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Goodwill and Acquired Client Relationships - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2019 | Mar. 31, 2018
Intangible Assets |  |
Amortization and impairment expenses of intangible assets | $ 29.6 | $ 23.2
Acquired Client Relationships |  |
Estimated Future Amortization Expense of Finite-Lived Intangibles |  |
Finite-lived intangible, future amortization expense in 2019 | 120.0 |
Finite-lived intangible, future amortization expense in 2020 | 90.0 |
Finite-lived intangible, future amortization expense in 2021 | 65.0 |
Finite-lived intangible, future amortization expense in 2022 | 65.0 |
Finite-lived intangible, future amortization expense in 2023 | 65.0 |
Acquired Client Relationships | Intangible amortization and impairments |  |
Intangible Assets |  |
Amortization and impairment expenses of intangible assets | $ 29.6 | $ 23.2

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- Definition Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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