LEASES - Reconciliation of future undiscounted cash flows to the operating and finance lease liabilities, and the related ROU assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Operating leases
2021 (excluding the six months ended March 31, 2021)	$ 2,732
2022	4,907
2023	3,984
2024	2,438
2025 and thereafter	7,173
Total minimum lease payments	21,234
Less: amounts representing interest	1,894
Present value of net minimum lease payments	19,340
Less: current portion of lease obligations	4,839
Non-current portion of lease obligations	14,501	$ 16,785
ROU assets	18,929	$ 21,390
Finance leases
2021 (excluding the six months ended March 31, 2021)	1,473
2022	3,015
2023	3,098
2024	3,181
2025 and thereafter	28,285
Total minimum lease payments	39,052
Less: amounts representing interest	9,625
Present value of net minimum lease payments	29,427
Less: current portion of lease obligations	2,001
Non-current portion of lease obligations	27,426
ROU assets	$ 25,182
Location of operating lease liabilities included on Consolidated Balance Sheets	us-gaap:OtherAccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent
Location of finance lease liabilities included on Consolidated Balance Sheets	us-gaap:OtherAccruedLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent
Location of operating lease ROU assets included on Consolidated Balance Sheets	ROU assets
Location of finance lease ROU assets included on Consolidated Balance Sheets	us-gaap:PropertyPlantAndEquipmentNet