Fair Value Of Assets And Liabilities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	$ 470.2		$ 426.1
Other investments	10.3		$ 10.5
Total Return Swap | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative notional amount	344.4
Market valuation gain (loss) recognized	$ 9.2	$ (31.4)