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Investment Portfolio - Summary of Market Value of Investments (Detail) - USD ($) | Jun. 30, 2016 | Dec. 31, 2015
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Investment Holdings [Line Items] |  |
Equity method investments | $ 26,752,420 |
Deferred compensation investments | 12,552,132 |
Total Investment portfolio | 57,981,889 | $ 52,490,820
Equity securities held in consolidated ETF |  |
Investment Holdings [Line Items] |  |
Trading investments | 17,793,918 |
Equity securities held in consolidated ETF | Total |  |
Investment Holdings [Line Items] |  |
Trading investments | 12,100,000 |
Equity securities held in consolidated ETF | Redeemable Noncontrolling Interest |  |
Investment Holdings [Line Items] |  |
Trading investments | 5,700,000 |
Seed capital investments |  |
Investment Holdings [Line Items] |  |
Trading investments | $ 883,419 |

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