LEASES - Reconciliation of future undiscounted cash flows to the operating and finance lease liabilities, and the related ROU assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Operating leases
2021 (excluding the six months ended March 31, 2021)	$ 1,378
2022	5,093
2023	4,324
2024	3,677
2025 and thereafter	21,976
Total minimum lease payments	36,448
Less: amounts representing interest	5,460
Present value of net minimum lease payments	30,988
Less: current portion of lease obligations	4,530
Non-current portion of lease obligations	26,458	$ 16,785
ROU assets	30,426	$ 21,390
Finance leases
2021 (excluding the six months ended March 31, 2021)	739
2022	3,015
2023	3,098
2024	3,181
2025 and thereafter	28,285
Total minimum lease payments	38,318
Less: amounts representing interest	9,320
Present value of net minimum lease payments	28,998
Less: current portion of lease obligations	1,859
Non-current portion of lease obligations	27,139
ROU assets	$ 24,689
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