Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases expense	$ 3,500
Sublease income	$ 1,300
Lease accrual			$ 1,415	$ 2,352
Weighted average discount rate			4.04%
Weighted average remaining lease term			1 year 9 months
Canada
Lessee, Lease, Description [Line Items]
Operating leases expense		$ 700
Lease accrual			$ 400	$ 600