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Investment Portfolio - Summary of Market Value of Investments (Detail) - USD ($) | Mar. 31, 2019 | Dec. 31, 2018
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Investment Holdings [Line Items] |  |
Company sponsored equity method investments | $ 46,260,613 | $ 16,339,649
Total Investments | 164,791,720 | 203,488,217
Securities held in Consolidated Funds |  |
Investment Holdings [Line Items] |  |
Fair value investments | 78,997,408 | 153,730,480
Securities held in Consolidated Funds | Parent |  |
Investment Holdings [Line Items] |  |
Fair value investments | 48,800,000 | 84,700,000
Securities held in Consolidated Funds | Redeemable Noncontrolling Interest |  |
Investment Holdings [Line Items] |  |
Fair value investments | 30,200,000 | 69,000,000
Company sponsored investments |  |
Investment Holdings [Line Items] |  |
Fair value investments | $ 39,533,699 | $ 33,418,088

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