Consolidated Investment Products (Beginning And Ending Fair Value Measurements For Level 3 Assets And Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 78.6	$ 11.8
Purchases	0.0	58.9
Deconsolidation of CIP	(89.4)	0.0
Gains and losses included in the Consolidated Statements of Income	10.8	7.9
Ending balance	0.0	78.6
Deconsolidated VIEs | Significant Unobservable Inputs (Level 3)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Gains and losses included in the Consolidated Statements of Income	$ 10.8	$ 7.9