Intangible Assets - Schedule of Finite-lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (154.7)	$ (140.9)
Gross Book Value	7,479.8	7,499.2
Net Book Value	7,325.1	7,358.3
Management contracts
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	319.2	319.3
Accumulated Amortization	(92.7)	(84.5)
Net Book Value	226.5	234.8
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	92.5	98.6
Accumulated Amortization	(35.0)	(31.7)
Net Book Value	57.5	66.9
Other
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	106.1	112.2
Accumulated Amortization	(27.0)	(24.7)
Net Book Value	79.1	87.5
Management contracts
Finite-Lived Intangible Assets [Line Items]
Book Value	$ 6,962.0	$ 6,969.1