| **LIQUIDITY AND SIGNIFICANT ACCOUNTING POLICIES: (Goodwill And Income Taxes) (Details) (USD $)In Millions, unless otherwise specified** |         |         | 3 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------|---------|---------|----------------|
||
| **Goodwill [Line Items]**                                                                                                               |    |    |           |
| Charge to be expensed, if an impairment of all the goodwill became necessary                                                            |    |    | $ 8.6          |
| Valuation allowance against deferred tax assets (percent)                                                                               | 100.00% | 100.00% |           |

| X                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the amount of loss which is contingent in nature related to write down of goodwill.
+ References
No definition available.
+ Details**Name:**dlhc_ContingentGoodwillImpairmentLoss**Namespace Prefix:**dlhc_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the percentage of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.
+ References
No definition available.
+ Details**Name:**dlhc_DeferredTaxAssetsValuationAllowancePercentage**Namespace Prefix:**dlhc_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_GoodwillLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |