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Significant Accounting Policies - Narrative (Detail) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2016 USD ($) Segment | Mar. 31, 2015 USD ($) | Dec. 31, 2015 USD ($)
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Cumulative-effect adjustment from the adoption of ASU 2015-02 (Note 2) | $ 4,031,756 | $ 0 |
Number of business segment | Segment | 1 |  |
Allowance for doubtful accounts | $ 0 |  | $ 0
Accounts Receivable, Related Parties | 9,100,000 |  | 9,200,000
Transfers between fair value levels | $ 0 |  | 0
Client Performance Period | 5 years |  |
Advance commissions amortization period | 12 months |  |
Liability for Uncertain Tax Positions, Current | $ 0 |  | $ 0
Alternative Investments, Fair Value Disclosure | 1,400,000 |  |
Level 1 Inputs |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Value of Investment | 95,736,885 |  |
Mutual Funds | Money Market Funds | Level 1 Inputs |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Cash Equivalent Fair Value | 41,000,000 |  |
Incentive Fees Method One [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Performance Incentive Fees | 0 | 0 |
Investment Advisory Services [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Revenue from Related Parties | 20,300,000 | 18,500,000 |
Mutual fund administrative services [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Revenue from Related Parties | $ 2,700,000 | $ 3,100,000 |
Class A [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Rate of Administrative Service Fees | 0.24% |  | 0.24%
Class C [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Rate of Administrative Service Fees | 0.24% |  | 0.24%
Class Y [Member] |  |  |
Business Organization And Significant Accounting Policies [Line Items] |  |  |
Rate of Administrative Service Fees | 0.10% |  | 0.10%

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