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Goodwill and Acquired Client Relationships - Narrative (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Acquired client relationships [Member] |  |  |
Goodwill [Line Items] |  |  |
Impairment | $ 0 | $ 102.2 |
Fair value | 864.0 | 859.4 | 667.6
Weighted average life | 10 years |  |
Future annual amortization expense | 100.0 |  |
Number of future annual periods of amortization expense presented | 5 years |  |
Acquired Client Relationships Mutual Fund Management Contract [Member] |  |  |
Goodwill [Line Items] |  |  |
Impairment | 0 | 102.2 |
Fair value |  | $ 38.2 |
Weighted average annual growth rate |  | 10.00% |
Discount rate |  | 15.00% |

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