| Description of Business and Summary of Significant Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2018 |
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | |
| Basis of Presentation | Basis of Presentation The accompanying consolidated financial statements include those of A10 Networks, Inc. and its subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (the “SEC”). All intercompany accounts and transactions have been eliminated in consolidation. |
| Reclassifications | Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation in the consolidated statements of cash flows. We have combined the line item “Accrued litigation expenses” into “Other” within net cash (used in) provided by operating activities. |
| Use of Estimates | Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Those estimates and assumptions affect revenue recognition and deferred revenue, the allowance for doubtful accounts, the sales return reserve, the valuation of inventory, the fair value of marketable securities, contingencies and litigation, accrued liabilities, deferred commissions and the determination of fair value of stock-based compensation. These estimates are based on information available as of the date of the consolidated financial statements; therefore, actual results could differ from management’s estimates. |
| Cash and Cash Equivalents | Cash and Cash Equivalents Cash and cash equivalents include bank deposits and short-term, highly liquid investments purchased with an original maturity of 90 days or less. Our cash equivalents consist of money market funds. |
| Marketable securities | Marketable securities We classify our investments in debt securities as available-for-sale and record these investments at fair value. We may sell these investments at any time before their maturities. Accordingly, we classified our securities, including those with maturities exceeding twelve months, as current assets and included in marketable securities on the consolidated balance sheets. Unrealized gains and losses are reported in accumulated other comprehensive loss, net of taxes, in stockholders’ equity. Realized gains and losses are determined based on the specific identification method. Realized gains and losses and other-than-temporary impairment charges, if any, on marketable securities are reported in interest and other income (expense), net as incurred in the consolidated statements of operations. We regularly review our investment portfolio to identify and evaluate investments that have indicators of possible impairment. Investments are considered impaired when a decline in fair value is judged to be other-than-temporary. If the cost of an individual investment exceeds its fair value, we evaluate, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and our intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, we will record an impairment charge and establish a new cost basis in the investment. |
| Fair Value Measurement | Fair Value Measurement Our financial instruments consist of cash, cash equivalents, marketable securities, accounts receivable and accounts payable. Our cash equivalents are measured and recorded at fair value on a recurring basis. Marketable securities are comprised of certificates of deposit, corporate securities, U.S. Treasury and agency securities, commercial paper and asset-backed securities and are measured at fair value on a recurring basis. Accounts receivable and accounts payable are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment. Financial instruments recorded at fair value are measured and classified using the three-level valuation hierarchy as described below: Level 1 — observable inputs for identical assets or liabilities, such as quoted prices in active markets. Level 2 — inputs other than the quoted prices in active markets that are observable either directly or indirectly. Level 3 — unobservable inputs in which there is little or no market data, which requires us to develop our own assumptions when pricing the financial instruments. |
| Accounts Receivable and Allowance for Doubtful Accounts | Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoice amounts, net of allowances for doubtful accounts. We evaluate the collectibility of our accounts receivable based on known collection risks and historical experience. In circumstances where we are aware of a specific customer’s inability to meet its financial obligations to us (for examples, bankruptcy filings or substantial downgrading of credit ratings), we record a specific reserve for bad debts against amounts due to reduce the net recognized receivable to the amount we reasonably believe will be collected. For all other customers, we record reserves for bad debts based on the length of time the receivables are past due and our historical experience of collections and write-offs. |
| Inventory | Inventory Inventory is stated at the lower of cost or net realizable value. Inventory cost is determined using first-in, first-out method. We evaluate inventory for excess and obsolete products, based on management’s assessment of future demand and market conditions. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. Inventory write downs are included as a component of cost of products revenue in the consolidated statements of operations. |
| Property and Equipment, Net | Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Depreciation on property and equipment, excluding leasehold improvements, ranges from 1 to 3 years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements ranges from 2 to 8 years. |
| Goodwill | Goodwill Goodwill represents the excess of purchase consideration over the fair values of assets acquired and liabilities assumed in a business combination. Goodwill is not amortized but is reviewed for possible impairment annually in the fourth quarter or more frequently if impairment indicators arise. We have identified a single reporting unit for the purpose of our goodwill impairment tests, and the fair value of our reporting unit has been determined by our enterprise value. We may elect to utilize a qualitative assessment to determine whether it is more likely than not that the fair value of our reporting unit is less than its carrying value. If, after assessing the qualitative factors, we determine that it is more likely than not that the fair value of our reporting unit is less than its carrying value, an impairment analysis will be performed. We compare the fair value of our reporting unit with its carrying amount and if the carrying value of the reporting unit exceeds its fair value, an impairment loss will be recognized. We did not identify impairment of goodwill for any periods presented. |
| Intangible Assets | Intangible Assets Intangible assets are recorded at fair value and amortized on a straight-line basis over their estimated useful lives, which range from 5 to 10 years. We did not have impairment of intangible assets during the years ended December 31, 2018 , 2017 and 2016 . |
| Impairment of Long-Lived Assets | Impairment of Long-Lived Assets We evaluate our property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of our long-lived assets may not be recoverable. Recoverability of an asset group is measured by comparison of its carrying amount to the expected future undiscounted cash flows that the asset group is expected to generate. If it is determined that an asset group is not recoverable, an impairment loss is recorded in the amount by which the carrying amount of the asset group exceeds its fair value. |
| Revenue Recognition | Revenue Recognition We recognize revenue when we transfer control of promised goods or services to our customers in an amount that reflects the consideration to which we expect to be entitled to in exchange for those goods or services. See Note 2 for further discussion on revenue. |
| Research and Development Costs | Research and Development Costs Research and development efforts are focused on new product development and on developing additional functionality for our existing products. These expenses consist of personnel costs, and to a lesser extent, prototype materials, depreciation and certain allocated facilities and information technology costs. We expense research and development costs as incurred. |
| Stock-Based Compensation | Stock-Based Compensation Stock-based compensation expense is measured on the grant date based on the fair value of the award and recognized on a straight-line basis over the requisite service period, reduced for actual forfeitures. The fair values of restricted stock units (“RSUs”) and performance-based restricted stock units (“PSUs”) are estimated using our stock price on the grant date. The fair value of options and employee stock purchase rights is estimated using the Black-Scholes model on the grant date. The Black-Scholes model determines the fair value of share-based payment awards based on assumptions including expected term, stock price volatility, and risk-free interest rate. The fair value of market-performance based restricted stock units (“MSUs”) is valued using the Monte Carlo simulation model, which uses the stock price, expected volatility and risk-free interest rate to determine the fair value. |
| Warranty Costs | Warranty Costs Our appliance hardware and software generally carry a warranty period of 90 days. Estimates of future warranty costs are based on historical returns and the application of the historical return rates to our in-warranty installed base. Warranty costs to repair or replace items sold to customers have been insignificant for the years ended December 31, 2018 , 2017 and 2016 . |
| Foreign Currency | Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in non-functional currencies are remeasured to the functional currency at the average exchange rate for the period. Non-functional currency monetary assets and liabilities are remeasured to the functional currency using the exchange rate in effect at the balance sheet date, and non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in interest and other income (expense), net in the consolidated statements of operations. |
| Income Taxes | Income Taxes We account for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our consolidated financial statements or in our tax returns. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets are expected to be realized or settled. We regularly assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through an adjustment to income tax expense. The factors used to assess the likelihood of realization of our deferred tax assets include our forecast of future taxable income and available tax planning strategies that could be implemented to realize the net deferred tax assets. Assumptions represent our best estimates and involve inherent uncertainties and the application of our judgment. We account for uncertainty in income taxes recognized in our consolidated financial statements by regularly reviewing our tax positions and benefits to be realized. We recognize tax liabilities based upon our estimate of whether, and the extent to which, additional taxes will be due when such estimates are more-likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained upon examination by taxing authorities. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. |
| Advertising Costs | Advertising Costs Advertising costs are expensed when incurred. |
| Segment Information | Segment Information An operating segment is a component of an enterprise for which its discrete financial information is available and its operating results are regularly reviewed by chief operating decision maker for resource allocation decisions and performance assessment. Our chief operating decision maker is our Chief Executive Officer. Our Chief Executive Officer reviews financial information presented on a consolidated basis for purposes of allocating resources and assessing performance of the Company. Accordingly, we have one reportable segment and one operating segment. |
| Vendor Business Concentration | Vendor Business Concentration We rely on third parties to manufacture our hardware appliances and we purchase raw materials from third-party vendors. We outsourced substantially all of our manufacturing services to three independent manufacturers. In addition, we purchase certain strategic component inventory which is consigned to our third-party manufacturers. Other hardware components included in our products are sourced from various suppliers by our manufacturers and are principally industry standard parts and components that are available from multiple vendors. |
| Concentration of Credit Risk and Significant Customers | Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents, marketable securities and accounts receivable. Our cash, cash equivalents and marketable securities are held and invested in high-credit quality financial instruments by recognized financial institutions and are subject to minimum credit risk. 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 periodic credit evaluations based on a number of factors, including past transaction experience, evaluation of credit history and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent 10% or more of our total revenue for each period presented or our gross accounts receivable balance as of each respective balance sheet date. |
| Recently Adopted Accounting Guidance/Recent Accounting Pronouncements Not Yet Effective | Recently Adopted Accounting Guidance In May 2017, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting, to provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. This standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. The amendments will be applied prospectively to an award modified on or after the adoption date. The adoption of ASU 2017-09 on January 1, 2018 did not impact our consolidated financial statements or disclosures. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as subsequently amended, which supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition. This ASU requires an entity to recognize revenue when it transfers 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. This ASU also includes Subtopic 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the capitalization of incremental customer acquisition costs and amortization of these costs over the contract period or estimated customer life which resulted in the recognition of a deferred commission asset on our consolidated balance sheet. We adopted ASU 2014-09 and its related amendments (collectively “ASC 606”) on January 1, 2018 using the modified retrospective method. See Note 2 for disclosure on the impact of adopting this standard. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118. These amendments add SEC guidance to the FASB Accounting Standards Codification regarding the Tax Cuts and Jobs Act pursuant to the issuance of SAB 118. The amendments are effective upon addition to the FASB Codification. See Note 9 in this report for disclosures related to the effect of the Tax Cuts and Jobs Act and our utilization of SAB 118. Recent Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as amended, to supersede existing guidance on accounting for leases in Topic 840, Leases. Topic 842 generally requires lessees to recognize operating and financing lease liabilities and corresponding right-of-use assets on the balance sheet and to provide enhanced disclosures surrounding the amount, timing and uncertainty of cash flows arising from leasing arrangements. We will adopt the new standard effective January 1, 2019 on a modified retrospective basis, under which we will recognize the cumulative effects of initially applying the standard as an adjustment to the opening balance of accumulated deficit on the adoption date and will not restate comparative periods. We will elect the package of practical expedients permitted under the transition guidance, which allows us to carry-forward our historical lease classification and our assessment on whether a contract is or contains a lease. We will also elect to apply the hindsight practical expedient which allows us to use hindsight in determining the lease term. Additionally, we will elect to not apply the new standard’s recognition requirements to leases with an initial term of 12 months or less and instead to recognize lease payments in the consolidated statements of operations on a straight-line basis over the lease term. On the adoption date, we estimate we will recognize on our consolidated balance sheet approximately $5.9 million of right-of-use assets, $6.6 million of lease liabilities, and derecognize existing deferred rent of approximately $0.7 million . These are preliminary estimates that are subject to change as we finalize our adoption. Other than described above, we do not expect the new standard to have any other material impacts on our consolidated financial statements. There are several other new accounting pronouncements issued by the FASB, which we will adopt. However, we do not believe any of those accounting pronouncements will have a material impact on our consolidated financial position, operating results or statements of cash flows. |
| Revenue Recognition | Revenue Recognition We derive revenue from two sources: (i) products revenue, which includes hardware, perpetual software license and subscription revenue; and (ii) services revenue, which includes post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those products or services. We apply the following five-step revenue recognition model: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, performance obligations are satisfied. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years as there is no discernable pattern of transfer related to these promises. Billed but unearned PCS revenue is included in deferred revenue. Professional service revenue primarily consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Revenue is recognized for training when the training course is delivered. Contracts with Multiple Performance Obligations Most of our contracts with customers, other than renewals of PCS, contain multiple performance obligations with a combination of products and PCS. Products and PCS generally qualify as distinct performance obligations. Our hardware includes embedded ACOS software, which together deliver the essential functionality of our products. For contracts which contain multiple performance obligations, we allocate revenue to each distinct performance obligation based on the standalone selling price (“SSP”). Judgment is required to determine the SSP for each distinct performance obligation. We use a range of amounts to estimate SSP for products and PCS sold together in a contract to determine whether there is a discount to be allocated based on the relative SSP of the various products and PCS. If we do not have an observable SSP, such as when we do not sell a product or service separately, then SSP is estimated using judgment and considering all reasonably available information such as market conditions and information about the size and/or purchase volume of the customer. We generally use a range of amounts to estimate SSP for individual products and services based on multiple factors including, but not limited to the sales channel (reseller, distributor or end customer), the geographies in which our products and services are sold, and the size of the end customer. We account for multiple contracts with a single partner as one arrangement if the contractual terms and/or substance of those agreements indicate that they may be so closely related that they are, in effect, parts of a single contract. We may occasionally accept returns to address customer satisfaction issues even though there is generally no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period shipments. Specific customer returns and allowances are considered when determining our sales return reserve estimate. Our policy applies to the accounting for individual contracts. However, we have elected a practical expedient to apply the guidance to a portfolio of contracts or performance obligations with similar characteristics so long as such application would not differ materially from applying the guidance to the individual contracts (or performance obligations) within that portfolio. Consequently, we have chosen to apply the portfolio approach when possible, which we do not believe will happen frequently. Additionally, we will evaluate a portfolio of data, when possible, in various situations, including accounting for commissions, rights of return and transactions with variable consideration. We report revenue net of sales taxes. We include shipping charges billed to customers in revenue and the related shipping costs are included in cost of product revenue. |
| Deferred Contract Acquisition Costs | In connection with the adoption of ASC 340-40, we capitalize certain contract acquisition costs consisting of incremental sales commissions incurred to obtain customer contracts. Deferred commissions related to product revenues are recognized upon transfer of control to customers. Deferred commissions related to services revenue are recognized as the related performance obligations are met. Deferred commissions that will be recognized during the succeeding 12-month period are recorded as prepaid expenses and other current assets, and the remaining portion is recorded as other non-current assets. Amortization of deferred commissions is included in sales and marketing expense. |
