INCOME TAXES - Effective income tax rate (Details)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
INCOME TAXES
Federal statutory income tax rate (as a percent)	21.00%	21.00%
Increases (decreases):
State and local income taxes, net of Federal tax benefit, if applicable	0.10%	(0.10%)
Other nondeductible expenses	(24.30%)	1.30%
Goodwill	3.30%	(3.10%)
Valuation allowance changes from activity	3.30%	(22.30%)
Valuation allowance changes from acquisitions	(81.40%)
Effective income tax rate	(78.00%)	(3.20%)