Investments - (Schedule of Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Allowance for credit losses as of the beginning of the period	$ 10.0	$ 3.2
Reductions for disposals	(0.3)
Additional credit losses on investments for which an allowance was previously recognized		4.1
Recoveries		(0.1)
Allowance for credit losses as of the end of the period	$ 9.7	$ 7.2