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Significant Accounting Policies - Textual (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2016 USD ($)
Business Organization And Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from the adoption of ASU 2015-02 (Note 2)					$ 4,031,756
Number of business segment | Segment	1
Allowance for doubtful accounts	$ 0	$ 0
Accounts receivable, related parties	9,400,000	11,600,000
Accumulated depreciation	$ 5,200,000	4,000,000
Client performance period	5 years
Revenue	$ 145,627,748	145,201,729	$ 136,103,075
Advance commissions amortization period	12 months
Variable rate fees
Business Organization And Significant Accounting Policies [Line Items]
Revenue	$ 1,400,000	200,000	6,400,000
Mutual fund administration revenue, net
Business Organization And Significant Accounting Policies [Line Items]
Revenue	10,309,943	12,513,267	14,457,926
Mutual fund administration revenue, net | Affiliated Entity
Business Organization And Significant Accounting Policies [Line Items]
Revenue from related parties	$ 10,300,000	$ 12,500,000	$ 11,900,000
Accounting Standards Update 2015-02
Business Organization And Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from the adoption of ASU 2015-02 (Note 2)					$ 4,000,000
Accounting Standards Update 2016-02 | Scenario, Forecast
Business Organization And Significant Accounting Policies [Line Items]
Right-of-use asset, operating leases				$ 3,600,000
Lease liability, operating leases				$ 3,600,000

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