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Significant Accounting Policies - Narrative (Detail) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 USD ($) Segment | Mar. 31, 2018 USD ($) | Dec. 31, 2018 USD ($)
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Number of business segment | Segment | 1 |  |
Cash Held in Consolidated ETF | $ 22,700,000 |  |
Cash held by noncontrolling shareholders | 10,000,000 |  |
Allowance for doubtful accounts | 0 |  | $ 0
Accounts receivable, related parties | $ 10,100,000 |  | $ 9,400,000
Client performance period | 5 years |  |
Revenue | $ 32,579,373 | $ 37,782,002 |
Advance commissions amortization period | 12 months |  |
Variable Rate Fees |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Revenue | $ 0 | $ 0 |

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