Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases expense	$ 3,500	$ 3,400
Sublease income	1,300	1,500
Lease accrual			$ 2,352
Weighted average discount rate			4.19%
Weighted average remaining lease term			2 years 6 months 18 days
Canada
Lessee, Lease, Description [Line Items]
Operating leases expense	$ 700	$ 800
Lease accrual			$ 600