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Goodwill and Acquired Client Relationships - Schedule of Changes in, and the Components of, Acquired Client Relationships (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014
Net Book Value |  |
Net book value balance at the beginning of the period | $ 1,778.4 |
Net book value balance at the end of the period | 1,686.4 | $ 1,778.4
Customer Relationships |  |
Definite-lived |  |
Gross book value balance at the beginning of the period | 1,255.1 | 1,039.5
Accumulated amortization balance at the beginning of the period | (565.0) | (442.8)
Net book value balance at the beginning of the period | 690.1 | 596.7
New Investments | 52.5 | 220.3
Amortization and impairments | (115.4) | (122.2)
Foreign currency translation | (5.8) | (4.7)
Gross book value balance at the end of the period | 1,301.8 | 1,255.1
Accumulated amortization balance at the end of the period | (680.4) | (565.0)
Net book value balance at the end of the period | 621.4 | 690.1
Indefinite-lived |  |
Net book value balance at the beginning of the period | 1,088.3 | 864.0
New investments | 0.0 | 244.7
Amortization and Impairment | 0.0 | 0.0
Foreign currency translation | (23.3) | (20.4)
Net book value balance at the end of the period | 1,065.0 | 1,088.3
Net Book Value |  |
Net book value balance at the beginning of the period | 1,778.4 | 1,460.7
New investments | 52.5 | 465.0
Amortization and Impairment | (115.4) | (122.2)
Foreign currency translation | (29.1) | (25.1)
Net book value balance at the end of the period | $ 1,686.4 | $ 1,778.4

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