Leases - Components of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease cost	$ 2,435	$ 2,389
Less: sublease income	(706)	(555)
Variable lease cost	443	351
Short-term lease cost	1,281	677
Total lease cost	$ 3,453	$ 2,862