Investments - Summary of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 0.6	$ 0.6
Equity securities	1,282.0	1,267.6
Other	87.8	95.9
Total investments	1,370.4	1,364.1
Less: Short-term Investments	(0.6)	(0.6)
Long-term investments	$ 1,369.8	$ 1,363.5

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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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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