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Significant Accounting Policies (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Number of business segment	1us-gaap_NumberOfOperatingSegments
Allowance for doubtful accounts	$ 0us-gaap_AllowanceForDoubtfulAccountsReceivable	$ 0us-gaap_AllowanceForDoubtfulAccountsReceivable
Fair Value, Transfers Between Level 1, Level 2, or Level 3, Amount	0dhil_FairValueTransfersBetweenLevel1Level2orLevel3Amount	0dhil_FairValueTransfersBetweenLevel1Level2orLevel3Amount
Rolling Client Investment Performance Period	5 years
Advance Commissions Amortization Period	12 months
Contractual Expense Reimbursement	1,849,786dhil_ContractualExpenseReimburseNet	375,825dhil_ContractualExpenseReimburseNet	0dhil_ContractualExpenseReimburseNet
Liability for Uncertain Tax Positions, Current	0us-gaap_LiabilityForUncertainTaxPositionsCurrent	0us-gaap_LiabilityForUncertainTaxPositionsCurrent
Money Market Funds | Mutual Funds | Level 1 Inputs
Schedule of Investments [Line Items]
Cash equivalent fair value	31,800,000dhil_CashEquivalentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / invest_InvestmentIssuerAxis = dhil_MutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember	16,800,000dhil_CashEquivalentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / invest_InvestmentIssuerAxis = dhil_MutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember
Incentive Fees Under Method One
Schedule of Investments [Line Items]
Performance Fees	$ 0us-gaap_PerformanceFees / us-gaap_IncomeStatementLocationAxis = dhil_IncentiveFeesMethodOneMember	$ 0us-gaap_PerformanceFees / us-gaap_IncomeStatementLocationAxis = dhil_IncentiveFeesMethodOneMember

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.4)

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Topic 210

-SubTopic 10

-Section S99

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Amount of revenue earned by the entity based on the investment results achieved. Excludes fees based upon a percentage of the assets under management not performance-related.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

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