Investments - Summary of Investments (Details) - USD ($) $ in Millions	Mar. 31, 2023	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 0.6	$ 12.6
Equity securities	915.0	928.8
Equity securities (other)	81.4	76.4
Other	56.9	50.8
Total investments	1,053.9	1,068.6
Less: Short-term Investments	(0.6)	(12.6)
Long-term investments	$ 1,053.3	$ 1,056.0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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