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Investment Portfolio - Summary of Market Value of Investments (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Company sponsored equity method investments	$ 29,753,573	$ 41,338,046
Total Investment portfolio	129,743,381	108,015,635
Securities held in Consolidated Funds
Investment Holdings [Line Items]
Trading investments	65,106,741	57,355,471
Securities held in Consolidated Funds | Parent
Investment Holdings [Line Items]
Trading investments	41,900,000	42,600,000
Securities held in Consolidated Funds | Redeemable Noncontrolling Interest
Investment Holdings [Line Items]
Trading investments	23,200,000	14,700,000
Company sponsored investments
Investment Holdings [Line Items]
Trading investments	$ 34,883,067	$ 9,322,118

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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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.

+ References

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))
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26626-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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-Name Accounting Standards Codification
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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