Leases - Components of lease costs (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Option to extend	true
Finance lease cost
Amortization of right-of-use assets	$ 2,056
Interest on lease liabilities	971
Operating lease cost	5,284
Total lease costs	$ 8,311
Maximum
Lessee, Lease, Description [Line Items]
Lease term	20 years