OTHER COMPREHENSIVE INCOME (LOSS) (Details) - Summary of other comprehensive income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	$ (9,344)	$ (39,454)	$ 34,384
Tax	3,168	7,650	(8,015)
Net of tax	(6,176)	(31,804)	26,369
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	5,601	(8,460)	9,403
Tax	0	0	0
Net of tax	5,601	(8,460)	9,403
Pension and other defined benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	(14,955)	(30,581)	24,081
Tax	3,171	7,526	(7,700)
Net of tax	(11,784)	(23,055)	16,381
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pre-tax	10	(413)	900
Tax	(3)	124	(315)
Net of tax	$ 7	$ (289)	$ 585