Investments - Summary of Investments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 0.3	$ 0.6
Equity securities (other)	105.8	96.0
Other	62.5	61.1
Total investments	168.6	157.7
Less: Short-term Investments	(0.3)	(0.6)
Long-term investments	$ 168.3	$ 157.1