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Goodwill and Acquired Client Relationships (Tables) | 12 Months Ended
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Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract] |
Schedule of Changes in Goodwill | The following tables present the changes in the Company’s consolidated Affiliates’ Goodwill and components of Acquired client relationships (net):
|  | Goodwill
|  | 2016 |  | 2017
Balance, as of January 1, |  | $ | 2,668.4 |  |  | $ | 2,628.1 |
Foreign currency translation |  | (40.3 | ) |  | 34.4 |
Balance, as of December 31, |  | $ | 2,628.1 |  |  | $ | 2,662.5 |
Schedule of Changes in, and the Components of, Acquired Client Relationships |
|  | Acquired Client Relationships (Net)
|  | Definite-lived |  | Indefinite-lived |  | Total
|  | Gross Book Value |  | Accumulated Amortization |  | Net Book Value |  | Net Book Value |  | Net Book Value
Balance, as of December 31, 2015 |  | $ | 1,301.8 |  |  | $ | (680.4 | ) |  | $ | 621.4 |  |  | $ | 1,065.0 |  |  | $ | 1,686.4 |
Intangible amortization and impairments |  | — |  |  | (107.7 | ) |  | (107.7 | ) |  | (2.5 | ) |  | (110.2 | )
Foreign currency translation |  | (11.8 | ) |  | — |  |  | (11.8 | ) |  | (67.0 | ) |  | (78.8 | )
Balance, as of December 31, 2016 |  | $ | 1,290.0 |  |  | $ | (788.1 | ) |  | $ | 501.9 |  |  | $ | 995.5 |  |  | $ | 1,497.4 |
Intangible amortization and impairments |  | — |  |  | (86.4 | ) |  | (86.4 | ) |  | — |  |  | (86.4 | )
Foreign currency translation |  | 5.5 |  |  | — |  |  | 5.5 |  |  | 33.2 |  |  | 38.7 |
Balance, as of December 31, 2017 |  | $ | 1,295.5 |  |  | $ | (874.5 | ) |  | $ | 421.0 |  |  | $ | 1,028.7 |  |  | $ | 1,449.7 |

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- Definition Tabular disclosure of intangibles assets, in total and by major class, including the gross carrying amount and accumulated amortization. A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company. + References No definition available. + Details
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- Definition Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule. + 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 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 + Details
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