31, 2015. Other software development costs were fully amortized as of December 31, 2014 and 2013. Amortization of capitalized software development costs was approximately $159 for the year ended December 31, 2013 . Accrued liabilities at December 31, 2015 and 2014 consisted of the following: December 31, 2015 2014 Accrued compensation $ 21,994 $ 15,206 Customer deposits 1,384 1,484 Accrued royalties 509 706 Other 11,166 6,824 $ 35,053 $ 24,220

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The goodwill activity and balances are presented below: December 31, 2015 2014 Opening balance $ 107,504 $ 63,764 Add: Goodwill from acquisitions 26,289 44,015 Less: Other adjustments to Goodwill (24 ) (275 ) Closing balance $ 133,769 $ 107,504 The goodwill balance as of December 31, 2015 was the result of the acquisitions of Fortiva, Inc., Secure Data in Motion, Inc., Everyone.net, Inc., Spam and Open Relay Blocking System from GFI Software Ltd., NextPage, Inc., Mail Distiller, eDynamics, Abaca, Armorize, Sendmail, Nexgate, NetCitadel and the Acquisitions completed during the year ended December 31, 2015 (see Note 2, "Acquisitions"). Intangible Assets Intangible assets excluding goodwill consisted of the following: December 31, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technology $ 57,268 $ (28,618 ) $ 28,650 $ 38,168 $ (21,538 ) $ 16,630 Customer relationships 23,382 (12,291 ) 11,091 16,382 (7,893 ) 8,489 Non-compete agreements 804 (691 ) 113 804 (462 ) 342 Trademark and patents 1,006 (502 ) 504 806 (264 ) 542 Order backlog 1,300 (328 ) 972 200 (17 ) 183 In-process research and development — — — 900 — 900 $ 83,760 $ (42,430 ) $ 41,330 $ 57,260 $ (30,174 ) $ 27,086 Amortization expense of intangibles totaled $12,256 , $8,790 and $4,044 during the years ended December 31, 2015, 2014 and 2013 , respectively. Future estimated amortization costs of intangible assets as of December 31, 2015 are presented below: Year Ended December 31, 2016 $ 12,519 2017 9,174 2018 8,530 2019 5,164 2020 2,806 Thereafter 3,137 $ 41,330

Fair Value Measurements and Inv

Fair Value Measurements and Investments	12 Months Ended
	Dec. 31, 2015
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. The following tables summarize, for each category of assets or liabilities carried at fair value, the respective fair value as of December 31, 2015 and 2014 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 $ 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 $ — Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 139,644 $ 139,644 $ — $ — Short-term investments: Corporate debt securities 31,651 — 31,651 — Commercial papers 2,998 — 2,998 — Total financial assets $ 174,293 $ 139,644 $ 34,649 $ — Based on quoted market prices as of December 31, 2015 , the fair value of the 0.75% and 1.25% Convertible Senior Notes (Note 8) were approximately $246,105 and $348,666 , respectively, determined using Level 2 inputs as they are not actively traded in markets. 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, 2015 and 2014 were as follows: 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 December 31, 2014 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 40,693 $ — $ — $ 40,693 Money market funds 139,644 — — 139,644 Total $ 180,337 $ — $ — $ 180,337 Short-term investments: Corporate debt securities $ 31,678 $ — $ (27 ) $ 31,651 Commercial papers 2,998 — — 2,998 Total $ 34,676 $ — $ (27 ) $ 34,649 As of December 31, 2015 and 2014 , 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 year ended December 31, 2015.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
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 February 2020. Premises rent expense was $3,831 , $3,283 and $1,774 for the years ended December 31, 2015, 2014 and 2013 , 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 are 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, 2015 , future annual minimum lease payments under noncancellable operating and capital leases were as follows: Capital Operating 2016 $ 41 $ 10,026 2017 41 6,056 2018 39 4,534 2019 37 3,989 2020 22 969 Thereafter — 625 Total minimum lease payments 180 $ 26,199 Less: Amount representing interest (25 ) Present value of capital lease obligations 155 Less: Current portion (32 ) Long-term portion of capital lease obligations $ 123 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. The Company and Armorize filed an answer to the complaint on February 10, 2014. On April 15, 2014, Finjan’s initial disclosures in the lawsuit alleged approximately $13,500 in damages, but provided no basis or facts in support of this sum. On April 2, 2015, the court ordered that the claims construction hearing be held in June 2015. On April 23, 2015, Finjan amended its infringement contentions pursuant to court order that Finjan amend its infringement contentions to comply with the Patent Local Rules. On June 24, 2015, the court held the claims construction hearing in this matter. On December 3, 2015, the court issued its claim construction order. On December 17, 2015, the court held its hearing on defendants’ motion to strike Finjan’s additional infringement contentions and ordered that trial be set for June 7, 2016. On February 16, 2016, the court issued its order on the motion to strike additional infringement contentions, granting the majority of defendants’ requests. On February 22, 2016, the Company and Armorize filed their motion for summary judgment with the court and a hearing on that motion is schedule for March 31, 2016. Based on the state of the infringement contentions and evaluation of the facts available at this time, the amount or range of reasonable possible losses to which the Company or Armorize is exposed cannot be estimated and the ultimate resolution of this matter and the associated financial statement impact, if any, remains uncertain at this time. The Company and Armorize are vigorously defending the lawsuit. Intellectual property litigation is subject to inherent uncertainties, and there can be no assurance that the expenses associated with defending any litigation or the resolution of this dispute would not have a material adverse impact on the Company's balance sheet, results of operations or cash flows. Regardless of the outcome, such proceedings and claims can have an adverse impact on the Company because of defense and settlement costs, diversion of resources and other factors, and there can be no assurances that favorable outcomes will be obtained.

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2015
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 1944 (the "Exchange Act"), as amended. 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 will use 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 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 the 0.75% 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. 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. At December 31, 2015 , the net carrying amount of the liability component of the Notes consists of: 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, 2015, 2014 and 2013 , the Company incurred the following interest expense related to the Notes: 2015 2014 2013 Interest expense related to contractual interest coupon $ 3,441 $ 2,511 $ 138 Amortization of debt discount and issuance costs 14,933 8,753 489 Total $ 18,374 $ 11,264 $ 627

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	Debt Equipment Financing Loans The Company entered into an equipment loan agreement with Silicon Valley Bank in April 2011 for an aggregate loan principal amount of $6,000 . Interest on the advances was equal to prime rate plus 0.50% . The Company had the ability to draw down on this equipment line through April 19, 2012. Each drawn amount was due 48 months after funding. The outstanding balance of equipment financing loans was fully repaid in the second quarter of 2015. Interest expense related to the equipment financing loans for the years ended December 31, 2015, 2014 and 2013 was $5 , $65 and $140 , respectively.

Equity Award Plans

Equity Award Plans	12 Months Ended
	Dec. 31, 2015
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 two equity incentive plans: the Company’s 2002 stock option plan (the “2002 Plan”) and the 2012 Plan. 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. All outstanding stock awards under the 2002 and 2012 Plans 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 2002 and 2012 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, 2015 , 5,119 shares were available for future grant. Restricted stock awards generally vest over a four -year period. The number of shares available for grant and issuance under the 2012 Plan will be increased automatically on each January 1 of 2013 through 2016 by an amount equal to 5% of the Company's shares outstanding on the immediately preceding December 31, but not to exceed 3,724 shares, unless the Board of Directors, in its discretion, determines to make a smaller increase. 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, 2015, 2014 and 2013 , was $28.20 , $20.25 and $9.50 , 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, 2015 2014 2013 Expected life (in years) 5.31 - 6.08 5.31 - 6.08 5.31 - 6.08 Volatility 50% - 52% 54% - 58% 57% - 61% Risk-free interest rate 1.6% - 1.8% 1.79% - 1.93% 0.9% - 1.8% 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. Since the Company's stock has been publicly traded for a limited time, the stock volatility assumptions represent an estimate of the historical volatilities of the common stock of a group of publicly-traded peer companies that operate in a similar industry. The estimate was determined based on the average historical volatilities of these peer companies. 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, 2012 9,636 $ 5.63 7.33 $ 64,719 Options granted 1,618 17.46 Options exercised (2,879 ) 4.69 Options forfeited and canceled (1,152 ) 8.65 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 Exercisable, December 31, 2015 3,088 $ 9.23 5.06 $ 172,232 Vested and expected to vest, December 31, 2015 3,950 $ 14.52 5.71 $ 199,447 The total intrinsic value of options exercised was $72,993 , $64,455 and $45,454 , for the years ended December 31, 2015, 2014 and 2013 , respectively. Total cash proceeds from such option exercises were $11,868 , $13,007 and $13,509 for the years ended December 31, 2015, 2014 and 2013 , respectively. The grant date fair value of options that vested was $9,520 , $10,755 and $8,206 during the years ended December 31, 2015, 2014 and 2013 , respectively. As of December 31, 2015, the Company had unrecognized stock-based compensation expense of $13,592 related to stock options that will be recognized, net of forfeitures, over the average remaining vesting term of the options of 1.94 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, 2012 1 $ 7.98 Awards granted 1,236 28.94 Awards vested (1 ) 24.15 Awards forfeited (22 ) 24.61 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 As of December 31, 2015 , there was $100,028 of unamortized stock-based compensation expense related to unvested RSUs, which are expected to be recognized over a weighted average period of 3.09 years. The Company granted 189 and 121 PSUs in the years ended December 31, 2015 and 2014, respectively. The PSU vesting conditions were based on individual performance targets. Unamortized expense was $3,903 as of December 31, 2015, 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 $5,676 and $1,771 as of December 31, 2015 and 2014, respectively. 30 and 22 shares of common stock earned under the stock bonus program were issued during the years ended December 31, 2015 and 2014, respectively. Stock based compensation expense related to stock bonus program were $3,792 , $1,771 and $852 for the years ended December 31, 2015, 2014 and 2013. 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. The Company recognized $1,884 of stock-based compensation expense related to these liability awards in the year ended December 31, 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, 2015 , there were 1,152 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, 2015 2014 2013 Expected life (in years) 0.50 0.50 0.50 - 0.54 Volatility 42% - 47% 45% - 52% 38% - 40% Risk-free interest rate 0.08% - 0.33% 0.05% - 0.07% 0.08% Dividend yield —% —% —% The Company issued 161 shares and 194 shares under the ESPP in 2015 and 2014, respectively, at a weighted average exercise price per share of $41.84 and $23.94 , respectively. As of December 31, 2015 , the Company expects to recognize $1,214 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 the total fair value of $2,357 and two -year cliff vesting in 2016. As of December 31, 2015, there was $982 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, 2015
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, 2015 2014 2013 Stock options to purchase common stock 4,042 5,288 7,223 Restricted stock units 3,311 2,934 1,214 Employee stock purchase plan 81 90 89 Common stock subject to repurchase 54 54 1 Bonus shares 174 37 22 Common stock warrants — — 2 1.25% Convertible senior notes 5,158 5,158 5,158 0.75% Convertible senior notes 2,831 — — Total 15,651 13,561 13,709

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2015
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. The following set forth total revenue by solutions offered by the Company and geographic area. Revenue by geographic area is based upon the billing address of the customer: Year Ended December 31, 2015 2014 2013 Total revenue by solution: Privacy, Protection and Security $ 213,194 $ 151,291 $ 101,083 Archiving and Governance 52,203 44,316 36,848 Total revenue $ 265,397 $ 195,607 $ 137,931 Year Ended December 31, 2015 2014 2013 Total revenue by geographic area: United States $ 218,424 $ 157,593 $ 113,819 Rest of world 46,973 38,014 24,112 Total revenue $ 265,397 $ 195,607 $ 137,931 The following sets forth long-lived tangible assets by geographic area: December 31, 2015 2014 Long-lived assets: United States $ 29,514 $ 15,974 Rest of world 4,987 2,744 Total long-lived assets $ 34,501 $ 18,718

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
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, 2015, 2014 and 2013 : Year Ended December 31, 2015 2014 2013 Domestic $ (109,195 ) $ (69,555 ) $ (34,284 ) Foreign 3,376 5,003 3,945 Loss before (provision for) benefit from income taxes $ (105,819 ) $ (64,552 ) $ (30,339 ) The (provision for) benefit from income taxes is comprised of: Year Ended December 31, 2015 2014 2013 Current tax expense: Federal $ — $ — $ — State 54 121 70 Foreign 514 530 641 Total current 568 651 711 Deferred tax expense: Federal 105 (792 ) — State (45 ) — — Foreign 7 (172 ) (3,519 ) Total deferred 67 (964 ) (3,519 ) Provision for (benefit from) income taxes $ 635 $ (313 ) $ (2,808 ) 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, 2015, 2014 and 2013 is as follows: Year Ended December 31, 2015 2014 2013 Tax at federal statutory rate $ (35,979 ) $ (21,948 ) $ (10,315 ) Foreign income tax rate differential (270 ) (600 ) (232 ) State, net of federal benefit (3,185 ) (1,692 ) (1,130 ) Stock compensation charges 2,393 1,304 636 SubPart F and other permanent items 1,434 2,579 1,583 Provision to return and other 749 3,621 937 Research and development credits (2,920 ) (2,052 ) (2,112 ) Uncertain tax positions 561 391 617 Valuation allowance 37,852 18,084 7,208 Provision (benefit from) for income taxes $ 635 $ (313 ) $ (2,808 ) 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 for the years ended December 31, 2015 and 2014 : Year Ended December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 98,882 $ 75,376 Tax credit carryforwards 10,856 9,566 Research expenditures 2,301 2,494 Deferred revenue 12,165 11,078 Stock compensation 13,289 7,228 Fixed assets 1,426 1,516 Accruals and other 8,997 8,505 Gross deferred tax assets 147,916 115,763 Valuation allowance (110,347 ) (90,929 ) Total deferred tax assets 37,569 24,834 Deferred tax liabilities: Intangible assets and other (7,547 ) (9,613 ) Convertible Senior Notes (28,267 ) (12,911 ) Total deferred tax liabilities (35,814 ) (22,524 ) Total net deferred tax assets $ 1,755 $ 2,310 Current deferred income tax assets (included in other current assets) $ — $ 3,903 Non-current deferred income tax assets (included in other long-term assets) $ 2,116 $ — Non-current deferred income tax liabilities (included in long-term liabilities) $ 411 $ 1,593 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 $19,418 , $19,877 and $2,400 during the years ended December 31, 2015, 2014 and 2013 , respectively. The total valuation allowance increase of $19,418 for the year ended December 31, 2015 included an increase of $1,356 resulting from the 2015 business acquisitions, and a decrease of $19,863 related to the Company's issuance of the 0.75% Notes. As of December 31, 2015 and 2014 , the Company had net operating loss carry-forwards for federal income tax purposes of $425,640 and $284,974 , respectively. The amount of federal net-operating loss carry-forwards at December 31, 2015 and 2014 for which a benefit will be recorded in APIC when realized is approximately $158,246 and $84,125 , respectively. The federal net operating losses will begin to expire in 2018. As of December 31, 2015 and 2014 , the Company had federal research credit carry-forwards of $6,642 and $5,071 respectively. The federal research and development credits will begin to expire in 2022. As of December 31, 2015 and 2014 , the Company had net operating loss carry-forwards for state income tax purposes of approximately $253,460 and $183,913 , respectively. The amount of state net-operating loss carry-forwards at December 31, 2015 and 2014 for which a benefit will be recorded in APIC when realized is approximately $90,849 and $44,407 , respectively. The state net operating losses expire between 2016 and 2034. As of December 31, 2015 and 2014 , the Company had research and development credit carry-forwards for state income tax purpose of $8,734 and $7,080 , respectively. The state research and development credits have no expiration period. There were no operating losses carry-forwards in non-U.S. locations as of December 31, 2015 and 2014 . In addition, as of December 31, 2015 and 2014 , the Company had research and development credit carry-forwards in its non-U.S. locations of approximately $2,058 and $2,878 , respectively. The non-U.S. research and development credits will begin to expire in 2030. 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, 2015 , the Company reduced income tax expense by $15 from interest and penalties related to tax contingencies and has $227 of interest and penalties recorded as a long-term income tax liability as of December 31, 2015 . During the year ended year ended December 31, 2014 , the Company accrued interest and penalties of $9 as a component of income tax expense related to tax contingencies and had $242 of interest and penalties recorded as a long-term income tax liability. 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. As of December 31, 2014 , the Company had recorded unrecognized tax benefits of $1,432 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, 2015 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 all major tax jurisdictions. 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, 2012 $ 2,740 Increase in balances related to tax positions taken during the current period 618 Increase in balances related to tax positions taken during the prior period 517 Decrease in balances related to tax positions taken during the prior period (40 ) Decrease in balances related to statute expirations during the current period (12 ) 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 As of December 31, 2015 , $180 of foreign withholding taxes associated with the repatriation of earning of foreign subsidiaries had been provided on $3,600 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, 2015 , 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, 2015 , the Company estimated that approximately $550 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 Si21

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation 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. 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 accounting principles generally accepted in the United States of America (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, 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. Inventories held at December 31, 2015 and 2014 consist primarily of finished goods.
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 probable. 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. 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, 2015 , the Company has not experienced material credit losses.
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, such as property and equipment, including intangible assets other than goodwill, 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.
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, 2015 . Intangible assets consist of developed technology, customer relationships, non-compete arrangements, trademarks and patents, order backlog and in-process research and development asset. 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.
Recent Accounting Pronouncements	Recent Accounting Policies In November 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes (ASU 2015-17). ASU 2015-17 requires that deferred tax assets and liabilities be classified as noncurrent in the balance sheet. ASU 2015-17 is effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years, with early adoption permitted. The Company early adopted this ASU on a prospective basis in the fourth quarter of 2015 and, as a result, classified $5,879 of current deferred tax assets within other long-term liabilities on the accompanying consolidated balance sheet as of December 31, 2015, and the prior periods were not retrospectively adjusted. In September 2015, FASB issued Accounting Standards Update No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 eliminates the requirement for an acquirer to retrospectively adjust provisional amounts recorded in a business combination to reflect new information about the facts and circumstances that existed as of the acquisition date and that, if known, would have affected measurement or recognition of amounts initially recognized. As an alternative, the amendment requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The amendments require that the acquirer record, in the financial statements of the period in which adjustments to provisional amounts are determined, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. The new standard is effective prospectively for fiscal years beginning after December 15, 2015, including interim periods within those fiscal years, with early adoption permitted. The Company does not expect any impact of ASU 2015-16 on its consolidated financial statements. In April 2015, FASB issued Accounting Standards Update No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015-03), which requires the Company to present such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs will continue to be reported as interest expense. ASU 2015-03 is effective for fiscal years beginning after December 15, 2015 and interim periods within those fiscal years, with early adoption permitted. The Company early adopted this ASU effective during the second quarter of 2015 and has applied it retrospectively to all prior periods presented. Consequently, other long-term assets and convertible senior notes liabilities as of December 31, 2014 included on the consolidated balance sheet herein were reduced by $234 . There was no impact on the Company's results of operations or cash flows due to the adoption of this guidance. 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 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 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 Company is currently evaluating the timing and impact of the adoption of ASU 2014-09 on its consolidated financial statements.

The Company and Summary of Si22

The Company and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
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

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Acquisition [Line Items]
Schedule of purchase price	The following table summarizes the fair values of acquired tangible and intangible assets, liabilities and goodwill: Estimated 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
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, 2015 2014 2013 Total revenue $ 264,904 $ 200,124 $ 166,577 Net loss (108,398 ) (75,066 ) (46,090 ) Basic and diluted net loss per share $ (2.72 ) $ (2.01 ) $ (1.32 )
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: Estimated Estimated Fixed assets acquired 25 N/A Developed technology 7,300 4 Goodwill 1,175 Indefinite $ 8,500
Emerging Threats [Member] [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: Estimated 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 in USD 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 in USD 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
Sendmail [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 in USD Estimated Tangible assets acquired $ 5,202 N/A Liabilities assumed (5,162 ) N/A Deferred revenue assumed (14,549 ) N/A Long-term debt assumed (7,933 ) N/A Trade name 400 5 Customer relationships 8,000 3 Patents 300 5 Core/developed technology 3,000 3 Goodwill 24,322 Indefinite $ 13,580
Armorize [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 in USD Estimated Tangible assets acquired $ 2,754 N/A Liabilities assumed (1,234 ) N/A Customer relationships 1,300 2 Non-compete agreements 500 3 Core/developed technology 3,850 5 Goodwill 18,791 Indefinite $ 25,961
Abaca Technologies [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 in USD Estimated Tangible assets acquired $ 311 N/A Liabilities assumed (962 ) N/A Customer relationships 40 3 Core/developed technology 1,770 5 Goodwill 264 Indefinite $ 1,423
eDynamics [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 in USD Estimated Customer relationships $ 243 3.5 Non-compete agreements 75 2 Core/developed technology 733 3.5 Goodwill 107 Indefinite $ 1,158
Mail Distiller [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 in USD Estimated Tangible assets acquired $ 204 N/A Liabilities assumed (1,052 ) N/A Trade name 7 1 Customer relationships 1,291 2 Non-compete agreements 123 2 Core/developed technology 2,475 7 Goodwill 1,452 Indefinite $ 4,500

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2013 $ 187 $ 91 $ (2 ) $ 276 Year ended December 31, 2014 $ 276 $ 158 $ (5 ) $ 429 Year ended December 31, 2015 $ 429 $ (169 ) $ (61 ) $ 199
Schedule of property and equipment	Property and equipment at December 31, 2015 and 2014 consist of the following: Useful Life (in years) December 31, 2015 2014 Computer equipment 2 to 4 $ 63,867 $ 42,933 Software 2 to 5 1,684 1,850 Furniture 5 1,074 170 Office equipment 2 to 5 347 582 Leasehold improvements 5 years, or lease term, if shorter 4,728 4,341 Other 2 59 59 Construction in progress 934 643 72,693 50,578 Less: Accumulated depreciation (38,192 ) (31,860 ) $ 34,501 $ 18,718
Schedule of property and equipment acquired under capital leases	Property and equipment acquired under capital leases: December 31, 2015 2014 Computer equipment $ 453 $ 346 Less: Accumulated depreciation (310 ) (336 ) $ 143 $ 10
Schedule of accrued liabilities	Accrued liabilities at December 31, 2015 and 2014 consisted of the following: December 31, 2015 2014 Accrued compensation $ 21,994 $ 15,206 Customer deposits 1,384 1,484 Accrued royalties 509 706 Other 11,166 6,824 $ 35,053 $ 24,220

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Components of intangible assets excluding goodwill	The goodwill activity and balances are presented below: December 31, 2015 2014 Opening balance $ 107,504 $ 63,764 Add: Goodwill from acquisitions 26,289 44,015 Less: Other adjustments to Goodwill (24 ) (275 ) Closing balance $ 133,769 $ 107,504
Intangible assets excluding goodwill	Intangible assets excluding goodwill consisted of the following: December 31, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technology $ 57,268 $ (28,618 ) $ 28,650 $ 38,168 $ (21,538 ) $ 16,630 Customer relationships 23,382 (12,291 ) 11,091 16,382 (7,893 ) 8,489 Non-compete agreements 804 (691 ) 113 804 (462 ) 342 Trademark and patents 1,006 (502 ) 504 806 (264 ) 542 Order backlog 1,300 (328 ) 972 200 (17 ) 183 In-process research and development — — — 900 — 900 $ 83,760 $ (42,430 ) $ 41,330 $ 57,260 $ (30,174 ) $ 27,086
Future estimated amortization costs of intangible assets	Future estimated amortization costs of intangible assets as of December 31, 2015 are presented below: Year Ended December 31, 2016 $ 12,519 2017 9,174 2018 8,530 2019 5,164 2020 2,806 Thereafter 3,137 $ 41,330

Fair Value Measurements and I26

Fair Value Measurements and Investments (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 and 2014 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 $ 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 $ — Balance as of Quoted Prices Significant Unobservable Assets Cash equivalents: Money market funds $ 139,644 $ 139,644 $ — $ — Short-term investments: Corporate debt securities 31,651 — 31,651 — Commercial papers 2,998 — 2,998 — Total financial assets $ 174,293 $ 139,644 $ 34,649 $ —
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, 2015 and 2014 were as follows: 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 December 31, 2014 Amortized Cost Unrealized Unrealized Fair Cash and cash equivalents: Cash $ 40,693 $ — $ — $ 40,693 Money market funds 139,644 — — 139,644 Total $ 180,337 $ — $ — $ 180,337 Short-term investments: Corporate debt securities $ 31,678 $ — $ (27 ) $ 31,651 Commercial papers 2,998 — — 2,998 Total $ 34,676 $ — $ (27 ) $ 34,649

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Future annual minimum lease payments under noncancellable operating and capital leases	At December 31, 2015 , future annual minimum lease payments under noncancellable operating and capital leases were as follows: Capital Operating 2016 $ 41 $ 10,026 2017 41 6,056 2018 39 4,534 2019 37 3,989 2020 22 969 Thereafter — 625 Total minimum lease payments 180 $ 26,199 Less: Amount representing interest (25 ) Present value of capital lease obligations 155 Less: Current portion (32 ) Long-term portion of capital lease obligations $ 123

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	12 Months Ended
	Dec. 31, 2015
Senior Notes [Abstract]
Schedule of liability and equity components of convertible debt	At December 31, 2015 , the net carrying amount of the liability component of the Notes consists of: 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, 2015, 2014 and 2013 , the Company incurred the following interest expense related to the Notes: 2015 2014 2013 Interest expense related to contractual interest coupon $ 3,441 $ 2,511 $ 138 Amortization of debt discount and issuance costs 14,933 8,753 489 Total $ 18,374 $ 11,264 $ 627

Equity Award Plans (Tables)

Equity Award Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Valuation assumptions	The weighted average fair value of stock options granted to employees during the years ended December 31, 2015, 2014 and 2013 , was $28.20 , $20.25 and $9.50 , 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, 2015 2014 2013 Expected life (in years) 5.31 - 6.08 5.31 - 6.08 5.31 - 6.08 Volatility 50% - 52% 54% - 58% 57% - 61% Risk-free interest rate 1.6% - 1.8% 1.79% - 1.93% 0.9% - 1.8% 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, 2012 9,636 $ 5.63 7.33 $ 64,719 Options granted 1,618 17.46 Options exercised (2,879 ) 4.69 Options forfeited and canceled (1,152 ) 8.65 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 Exercisable, December 31, 2015 3,088 $ 9.23 5.06 $ 172,232 Vested and expected to vest, December 31, 2015 3,950 $ 14.52 5.71 $ 199,447
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, 2012 1 $ 7.98 Awards granted 1,236 28.94 Awards vested (1 ) 24.15 Awards forfeited (22 ) 24.61 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
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, 2015 2014 2013 Expected life (in years) 0.50 0.50 0.50 - 0.54 Volatility 42% - 47% 45% - 52% 38% - 40% Risk-free interest rate 0.08% - 0.33% 0.05% - 0.07% 0.08% Dividend yield —% —% —%

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 2014 2013 Stock options to purchase common stock 4,042 5,288 7,223 Restricted stock units 3,311 2,934 1,214 Employee stock purchase plan 81 90 89 Common stock subject to repurchase 54 54 1 Bonus shares 174 37 22 Common stock warrants — — 2 1.25% Convertible senior notes 5,158 5,158 5,158 0.75% Convertible senior notes 2,831 — — Total 15,651 13,561 13,709

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Revenue from external customers by products and services	The following set forth total revenue by solutions offered by the Company and geographic area. Revenue by geographic area is based upon the billing address of the customer: Year Ended December 31, 2015 2014 2013 Total revenue by solution: Privacy, Protection and Security $ 213,194 $ 151,291 $ 101,083 Archiving and Governance 52,203 44,316 36,848 Total revenue $ 265,397 $ 195,607 $ 137,931
Revenue from external customers by geographic areas	Year Ended December 31, 2015 2014 2013 Total revenue by geographic area: United States $ 218,424 $ 157,593 $ 113,819 Rest of world 46,973 38,014 24,112 Total revenue $ 265,397 $ 195,607 $ 137,931
Long-lived assets by geographic area	The following sets forth long-lived tangible assets by geographic area: December 31, 2015 2014 Long-lived assets: United States $ 29,514 $ 15,974 Rest of world 4,987 2,744 Total long-lived assets $ 34,501 $ 18,718

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015, 2014 and 2013 : Year Ended December 31, 2015 2014 2013 Domestic $ (109,195 ) $ (69,555 ) $ (34,284 ) Foreign 3,376 5,003 3,945 Loss before (provision for) benefit from income taxes $ (105,819 ) $ (64,552 ) $ (30,339 )
Schedule of components of income tax expense	The (provision for) benefit from income taxes is comprised of: Year Ended December 31, 2015 2014 2013 Current tax expense: Federal $ — $ — $ — State 54 121 70 Foreign 514 530 641 Total current 568 651 711 Deferred tax expense: Federal 105 (792 ) — State (45 ) — — Foreign 7 (172 ) (3,519 ) Total deferred 67 (964 ) (3,519 ) Provision for (benefit from) income taxes $ 635 $ (313 ) $ (2,808 )
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, 2015, 2014 and 2013 is as follows: Year Ended December 31, 2015 2014 2013 Tax at federal statutory rate $ (35,979 ) $ (21,948 ) $ (10,315 ) Foreign income tax rate differential (270 ) (600 ) (232 ) State, net of federal benefit (3,185 ) (1,692 ) (1,130 ) Stock compensation charges 2,393 1,304 636 SubPart F and other permanent items 1,434 2,579 1,583 Provision to return and other 749 3,621 937 Research and development credits (2,920 ) (2,052 ) (2,112 ) Uncertain tax positions 561 391 617 Valuation allowance 37,852 18,084 7,208 Provision (benefit from) for income taxes $ 635 $ (313 ) $ (2,808 )
Schedule of deferred tax assets and liabilities	Significant components of the Company's deferred tax assets were as follows for the years ended December 31, 2015 and 2014 : Year Ended December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 98,882 $ 75,376 Tax credit carryforwards 10,856 9,566 Research expenditures 2,301 2,494 Deferred revenue 12,165 11,078 Stock compensation 13,289 7,228 Fixed assets 1,426 1,516 Accruals and other 8,997 8,505 Gross deferred tax assets 147,916 115,763 Valuation allowance (110,347 ) (90,929 ) Total deferred tax assets 37,569 24,834 Deferred tax liabilities: Intangible assets and other (7,547 ) (9,613 ) Convertible Senior Notes (28,267 ) (12,911 ) Total deferred tax liabilities (35,814 ) (22,524 ) Total net deferred tax assets $ 1,755 $ 2,310 Current deferred income tax assets (included in other current assets) $ — $ 3,903 Non-current deferred income tax assets (included in other long-term assets) $ 2,116 $ — Non-current deferred income tax liabilities (included in long-term liabilities) $ 411 $ 1,593
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, 2012 $ 2,740 Increase in balances related to tax positions taken during the current period 618 Increase in balances related to tax positions taken during the prior period 517 Decrease in balances related to tax positions taken during the prior period (40 ) Decrease in balances related to statute expirations during the current period (12 ) 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

The Company and Summary of Si33

The Company and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax asset current	$ 0	$ 3,903
Foreign currency remeasurement and transactions:
Aggregate foreign currency transaction loss	$ 1,657	2,182	$ 180
Minimum [Member]
Deferred product costs:
Number of months deferred product costs are recognized	12 months
Maximum [Member]
Deferred product costs:
Number of months deferred product costs are recognized	36 months
Other Long-term Liabilities [Member] | Adjustments for New Accounting Principle, Early Adoption [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax asset current	$ 5,879
Convertible Senior Notes Liabilities [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred finance costs		234
Other Long-term Assets [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred finance costs		$ 234

The Company and Summary of Si34

The Company and Summary of Significant Accounting Policies - Goodwill and Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Intangible assets:
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

Acquisitions - 2015 Acquisition

Acquisitions - 2015 Acquisitions (Details) $ in Thousands	Jul. 22, 2015USD ($)	Mar. 06, 2015USD ($)	Dec. 31, 2015USD ($)business	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Business Acquisition [Line Items]
Purchase price			$ 11,568
Acquisition-related costs			$ 355	$ 277
Number of businesses acquired | business			2
Revenue				265,397	$ 195,607	$ 137,931
Fair value of assets acquired and liabilities assumed
Goodwill			$ 133,769	133,769	$ 107,504	$ 63,764
Acquisition in 4th Quarter of 2015 [Member]
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] [Member]
Business Acquisition [Line Items]
Percentage of voting interests acquired		100.00%
Purchase price		$ 31,803
Acquisition-related costs				277
Cash acquired from acquisitions		52
Escrow		6,000
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)
Holdback liability to the sellers		(3,662)
Goodwill		19,054
Recognized identifiable assets acquired and liabilities assumed, net		28,193
Trademarks and trademarks[Member] | Emerging Threats [Member] [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] [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] [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] [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, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired				$ 51,553	$ 53,680	$ 40,972
Acquisition-related costs			$ 355	277
Fair value of assets acquired and liabilities assumed
Goodwill			$ 133,769	$ 133,769	107,504	$ 63,764
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
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
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
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
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
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
Intangible assets		$ 5,500
Acquired finite-lived intangible assets, weighted average useful life (in years)		5 years

Acquisitions - 2013 Acquisition

Acquisitions - 2013 Acquisitions(Details) - USD ($) $ in Thousands	Oct. 01, 2013	Sep. 05, 2013	Jul. 19, 2013	Jul. 10, 2013	Apr. 05, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Revenue							$ 265,397	$ 195,607	$ 137,931
Payments to acquire businesses, net of cash acquired							51,553	53,680	40,972
Payment of contingent earn-out							0	487	99
Acquisition-related costs						$ 355	277
Fair value of assets acquired and liabilities assumed
Goodwill						$ 133,769	$ 133,769	107,504	63,764
Sendmail [Member]
Business Acquisition [Line Items]
Revenue									2,975
Payments to acquire businesses, net of cash acquired	$ 12,463
Cash acquired from acquisitions	1,117
Contingent consideration arrangements, range of outcomes, value, high	3,422
Amount of indemnification obligation recovery								$ 719
Acquisition-related costs									1,877
Fair value of assets acquired and liabilities assumed
Tangible assets acquired	5,202
Liabilities assumed	(5,162)
Deferred revenue assumed	(14,549)
Long-term debt assumed	(7,933)
Goodwill	24,322
Recognized identifiable assets acquired and liabilities assumed, net	13,580
Armorize [Member]
Business Acquisition [Line Items]
Revenue									781
Payments to acquire businesses, net of cash acquired		$ 24,215
Cash acquired from acquisitions		1,746
Acquisition-related costs									747
Fair value of assets acquired and liabilities assumed
Tangible assets acquired		2,754
Liabilities assumed		(1,234)
Goodwill		18,791
Recognized identifiable assets acquired and liabilities assumed, net		25,961
Abaca Technologies [Member]
Business Acquisition [Line Items]
Revenue									311
Payments to acquire businesses, net of cash acquired			$ 23
Cash acquired from acquisitions			3
Contingent consideration arrangements, range of outcomes, value, high			1,520
Liabilities arising from contingencies, amount recognized			1,397
Acquisition-related costs									218
Fair value of assets acquired and liabilities assumed
Tangible assets acquired			311
Liabilities assumed			(962)
Goodwill			264
Recognized identifiable assets acquired and liabilities assumed, net			1,423
eDynamics [Member]
Business Acquisition [Line Items]
Cash consideration for acquisition				$ 500
Acquisition-related costs									6
Fair value of assets acquired and liabilities assumed
Goodwill				107
Recognized identifiable assets acquired and liabilities assumed, net				1,158
Mail Distiller [Member]
Business Acquisition [Line Items]
Revenue									216
Payments to acquire businesses, net of cash acquired					$ 3,771
Cash acquired from acquisitions					60
Contingent consideration arrangements, range of outcomes, value, high									669
Acquisition-related costs									258
Fair value of assets acquired and liabilities assumed
Tangible assets acquired					204
Liabilities assumed					(1,052)
Goodwill					1,452
Recognized identifiable assets acquired and liabilities assumed, net					4,500
Trademarks and trade names [Member] | Sendmail [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 400
Acquired finite-lived intangible assets, weighted average useful life (in years)	5 years
Trademarks and trade names [Member] | Mail Distiller [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets					$ 7
Acquired finite-lived intangible assets, weighted average useful life (in years)					1 year
Customer relationships [Member] | Sendmail [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 8,000
Acquired finite-lived intangible assets, weighted average useful life (in years)	3 years
Customer relationships [Member] | Armorize [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 1,300
Acquired finite-lived intangible assets, weighted average useful life (in years)		2 years
Customer relationships [Member] | Abaca Technologies [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets			$ 40
Acquired finite-lived intangible assets, weighted average useful life (in years)			3 years
Customer relationships [Member] | eDynamics [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets				$ 243
Acquired finite-lived intangible assets, weighted average useful life (in years)				3 years 6 months
Customer relationships [Member] | Mail Distiller [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets					$ 1,291
Acquired finite-lived intangible assets, weighted average useful life (in years)					2 years
Patents [Member] | Sendmail [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets	$ 300
Acquired finite-lived intangible assets, weighted average useful life (in years)	5 years
Patents [Member] | Mail Distiller [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets					$ 123
Acquired finite-lived intangible assets, weighted average useful life (in years)					2 years
Non-compete agreements [Member] | Armorize [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 500
Acquired finite-lived intangible assets, weighted average useful life (in years)		3 years
Non-compete agreements [Member] | eDynamics [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets				$ 75
Acquired finite-lived intangible assets, weighted average useful life (in years)				2 years
Core/developed technology [Member] | Sendmail [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)	3 years
Core/developed technology [Member] | Armorize [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets		$ 3,850
Acquired finite-lived intangible assets, weighted average useful life (in years)		5 years
Core/developed technology [Member] | Abaca Technologies [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets			$ 1,770
Acquired finite-lived intangible assets, weighted average useful life (in years)			5 years
Core/developed technology [Member] | eDynamics [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets				$ 733
Acquired finite-lived intangible assets, weighted average useful life (in years)				3 years 6 months
Core/developed technology [Member] | Mail Distiller [Member]
Fair value of assets acquired and liabilities assumed
Finite lived intangible assets					$ 2,475
Acquired finite-lived intangible assets, weighted average useful life (in years)					7 years
Earn-out consideration [Member] | eDynamics [Member]
Business Acquisition [Line Items]
Contingent consideration arrangements, range of outcomes, value, high				$ 600
Liabilities arising from contingencies, amount recognized				586
Payment of contingent earn-out									$ 100
Indemnification obligations [Member] | eDynamics [Member]
Business Acquisition [Line Items]
Contingent consideration arrangements, range of outcomes, value, high				100
Liabilities arising from contingencies, amount recognized				$ 72

Acquisitions - Pro Forma Financ

Acquisitions - Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Combinations [Abstract]
Total revenue		$ 264,904	$ 200,124	$ 166,577
Net loss		$ (108,398)	$ (75,066)	$ (46,090)
Basic net loss per share (in dollars per share)		$ (2.72)	$ (2.01)	$ (1.32)
Diluted net loss per share (in dollars per share)		$ (2.72)	$ (2.01)	$ (1.32)
Acquisition-related costs	$ 355	$ 277

Concentration of Risks (Details

Concentration of Risks (Details) - customer	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Total revenue [Member]
Concentration Risk [Line Items]
Number of customers	0
Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of customers		0
Major Customer 1 [Member] | Total revenue [Member]
Concentration Risk [Line Items]
Number of customers		1
Concentration risk percentage		12.00%	14.00%
Major Customer 1 [Member] | Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of customers	1
Concentration risk percentage	16.00%

Balance Sheet Components - Allo

Balance Sheet Components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Period	$ 429	$ 276	$ 187
Additions (Reversals) to Costs and Expenses		158	91
Allowance for Doubtful Accounts Receivable, Recoveries	(169)
Write Offs	(61)	(5)	(2)
Balance at End of Period	$ 199	$ 429	$ 276

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment
Property and equipment, gross	$ 72,693	$ 50,578
Less: Accumulated depreciation	(38,192)	(31,860)
Property and equipment, net	34,501	18,718
Computer equipment [Member]
Property and Equipment
Property and equipment, gross	$ 63,867	42,933
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	$ 1,684	1,850
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	$ 1,074	170
Office equipment [Member]
Property and Equipment
Property and equipment, gross	$ 347	582
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	$ 4,728	4,341
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	$ 934	$ 643

Balance Sheet Components - Pr42

Balance Sheet Components - Property and Equipment, Other Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property and equipment acquired under capital leases
Depreciation expense	$ 12,644	$ 9,033	$ 5,923
Capitalized software development costs	203
Amortization of capitalized software development costs			159
Computer equipment [Member]
Property and equipment acquired under capital leases
Capital leased assets, gross	453	346
Less: Accumulated depreciation	(310)	(336)
Capital leased assets, net	143	10
Capital leases [Member]
Property and equipment acquired under capital leases
Depreciation expense	$ 23	$ 19	$ 48

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued compensation	$ 21,994	$ 15,206
Customer deposits	1,384	1,484
Accrued royalties	509	706
Other	11,166	6,824
Total accrued liabilities	$ 35,053	$ 24,220

Goodwill and Intangible Asset44

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill activity and balances
Opening balance	$ 107,504	$ 63,764
Add: Goodwill from acquisitions	26,289	44,015
Less: Other adjustments to Goodwill	(24)	(275)
Closing balance	$ 133,769	$ 107,504

Goodwill and Intangible Asset45

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Intangible assets excluding goodwill:
Gross Carrying Amount	$ 83,760	$ 57,260
Accumulated Amortization	(42,430)	(30,174)
Net Carrying Amount	41,330	27,086
Intangible amortization expense	12,256	8,790	$ 4,044
Future estimated amortization costs of intangible assets:
2,016	12,519
2,017	9,174
2,018	8,530
2,019	5,164
2,020	2,806
Thereafter	3,137
Net Carrying Amount	41,330	27,086
Developed technology [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	57,268	38,168
Accumulated Amortization	(28,618)	(21,538)
Net Carrying Amount	28,650	16,630
Future estimated amortization costs of intangible assets:
Net Carrying Amount	28,650	16,630
Customer relationships [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	23,382	16,382
Accumulated Amortization	(12,291)	(7,893)
Net Carrying Amount	11,091	8,489
Future estimated amortization costs of intangible assets:
Net Carrying Amount	11,091	8,489
Non-compete agreements [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	804	804
Accumulated Amortization	(691)	(462)
Net Carrying Amount	113	342
Future estimated amortization costs of intangible assets:
Net Carrying Amount	113	342
Trademark and patents [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	1,006	806
Accumulated Amortization	(502)	(264)
Net Carrying Amount	504	542
Future estimated amortization costs of intangible assets:
Net Carrying Amount	504	542
Order Backlog [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	1,300	200
Accumulated Amortization	(328)	(17)
Net Carrying Amount	972	183
Future estimated amortization costs of intangible assets:
Net Carrying Amount	972	183
In Process Research and Development [Member]
Intangible assets excluding goodwill:
Gross Carrying Amount	0	900
Accumulated Amortization	0	0
Net Carrying Amount	0	900
Future estimated amortization costs of intangible assets:
Net Carrying Amount	$ 0	$ 900

Fair Value Measurements and I46

Fair Value Measurements and Investments - Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Jun. 17, 2015	Dec. 31, 2014	Dec. 11, 2013
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	$ 346,205		$ 180,337
Short-term investments, fair value disclosure	60,032		34,649
Assets, fair value disclosure	379,189		174,293
Money market funds
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	306,983		139,644
Corporate debt securities
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	3,178
Short-term investments, fair value disclosure	36,527		31,651
Commercial papers
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	8,996
Short-term investments, fair value disclosure	16,290		2,998
U.S. agency securities
Fair value measurements and investments:
Short-term investments, fair value disclosure	5,414
U.S. Treasury securities
Fair value measurements and investments:
Short-term investments, fair value disclosure	1,801
Quoted prices in active markets for indentical assets (Level 1)
Fair value measurements and investments:
Assets, fair value disclosure	306,983		139,644
Quoted prices in active markets for indentical assets (Level 1) | Money market funds
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	306,983		139,644
Significant other observable inputs (Level 2)
Fair value measurements and investments:
Assets, fair value disclosure	72,206		34,649
Significant other observable inputs (Level 2) | Corporate debt securities
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	3,178
Short-term investments, fair value disclosure	36,527		31,651
Significant other observable inputs (Level 2) | Commercial papers
Fair value measurements and investments:
Cash and cash equivalents, fair value disclosure	8,996
Short-term investments, fair value disclosure	16,290		$ 2,998
Significant other observable inputs (Level 2) | U.S. agency securities
Fair value measurements and investments:
Short-term investments, fair value disclosure	5,414
Significant other observable inputs (Level 2) | U.S. Treasury securities
Fair value measurements and investments:
Short-term investments, fair value disclosure	1,801
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]
Convertible debt, fair value disclosures	246,105
Interest rate, stated percentage		0.75%
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]
Convertible debt, fair value disclosures	$ 348,666
Interest rate, stated percentage				1.25%

Fair Value Measurements and I47

Fair Value Measurements and Investments - Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, at carrying value	$ 346,205	$ 180,337	$ 243,786	$ 39,254
Cash and cash equivalents, fair value disclosure	346,205	180,337
Short-term investments, amortized cost basis	60,055	34,676
Short-term investments, gross unrealized gains	0	0
Short-term investments, gross unrealized losses	(23)	(27)
Short-term investments, fair value disclosure	$ 60,032	34,649
Maximum investment maturity term	1 year
Cash [Member]
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, at carrying value	$ 27,048	40,693
Cash and cash equivalents, fair value disclosure	27,048	40,693
Money market funds
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, at carrying value	306,983	139,644
Cash and cash equivalents, fair value disclosure	306,983	139,644
Corporate debt securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, at carrying value	3,178
Cash and cash equivalents, fair value disclosure	3,178
Short-term investments, amortized cost basis	36,549	31,678
Short-term investments, gross unrealized gains	0	0
Short-term investments, gross unrealized losses	(22)	(27)
Short-term investments, fair value disclosure	36,527	31,651
Commercial papers
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Cash and cash equivalents, at carrying value	8,996
Cash and cash equivalents, fair value disclosure	8,996
Short-term investments, amortized cost basis	16,290	2,998
Short-term investments, gross unrealized gains	0	0
Short-term investments, gross unrealized losses	0	0
Short-term investments, fair value disclosure	16,290	$ 2,998
U.S. agency securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Short-term investments, amortized cost basis	5,415
Short-term investments, gross unrealized gains	0
Short-term investments, gross unrealized losses	(1)
Short-term investments, fair value disclosure	5,414
U.S. Treasury securities
Schedule of Cash and Cash Equivalents, and Investments [Line Items]
Short-term investments, amortized cost basis	1,801
Short-term investments, gross unrealized gains	0
Short-term investments, gross unrealized losses	0
Short-term investments, fair value disclosure	$ 1,801

Commitments and Contingencies48

Commitments and Contingencies (Details) $ in Thousands	Apr. 15, 2014USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jul. 31, 2015	Jul. 31, 2012lease_agreement
Commitments and Contingencies Disclosure [Abstract]
Operating leases rent expense		$ 3,831	$ 3,283	$ 1,774
Capital Leases
2,016		41
2,017		41
2,018		39
2,019		37
2,020		22
Thereafter		0
Total minimum capital lease payments		180
Less: Amount representing interest		(25)
Present value of capital lease obligations		155
Less: Current portion		(32)
Long-term portion of capital lease obligations		123
Operating Leases
2,016		10,026
2,017		6,056
2,018		4,534
2,019		3,989
2,020		969
Thereafter		625
Total minimum operating lease payments		$ 26,199
Commitments and contingencies:
Damages sought, value	$ 13,500
Capital leases
Commitments and contingencies:
Number of lease agreement | lease_agreement						2
Interest rate, stated percentage					6.50%	4.50%

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, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Debt:
Proceeds from convertible debt			$ 223,790,000	$ 0	$ 195,641,000
Convertible Debt, Noncurrent			345,699,000	$ 161,396,000
Senior Notes [Member]
Debt:
Face amount			431,250,000
Convertible Debt, Noncurrent			345,699,000
Carrying amount of the equity component net			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
Face amount, optional	30,000,000
Debt issuance cost	6,581,000
Proceeds from convertible debt	$ 223,419,000
Debt interest rate	0.75%		0.75%
Conversion ratio, initial	12.3108
Number of shares convertible, initial rate | shares	2,831
Conversion price per share, initial | $ / shares	$ 81.23
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 Debt, Noncurrent	$ 174,359,000		$ 175,048,000
Carrying amount of the equity component net	55,641,000		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
Face amount, optional		26,250,000
Debt issuance cost		5,803,000
Proceeds from convertible debt		$ 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 | $ / shares		$ 39.02
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 Debt, Noncurrent		$ 156,672,000	170,651,000
Carrying amount of the equity component net		44,578,000	$ 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, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 17, 2015	Dec. 11, 2013
Liability component:
Convertible senior notes	$ 345,699,000	$ 161,396,000
Interest Expense, Debt
Interest expense, 1.25% coupon	3,441,000	2,511,000	$ 138,000
Amortization of debt issuance costs and accretion of debt discount	14,933,000	8,753,000	489,000
Interest expense, total	18,374,000	$ 11,264,000	$ 627,000
Senior Notes [Member]
Liability component:
Principal	431,250,000
Less: debt discount, net of amortization	(85,551,000)
Convertible senior notes	345,699,000
Carrying amount of the equity component net	97,342,000
Senior Notes [Member] | Convertible Senior Notes 1.25% [Member]
Liability component:
Principal	201,250,000				$ 175,000,000
Less: debt discount, net of amortization	(30,599,000)
Convertible senior notes	170,651,000				156,672,000
Carrying amount of the equity component net	43,293,000				$ 44,578,000
Senior Notes [Member] | 0.75% Convertible Senior Notes, Due June 2020 [Member]
Liability component:
Principal	230,000,000			$ 200,000,000
Less: debt discount, net of amortization	(54,952,000)
Convertible senior notes	175,048,000			174,359,000
Carrying amount of the equity component net	$ 54,049,000			$ 55,641,000

Debt (Details)

Debt (Details) - Loans payable [Member] - USD ($) $ in Thousands	Apr. 30, 2011	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt:
Long-term Debt	$ 6,000
Duration until repayment date after a loan amount is drawn	48 months
Interest expense		$ 5	$ 65	$ 140
Prime Rate [Member]
Debt:
Basis spread on variable rate	0.50%

Equity Award Plans - Stock-Base

Equity Award Plans - Stock-Based Compensation Plans (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2015planshares
Stock-based compensation:
Equity incentive plans held by the Company (number of plans) | plan	2
2012 Equity Incentive Plan [Member]
Stock-based compensation:
Shares authorized for issuance (in shares)	20,316
Options available for future grant under the stock plans	5,119
Annual percentage increase in number of shares authorized	5.00%
Maximum number of additional shares to be authorized	3,724
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] | Employee stock option [Member] | Minimum [Member]
Stock-based compensation:
Award vesting period	3 years
2012 Equity Incentive Plan [Member] | Restricted stock [Member]
Stock-based compensation:
Award vesting period	4 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, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation:
Weighted-average fair value of stock options granted	$ 28.20	$ 20.25	$ 9.50
Fair value assumptions:
Dividend yield	0.00%	0.00%	0.00%
Shares subject to options outstanding, weighted average exercise price:
Total intrinsic value of options exercised	$ 72,993	$ 64,455	$ 45,454
Total proceeds from option exercises	11,868	13,007	13,509
Fair value of option grants that vested	$ 9,520	$ 10,755	$ 8,206
2012 Equity Incentive Plan [Member]
Stock option activity under the Plan:
Outstanding, beginning of period (in shares)	5,288	7,223	9,636
Options granted (in shares)	284	563	1,618
Options exercised (in shares)	(1,429)	(1,984)	(2,879)
Options forfeited and canceled (in shares)	(101)	(514)	(1,152)
Outstanding, end of period (in shares)	4,042	5,288	7,223	9,636
Exercisable (in shares)	3,088
Vested and expected to vest (in shares)	3,950
Shares subject to options outstanding, weighted average exercise price:
Balance at beginning of period (USD per share)	$ 11.06	$ 8.17	$ 5.63
Options granted (USD per share)	57.47	36.91	17.46
Options exercised (USD per share)	8.31	6.56	4.69
Options forfeited and canceled (USD per share)	19.11	16.25	8.65
Balance at end of period (USD per share)	15.10	$ 11.06	$ 8.17	$ 5.63
Exercisable (in USD per share)	9.23
Vested and expected to vest (in USD per share)	$ 14.52
Weighted average remaining contractual term	5 years 9 months 7 days	6 years 3 months 22 days	6 years 9 months 26 days	7 years 3 months 29 days
Weighted average remaining contractual term, Exercisable	5 years 22 days
Weighted average remaining contractual term, Vested and expected to vest	5 years 8 months 16 days
Aggregate intrinsic value	$ 201,736	$ 196,608	$ 180,543	$ 64,719
Aggregate intrinsic value, exercisable	172,232
Aggregate intrinsic value, vested and expected to vest	199,447
Unrecognized stock-based compensation expense	$ 13,592
Average remaining vesting term	1 year 11 months 9 days
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%	61.00%
Risk-free interest rate	1.80%	1.93%	1.80%
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%	57.00%
Risk-free interest rate	1.60%	1.79%	0.90%

Equity Award Plans - Restricted

Equity Award Plans - Restricted Stock Units (Details) - Restricted stock units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
RSUs Outstanding, Granted Fair Value Per Unit:
Average remaining vesting term	3 years 1 month 2 days
2012 Equity Incentive Plan [Member]
RSU's Outstanding, Number of Shares:
Awarded at beginning of period (in shares)	2,934	1,214	1
Awards granted (in shares)	1,541	2,362	1,236
Awards vested (in shares)	(897)	(396)	(1)
Awards forfeited (in shares)	(267)	(246)	(22)
Awarded at end of period (in shares)	3,311	2,934	1,214
RSUs Outstanding, Granted Fair Value Per Unit:
Awarded at beginning of period (USD per share)	$ 37.45	$ 29.57	$ 7.98
Awards granted (USD per share)	61.48	39.77	28.94
Awards vested (USD per share)	38.70	30.79	24.15
Awards forfeited (USD per share)	41.89	31.59	24.61
Awarded at end of period (USD per share)	$ 47.94	$ 37.45	$ 29.57
Unamortized stock-based compensation expense	$ 100,028

Equity Award Plans - Performanc

Equity Award Plans - Performance Stock Units (Details) - USD ($) shares in Thousands, $ in Thousands	Mar. 06, 2015	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 2,000
Fair value of liability awards issued	$ 6,885
Performance Shares [Member] | 2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)		0	0
Unamortized stock-based compensation expense		$ 3,903

Equity Award Plans - Stock Bonu

Equity Award Plans - Stock Bonus Awards (Details) - USD ($) shares in Thousands, $ in Thousands	Mar. 06, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 2,000
Fair value of liability awards issued	$ 6,885
2012 Equity Incentive Plan [Member] | Stock Bonus Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total accrued liability		$ 5,676	$ 1,771
Shares of common stock issued		0	22
Stock-based compensation expense		$ 3,792	$ 1,771	$ 1

Equity Award Plans - Employee S

Equity Award Plans - Employee Stock Purchase Plan (Details) - ESPP 2012 Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 30, 2012
Stock-based compensation:
Shares authorized for issuance (in shares)				745,000
Maximum number of additional shares to be authorized				1,490,000
Increase in common stock reserved and available for issuance ESPP	1,152,000
Shares issued	161	194
Weighted average price per share	$ 41.84	$ 23.94
Fair value assumptions:
Expected life (in years)	6 months	6 months
Risk-free interest rate			0.08%
Dividend yield	0.00%	0.00%	0.00%
Unamortized stock-based compensation expense	$ 1,214
Average remaining vesting term	4 months 13 days
Minimum [Member]
Fair value assumptions:
Expected life (in years)			6 months
Volatility	42.00%	45.00%	38.00%
Risk-free interest rate	0.08%	0.05%
Maximum [Member]
Fair value assumptions:
Expected life (in years)			6 months 15 days
Volatility	47.00%	52.00%	40.00%
Risk-free interest rate	0.33%	0.07%

Equity Award Plans - Restrict58

Equity Award Plans - Restricted Stock (Details) - 2012 Equity Incentive Plan [Member] - Restricted stock [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted in period	54
Fair value of shares granted	$ 2,357
Award vesting period		4 years
Unrecognized stock-based compensation expense		$ 982
Cliff Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	2 years

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Common Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	15,651	13,561	13,709
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)	4,042	5,288	7,223
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)	3,311	2,934	1,214
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)	81	90	89
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)	54	54	1
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)	174	37	22
Common stock warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from computation of earnings per share (in shares)	0	0	2
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	0	0

Segment Reporting - Revenue by

Segment Reporting - Revenue by Solution (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)segment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Revenue from External Customer [Line Items]
Number of segments | segment	1
Revenue	$ 265,397	$ 195,607	$ 137,931
Privacy, protection and security [Member]
Revenue from External Customer [Line Items]
Revenue	213,194	151,291	101,083
Archiving and governance [Member]
Revenue from External Customer [Line Items]
Revenue	$ 52,203	$ 44,316	$ 36,848

Segment Reporting - by Geograph

Segment Reporting - by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment reporting:
Revenue	$ 265,397	$ 195,607	$ 137,931
Long-lived assets	34,501	18,718
United States [Member]
Segment reporting:
Revenue	218,424	157,593	113,819
Long-lived assets	29,514	15,974
Rest of world [Member]
Segment reporting:
Revenue	46,973	38,014	$ 24,112
Long-lived assets	$ 4,987	$ 2,744

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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
Domestic	$ (109,195)	$ (69,555)	$ (34,284)
Foreign	3,376	5,003	3,945
Loss before (provision for) benefit from income taxes	$ (105,819)	$ (64,552)	$ (30,339)

Income Taxes - Expense for Inco

Income Taxes - Expense for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current tax expense:
Federal	$ 0	$ 0	$ 0
State	54	121	70
Foreign	514	530	641
Total current	568	651	711
Deferred tax expense:
Federal	105	(792)	0
State	(45)	0	0
Foreign	7	(172)	(3,519)
Total deferred	67	(964)	(3,519)
Provision for (benefit from) income taxes	$ 635	$ (313)	$ (2,808)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax at federal statutory rate	$ (35,979)	$ (21,948)	$ (10,315)
Foreign income tax rate differential	(270)	(600)	(232)
State, net of federal benefit	(3,185)	(1,692)	(1,130)
Stock compensation charges	2,393	1,304	636
SubPart F and other permanent items	1,434	2,579	1,583
Provision to return and other	749	3,621	937
Research and development credits	(2,920)	(2,052)	(2,112)
Uncertain tax positions	561	391	617
Valuation allowance	37,852	18,084	7,208
Provision for (benefit from) income taxes	$ 635	$ (313)	$ (2,808)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 98,882	$ 75,376
Tax credit carryforwards	10,856	9,566
Research expenditures	2,301	2,494
Deferred revenue	12,165	11,078
Stock compensation	13,289	7,228
Fixed assets	1,426	1,516
Accruals and other	8,997	8,505
Gross deferred tax assets	147,916	115,763
Valuation allowance	(110,347)	(90,929)
Total deferred tax assets	37,569	24,834
Deferred tax liabilities:
Intangible assets and other	(7,547)	(9,613)
Convertible Senior Notes	(28,267)	(12,911)
Total deferred tax liabilities	(35,814)	(22,524)
Total net deferred tax assets	1,755	2,310
Current deferred income tax assets (included in other current assets)	0	3,903
Non-current deferred income tax assets (included in other long-term assets)	2,116	0
Non-current deferred income tax liabilities (included in long-term liabilities)	$ 411	$ 1,593

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 4,229	$ 3,823	$ 2,740
Increase in balances related to tax positions taken during the current period	806	524	618
Increase in balances related to tax positions taken during the prior period	0	0	517
Decrease in balances related to tax positions taken during the prior period	(130)	(87)	(40)
Decrease in balances related to statute expirations during the current period	(85)	(31)	(12)
Ending balance	$ 4,820	$ 4,229	$ 3,823

Income Taxes - Other (Details)

Income Taxes - Other (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 17, 2015
Income Tax [Line Items]
Federal statutory income tax rate	34.00%	34.00%
Valuation allowance increase (decrease)	$ 19,418	$ 19,877	$ 2,400
Accrued interest and penalties	15	9
Liability recorded on interest and penalties	227	242
Uncertain tax benefits that would affect effective tax rate if recognized	1,202	1,432
Foreign withholdings	180
Undistributed earnings of foreign subsidiaries	3,600
Estimated additional tax liability if foreign undistributed earnings were repatriated	550
Federal [Member]
Income Tax [Line Items]
Operating loss carryforwards	425,640	284,974
Operating loss carryforwards, benefit recognized	158,246	84,125
State [Member]
Income Tax [Line Items]
Operating loss carryforwards	253,460	183,913
Operating loss carryforwards, benefit recognized	90,849	44,407
Research tax credit carryforward [Member] | Federal [Member]
Income Tax [Line Items]
Tax credit carryforward	6,642	5,071
Research tax credit carryforward [Member] | State [Member]
Income Tax [Line Items]
Tax credit carryforward	8,734	7,080
Research tax credit carryforward [Member] | Foreign [Member]
Income Tax [Line Items]
Tax credit carryforward	2,058	$ 2,878
Nexgate [Member] | Foreign deferred tax asset, change in valuation allowance [Member]
Income Tax [Line Items]
Valuation allowance increase (decrease)	1,356
NetCitadel [Member] | Convertible debt [Member]
Income Tax [Line Items]
Valuation allowance increase (decrease)	$ (19,863)
0.75% Convertible Senior Notes, Due June 2020 [Member] | Senior Notes [Member]
Income Tax [Line Items]
Interest rate, stated percentage	0.75%			0.75%