Fair Value Of Assets And Liabilities (Narrative) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	May 24, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign time deposits	$ 26.5	$ 26.5		$ 28.1
Equity method investments	338.2	338.2		296.3
Other investments	16.0	$ 16.0		5.9
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed growth rate of Assets under Management (percent)		(9.44%)
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed growth rate of Assets under Management (percent)		5.73%
Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed growth rate of Assets under Management (percent)		(0.54%)
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 2,296.6	$ 2,296.6		$ 2,408.8
Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inputs used to determine liability (percent)	0.0354	0.0354
Put Option
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional put option contract purchased		$ 3.9
Total Return Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative notional amount	$ 162.5	162.5
Market valuation gain recognized	1.6	9.7
Total Return Swap | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative notional amount	127.9	127.9
Market valuation loss recognized	$ (0.4)	$ 11.1
OppenheimerFunds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability acquired			$ 13.6
OppenheimerFunds | Assumed growth rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inputs used to determine liability (percent)	0.28	0.28
OppenheimerFunds | Assumed growth rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inputs used to determine liability (percent)	0.33	0.33
OppenheimerFunds | Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inputs used to determine liability (percent)	0.107	0.107