| **Commitment and Contingencies (Details)**                                           | Dec. 31, 2024 USD ($) | Apr. 27, 2015 USD ($) ft² loan_extension | Sep. 30, 2015 USD ($) | Sep. 30, 2014 USD ($) |
|--------------------------------------------------------------------------------------|-----------------------|-----------------------------------------------|-----------------------|-----------------------|
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                     |                  |                                          |                  |                  |
| Area of Real Estate Property | ft²                                              |                  | 12,275                                        |                  |                  |
| Accrued workers compensation insurance                                               |                  |                                          | $ 945,000             | $ 767,000             |
| Lessee Leasing Arrangements, Operating Leases, Term of Contract                      |                  | 8 years 8 months 12 days                      |                  |                  |
| Operating Leases, Rent Expenses Per Month, Net                                       |                  | $ 20,970                                      |                  |                  |
| Operating Lease, Rent Expense Excused                                                |                  | $ 120,000                                     |                  |                  |
| Leesee Leasing Arrangement, Operating Leases, Term of Excused Rent                   |                  | 8 months                                      |                  |                  |
| Unoccupied Area of Real Estate | ft²                                            |                  | 4,000                                         |                  |                  |
| Lessee Leasing Arrangements, Operating Leases, Initial Term of Contract              |                  | 2 years                                       |                  |                  |
| Lessee Leasing Arrangements, Operating Leases, Number of Extensions | loan_extension |                  | 1                                             |                  |                  |
| Lessee Leasing Arrangements, Operating Leases, Renewal Term                          |                  | 5 years                                       |                  |                  |
| Forecast                                                                             |                  |                                          |                  |                  |
| **Accounts, Notes, Loans and Financing Receivable [Line Items]**                     |                  |                                          |                  |                  |
| Operating Leases, Rent Expenses Per Month, Net                                       | $ 25,552              |                                          |                  |                  |

| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Leesee Leasing Arrangement, Operating Leases, Term of Excused Rent
+ References
No definition available.
+ Details**Name:**dlhc_LeeseeLeasingArrangementOperatingLeasesTermofExcusedRent**Namespace Prefix:**dlhc_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Lessee Leasing Arrangements, Operating Leases, Initial Term of Contract
+ References
No definition available.
+ Details**Name:**dlhc_LesseeLeasingArrangementsOperatingLeasesInitialTermofContract**Namespace Prefix:**dlhc_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Lessee Leasing Arrangements, Operating Leases, Number of Extensions
+ References
No definition available.
+ Details**Name:**dlhc_LesseeLeasingArrangementsOperatingLeasesNumberofExtensions**Namespace Prefix:**dlhc_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Operating Lease, Rent Expense Excused
+ References
No definition available.
+ Details**Name:**dlhc_OperatingLeaseRentExpenseExcused**Namespace Prefix:**dlhc_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Operating Leases, Rent Expenses Per Month, Net
+ References
No definition available.
+ Details**Name:**dlhc_OperatingLeasesRentExpensesPerMonthNet**Namespace Prefix:**dlhc_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Unoccupied Area of Real Estate
+ References
No definition available.
+ Details**Name:**dlhc_UnoccupiedAreaofRealEstate**Namespace Prefix:**dlhc_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
+ Details**Name:**us-gaap_AccountsNotesAndLoansReceivableLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Area of a real estate property.
+ References
No definition available.
+ Details**Name:**us-gaap_AreaOfRealEstateProperty**Namespace Prefix:**us-gaap_**Data Type:**num:areaItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer).
+ References
No definition available.
+ Details**Name:**us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
No definition available.
+ Details**Name:**us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm**Namespace Prefix:**us-gaap_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
No definition available.
+ Details**Name:**us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |