Investments - Schedule of Investments (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 0.3	$ 0.6
Equity securities (other)	105.9	96.0
Other	62.8	61.1
Total investments	169.0	157.7
Less: Short-term investments	(0.3)	(0.6)
Long-term investments	$ 168.7	$ 157.1