Investments - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Schedule Of Available For Sale Securities [Line Items]
Realized gains (losses)	$ (4,000)	$ (1,000)	$ (22,000)	$ (1,000)
Gain on investments, net	$ (4,000)	1,727,000	$ (22,000)	1,996,000
Debt Security
Schedule Of Available For Sale Securities [Line Items]
Gain on investments, net		$ 1,700,000		$ 2,000,000.0