Overview and Basis of Presentation	3 Months Ended
Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Overview and Basis of Presentation	Overview and Basis of Presentation Organization Arista Networks, Inc. (together with our subsidiaries, “we,” “our” or “us”) is a supplier of cloud networking solutions that use software innovations to address the needs of large-scale Internet companies, cloud service providers and next-generation enterprises. Our cloud networking solutions consist of our Extensible Operating System, a set of network applications and our 10/25/40/50/100 Gigabit Ethernet switches. We were incorporated in October 2004 and reincorporated in the state of Delaware in March 2014. Our corporate headquarters are located in Santa Clara, California, and we have wholly-owned subsidiaries throughout the world, including North America, Europe, Asia and Australia. Basis of Presentation 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" or "GAAP") and following the requirements of the U.S. Securities and Exchange Commission (the “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. In management’s opinion, the unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of our financial information. The results for the three months ended March 31, 2016, are not necessarily indicative of the results expected for the full fiscal year. The condensed consolidated balance sheet as of December 31, 2015 has been derived from the audited consolidated financial statements at that date but does not include all of the information and notes required by generally accepted accounting principles for complete financial statements. The accompanying unaudited condensed consolidated financial statements include the accounts of Arista Networks, Inc. and its wholly-owned subsidiaries and are prepared in accordance with GAAP. All significant intercompany accounts and transactions have been eliminated. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and related footnotes included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2015, filed with the SEC on February 25, 2016. Use of Estimates The preparation of the accompanying unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported and disclosed in the unaudited condensed consolidated financial statements and accompanying notes. Those estimates and assumptions include, but are not limited to, revenue recognition and deferred revenue; allowance for doubtful accounts and sales return reserve; determination of fair value for stock-based awards; accounting for income taxes, including the valuation allowance on deferred tax assets and reserves for uncertain tax positions; valuation of inventory; valuation of warranty accruals; and the recognition and measurement of contingent liabilities. We evaluate our estimates and assumptions on an ongoing basis using historical experience and other factors and adjust those estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ from these estimates, and those differences could be material to the unaudited condensed consolidated financial statements. Significant Accounting Policies There have been no material 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 fiscal year ended December 31, 2015. Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers, which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The new standard provides principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires significantly expanded disclosures about revenue recognition. In July 2015, the FASB deferred the effective date of the new revenue standard by one year. In March 2016, the FASB issued ASU No. 2016-08, Revenue From Contracts With Customers-Principal versus Agent Considerations (Reporting Revenue Gross versus Net), and ASU No. 2016-10, Revenue From Contracts With Customers-Identifying Performance Obligations and Licensing. ASU No. 2016-08 clarifies the implementation guidance regarding principal versus agent identification and related considerations. Specifically, the guidance provides clarification around performance obligations for goods or services provided by another entity, assisting in determining whether the entity is the provider of the goods or services, the principal, or whether the entity is providing for the arrangement of the goods or services, the agent. ASU No. 2016-10 provides guidance around identifying whether promised goods or services are distinct and separately identifiable, whether promised goods or services are material or immaterial to the contract, and whether shipping and handling is considered an activity to fulfill a promise or an additional promised service. ASU No. 2016-10 also provides guidance around an entity's promise to grant a license providing a customer with either a right to use or a right to access the license, which then determines whether the obligation is satisfied at a point in time or over time, respectively. The above standards are effective for fiscal years (and interim reporting periods within those years) beginning after December 15, 2017. The guidance is effective for us beginning in our first quarter of fiscal 2018. Early adoption would be permitted for all entities but not until the fiscal year beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. The retrospective method requires a retrospective approach to each prior reporting period presented with the option to elect certain practical expedients as defined within the guidance. The cumulative approach requires a retrospective approach with the cumulative effect of initially applying the guidance recognized at the date of initial application and providing certain additional disclosures as defined per the guidance. We are currently reviewing the provisions of the standard and have not yet selected a transition method nor have we determined the effect of the standard on our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-05, Intangibles—Goodwill and Other—Internal-Use Software, which clarifies the circumstances under which a cloud computing customer would account for the arrangement as a license of internal-use software. A cloud computing arrangement would include a software license if (1) the customer has a contractual right to take possession of the software at any time during the hosting period without significant penalty and (2) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. If the arrangement does not contain a software license, it would be accounted for as a service contract. The guidance is effective for fiscal years beginning after December 15, 2015. The standard was effective for us for our first quarter of fiscal 2016, the adoption of which had no material impact on our consolidated financial statements. In July 2015, the FASB issued ASU No, 2015-11, Inventory: Simplifying the Measurement of Inventory, which simplifies the measurement of inventory to be measured at the lower of cost or net realizable value. The guidance applies to inventory measured using First in First Out ("FIFO") or average cost. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2017. The guidance can be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance. In November 2015, the FASB issued ASU 2015-17, Income Taxes - Balance Sheet Classification of Deferred Taxes, which will require the presentation of deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The guidance can be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company early adopted the guidance prospectively beginning in the fourth quarter of fiscal 2015. The adoption of the standard impacted presentation on the Company's Consolidated Financial Statements and related disclosures. No prior periods were retrospectively adjusted. In January 2016, the FASB issued ASU No, 2016-01, Financial Instruments-Recognition and Measurement of Financial Assets and Financial Liabilities, which enhances the reporting model for financial instruments to provide users of financial statements with more decision-useful information. The guidance will address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. The guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2018. The guidance may be early adopted under early application guidance. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance. In February 2016, the FASB issued ASU No, 2016-02, Leases, which addresses the classification and recognition of lease assets and liabilities formerly classified as operating leases under GAAP. The guidance will address certain aspects of recognition and measurement, and quantitative and qualitative aspects of presentation and disclosure. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2019. The guidance will be applied to the earliest period presented using a modified retrospective approach. The guidance includes practical expedients that relate to identification, classification, and initial direct costs associated with leases commencing prior to the effective date, and the ability to apply hindsight in evaluating lease options related to extensions, terminations or asset purchases. A practical expedient also exists to treat leases entered into prior effective date under existing GAAP unless the lease has been modified. The guidance may be early adopted. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance. In March 2016, the FASB amended the existing accounting standards for stock-based compensation, ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which impact several aspects of accounting for share-based payment transactions, including the income tax consequences, forfeitures, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2017. The guidance may be early adopted under early application guidance. If early adoption is elected, all amendments must be adopted in the same period. The manner of application varies by the various provisions of the guidance, with certain provisions applied on a retrospective or modified retrospective approach, while others are applied prospectively. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance.

Overview and Basis of Presentation

Organization

Arista Networks, Inc. (together with our subsidiaries, “we,” “our” or “us”) is a supplier of cloud networking solutions that use software innovations to address the needs of large-scale Internet companies, cloud service providers and next-generation enterprises. Our cloud networking solutions consist of our Extensible Operating System, a set of network applications and our 10/25/40/50/100 Gigabit Ethernet switches. We were incorporated in October 2004 and reincorporated in the state of Delaware in March 2014. Our corporate headquarters are located in Santa Clara, California, and we have wholly-owned subsidiaries throughout the world, including North America, Europe, Asia and Australia.

Basis of Presentation

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" or "GAAP") and following the requirements of the U.S. Securities and Exchange Commission (the “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. In management’s opinion, the unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of our financial information. The results for the three months ended March 31, 2016, are not necessarily indicative of the results expected for the full fiscal year.

The condensed consolidated balance sheet as of December 31, 2015 has been derived from the audited consolidated financial statements at that date but does not include all of the information and notes required by generally accepted accounting principles for complete financial statements.

The accompanying unaudited condensed consolidated financial statements include the accounts of Arista Networks, Inc. and its wholly-owned subsidiaries and are prepared in accordance with GAAP. All significant intercompany accounts and transactions have been eliminated.

The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and related footnotes included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2015, filed with the SEC on February 25, 2016.

Use of Estimates

The preparation of the accompanying unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported and disclosed in the unaudited condensed consolidated financial statements and accompanying notes. Those estimates and assumptions include, but are not limited to, revenue recognition and deferred revenue; allowance for doubtful accounts and sales return reserve; determination of fair value for stock-based awards; accounting for income taxes, including the valuation allowance on deferred tax assets and reserves for uncertain tax positions; valuation of inventory; valuation of warranty accruals; and the recognition and measurement of contingent liabilities. We evaluate our estimates and assumptions on an ongoing basis using historical experience and other factors and adjust those estimates and assumptions when facts and circumstances dictate. As future events and their effects cannot be determined with precision, actual results could differ from these estimates, and those differences could be material to the unaudited condensed consolidated financial statements.

Significant Accounting Policies

There have been no material 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 fiscal year ended December 31, 2015.

Recent Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers, which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The new standard provides principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires significantly expanded disclosures about revenue recognition. In July 2015, the FASB deferred the effective date of the new revenue standard by one year. In March 2016, the FASB issued ASU No. 2016-08, Revenue From Contracts With Customers-Principal versus Agent Considerations (Reporting Revenue Gross versus Net), and ASU No. 2016-10, Revenue From Contracts With Customers-Identifying Performance Obligations and Licensing. ASU No. 2016-08 clarifies the implementation guidance regarding principal versus agent identification and related considerations. Specifically, the guidance provides clarification around performance obligations for goods or services provided by another entity, assisting in determining whether the entity is the provider of the goods or services, the principal, or whether the entity is providing for the arrangement of the goods or services, the agent. ASU No. 2016-10 provides guidance around identifying whether promised goods or services are distinct and separately identifiable, whether promised goods or services are material or immaterial to the contract, and whether shipping and handling is considered an activity to fulfill a promise or an additional promised service. ASU No. 2016-10 also provides guidance around an entity's promise to grant a license providing a customer with either a right to use or a right to access the license, which then determines whether the obligation is satisfied at a point in time or over time, respectively.

The above standards are effective for fiscal years (and interim reporting periods within those years) beginning after December 15, 2017. The guidance is effective for us beginning in our first quarter of fiscal 2018. Early adoption would be permitted for all entities but not until the fiscal year beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. The retrospective method requires a retrospective approach to each prior reporting period presented with the option to elect certain practical expedients as defined within the guidance. The cumulative approach requires a retrospective approach with the cumulative effect of initially applying the guidance recognized at the date of initial application and providing certain additional disclosures as defined per the guidance. We are currently reviewing the provisions of the standard and have not yet selected a transition method nor have we determined the effect of the standard on our consolidated financial statements.

In April 2015, the FASB issued ASU No. 2015-05, Intangibles—Goodwill and Other—Internal-Use Software, which clarifies the circumstances under which a cloud computing customer would account for the arrangement as a license of internal-use software. A cloud computing arrangement would include a software license if (1) the customer has a contractual right to take possession of the software at any time during the hosting period without significant penalty and (2) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. If the arrangement does not contain a software license, it would be accounted for as a service contract. The guidance is effective for fiscal years beginning after December 15, 2015. The standard was effective for us for our first quarter of fiscal 2016, the adoption of which had no material impact on our consolidated financial statements.

In July 2015, the FASB issued ASU No, 2015-11, Inventory: Simplifying the Measurement of Inventory, which simplifies the measurement of inventory to be measured at the lower of cost or net realizable value. The guidance applies to inventory measured using First in First Out ("FIFO") or average cost. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2017. The guidance can be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance.

In November 2015, the FASB issued ASU 2015-17, Income Taxes - Balance Sheet Classification of Deferred Taxes, which will require the presentation of deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The guidance can be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company early adopted the guidance prospectively beginning in the fourth quarter of fiscal 2015. The adoption of the standard impacted presentation on the Company's Consolidated Financial Statements and related disclosures. No prior periods were retrospectively adjusted.

In January 2016, the FASB issued ASU No, 2016-01, Financial Instruments-Recognition and Measurement of Financial Assets and Financial Liabilities, which enhances the reporting model for financial instruments to provide users of financial statements with more decision-useful information. The guidance will address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. The guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2018. The guidance may be early adopted under early application guidance. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance.

In February 2016, the FASB issued ASU No, 2016-02, Leases, which addresses the classification and recognition of lease assets and liabilities formerly classified as operating leases under GAAP. The guidance will address certain aspects of recognition and measurement, and quantitative and qualitative aspects of presentation and disclosure. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2019. The guidance will be applied to the earliest period presented using a modified retrospective approach. The guidance includes practical expedients that relate to identification, classification, and initial direct costs associated with leases commencing prior to the effective date, and the ability to apply hindsight in evaluating lease options related to extensions, terminations or asset purchases. A practical expedient also exists to treat leases entered into prior effective date under existing GAAP unless the lease has been modified. The guidance may be early adopted. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance.

In March 2016, the FASB amended the existing accounting standards for stock-based compensation, ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting, which impact several aspects of accounting for share-based payment transactions, including the income tax consequences, forfeitures, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The guidance is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. The standard is effective for us for our first quarter of fiscal 2017. The guidance may be early adopted under early application guidance. If early adoption is elected, all amendments must be adopted in the same period. The manner of application varies by the various provisions of the guidance, with certain provisions applied on a retrospective or modified retrospective approach, while others are applied prospectively. We are currently assessing the impact this guidance may have on our consolidated financial statements as well as the transition method that we will use to adopt the guidance.