Investment and Other Income (Losses), Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Other Income and Expenses [Abstract]
Net gains (losses) recognized on equity securities measured at fair value and trading debt securities	$ 46.5	$ (2.6)	$ (0.1)

Amount of unrealized gain (loss) on investment in debt and equity securities.

No definition available.

Name:	us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration