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Significant Accounting Policies - Revenues From Contracts with Customers (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 36,294,930	$ 33,990,503
Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	34,351,793	32,042,459
Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	1,943,137	1,948,044
Diamond Hill Funds
Disaggregation of Revenue [Line Items]
Revenue	24,038,320	23,331,587
Diamond Hill Funds | Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	22,095,183	21,383,543
Diamond Hill Funds | Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	1,943,137	1,948,044
Separately managed accounts
Disaggregation of Revenue [Line Items]
Revenue	6,779,253	6,264,361
Separately managed accounts | Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	6,779,253	6,264,361
Separately managed accounts | Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	0	0
Other pooled vehicles
Disaggregation of Revenue [Line Items]
Revenue	2,770,713	2,131,681
Other pooled vehicles | Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	2,770,713	2,131,681
Other pooled vehicles | Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	0	0
Model delivery
Disaggregation of Revenue [Line Items]
Revenue	1,309,634	1,361,753
Model delivery | Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	1,309,634	1,361,753
Model delivery | Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	0	0
Collective investment trusts
Disaggregation of Revenue [Line Items]
Revenue	1,397,010	901,121
Collective investment trusts | Investment advisory
Disaggregation of Revenue [Line Items]
Revenue	1,397,010	901,121
Collective investment trusts | Mutual fund administration, net
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0

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