Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include our accounts and the accounts of our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Cash Equivalents	Cash Equivalents Cash equivalents consist of money market accounts and other highly liquid investments purchased with an original maturity of three months or less. The carrying amounts approximate fair value due to the short maturities of these investments.
Marketable Securities	Marketable Securities Marketable securities consist of certificates of deposit, commercial paper, corporate bonds and government municipal bonds. All marketable securities are accounted for as available-for-sale and are carried at fair value on our consolidated balance sheets with unrealized gains and losses recorded in accumulated other comprehensive loss within stockholders’ equity. In order to estimate the fair value for each security in our investment portfolio, we obtain quoted market prices and trading activity for each security where available. We obtain relevant information from our investment advisor and, if warranted, also may review the financial solvency of certain security issuers. We regularly monitor and evaluate the value of our marketable securities. When assessing marketable securities for other-than-temporary declines in value, we consider several factors. These factors include: how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the underlying factors contributing to a decline in the prices of securities in a single asset class, the performance of the issuer’s stock price in relation to the stock price of its competitors within the industry, expected market volatility, analyst recommendations, the views of external investment managers, any news or financial information that has been released specific to the investee and the outlook for the overall industry in which the issuer operates. If events and circumstances indicate that a decline in the value of a security has occurred and is other-than-temporary, we would record a charge to other income (expense).
Accounts Receivable	Accounts Receivable Accounts receivable are stated at the amount we expect to collect, which is net of an allowance for doubtful accounts for estimated losses resulting from the inability of our customers to make required payments. The following factors are considered when determining the collectability of specific customer accounts: customer creditworthiness, past transaction history with the customer, and changes in customer payment terms or practices. In addition, overall historical collection experience, current economic industry trends, and a review of the current status of trade accounts receivable are considered when determining the required allowance for doubtful accounts. Based on our assessment, we provide for estimated uncollectible amounts through a charge to earnings and a credit to our allowance for doubtful accounts. Balances that remain outstanding after we have used reasonable collection efforts are written off through a charge to the allowance for doubtful accounts and a credit to accounts receivable.
Inventories	Inventories Inventories are stated at the lower of cost or fair market value, with cost determined using the first-in, first-out method. Appropriate consideration is given to deterioration, obsolescence and other factors in evaluating fair market value.
Property, Equipment and Improvements, Net	Property, Equipment and Improvements, Net Property, equipment and improvements are carried at cost, net of accumulated depreciation. Depreciation is provided by charges to operations using the straight-line method over the estimated asset useful lives. Furniture and fixtures and other equipment are depreciated over a period of three to five years. Building improvements and buildings are depreciated over ten and thirty-nine years, respectively. Expenditures for maintenance and repairs are charged to operations as incurred, while major renewals and betterments are capitalized. The assets and related accumulated depreciation accounts are adjusted for asset retirements and disposals with the resulting gain or loss included in operations.
Identifiable Intangible Assets	Identifiable Intangible Assets Purchased proven technology, license agreements, covenants not to compete and other identifiable intangible assets are recorded at fair value when acquired in a business acquisition, or at cost when not purchased in a business acquisition. Purchased in-process research and development costs (IPR&D) related to business combinations are capitalized and amortized once placed in service. All other identifiable intangible assets are amortized on either a straight-line basis over their estimated useful lives of three to thirteen years or based on the pattern in which the asset is consumed. Useful lives for identifiable intangible assets are estimated at the time of acquisition based on the periods of time from which we expect to derive benefits from the identifiable intangible assets. Amortization of purchased and core technology is included in cost of product in the Consolidated Statements of Operations. Amortization of all other acquired identifiable intangible assets is charged to operating expenses as a component of general and administrative expense. Identifiable intangible assets are reviewed for impairment annually or whenever events or circumstances indicate that undiscounted expected future cash flows are not sufficient to recover the carrying value amount. We measure impairment loss by utilizing an undiscounted cash flow valuation technique using fair values indicated by the income approach. Impairment losses, if any, would be recorded in the period the impairment is identified.
Goodwill	Goodwill Goodwill represents the excess of cost over the fair value of identifiable assets acquired. Goodwill is tested for impairment on an annual basis as of June 30, or more frequently if events or circumstances occur which could indicate impairment. The calculation of goodwill impairment requires us to make assumptions about the fair value of our one reporting unit, which historically has been approximated by using our market capitalization plus a control premium. Control premium assumptions require judgment and actual results may differ from assumed or estimated amounts.
Warranties	Warranties In general, we warrant our hardware products to be free from defects in material and workmanship under normal use and service. The warranty periods generally range from one to five years. We typically have the option to either repair or replace hardware products we deem defective with regard to material or workmanship. Estimated warranty costs are accrued in the period that the related revenue is recognized based upon an estimated average per unit repair or replacement cost applied to the estimated number of units under warranty. These estimates are based upon historical warranty incidents and are evaluated on an ongoing basis to ensure the adequacy of the warranty accrual.
Revenue Recognition	Revenue Recognition We recognize revenue in accordance with authoritative guidance issued by FASB related to revenue recognition. Hardware product revenue as a percentage of total revenue was 91.8%, 89.7% and 88.6% in fiscal 2015, 2014 and 2013, respectively. We recognize hardware product revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, collectability is reasonably assured and there are no post-delivery obligations, other than warranty. Under these criteria, product revenue generally is recognized upon shipment of product to customers. Sales to authorized domestic and foreign distributors and Direct / OEMs are made with certain rights of return and price adjustment provisions. Estimated reserves for future returns and pricing adjustments are established by us based on an analysis of historical patterns of returns and price adjustments as well as an analysis of authorized returns compared to received returns and distribution sales for the current period. Estimated reserves for future returns and price adjustments are charged against revenue in the same period as the corresponding revenue is recorded. Service revenue as a percentage of total revenue represented 8.2%, 10.3% and 11.4% in fiscal 2015, 2014 and 2013, respectively. Our service revenue is derived primarily from professional and engineering services performed by our Etherios customer relationship management (CRM) services and our wireless design services. We also have some service revenue that is derived from our Digi Device Cloud, which is a platform-as-a-service (PaaS) offering in which customers pay for services consumed in terms of devices being managed and monitored, or as a monthly service fee for access to information. In addition, we have small amounts of revenue from our enterprise support services. We recognize service revenue from our Etherios CRM services, wireless design services, and Device Cloud based upon performance, including final product delivery and customer acceptance. In addition, we recognize small amounts of revenue from and enterprise support services which is recognized over the life of the contract, and training as the services are performed.
Research and Development	Research and Development Research and development costs are expensed when incurred. Research and development costs include compensation, allocation of corporate costs, depreciation, utilities, professional services and prototypes. Software development costs are expensed as incurred until the point that technological feasibility and proven marketability of the product are established. To date, the time period between the establishment of technological feasibility and completion of software development has been short, and no significant development costs have been incurred during that period. Accordingly, we have not capitalized any software development costs to date.
Income Taxes	Income Taxes Deferred income taxes are recognized for the tax consequences in future years of differences between the tax basis of assets and liabilities and their financial reporting amounts at each year end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. Income tax expense is equal to the tax payable for the period and the change during the period in deferred tax assets and liabilities and also changes in income tax reserves.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. This cost must be recognized over the period during which an employee is required to provide the service (usually the vesting period).
Foreign Currency Translation	Foreign Currency Translation Financial position and results of operations of our international subsidiaries are measured using local currencies as the functional currency, except for our Singapore location which uses the U.S. Dollar as its local currency. Assets and liabilities of these operations are translated at the exchange rates in effect at the end of each reporting period. For our larger international subsidiaries, statements of operations accounts are translated at the daily rate. For all other international subsidiaries, our statements of operations accounts are translated at the weighted average rates of exchange prevailing during each reporting period. Translation adjustments arising from the use of differing currency exchange rates from period to period are included in accumulated other comprehensive loss in stockholders’ equity. Gains and losses on foreign currency exchange transactions, as well as translation gains or losses on transactions denominated in currencies other than an entity’s functional currency, are reflected in the statement of operations. During fiscal 2015, 2014 and 2013, there were net transaction gains of $0.6 million, 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) $0.5 million and $0.4 million, respectively, that were recorded in other income (expense). We manage our net asset or net liability position for U.S. dollar accounts in our foreign locations to reduce our foreign currency risk. We have not implemented a formal hedging strategy.
Net Income Per Common Share	Net Income Per Common Share Basic net income per common share is calculated based on the weighted average number of common shares outstanding during the period. Diluted net income per common share is computed by dividing net income by the weighted average number of common and potentially dilutive common shares outstanding during the period. Potentially dilutive common shares of our stock result from dilutive common stock options and restricted stock units. We use the treasury stock method to calculate the weighted-average shares used in the diluted earnings per share computation. Under the treasury stock method, the proceeds from exercise of an option, the amount of compensation cost, if any, for future service that we have not yet recognized, and the amount of estimated tax benefits that would be recorded in paid-in capital, if any, when the option is exercised are assumed to be used to repurchase shares in the current period.
Use of Estimates and Risks and Uncertainties	Use of Estimates and Risks and Uncertainties The preparation of consolidated financial statements in conformity with generally accepted accounting principles in the United States 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 amount of revenue and expenses during the reporting period. Actual results could differ from those estimates. Estimates that could significantly affect our results of operations or financial condition involve the assignment of fair values upon acquisition of goodwill and other intangible assets and testing for impairment; the determination of our allowance for doubtful accounts and reserve for future returns and pricing adjustments; the estimation of our inventory obsolescence, warranty reserve, income tax reserves and other contingencies.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Our comprehensive income (loss) is comprised of net income, foreign currency translation adjustments and unrealized gains and losses on available-for-sale marketable securities, which are charged or credited to the accumulated other comprehensive loss account in stockholders’ equity.
Recent Accounting Developments	Recent Accounting Developments Adopted In July 2013, the Financial Accounting Standards Board (“FASB”) issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists.” This guidance relates to the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The standard update provides that a liability related to an unrecognized tax benefit should be offset against same jurisdiction deferred tax assets for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. This guidance was effective prospectively for fiscal years (and interim reporting periods within those years) beginning after December 15, 2013. We adopted this guidance during the fiscal quarter ended December 31, 2014, resulting in a reclassification of $0.4 million of unrecognized tax benefits to noncurrent deferred tax assets. In March 2013, FASB issued ASU 2013-05, “Foreign Currency Matters (Topic 830): Parent’s Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity.” This guidance applies to the release of the cumulative translation adjustment into net income when a parent either sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a business within a foreign entity. ASU 2013-05 was effective prospectively for fiscal years (and interim reporting periods within those years) beginning after December 15, 2013. We adopted this guidance during the fiscal quarter ended December 31, 2014. There was no impact on our condensed consolidated financial statements as we have not sold any foreign entities for which we hold a controlling financial interest. Not Yet Adopted In September 2015, FASB issued ASU 2015-16, "Simplifying the Accounting for Measurement-Period Adjustments." To simplify the accounting for adjustments made to provisional amounts recognized in a business combination, the amendments in this update eliminate the requirement to retrospectively account for those adjustments. The amendments in this update are effective for fiscal years beginning after December 15, 2015, including interim periods within those years, which for us will be the first fiscal quarter ending December 31, 2016. Earlier application is permitted for financial statements that have not been issued. We are currently evaluating the impact of the adoption of ASU 2015-16. In July 2015, FASB issued ASU 2015-11, "Simplifying the Measurement of Inventory." This provision would require inventory that was previously recorded using first-in, first-out (FIFO) to lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. This guidance is effective for fiscal years beginning after December 15, 2016 and interim periods within those years, which for us will be the first fiscal quarter ending December 31, 2017. The amendments in this guidance should be applied prospectively with earlier application permitted as of the beginning of an interim or annual period. We are currently evaluating the impact of the adoption of ASU 2015-11 and whether it would have a material impact on our consolidated financial statements. In April 2015, FASB issued ASU 2015-05, “Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. The new standard provides guidance to customers about whether a cloud computing arrangement includes a software license. If the arrangement does include a software license, the software license element of the arrangement should be accounted for in the same manner as the acquisition of other software licenses. This guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2015, with early adoption permitted. We expect to adopt this guidance beginning with our fiscal quarter ending December 31, 2016. We do not expect this guidance to have a material impact on our consolidated financial statements. In August 2014, FASB issued ASU 2014-15, “Presentation of Financial Statements - Going Concern.” This guidance requires management to evaluate whether there is substantial doubt about a company’s ability to continue as a going concern and to provide related footnote disclosures. These amendments are effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter, which for us, will be the fourth fiscal quarter ended September 30, 2017. Early adoption is permitted. While we are evaluating the impact of the adoption of ASU 2014-15, we do not expect it to have an impact on our consolidated financial statements. 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED) In May 2014, FASB issued ASU 2014-09, “Revenue from Contracts with Customers.” This guidance provides a five-step analysis in determining when and how revenue is recognized so that an entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects what it expects in exchange for the goods and services. It also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB issued ASU 2015-14 "Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date" which approved a one-year deferral of the effective date of ASU 2014-09. As a result of this deferral, ASU 2014-09 is effective for our fiscal 2019, including interim periods within that reporting period. The FASB also agreed to allow us to choose to adopt the standard effective for our fiscal 2018. We are assessing the adoption date and potential impact of adopting this ASU on our consolidated financial statements and related disclosures.