Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of DLH Holdings Corp. and its subsidiaries (together with its subsidiaries, "DLH" or the "Company" and also referred to as "we," "us," and "our"), all of which are wholly owned. All significant intercompany balances and transactions have been eliminated in consolidation. The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") and with the instructions to Form 10-K, Regulation S-X, and Regulation S-K.
Reclassifications	Certain reclassifications have been made to the prior year’s consolidated financial statements to conform to the current year presentation.
New Accounting Pronouncements	New Accounting Pronouncements In February 2016, the FASB issued new accounting guidance included in Accounting Standard Codification ("ASC") 842 related to leases. This new accounting guidance is intended to improve financial reporting about leasing transactions. This accounting standard will require organizations that lease assets, referred to as “Lessees”, to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases with terms of more than twelve months. An organization is to provide disclosures designed to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. These disclosures include qualitative and quantitative requirements concerning additional information about the amounts recorded in the financial statements.The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. However, unlike current GAAP which requires only capital leases to be recognized on the balance sheet, new guidance will require both types of leases (i.e., operating and finance) to be recognized. Finance leases will be accounted for in substantially the same manner as capital leases. Public companies will be required to adopt the new leasing standard for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted for all companies and organizations. Accounting Standard Update ("ASU") 2018-11 allows companies to elect not to recast comparative periods presented when transitioning to ASC 842. The Company expects an impact in balance sheet net assets and liabilities resulting from the adoption of this new lease accounting guidance of approximately $32.7 million of lease obligations as of September 30, 2019 that will be further evaluated as the implementation of this guidance becomes effective. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment, which simplifies the accounting for goodwill impairments by eliminating step two from the goodwill impairment test. Instead, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss shall be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. ASU 2017-04 also clarifies that an entity should consider income tax effects from any tax-deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable. The new standard is effective for fiscal years beginning after December 15, 2019 for both interim and annual reporting periods. The Company is currently assessing the potential impact of the adoption of ASU 2017-04 on its consolidated financial statements. In May 2017, the FASB issued Accounting Standards Update ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The Company adopted this standard in the first quarter of fiscal 2019 and adoption did not have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07 Improvements to Nonemployee Share-Based Payment Accounting, which simplifies the accounting for share-based payments granted to nonemployees for goods and services. Under the ASU, most of the guidance on such payments to nonemployees would be aligned with the requirements for share-based payments granted to employees. The amendments are effective for fiscal years beginning after December 15, 2018, including interim periods. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company is currently assessing the potential impact on the Company’s consolidated financial statements and related disclosures.
Revenue Recognition	Revenue Recognition On October 1, 2018, we adopted ASC 606, Revenue from Contracts with Customers using the modified retrospective method. ASC 606 outlines a five-step model whereby revenue is recognized as performance obligations within the contract are satisfied. ASC 606 also requires new, expanded disclosures regarding revenue recognition. We recognized the impact of adopting ASC 606, but did not record an entry as the impact was immaterial at less than $10 thousand. Results for reporting periods beginning after October 1, 2018 are presented under ASC 606, while prior period amounts were not adjusted and will continue to be reported under ASC 605, the accounting standards in effect for those periods. In past periods, the Company recognized and recorded revenue on government contracts when: (a) persuasive evidence of an arrangement existed; (b) the services had been delivered to the customer; (c) the sales price was fixed or determinable and free of contingencies or significant uncertainties; and (d) collectibility was reasonably assured. We account for a contract when both we and the customer approve and commit; our rights and those of the customer are identified; payment terms are identified; the contract has commercial substance; and collectability of consideration is probable. At contract inception, we identify the distinct goods or services promised in the contract, referred to as performance obligations. At September 30, 2019 we have identified a single performance obligation for completed and in-process contracts. Then we determine the total transaction price for the contract; which is the total consideration which we can expect in exchange for the promised goods or services in the contract. The transaction price may include fixed or variable amounts. Due to our contracts being predominantly time and material, the Company does not have variable consideration. The transaction price is allocated to each distinct performance obligation, using our best estimate of the standalone selling price for each service promised in the contract. The primary method used to estimate standalone selling price is the hourly billing rate for each labor category identified in the contract with the customer. Revenue is recognized when, or as, the performance obligation is satisfied. We recognize revenue over time when there is a continuous transfer of control to our customer. For our U.S. government contracts, this continuous transfer of control to the customer is supported by clauses in the contract that allow the U.S. government to unilaterally terminate the contract for convenience, pay us for costs incurred plus a reasonable profit and take control of any work in process. When control is transferred over time, revenue is recognized based on the extent of progress towards completion of the performance obligation. For services contracts, we satisfy our performance obligations as services are rendered. We use a cost-based input method to measure progress. Contract costs include labor, material and allocable indirect expenses. For time-and-material contracts, we bill the customer per labor hour and per material, and revenue is recognized in the amount invoiced since the amount corresponds directly to the value of our performance to date. We consider control to transfer when we have a present right to payment. Essentially, all of our contracts satisfy their performance obligations over time. Contracts are often modified to account for changes in contract specifications and requirements. Contract modifications impact performance obligations when the modification either creates new or changes the existing enforceable rights and obligations. The effect of a contract modification on the transaction price and our measure of progress for the performance obligation to which it relates is recognized as an adjustment to revenue and profit cumulatively. Furthermore, a significant change in one or more estimates could affect the profitability of our contracts. We recognize adjustments in estimated profit on contracts in the period identified. For time-and-materials contracts, revenue is recognized to the extent of billable rates times hours delivered plus materials and other reimbursable costs incurred. Revenue for cost-reimbursable contracts is recorded as reimbursable costs are incurred, including an estimated share of the applicable contractual fees earned. Contract costs are expensed as incurred. Estimated losses are recognized when identified. Contract assets - Amounts are invoiced as work progresses in accordance with agreed-upon contractual terms. In part, revenue recognition occurs before we have the right to bill, resulting in contract assets. These contract assets are reported within receivables, net on our consolidated balance sheets and are invoiced in accordance with payment terms, which are typically 30 days, defined in each contract. Period end balances will vary from period to period due to agreed-upon contractual terms. Contract liabilities - Amounts are a result of billings in excess of costs incurred. Disaggregation of revenue from contracts with customers We disaggregate our revenue from contracts with customers by customer, contract type, as well as whether the Company acts as prime contractor or subcontractor. We believe these categories best depict how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted 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 amounts of revenues and expenses during the reporting period. Significant estimates include valuation of goodwill and intangible assets, measurement of prepaid workers’ compensation, valuation allowances established against deferred tax assets, measurement of contingent liabilities, accounts payable, workers’ compensation claims, and accrued expenses and the valuation of derivative financial instruments associated with debt agreements. In addition, the Company estimates overhead charges and allocates such charges throughout the year. We evaluate these estimates and judgments on an ongoing basis and base our estimates on historical experience, current and expected future outcomes, third-party evaluations and various other assumptions that we believe are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. We revise material accounting estimates if changes occur, such as more experience is acquired, additional information is obtained, or there is new information on which an estimate was or can be based. Actual results could differ from those estimates. In particular, a material reduction in the fair value of goodwill would have a material adverse effect on the Company’s financial position and results of operations.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company's cash and cash equivalents, accounts receivable, unbilled receivables, contract assets, accrued expenses, and accounts payable approximate fair value due to the short-term nature of these instruments. The fair values of the Company's debt instruments approximate fair value because the underlying interest rates approximate market rates that the Company could obtain for similar instruments at the balance sheet dates.
Goodwill and Other Intangible Assets	Goodwill and other intangible assets We have used the acquisition method of accounting for the S3 transaction, whereby the assets acquired and liabilities assumed are recognized based upon their estimated fair values at the acquisition date. The fair values of assets acquired and liabilities assumed are based on all available information. Final values of purchase price allocation are shown under Note 15, Business Combinations. The Company recognized amortization expense of approximately $1.0 million for the acquired identifiable intangible assets of S3. The Company continues to review its goodwill and other intangible assets for possible impairment or loss of value at least annually or more frequently upon the occurrence of an event or when circumstances indicate that a reporting unit’s carrying amount is greater than its fair value. At September 30, 2019, we performed a goodwill impairment evaluation on the year-end carrying value of approximately $52.8 million. We performed a qualitative assessment of factors to determine whether it was necessary to perform the goodwill impairment test. Based on the results of the work performed, the Company has concluded that no impairment loss was warranted at September 30, 2019, as no change in business conditions occurred which would have a material adverse effect on the valuation of goodwill. Notwithstanding this evaluation, factors including non-renewal of a major contract or other substantial changes in business conditions could have a material adverse effect on the valuation of goodwill in future periods and the resulting charge could be material to future periods’ results of operations. Similarly, there were no impairments during the prior year ended September 30, 2018.
Long Lived Assets	Long Lived Assets Equipment and improvements are stated at cost. Depreciation and amortization are provided using the straight-line method over the estimated useful asset lives (3 to 7 years) and the shorter of the initial lease term or estimated useful life for leasehold improvements.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with the liability method, whereby deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities, using enacted tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reflected on the consolidated balance sheet when it is determined that it is more likely than not that the asset will be realized. This guidance also requires that deferred tax assets be reduced by a valuation allowance if it is more likely than not that some or all of the deferred tax asset will not be realized. We account for uncertain tax positions by recognizing the financial statement effects of a tax position only when, based upon the technical merits, it is "more-likely-than-not" that the position will be sustained upon examination.
Share-based Equity Compensation	Stock-based Equity Compensation The Company uses the fair value-based method for stock-based equity compensation. Options issued are designated as either an incentive stock or a non-statutory stock option. No option may be granted with a term of more than 10 years from the date of grant. Option awards may depend on achievement of certain performance measures determined by the Compensation Committee of our Board. Shares issued upon option exercise are newly issued common shares. All awards to employees and non-employees are recorded at fair value on the date of the grant and expensed over the period of vesting. The Company uses a binomial option pricing model to estimate the fair value of each stock option at the date of grant. Any consideration paid by the option holders to purchase shares is credited to capital stock.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. We maintain cash balances at financial institutions that are insured by the Federal Deposit Insurance Corporation (“FDIC”) up to $250,000. Deposits held with financial institutions may exceed the $250,000 limit.
Earnings per Share	Earnings per Share Basic earnings per share is calculated by dividing income available to common shareholders by the weighted average number of common stock outstanding and restricted stock grants that vested or are likely to vest during the period. Diluted earnings per share is calculated by dividing income available to common shareholders by the weighted average number of basic common shares outstanding, adjusted to reflect potentially dilutive securities such as common stock warrants and stock options. Diluted earnings per share is calculated using the treasury stock method.