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Investment Portfolio - Summary of Cash and Cash Equivalent Investments, Excluding Money Market Funds (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Summary of market value of investments
Total Investment Portfolio	$ 52,490,820	$ 45,427,456
Corporate Investments [Member]
Summary of market value of investments
Total Investment Portfolio	44,529,408	39,748,692
Corporate Investments [Member] | Diamond Hill Mid Cap Fund
Summary of market value of investments
Total Investment Portfolio	10,749,860	10,729,930
Corporate Investments [Member] | Diamond Hill Research Opportunities Fund
Summary of market value of investments
Total Investment Portfolio	10,306,395	13,143,281
Corporate Investments [Member] | Diamond Hill Financial Long-Short Fund
Summary of market value of investments
Total Investment Portfolio	967,721	1,222,892
Corporate Investments [Member] | Diamond Hill Valuation-Weighted 500 ETF
Summary of market value of investments
Total Investment Portfolio	11,221,323	0
Corporate Investments [Member] | Diamond Hill Valuation-Weighted 500, L.P.
Summary of market value of investments
Total Investment Portfolio	0	3,398,035
Corporate Investments [Member] | Diamond Hill High Yield Fund, L.P.
Summary of market value of investments
Total Investment Portfolio	9,874,099	9,764,814
Corporate Investments [Member] | Diamond Hill Global Fund, L.P.
Summary of market value of investments
Total Investment Portfolio	1,410,010	1,489,740
Investments in Deferred Compensation Plans [Member]
Summary of market value of investments
Total Investment Portfolio	$ 7,961,412	$ 5,678,764

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Market value of investments.

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No definition available.

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Sum of the carrying amounts as of the balance sheet date of all investments.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(h))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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