| **Significant Accounting Policies - Goodwill And Income Taxes (Details) (USD $)** |              |              |         | 12 Months Ended |
|-----------------------------------------------------------------------------------|--------------|--------------|---------|-----------------|
||
| **Goodwill [Line Items]**                                                         |         |         |    |            |
| Deferred Tax Assets, Valuation Allowance                                          | $ 11,100,000 | $ 16,037,000 |    |            |
| Charge to be expensed, if an impairment of all the goodwill became necessary      |         |         |    | $ 8,600,000     |
| Valuation allowance against deferred tax assets (percent)                         |         |         | 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
Deferred Tax Assets, Valuation Allowance, Current and Noncurrent
+ References
No definition available.
+ Details**Name:**dlhc_DeferredTaxAssetsValuationAllowanceCurrentandNoncurrent**Namespace Prefix:**dlhc_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| 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 |