Organization and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include the accounts of Arista Networks, Inc. and its wholly owned subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and 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 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 six months ended June 30, 2020, are not necessarily indicative of the results expected for the full fiscal year. The condensed consolidated balance sheet as of December 31, 2019 has been derived from the audited consolidated financial statements at that date but does not include all of the information and notes required by GAAP for complete financial statements. All significant inter-company accounts and transactions have been eliminated. Our condensed consolidated financial statements and related financial information in this Quarterly Report on Form 10-Q 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, 2019, filed with the SEC on February 14, 2020.
Use of Estimates	Use of Estimates The preparation of the accompanying condensed consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported and disclosed in the 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, sales rebates and return reserves; valuation of goodwill and acquisition-related intangible assets, accounting for income taxes, including the valuation allowance on deferred tax assets and reserves for uncertain tax positions; estimate of useful lives of long-lived assets including intangible assets; valuation of inventory and contract manufacturer/supplier liabilities; and the recognition and measurement of contingent liabilities. We evaluate our estimates and assumptions based on historical experience and other factors and adjust those estimates and assumptions when facts and circumstances dictate. Actual results could differ materially from those estimates.
Recently Adopted Accounting Pronouncements and Recent Accounting Pronouncements Not Yet Effective	Recently Adopted Accounting Pronouncements Credit Losses of Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, to replace the incurred loss impairment methodology under current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The standard requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. For trade receivables, we are required to estimate lifetime expected credit losses. For available-for-sale debt securities, we are required to recognize an allowance for credit losses rather than a reduction to the carrying value of the asset. We adopted the new guidance in our first quarter of 2020 under a modified retrospective approach, and there was no material impact to our financial statements upon adoption. In addition, we do not anticipate that it will have a material impact on our consolidated statement of operations or consolidated statements of cash flows going forward.