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Intangible Assets - Schedule of Changes in Goodwill (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2015 USD ($)
Goodwill [Roll Forward] |  |
Beginning balance | $ 2,652.8 |
New investments | 29.0 | [1]
Foreign currency translation | (34.5) |
Ending balance | 2,647.3 |
Institutional |  |
Goodwill [Roll Forward] |  |
Beginning balance | 1,159.1 |
New investments | 1.6 | [1]
Foreign currency translation | (21.8) |
Ending balance | 1,138.9 |
Mutual Fund |  |
Goodwill [Roll Forward] |  |
Beginning balance | 1,125.3 |
New investments | 0.0 | [1]
Foreign currency translation | 0.7 |
Ending balance | 1,126.0 |
High Net Worth |  |
Goodwill [Roll Forward] |  |
Beginning balance | 368.4 |
New investments | 27.4 | [1]
Foreign currency translation | (13.4) |
Ending balance | $ 382.4 |
[1] | On April 1, 2015, the Company completed its investment in Baker Street Advisors, LLC.

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