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v2.4.0.6

Operating Leases (Details Textual) | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 sqft Location
Operating Leases (Textual) [Abstract] |  |
Area of operating lease |  | 25,500
Number of office space locations |  | 2
Operating expenses | 9.80 | 9.69

X
- Definition Operating expenses per square foot. + References No definition available. + Details
Name: | dhil_OperatingExpensesPerSquareFoot
Namespace Prefix: | dhil_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Area leased by company as of balance sheet date. + References No definition available. + Details
Name: | dhil_OperatingLeases
Namespace Prefix: | dhil_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | dhil_OperatingLeasesTextualAbstract
Namespace Prefix: | dhil_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of units (items of property) under operating lease arrangements. + References No definition available. + Details
Name: | us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNumberOfUnits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant