Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 65.3	$ 62.6
Other comprehensive (loss) income	32.8	(14.4)	$ (1.6)
Available-for-sale investments	65.0	61.4
Allowance for credit losses related to our available-for-sale debt securities	0.0
Available-for-sale investments, accumulated unrealized losses	0.6	1.3
Available-for-sale investments, fair value of securities with unrealized losses	34.5	53.7
Unrealized Gain (Loss) on Available-for-Sale Securities
Debt Securities, Available-for-sale [Line Items]
Other comprehensive (loss) income	0.6	$ (1.4)	$ (0.4)
State and Local Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 65.3