Intangible Assets - Schedule of Changes in the Components of Acquired Client Relationships (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Total
Beginning balance, net (in dollars)		$ 1,778.4
Ending balance, net (in dollars)	1,724.7	1,778.4
Acquired Client Relationships
Definite-lived
Beginning balance, gross (in dollars)	1,255.1
Beginning balance, accumulated amortization	(565.0)
Beginning balance, net (in dollars)	690.1
New investments	0
Amortization and impairments	(27.8)
Foreign currency translation	(5.1)
Ending balance, gross (in dollars)	1,250.0
Ending balance, accumulated amortization	(592.8)
Ending balance, net (in dollars)	657.2
Indefinite-lived
Beginning balance, net (in dollars)	1,088.3
New investments	0
Amortization and impairments	0
Foreign currency translation	(20.8)
Ending balance, net (in dollars)	1,067.5
Total
Beginning balance, net (in dollars)	1,778.4
New investments	0
Amortization and impairments	(27.8)
Foreign currency translation	(25.9)
Ending balance, net (in dollars)	$ 1,724.7

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Represents the amount of increase (decrease) to assets, excluding financial assets and goodwill, for foreign currency translation adjustments.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, resulting from a business combination.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

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Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.

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Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, resulting from a business combination.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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