Intangible Assets (Schedule of finite-lived intangible assets by major class) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	$ 7,512.6	$ 7,499.2
Accumulated Amortization	(207.0)	(140.9)
Net Book Value	7,305.6	7,358.3
Management contracts
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	319.9	319.3
Accumulated Amortization	(118.7)	(84.5)
Net Book Value	201.2	234.8
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	99.2	98.6
Accumulated Amortization	(50.9)	(31.7)
Net Book Value	48.3	66.9
Other
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	110.8	112.2
Accumulated Amortization	(37.4)	(24.7)
Net Book Value	73.4	87.5
Management contracts
Finite-Lived Intangible Assets [Line Items]
Gross Book Value	$ 6,982.7	$ 6,969.1