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Investments - Narrative (Details) - USD ($)	Sep. 30, 2025	Dec. 31, 2024
Schedule of Equity Method Investments [Line Items]
Equity method investment, deferred compensation plans	$ 10,800,000
Carrying value of investment	$ 113,073,310	$ 94,023,248
DHMF
Schedule of Equity Method Investments [Line Items]
Ownership percentage	81.00%
Carrying value of investment	$ 23,700,000
Diamond Hill International Fund
Schedule of Equity Method Investments [Line Items]
Ownership percentage	22.00%
Diamond Hill Core Plus Bond Fund
Schedule of Equity Method Investments [Line Items]
Ownership percentage	40.00%
Diamond Hill Large Cap Concentrated ETF
Schedule of Equity Method Investments [Line Items]
Ownership percentage	45.00%

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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