Investment and Other Income, net - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Other Income and Expenses [Abstract]
Net gains (losses) recognized on equity securities measured at fair value and trading debt securities	$ 9.5	$ 13.1	$ 86.1	$ 78.2