SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in the balances of intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance	$ 2,883	$ 3,334
Acquisition of PCRS	2,081
Amortization	(703)	(451)
Amortization of intangible assets ending balance	4,261	2,883
Trademarks [Member]
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance	1,072	1,150
Acquisition of PCRS	460
Amortization	(103)	(78)
Amortization of intangible assets ending balance	1,429	1,072
Client Relationships [Member]
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance	1,670	1,918
Acquisition of PCRS	1,280
Amortization	(380)	(248)
Amortization of intangible assets ending balance	2,570	1,670
Noncompete Agreements [Member]
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance	131	178
Acquisition of PCRS	220
Amortization	(93)	(47)
Amortization of intangible assets ending balance	258	131
Backlog [Member]
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance		72
Acquisition of PCRS	121
Amortization	(121)	(72)
Patents [Member]
Finite-lived Intangible Assets [Roll Forward]
Amortization of intangible assets beginning balance	10	16
Acquisition of PCRS	0
Amortization	(6)	(6)
Amortization of intangible assets ending balance	$ 4	$ 10