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v3.20.4

Subsequent Events (Details) - Subsequent Event $ / shares in Units, $ in Millions | Feb. 25, 2021 $ / shares | Feb. 02, 2021 USD ($) payment
--- | --- | ---
Subsequent Event [Line Items] |  |
Dividend declared (in dollars per share) | $ / shares | $ 1.00 |
Acquired Funds | Disposal Group, Disposed of by Sale, Not Discontinued Operations |  |
Subsequent Event [Line Items] |  |
Consideration received |  | $ 9.0
Number of additional payments | payment |  | 2
Additional payment amount |  | $ 13.0
Term of additional payment |  | 1 year

X
- Definition Disposal Group, Including Discontinued Operation, Additional Consideration + References No definition available. + Details
Name: | dhil_DisposalGroupIncludingDiscontinuedOperationAdditionalConsideration
Namespace Prefix: | dhil_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Disposal Group, Including Discontinued Operation, Additional Consideration, Term + References No definition available. + Details
Name: | dhil_DisposalGroupIncludingDiscontinuedOperationAdditionalConsiderationTerm
Namespace Prefix: | dhil_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Disposal Group, Including Discontinued Operation, Number Of Additional Payments + References No definition available. + Details
Name: | dhil_DisposalGroupIncludingDiscontinuedOperationNumberOfAdditionalPayments
Namespace Prefix: | dhil_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 + Details
Name: | us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation. + References No definition available. + Details
Name: | us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=dhil_AcquiredFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |