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Equity Method Investments in Affiliates - Aggregate Purchase Price Allocation (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Deferred Tax Liability | $ (702.3) |  | $ (702.3) |  | $ (660.8)
Goodwill | 2,661.8 |  | 2,661.8 |  | 2,628.1
Intangible amortization and impairments | 21.2 | $ 26.9 | 65.1 | $ 82.2 |
Acquired Client Relationships |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Definite-lived acquired client relationships | 441.8 |  | 441.8 |  | 501.9
Indefinite-lived acquired client relationships | 1,025.4 |  | 1,025.4 |  | 995.5
Equity Method Investee | Acquired Client Relationships |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Intangible amortization and impairments | $ 25.9 | $ 14.0 | $ 71.7 | $ 43.0 |
Equity Method Investee | 2016 New Seven Equity Method Investments |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Consideration paid |  |  |  |  | 1,362.3
Tangible assets |  |  |  |  | 2.0
Deferred Tax Liability |  |  |  |  | (91.8)
Goodwill |  |  |  |  | 854.4
Equity Method Investments |  |  |  |  | 1,362.3
Equity Method Investee | 2016 New Seven Equity Method Investments | Acquired Client Relationships |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Definite-lived acquired client relationships |  |  |  |  | 560.8
Indefinite-lived acquired client relationships |  |  |  |  | $ 36.9

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