OTHER COMPREHENSIVE INCOME (LOSS) - Accumulated other comprehensive income (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
SHAREHOLDERS’ EQUITY	$ 807,158	$ 700,151	$ 477,763	$ 474,391
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
SHAREHOLDERS’ EQUITY	(19,250)	(25,683)
Pension and other defined benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
SHAREHOLDERS’ EQUITY	(28,802)	(46,598)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
SHAREHOLDERS’ EQUITY	2,075	189
AOCI attributable to parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
SHAREHOLDERS’ EQUITY	$ (45,977)	$ (72,092)	$ (65,916)	$ (34,112)