Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Accounting	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") 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 and nine months ended September 30, 2014, are not necessarily indicative of the results expected for the full fiscal year.
Consolidation	The condensed consolidated balance sheet as of December 31, 2013 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 our wholly owned subsidiaries. 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 prospectus filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the “Securities Act”), with the SEC on June 6, 2014 (the “Prospectus”).
Significant Accounting Policies [Text Block]	New Accounting Policy Investments We have recorded our equity investment in a privately-held company under the cost method. Initial measurement of our investment under the cost method is recorded at historical cost which represents our initial investment in the privately-held company. We will periodically assess and evaluate our cost method investment for impairment and perform an assessment based on evaluation of overall financial performance, industry and market conditions, and other relevant events or factors deemed necessary that may affect carrying value. If we determine that a decrease in the equity investment should be recognized given impairment that is considered “other than temporary” in nature, we will write-down the carrying amount to its revised new fair value.
Use of Estimates	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; 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.
Business Concentrations	Business Concentrations We work closely with third parties to manufacture and deliver our products. As of September 30, 2014 and December 31, 2013, two suppliers provided all of our electronic manufacturing services. Our products rely on key components, including certain integrated circuit components and power supplies some of which our contract manufacturers purchase on our behalf from a limited number of suppliers, including certain sole source providers. We do not have guaranteed supply contracts with any of our component suppliers, and our suppliers could delay shipments or cease manufacturing such products or selling them to us at any time. If we are unable to obtain a sufficient quantity of these components on commercially reasonable terms or in a timely manner, sales of our products could be delayed or halted entirely or we may be required to redesign our products. Quality or performance failures of our products or changes in our contractors’ or vendors’ financial or business condition could disrupt our ability to supply quality products to our customers. Any of these events could result in lost sales and damage to our end-customer relationships, which would adversely impact our business, financial condition and results of operations.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, accounts receivable and notes receivable. Our cash, cash equivalents and restricted cash are invested in high quality financial instruments with banks and financial institutions. Such deposits may be in excess of insured limits provided on such deposits. Our accounts receivable are unsecured and represent amounts due to us based on contractual obligations of our customers. We mitigate credit risk in respect to accounts receivable by performing ongoing credit evaluations of our customers to assess the probability of accounts receivable collection based on a number of factors, including past transaction experience with the customer, evaluation of their credit history, the credit limits extended and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. We have recorded an allowance for doubtful accounts for those receivables that we have determined not to be collectible. Our notes receivable are secured and represent amounts due to us from a private company. We mitigate credit risk in respect to the notes receivable by performing ongoing credit evaluations of the borrower to assess the probability of collecting all amounts due to us under the existing contractual terms. We market and sell our products through both our direct sales force and our channel partners, including distributors, value-added resellers, system integrators and original equipment manufacturer (“OEM”) partners.
Reclassifications [Text Block]	Reclassifications As a result of a change in classification, we have reclassified our spare parts inventory from inventory to other current and non-current assets as of September 30, 2014. Spare parts inventory are used to satisfy our warranty obligations, and are not available for sale or used in the production process. Prior year balances have been adjusted to conform to this new classification for comparability purposes.
Recently Issued and Adopted Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers ("ASU 2014-09"), which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. ASU 2014-09 is effective for fiscal years (and interim reporting periods within those years) beginning after December 15, 2016. Early application is not permitted. ASU 2014-09 permits the use of either the retrospective or cumulative effect transition method. We are currently reviewing the provisions of ASU 2014-09 and have not yet selected a transition method nor have we determined the effect of the standard on our consolidated financial statements.

Organization and Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2014

Organization, Consolidation and Presentation of Financial Statements [Abstract]

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") 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 and nine months ended September 30, 2014, are not necessarily indicative of the results expected for the full fiscal year.

Consolidation

The condensed consolidated balance sheet as of December 31, 2013 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 our wholly owned subsidiaries. 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 prospectus filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the “Securities Act”), with the SEC on June 6, 2014 (the “Prospectus”).

Significant Accounting Policies [Text Block]

New Accounting Policy

Investments

We have recorded our equity investment in a privately-held company under the cost method. Initial measurement of our investment under the cost method is recorded at historical cost which represents our initial investment in the privately-held company. We will periodically assess and evaluate our cost method investment for impairment and perform an assessment based on evaluation of overall financial performance, industry and market conditions, and other relevant events or factors deemed necessary that may affect carrying value. If we determine that a decrease in the equity investment should be recognized given impairment that is considered “other than temporary” in nature, we will write-down the carrying amount to its revised new fair value.

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; 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.

Business Concentrations

We work closely with third parties to manufacture and deliver our products. As of September 30, 2014 and December 31, 2013, two suppliers provided all of our electronic manufacturing services. Our products rely on key components, including certain integrated circuit components and power supplies some of which our contract manufacturers purchase on our behalf from a limited number of suppliers, including certain sole source providers. We do not have guaranteed supply contracts with any of our component suppliers, and our suppliers could delay shipments or cease manufacturing such products or selling them to us at any time. If we are unable to obtain a sufficient quantity of these components on commercially reasonable terms or in a timely manner, sales of our products could be delayed or halted entirely or we may be required to redesign our products. Quality or performance failures of our products or changes in our contractors’ or vendors’ financial or business condition could disrupt our ability to supply quality products to our customers. Any of these events could result in lost sales and damage to our end-customer relationships, which would adversely impact our business, financial condition and results of operations.

Concentrations of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, accounts receivable and notes receivable. Our cash, cash equivalents and restricted cash are invested in high quality financial instruments with banks and financial institutions. Such deposits may be in excess of insured limits provided on such deposits.

Our accounts receivable are unsecured and represent amounts due to us based on contractual obligations of our customers. We mitigate credit risk in respect to accounts receivable by performing ongoing credit evaluations of our customers to assess the probability of accounts receivable collection based on a number of factors, including past transaction experience with the customer, evaluation of their credit history, the credit limits extended and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. We have recorded an allowance for doubtful accounts for those receivables that we have determined not to be collectible.

Our notes receivable are secured and represent amounts due to us from a private company. We mitigate credit risk in respect to the notes receivable by performing ongoing credit evaluations of the borrower to assess the probability of collecting all amounts due to us under the existing contractual terms.

We market and sell our products through both our direct sales force and our channel partners, including distributors, value-added resellers, system integrators and original equipment manufacturer (“OEM”) partners.

Reclassifications [Text Block]

Reclassifications

As a result of a change in classification, we have reclassified our spare parts inventory from inventory to other current and non-current assets as of September 30, 2014. Spare parts inventory are used to satisfy our warranty obligations, and are not available for sale or used in the production process. Prior year balances have been adjusted to conform to this new classification for comparability purposes.

Recently Issued and Adopted Accounting Pronouncements

Recent Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue From Contracts With Customers ("ASU 2014-09"), which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. ASU 2014-09 is effective for fiscal years (and interim reporting periods within those years) beginning after December 15, 2016. Early application is not permitted. ASU 2014-09 permits the use of either the retrospective or cumulative effect transition method. We are currently reviewing the provisions of ASU 2014-09 and have not yet selected a transition method nor have we determined the effect of the standard on our consolidated financial statements.

- Definition

Disclosure of accounting policy for credit risk.

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- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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- Definition

The entire disclosure for all significant accounting policies of the reporting entity.

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