Investments - Summary of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 0.6	$ 0.6
Equity securities (other)	98.5	96.0
Other	63.4	61.1
Total investments	162.5	157.7
Less: Short-term Investments	(0.6)	(0.6)
Long-term investments	$ 161.9	$ 157.1

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 without readily determinable fair value.

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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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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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Amount of investments classified as other.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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