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Equity Method Investments in Affiliates (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Jan. 04, 2016
Schedule of Equity Method Investments |  |  |  |
Amortization period for tax deductible goodwill | 15 years |  |  |
Amortization expense during the period | $ 115.4 | $ 122.2 | $ 128.2 |
Annual amortization expense Year 1 | 37.1 |  |  |
Annual amortization expense Year 2 | 37.1 |  |  |
Annual amortization expense Year 3 | 37.1 |  |  |
Annual amortization expense Year 4 | 37.1 |  |  |
Annual amortization expense Year 5 | 37.1 |  |  |
Undistributed earnings from equity method investments | $ 101.5 |  |  |
Acquired Client Relationships Under Equity Method Investments |  |  |  |
Schedule of Equity Method Investments |  |  |  |
Weighted average life | 14 years |  |  |
Amortization expense during the period | $ 34.3 | $ 32.3 |  |
Ivory Investment Management, L.P. | Acquired Client Relationships Under Equity Method Investments |  |  |  |
Schedule of Equity Method Investments |  |  |  |
Acquired client relationships | 200.0 |  |  |
Payment of contingent payment liability | $ 23.3 |  |  |
Abax Investments (Pty) Ltd and Ivory Investment Management, L.P. [Member] | Acquired Client Relationships Under Equity Method Investments |  |  |  |
Schedule of Equity Method Investments |  |  |  |
Amortization period for tax deductible goodwill | 15 years |  |  |
Subsequent Event | Systematica Investment LP and Baring Private Equity Asia | Acquired Client Relationships Under Equity Method Investments |  |  |  |
Schedule of Equity Method Investments |  |  |  |
Acquired client relationships |  |  |  | $ 550.0

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