Leases - Components of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating lease cost	$ 1,457	$ 2,146	$ 2,435
Less: sublease income	(515)	(685)	(706)
Variable lease cost	369	457	443
Short-term lease cost	1,864	1,643	1,281
Total lease cost	$ 3,175	$ 3,561	$ 3,453