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Intangible Assets - Schedule of Changes in Goodwill (Details) $ in Millions | 6 Months Ended
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Jun. 30, 2015 USD ($)
Goodwill [Roll Forward] |  |
Beginning balance |  | $ 2,652.8
New investments | [1] | 29.0
Foreign currency translation |  | (11.8)
Ending balance |  | 2,670.0
Institutional |  |
Goodwill [Roll Forward] |  |
Beginning balance |  | 1,159.1
New investments | [1] | 1.6
Foreign currency translation |  | (13.3)
Ending balance |  | 1,147.4
Mutual Fund |  |
Goodwill [Roll Forward] |  |
Beginning balance |  | 1,125.3
New investments | [1] | 0.0
Foreign currency translation |  | 10.6
Ending balance |  | 1,135.9
High Net Worth |  |
Goodwill [Roll Forward] |  |
Beginning balance |  | 368.4
New investments | [1] | 27.4
Foreign currency translation |  | (9.1)
Ending balance |  | $ 386.7
[1] | On April 1, 2015, the Company completed its investment in Baker Street Advisors, LLC.

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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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