Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	May 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The consolidated financial statements include Electro Rent Corporation and its wholly owned subsidiaries, Electro Rent, LLC, ER International, Inc., Electro Rent Europe NV, Electro Rent Asia, Inc. and Electro Rent (Beijing) Test and Measurement Equipment Rental Co., Ltd. (collectively “we”, “us”, or “our” hereafter). All intercompany balances and transactions have been eliminated in consolidation.
Business and Organization	Business and Organization: We are a global organization devoted to the rental, lease and sale of new and used electronic test and measurement (“T&M”) equipment. We purchase T&M equipment from leading manufacturers such as Keysight Technologies, Inc. (formerly Agilent Technologies, Inc., “Keysight”), Anritsu, Inc. ("Anritsu"), Rohde & Schwarz Gmbh & Co. KG ("Rohde & Schwarz") and Tektronix Inc. Our customers rent, lease and buy our T&M equipment, and use that equipment primarily in the aerospace and defense, telecommunications, electronics, industrial and semiconductor markets. In addition, we purchase personal computers from manufacturers including Dell, HP, IBM, Toshiba and Apple for our Data Products ("DP") division. Our reseller agreement with Keysight was not renewed after its May 31, 2015 expiration date. The expiration of the Keysight reseller agreement materially affected our revenues and net profits.
Use of Estimates	Use of Estimates: The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities as well as the disclosures of contingent assets and liabilities as of the date of these financial statements and the reported amounts of revenues and expenses during the reporting period. On a regular basis, we review these estimates including those related to asset lives and depreciation methods, impairment of long-lived assets, including rental and lease equipment, goodwill and intangibles, allowance for doubtful accounts, income taxes, contingencies and litigation. These estimates are based on our evaluation of current business and economic conditions, historical experience and on various other assumptions believed to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions. We believe, however, that our estimates, including those for the above-listed items, are reasonable.
Revenue Recognition	Revenue Recognition: We generate revenues primarily through the rental and leasing of T&M and DP equipment and through the sale of new and used equipment. Rental revenues comprise short term agreements that can be daily, weekly or monthly. Rental revenues are recognized in the month they are due on the accrual basis of accounting. Our operating lease agreements have varying terms, typically one to three years. Upon lease termination, customers have the option to renew the lease term, purchase the equipment at fair market value, or continue to rent on a month-to-month basis. Our operating leases do not provide for contingent rentals. Revenues related to operating leases are recognized on a straight-line basis over the term of the lease. Negotiated lease early-termination charges are recognized upon receipt. Rentals and leases are primarily billed to customers in advance, and unearned billings are recorded as deferred revenue. We enter into finance leases as lessor for some of our equipment. Our finance lease agreements contain bargain purchase options and are accounted for as sale-type leases. Revenues from finance leases, which are recorded at the present value of the aggregate future lease payments, net of unearned interest, are included in sales of equipment and other revenues in our consolidated statements of operations. Unearned interest is recognized over the life of the finance lease term using the effective interest method. Our finance lease terms vary, and are typically one to three years. The net investment in finance leases, which represents the receivables due from lessees, net of unearned interest, is included in other assets in our consolidated balance sheets. Historically, we have not required security deposits based on our assessed credit risk within our customer bases. Initial direct costs for operating and finance leases are insignificant. Sales of new equipment through our resale channel are recognized in the period in which the equipment is delivered and risk of loss passes to the customer, while sales of used equipment from our rental and lease equipment pool are recognized in the period in which the equipment is shipped and risk of loss passes to the customer. In the case of equipment sold to customers that is already on rent or lease to the same party, revenue is recognized at the agreed-upon date when the rent or lease term ends and risk of loss passes to the customer. The amount of revenue recognized for sales of new equipment depends on whether we sell as principal or as agent for the original equipment manufacturer. Prior to May 31, 2015, our sales of new equipment were derived primarily from the reseller agreement with Keysight Technologies, Inc. In fiscal 2016, we entered into reseller agreements with other T&M equipment manufacturers, including Anritsu and Rohde & Schwarz. Under the terms of these agreements we act as the principal with respect to sales of new equipment, based on several factors, including: (1) We act as the primary obligor by working directly with our customers to define their needs, providing them with options to satisfy such needs, contracting directly with the customer, and, to the extent required, providing customers with instruction on the use of the product and additional technical support once the product is received by the customer. The original equipment manufacturer is not a party to our customer sales agreements, nor is it referenced in the agreements, and therefore has no obligation to our customers with the exception of the manufacturer’s standard warranty on the product; (2) We bear back-end risk of inventory loss with respect to any product return from the customer as the original equipment manufacturer is not required to accept returns of equipment from us. Under the reseller agreement with Keysight, we also bore front-end risk of inventory loss in those cases where we acquired products for resale into our equipment pool prior to shipment to customers; (3) We have full discretion in setting pricing terms with our customers and negotiate all such terms ourselves; and (4) We assume all credit risk. In situations where we act as principal, the gross sales of new equipment are recorded in sales of equipment and other revenues, while the related equipment costs, including the purchase price from the original equipment manufacturer, are recorded in costs of sales of equipment and other revenues in our consolidated statements of operations. In situations where we act as an agent for the original equipment manufacturer, we recognize revenue only on the commissions that we receive, which are recorded in other revenue within the sales of equipment and other revenues in our consolidated statement of operations. Other revenues, consisting primarily of billings to customers for delivery and repairs, are recognized in the period in which the respective services are performed.
Operating expenses	Operating Expenses: Costs of rentals and leases, excluding depreciation, primarily include labor related costs of our operations personnel, supplies, repairs, insurance and warehousing costs associated with our rental and lease equipment, relating to our rental and lease revenues. Costs of sales of equipment and other revenues primarily include the cost of new equipment and the carrying value of used equipment sold. Selling, general and administrative expenses include sales and advertising costs, payroll and related benefit costs, insurance expenses, property taxes on our property and rental and lease equipment, legal and professional fees, and administrative overhead. Advertising costs are expensed as incurred. Total advertising expenses were $1,133, $982 and $982 for fiscal 2016, 2015 and 2014, respectively. Selling, general and administrative expenses also include shipping and handling costs of $3,634, $3,953 and $3,977 for fiscal 2016, 2015 and 2014, respectively.
Rental and Lease Equipment and Other Property	Rental and Lease Equipment and Other Property: Assets are generally stated at cost, less accumulated depreciation. Upon retirement or disposal of assets, the cost and the related accumulated depreciation are eliminated from the accounts and any gain or loss is recognized. We depreciate our buildings over 31.5 years, building improvements over useful life, furniture and other equipment over three to ten years, and leasehold improvements over the shorter of the lease term, typically three to five years, or useful life. Each is depreciated on a straight-line basis. Depreciation of rental and lease equipment is provided over the estimated useful lives of the respective assets. We depreciated $407,807 and $440,495 of equipment, at acquisition cost, at May 31, 2016 and 2015, respectively, using straight-line methods ranging from two to ten years, and $27,106 and $32,292 of equipment, at acquisition cost, at May 31, 2016 and 2015, respectively, using accelerated methods ranging from two to four years. We generally use straight-line methods for our T&M equipment, which we believe maintains its value consistently throughout the equipment’s useful life, and accelerated methods primarily for our DP equipment, which tends to depreciate faster due to frequent technological advancements. Depreciation methods and useful lives are periodically reviewed and revised, as deemed appropriate, including revisions to reflect shorter useful lives to more closely match depreciation expense with rental revenue for rental arrangements where the customer can acquire title through payment of all required rentals. Normal maintenance and repairs are expensed as incurred. Depreciation expense for rental and lease equipment was $55,931, $56,445 and $57,034 for fiscal 2016, 2015 and 2014, respectively. Rental and lease equipment at net book value was comprised of $194,618 of T&M equipment and $4,908 of DP equipment at May 31, 2016, and $225,222 of T&M equipment and $6,449 of DP equipment at May 31, 2015.
Income Taxes	Income Taxes: We recognize a liability or asset for the deferred tax consequences of temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements. These temporary differences will result in taxable or deductible amounts in future years when reported amounts of the assets or liabilities are recovered or settled. Deferred tax assets are periodically reviewed for recoverability. We recognize the tax impact from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax impact recognized in the financial statements from such a position is measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate resolution. We recognize interest, penalties and foreign currency gains and losses with respect to uncertain tax positions as components of our income tax provision. Accrued interest and penalties are included within accrued expenses in the consolidated balance sheet. Significant judgment is required in the identification of uncertain tax positions and in the estimation of penalties and interest on uncertain tax positions (see Note 5 for further discussion.)
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets: The carrying value of equipment held for rental and lease is assessed when circumstances indicate that the carrying amount of equipment may not be recoverable. Recoverability of equipment to be rented and leased is measured by a comparison of the carrying amount to the undiscounted future cash flows expected to be generated by the asset. If the current carrying value exceeds the estimated undiscounted cash flows, an impairment loss is recorded equal to the difference between the asset’s current carrying value and its fair value as described in FASB ASC Topics No. 360, Impairment and Disposal of Long-Lived Assets and No. 820, Fair Value Measurements and Disclosures. We determine the fair value based upon the projected net cash flows from model's rental and sale considering current market conditions. Based upon such periodic assessments, costs of rentals and leases included impairment charges of $443 related to our T&M rental and lease equipment during the year ended May 31, 2016. No impairments occurred during fiscal 2015 and 2014.
Goodwill and Intangible Assets	Goodwill: Goodwill, which represents the excess of purchase price over the fair value of net assets acquired is discussed further in Note 3. Pursuant to FASB ASC Topic No. 350, Intangibles – Goodwill and Other, goodwill is not amortized but tested annually for impairment, or on an interim basis if an event occurs or circumstances change that would reduce the fair value of a reporting unit below its carrying value. In connection with the annual impairment test for goodwill, we have elected the option to perform a qualitative assessment to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If we determine that it was more likely than not that the fair value of the reporting unit is less than its carrying amount, then we perform the impairment test. The impairment test involves a two-step process. The first step involves comparing the fair values of the applicable reporting units with their aggregate carrying values, including goodwill. We generally determine the fair value of our reporting units using the market approach methodology of valuation. If the carrying value of a reporting unit exceeds the reporting unit’s fair value, we perform the second step of the test to determine the amount of impairment loss. The second step involves measuring the impairment by comparing the implied fair value of the affected reporting unit’s goodwill with its carrying value. We completed the required impairment review at the end of fiscal 2016, 2015 and 2014 and concluded that there were no impairments.
Cash and Cash Equivalents	Cash and Cash Equivalents: We consider highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. We held no cash equivalents at May 31, 2016 and 2015 except for the money market funds that are part of our supplemental executive retirement plan (SERP) assets included in other assets.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts: We maintain an allowance for doubtful accounts for estimated losses resulting from the inability of customers to make rental and lease payments. The estimated losses are based on historical collection experience in conjunction with an evaluation of the current status of the existing accounts. If the financial condition of our customers were to deteriorate, then additional allowances could be required that would reduce income. Conversely, if the financial condition of our customers were to improve or if legal remedies to collect past due amounts were more successful than expected, then the allowance for doubtful accounts may need to be reduced and income would be increased.
Other Assets	Other Assets: We include demonstration equipment used in connection with our resale activity, totaling $4,851 and $81 as of May 31, 2016 and 2015, respectively, in other assets for a period up to two years. Demonstration equipment is recorded at the lower of cost or estimated market value until the units are transferred to our rental and lease equipment pool. Once transferred to our rental and lease equipment pool, the equipment is depreciated over its remaining estimated useful life.
Concentration of Credit Risk	Concentration of Credit Risk: Financial instruments that potentially expose us to concentration of credit risk primarily consist of trade accounts receivable. To mitigate the risk, we sell primarily on 30-day terms, perform credit evaluation procedures on each customer’s individual transactions and require security deposits or personal guarantees from our customers when significant credit risks are identified. Typically, most customers are large, established firms. We purchase rental and lease equipment from numerous vendors. During fiscal 2016, 2015 and 2014, Keysight accounted for approximately 56.0%, 70.7% and 65.6%, respectively, of all new equipment purchases, including rental equipment and equipment purchased for resale. Anritsu equipment purchases during fiscal 2016 accounted for 12.3% of our new equipment purchases while Anritsu equipment purchases during fiscal 2015 and fiscal 2014 were below 10.0%. No other vendor accounted for more than 10.0% of such purchases.
Foreign Currency	Foreign Currency: The U.S. dollar has been determined to be the functional currency of all foreign subsidiaries. The assets and liabilities of our foreign subsidiaries are remeasured from their local currency to U.S. dollars at current or historic exchange rates, as appropriate. Revenues and expenses are remeasured from foreign currencies to U.S. dollars using historic or average monthly exchange rates, as appropriate, for the month in which the transaction occurred. Remeasurement gains and losses are included in selling, general and administrative expenses or income taxes, as appropriate. The assets, liabilities, revenues and expenses of our foreign subsidiaries are individually less than 10.0% of our respective consolidated amounts. The euro, British pound sterling, Canadian dollar and Chinese yuan are our primary foreign currencies. Net remeasurement gains and losses have not been significant. We enter into forward contracts to hedge against unfavorable currency fluctuations in our monetary assets and liabilities in our European and Canadian operations. These contracts are designed to minimize the effect of fluctuations in foreign currencies. To qualify for hedge accounting, contracts must reduce the foreign currency exchange rate and interest rate risk otherwise inherent in the amount and duration of the hedged exposures and comply with established risk management policies. Our derivative instruments are not designated as hedging instruments and, therefore, are recorded at fair value as an asset or liability, and any changes in fair value are recorded in our consolidated statements of operations. We do not use derivative financial instruments for speculative trading purposes.
Net Income Per Common and Common Equivalent Share	Net Income Per Common and Common Equivalent Share: Basic earnings per share (“EPS”) is computed as net income divided by the weighted average number of shares of common stock outstanding and shares issuable for vested restricted stock units for the reported year, excluding the dilutive effects of any potentially anti-dilutive securities. Diluted EPS is computed as net income divided by the weighted average number of shares outstanding of common stock and common stock equivalents for the reported year. The dilutive effect of restricted stock units is computed using the treasury stock method.
Stock-Based Compensation	Share-Based Compensation: Share-based payments to employees are recognized in the consolidated financial statements as compensation expense over the period that an employee provides service in exchange for the award based on its fair value on the date of grant. Compensation expense resulting from restricted stock units is measured at fair value on the date of grant and is recognized in selling, general and administrative expenses over the vesting period (see Note 11 for further discussion).
Recent Accounting Pronouncements	Recent Accounting Pronouncements: In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718). Under the new guidance, all excess tax benefits and tax deficiencies will be recognized in the income statement as they occur. This will replace the current guidance, which requires tax benefits that exceed compensation cost (windfalls) to be recognized in equity. It will also eliminate the need to maintain a “windfall pool,” and will remove the requirement to delay recognizing a windfall until it reduces current taxes payable. The new guidance will also change the cash flow presentation of excess tax benefits, classifying them as operating inflows, consistent with other cash flows related to income taxes. The amendments in this guidance are effective for fiscal years beginning after December 15, 2016 and interim periods within those fiscal years. The Company is evaluating the impact of this new guidance on its consolidated financial statements. In February 2016, the FASB issued guidance that will require lessees to put most leases on their balance sheets but recognize expenses in the income statement. For lessors, the standard will be similar to the current model but will be updated to align with certain changes to the lessee model. Lessors will continue to classify leases as operating, direct financing or sales-type leases. The standard is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The impact this guidance will have on the consolidated financial statements cannot be determined at this time. In May 2014, the FASB and the International Accounting Standards Board ("IASB") issued guidance to establish a new, more robust framework for the recognition of revenue related to the transfer of goods and services to customers. This guidance is effective for reporting periods beginning after December 15, 2017, including interim reporting periods within that reporting period. The impact this guidance will have on the consolidated financial statements cannot be determined at this time.
Other Comprehensive Income	Other Comprehensive Income: Comprehensive income is equivalent to net income for all periods presented.