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Equity Method Investments in Affiliates - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Schedule of Equity Method Investments [Line Items] |  |  |  |
Amortization expense during the period | $ 22.0 | $ 28.6 | $ 43.9 | $ 55.3
Acquired Client Relationships |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Weighted average client-acquired relationships |  |  | 12 years |
Finite-lived intangible, future amortization expense, next twelve months | 85.0 |  | $ 85.0 |
Finite-lived intangible, future amortization expense, year 2 | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 3 | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 4 | 50.0 |  | 50.0 |
Finite-lived intangible, future amortization expense, year 5 | 30.0 |  | 30.0 |
Equity Method Investee |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Revenue from equity method investments | 259.2 | 222.4 | 524.8 | 428.5
Net income from equity method investments | 144.4 | 122.9 | $ 293.0 | 234.6
Equity Method Investee | Acquired Client Relationships |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Weighted average client-acquired relationships |  |  | 13 years |
Amortization expense during the period | 24.0 | 14.8 | $ 45.8 | 29.0
Finite-lived intangible, future amortization expense, next twelve months | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 2 | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 3 | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 4 | 85.0 |  | 85.0 |
Finite-lived intangible, future amortization expense, year 5 | 85.0 |  | 85.0 |
Systematica Investment LP and Baring Private Equity Asia | Equity Method Investee | Acquired Client Relationships |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Amortization expense during the period | $ 3.7 | $ 4.5 | $ 7.4 | $ 7.4

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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