Description of Business and Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Description of Business FireEye, Inc., with principal executive offices located in Milpitas, California, was incorporated as NetForts, Inc. on February 18, 2004, under the laws of the State of Delaware, and changed its name to FireEye, Inc. on September 7, 2005. FireEye, Inc. and its wholly owned subsidiaries (collectively, the “Company”, “we”, “us” or “our”) is a leader in stopping advanced cyber attacks that use advanced malware, zero-day exploits, and APT (“Advanced Persistent Threat”) tactics. Our solutions supplement traditional and next-generation firewalls, Intrusion Prevention Systems (“IPS”), anti-virus, and gateways, which cannot stop advanced threats, leaving security holes in networks. We offer a solution that detects and blocks attacks across Web, email, endpoint, file and mobile threat vectors, as well as latent malware resident on file shares. Our solutions address all stages of an attack lifecycle with a signature-less engine utilizing stateful attack analysis to detect zero-day threats. In February 2016, we acquired Invotas International Corporation (“Invotas”), a provider of security automation and orchestration technology. We paid upfront cash consideration of $17.7 million and issued 742,026 shares of our common stock with an estimated fair value of $11.1 million. In January 2016, we acquired iSIGHT Security, Inc. (d/b/a iSIGHT Partners, Inc.) (“iSIGHT”), one of the world’s leading providers of cyber threat intelligence for global enterprises. We paid upfront cash consideration of $192.8 million, incurred liabilities of $35.6 million contingent upon the achievement of a threat intelligence bookings target on or before the end of the second quarter of 2018, and issued 1,793,305 shares of our common stock with an estimated fair value of $28.2 million. In June 2015, we issued $460.0 million principal amount of 1.000% Convertible Senior Notes due 2035 (the “Series A Notes”) and $460.0 million principal amount of 1.625% Convertible Senior Notes due 2035 (the “Series B Notes” and together with the Series A Notes, the “Convertible Senior Notes”), in a private placement to qualified institutional purchasers pursuant to an exemption from registration provided by Section 4(a)(2) and Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). We recognized total net proceeds after the initial purchasers' discount and issuance costs of $896.5 million. In connection with the issuance of the Convertible Senior Notes, we also entered into privately negotiated prepaid forward stock purchase transactions (each a “Prepaid Forward”) with one of the initial purchasers of the Convertible Senior Notes, pursuant to which we paid approximately $150.0 million. The amount prepaid is equivalent to approximately 3.3 million shares which are to be settled on or around June 1, 2020 and June 1, 2022, respectively, subject to any early settlement in whole or part of each Prepaid Forward. We sell the majority of our products, subscriptions and services to end-customers through distributors, resellers, and strategic partners, with a lesser percentage of sales directly to end-customers. Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements include the accounts of FireEye, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”), and following the requirements of the Securities and Exchange Commission (“SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, that are necessary for a fair statement of our financial information. The results of operations for the three months ended March 31, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The balance sheet as of December 31, 2015 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for annual consolidated financial statements. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2015 included in our Annual Report on Form 10-K, which was filed with the SEC on February 26, 2016. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. 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 revenue and expenses during the reporting period. Such management estimates include, but are not limited to, the best estimate of selling price for our products and services, commissions expense, future taxable income, contract manufacturer liabilities, litigation and settlement costs and other loss contingencies, fair value of our stock options and the purchase price allocation of acquired businesses. We base our estimates on historical experience and also on assumptions that we believe are reasonable. Changes in facts or circumstances may cause us to change our assumptions and estimates in future periods, and it is possible that actual results could differ from current or revised future estimates. Summary of Significant Accounting Policies There have been no significant changes to our significant accounting policies as of and for the three months ended March 31, 2016, as compared to the significant accounting policies described in our Annual Report on Form 10-K for the year ended December 31, 2015, except with respect to changes in our policy on Stock-Based Compensation. Stock-Based Compensation As permitted under ASU 2016-09, we have elected to recognize forfeitures as they occur, and no longer estimate a forfeiture rate when calculating the stock-based compensation for our equity awards. Recent Accounting Pronouncements In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (Topic 718). This standard simplifies various aspects related to how share-based payments are accounted for and presented in the financial statements, including income taxes, forfeitures and statutory tax withholding requirements. The guidance is effective for us beginning in the first quarter of 2017. Early adoption is permitted. We elected to early adopt this standard in the current quarter. As a result of adopting this standard, we have made an accounting policy election to account for forfeitures as they occur. This change has been applied on a modified retrospective basis, resulting in a cumulative-effect adjustment to decrease retained earnings by $3.4 million as of January 1, 2016; the date of adoption. The adoption of this guidance also requires excess tax benefits and tax deficiencies be recorded in the income statement as opposed to additional paid-in capital when the awards vest or are settled. This change should be applied prospectively, and therefore our tax deficiencies of less than $0.1 million for the three months ended March 31, 2016 has been recorded as a component of our benefit from income taxes. The adoption of additional amendments related to the timing of when excess tax benefits are recognized and the accounting for minimum statutory withholding tax requirements included in this guidance has no impact on our current condensed consolidated financial statements or on any prior period financial statements presented. This guidance also requires changes in the classification of shares withheld to pay employee taxes and excess tax benefits on the consolidated statements of cash flows. The amendments require cash paid by an employer when directly withholding shares for tax-withholding purposes be classified as a financing activity, and be applied retrospectively to all prior periods presented. As these cash flows have previously been presented as financing activities, there is no change resulting from the adoption of this amendment. The amendments also require excess tax benefits be classified as an operating activity, consistent with other income tax cash flows, and may be applied either on a retrospective or prospective basis. We have elected to apply this amendment on a prospective basis, as there is no impact to our prior period consolidated statements of cash flows. As such, prior periods have not been adjusted. In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force). This standard clarifies the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. The guidance is effective for us beginning in the first quarter of 2017 and should be applied on a modified retrospective basis to existing debt instruments as of the beginning of the fiscal year for which the amendments are effective. Early adoption is permitted. As we previously assessed the embedded call (put) options associated with our Convertible Senior Notes in accordance with the requirements in this guidance, the adoption of this standard will have no impact on our consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This standard is intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The guidance is effective for us beginning in the first quarter of 2019, and should be applied on a modified retrospective basis. Early adoption is permitted. We expect the adoption of this standard to have a material impact on our consolidated financial statements and related disclosures. In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. This standard eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Under this guidance, measurement-period adjustments will be recognized during the period in which they are determined. We adopted this standard in the current quarter and the adoption did not have a material impact on our consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). This standard provides a single model for revenue arising from contracts with customers and supersedes current revenue recognition guidance. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In July 2015, the FASB decided to defer the effective date by one year, and as a result, the guidance is effective for us beginning in the first quarter of 2018. Early adoption as of the original effective date would be permitted. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), and in April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing. These standards were issued to address implementation issues raised by the FASB-IASB Joint Transition Resource Group for Revenue Recognition (TRG). We are currently evaluating the impact the adoption of the new revenue guidance and related updates will have on our consolidated financial statements and related disclosures. In August 2014, the FASB issued ASU 2014-15, Disclosures of Uncertainties About an Entity’s Ability to Continue as a Going Concern. This standard provides guidance on how and when reporting entities must disclose going-concern uncertainties in their financial statements. The guidance is effective for us beginning in the first quarter of 2017. Early adoption is permitted. The adoption of this standard is not expected to have an impact on our consolidated financial statements.

Description of Business and Summary of Significant Accounting Policies

Description of Business

FireEye, Inc., with principal executive offices located in Milpitas, California, was incorporated as NetForts, Inc. on February 18, 2004, under the laws of the State of Delaware, and changed its name to FireEye, Inc. on September 7, 2005.

FireEye, Inc. and its wholly owned subsidiaries (collectively, the “Company”, “we”, “us” or “our”) is a leader in stopping advanced cyber attacks that use advanced malware, zero-day exploits, and APT (“Advanced Persistent Threat”) tactics. Our solutions supplement traditional and next-generation firewalls, Intrusion Prevention Systems (“IPS”), anti-virus, and gateways, which cannot stop advanced threats, leaving security holes in networks. We offer a solution that detects and blocks attacks across Web, email, endpoint, file and mobile threat vectors, as well as latent malware resident on file shares. Our solutions address all stages of an attack lifecycle with a signature-less engine utilizing stateful attack analysis to detect zero-day threats.

In February 2016, we acquired Invotas International Corporation (“Invotas”), a provider of security automation and orchestration technology. We paid upfront cash consideration of $17.7 million and issued 742,026 shares of our common stock with an estimated fair value of $11.1 million.

In January 2016, we acquired iSIGHT Security, Inc. (d/b/a iSIGHT Partners, Inc.) (“iSIGHT”), one of the world’s leading providers of cyber threat intelligence for global enterprises. We paid upfront cash consideration of $192.8 million, incurred liabilities of $35.6 million contingent upon the achievement of a threat intelligence bookings target on or before the end of the second quarter of 2018, and issued 1,793,305 shares of our common stock with an estimated fair value of $28.2 million.

In June 2015, we issued $460.0 million principal amount of 1.000% Convertible Senior Notes due 2035 (the “Series A Notes”) and $460.0 million principal amount of 1.625% Convertible Senior Notes due 2035 (the “Series B Notes” and together with the Series A Notes, the “Convertible Senior Notes”), in a private placement to qualified institutional purchasers pursuant to an exemption from registration provided by Section 4(a)(2) and Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). We recognized total net proceeds after the initial purchasers' discount and issuance costs of $896.5 million. In connection with the issuance of the Convertible Senior Notes, we also entered into privately negotiated prepaid forward stock purchase transactions (each a “Prepaid Forward”) with one of the initial purchasers of the Convertible Senior Notes, pursuant to which we paid approximately $150.0 million. The amount prepaid is equivalent to approximately 3.3 million shares which are to be settled on or around June 1, 2020 and June 1, 2022, respectively, subject to any early settlement in whole or part of each Prepaid Forward.

We sell the majority of our products, subscriptions and services to end-customers through distributors, resellers, and strategic partners, with a lesser percentage of sales directly to end-customers.

Basis of Presentation and Consolidation

The accompanying unaudited condensed consolidated financial statements include the accounts of FireEye, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”), and following the requirements of the Securities and Exchange Commission (“SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, that are necessary for a fair statement of our financial information. The results of operations for the three months ended March 31, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The balance sheet as of December 31, 2015 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for annual consolidated financial statements.

The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2015 included in our Annual Report on Form 10-K, which was filed with the SEC on February 26, 2016.

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with U.S. 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 revenue and expenses during the reporting period. Such management estimates include, but are not limited to, the best estimate of selling price for our products and services, commissions expense, future taxable income, contract manufacturer liabilities, litigation and settlement costs and other loss contingencies, fair value of our stock options and the purchase price allocation of acquired businesses. We base our estimates on historical experience and also on assumptions that we believe are reasonable. Changes in facts or circumstances may cause us to change our assumptions and estimates in future periods, and it is possible that actual results could differ from current or revised future estimates.

Summary of Significant Accounting Policies

There have been no significant changes to our significant accounting policies as of and for the three months ended March 31, 2016, as compared to the significant accounting policies described in our Annual Report on Form 10-K for the year ended December 31, 2015, except with respect to changes in our policy on Stock-Based Compensation.

Stock-Based Compensation

As permitted under ASU 2016-09, we have elected to recognize forfeitures as they occur, and no longer estimate a forfeiture rate when calculating the stock-based compensation for our equity awards.

Recent Accounting Pronouncements

In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (Topic 718). This standard simplifies various aspects related to how share-based payments are accounted for and presented in the financial statements, including income taxes, forfeitures and statutory tax withholding requirements. The guidance is effective for us beginning in the first quarter of 2017. Early adoption is permitted. We elected to early adopt this standard in the current quarter.

As a result of adopting this standard, we have made an accounting policy election to account for forfeitures as they occur. This change has been applied on a modified retrospective basis, resulting in a cumulative-effect adjustment to decrease retained earnings by $3.4 million as of January 1, 2016; the date of adoption. The adoption of this guidance also requires excess tax benefits and tax deficiencies be recorded in the income statement as opposed to additional paid-in capital when the awards vest or are settled. This change should be applied prospectively, and therefore our tax deficiencies of less than $0.1 million for the three months ended March 31, 2016 has been recorded as a component of our benefit from income taxes. The adoption of additional amendments related to the timing of when excess tax benefits are recognized and the accounting for minimum statutory withholding tax requirements included in this guidance has no impact on our current condensed consolidated financial statements or on any prior period financial statements presented.

This guidance also requires changes in the classification of shares withheld to pay employee taxes and excess tax benefits on the consolidated statements of cash flows. The amendments require cash paid by an employer when directly withholding shares for tax-withholding purposes be classified as a financing activity, and be applied retrospectively to all prior periods presented. As these cash flows have previously been presented as financing activities, there is no change resulting from the adoption of this amendment. The amendments also require excess tax benefits be classified as an operating activity, consistent with other income tax cash flows, and may be applied either on a retrospective or prospective basis. We have elected to apply this amendment on a prospective basis, as there is no impact to our prior period consolidated statements of cash flows. As such, prior periods have not been adjusted.

In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the Emerging Issues Task Force). This standard clarifies the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. The guidance is effective for us beginning in the first quarter of 2017 and should be applied on a modified retrospective basis to existing debt instruments as of the beginning of the fiscal year for which the amendments are effective. Early adoption is permitted. As we previously assessed the embedded call (put) options associated with our Convertible Senior Notes in accordance with the requirements in this guidance, the adoption of this standard will have no impact on our consolidated financial statements and related disclosures.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This standard is intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The guidance is effective for us beginning in the first quarter of 2019, and should be applied on a modified retrospective basis. Early adoption is permitted. We expect the adoption of this standard to have a material impact on our consolidated financial statements and related disclosures.

In September 2015, the FASB issued ASU No. 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments. This standard eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Under this guidance, measurement-period adjustments will be recognized during the period in which they are determined. We adopted this standard in the current quarter and the adoption did not have a material impact on our consolidated financial statements.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). This standard provides a single model for revenue arising from contracts with customers and supersedes current revenue recognition guidance. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.

In July 2015, the FASB decided to defer the effective date by one year, and as a result, the guidance is effective for us beginning in the first quarter of 2018. Early adoption as of the original effective date would be permitted. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment.

In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), and in April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing. These standards were issued to address implementation issues raised by the FASB-IASB Joint Transition Resource Group for Revenue Recognition (TRG).

We are currently evaluating the impact the adoption of the new revenue guidance and related updates will have on our consolidated financial statements and related disclosures.

In August 2014, the FASB issued ASU 2014-15, Disclosures of Uncertainties About an Entity’s Ability to Continue as a Going Concern. This standard provides guidance on how and when reporting entities must disclose going-concern uncertainties in their financial statements. The guidance is effective for us beginning in the first quarter of 2017. Early adoption is permitted. The adoption of this standard is not expected to have an impact on our consolidated financial statements.