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Significant Accounting Policies - Mutual Fund Administration Gross and Net Revenue (Detail) - USD ($) | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Revenue from External Customer [Line Items] |  |
Revenue | $ 39,014,433 | $ 31,925,745
Administration revenue, gross |  |
Revenue from External Customer [Line Items] |  |
Revenue | 6,926,414 | 5,592,658
Fund related expense |  |
Revenue from External Customer [Line Items] |  |
Expenses | 4,466,157 | 3,827,249
Revenue, net of related expenses |  |
Revenue from External Customer [Line Items] |  |
Revenue | 2,460,257 | 1,765,409
Broker Commission |  |
Revenue from External Customer [Line Items] |  |
Revenue | 33,594 | 63,542
Expenses | 48,521 | 60,886
Financing activity, net |  |
Revenue from External Customer [Line Items] |  |
Revenue | (14,927) | 2,656
Mutual fund administration revenue, net |  |
Revenue from External Customer [Line Items] |  |
Revenue | $ 2,445,330 | $ 1,768,065

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