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Significant Accounting Policies - Mutual Fund Administration Gross and Net Revenue (Detail) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Revenue from External Customer [Line Items] |  |  |  |
Revenue | $ 33,545,016 | $ 35,927,715 | $ 66,124,389 | $ 73,709,717
Administrative revenue, gross |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | 5,519,437 | 5,993,719 | 10,922,165 | 12,601,056
Fund related expense |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Expenses | 3,491,604 | 3,595,555 | 6,841,145 | 7,063,880
Revenue, net of related expense |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | 2,027,833 | 2,398,164 | 4,081,020 | 5,537,176
Broker Commission |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | 53,782 | 83,380 | 118,994 | 179,858
Expenses | 47,271 | 80,102 | 99,014 | 164,880
Financing activity, net |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | 6,511 | 3,278 | 19,980 | 14,978
Mutual fund administration, net |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | $ 2,034,344 | $ 2,401,442 | $ 4,101,000 | $ 5,552,154

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