LEASES - Right-of-use lease assets and lease liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Right-of-use lease assets and lease liabilities
Operating right-of-use assets, net	$ 8,695	$ 4,001
Current portion of operating lease liabilities	1,916	866
Long-term operating lease liabilities	6,884	3,344
Total operating lease liabilities	8,800	4,210
Finance right-of-use assets, net	66	4,778
Current portion of finance lease liabilities	29	4,728
Long-term finance lease liabilities	39	44
Total finance lease liabilities	$ 68	$ 4,772