Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 53.3	$ 56.4
Other comprehensive (loss) income	(1.6)	3.7	$ (17.2)
Available-for-sale investments	54.0	57.7
Allowance for credit losses related to our available-for-sale debt securities	0.0
Available-for-sale investments, accumulated unrealized losses	0.1	0.1
Available-for-sale investments, fair value of securities with unrealized losses	12.2	6.1
Unrealized Gain (Loss) on Available-for-Sale Securities
Debt Securities, Available-for-sale [Line Items]
Other comprehensive (loss) income	(0.4)	$ 0.4	$ 2.6
State and Local Municipal Bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 53.3