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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 | 1 us-gaap_NumberOfOperatingSegments |  |
Allowance for doubtful accounts | $ 0 us-gaap_AllowanceForDoubtfulAccountsReceivable | $ 0 us-gaap_AllowanceForDoubtfulAccountsReceivable |
Fair Value, Transfers Between Level 1, Level 2, or Level 3, Amount | 0 dhil_FairValueTransfersBetweenLevel1Level2orLevel3Amount | 0 dhil_FairValueTransfersBetweenLevel1Level2orLevel3Amount |
Rolling Client Investment Performance Period | 5 years |  |
Advance Commissions Amortization Period | 12 months |  |
Contractual Expense Reimbursement | 1,849,786 dhil_ContractualExpenseReimburseNet | 375,825 dhil_ContractualExpenseReimburseNet | 0 dhil_ContractualExpenseReimburseNet
Liability for Uncertain Tax Positions, Current | 0 us-gaap_LiabilityForUncertainTaxPositionsCurrent | 0 us-gaap_LiabilityForUncertainTaxPositionsCurrent |
Money Market Funds | Mutual Funds | Level 1 Inputs |  |  |
Schedule of Investments [Line Items] |  |  |
Cash equivalent fair value | 31,800,000 dhil_CashEquivalentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / invest_InvestmentIssuerAxis = dhil_MutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_MoneyMarketFundsMember | 16,800,000 dhil_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 | $ 0 us-gaap_PerformanceFees / us-gaap_IncomeStatementLocationAxis = dhil_IncentiveFeesMethodOneMember | $ 0 us-gaap_PerformanceFees / us-gaap_IncomeStatementLocationAxis = dhil_IncentiveFeesMethodOneMember |

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- Definition For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. + References 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) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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