Investments - Summary of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 6.0	$ 0.0
Equity securities (other)	106.0	106.0
Other	59.0	63.0
Total investments	171.0	169.0
Less: Short-term Investments	(6.0)	0.0
Long-term investments	$ 165.0	$ 169.0