INCOME TAXES - Schedule of effective income tax rate reconciliation (Details)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
U.S. Federal income tax provision rate	21.00%	21.00%	21.00%
State and local taxes, net of Federal benefit	4.70%	7.80%	9.10%
Non-U.S. taxes - foreign permanent items and taxes	3.00%	4.20%	3.10%
Change in tax contingency reserves	0.20%	0.20%	(1.10%)
Impact of foreign rate change on deferred tax balances	2.80%	0.00%	0.00%
Tax Reform-Repatriation of Foreign Earnings and GILTI	0.40%	0.30%	1.60%
Change in valuation allowance	0.40%	(2.60%)	5.00%
Other non-deductible/non-taxable items, net	0.004	0.013	0.059
Non-deductible officer's compensation	4.00%	5.40%	8.20%
Research and U.S. foreign tax credits	(0.10%)	1.40%	(6.40%)
Share based compensation	(2.00%)	0.00%	0.60%
Other	1.10%	(0.80%)	(2.10%)
Effective tax provision (benefit) rate	35.90%	38.20%	44.90%