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Significant Accounting Policies - Mutual Fund Administration Revenue (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue from External Customer [Line Items]
Total revenue	$ 145,627,748	$ 145,201,729	$ 136,103,075
Administration revenue, gross
Revenue from External Customer [Line Items]
Total revenue	24,463,538	26,219,881	26,664,635
12b-1/Service Fees And Commissions
Revenue from External Customer [Line Items]
Total revenue	0	0	6,360,400
Expenses	0	0	(5,660,430)
Fund related expense
Revenue from External Customer [Line Items]
Expenses	(14,183,370)	(13,748,445)	(12,937,067)
Revenue, net of related expenses
Revenue from External Customer [Line Items]
Total revenue	10,280,168	12,471,436	14,427,538
Broker Commission
Revenue from External Customer [Line Items]
Total revenue	332,680	416,614	691,228
Expenses	(302,905)	(374,783)	(660,840)
Financing activity, net
Revenue from External Customer [Line Items]
Total revenue	29,775	41,831	30,388
Mutual fund administration revenue, net
Revenue from External Customer [Line Items]
Total revenue	$ 10,309,943	$ 12,513,267	$ 14,457,926

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