Investments - (Schedule of Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Allowance for credit losses as of the beginning of the period	$ 8.6	$ 8.5	$ 10.0	$ 3.2
Reductions for writedowns			(3.0)
Reductions for disposals	(1.3)		(1.6)
Additional credit losses on investments for which an allowance was previously recognized	0.2		2.1	5.4
Recoveries				(0.1)
Allowance for credit losses as of the end of the period	$ 7.5	$ 8.5	$ 7.5	$ 8.5