ACCUMULATED OTHER COMPREHENSIVE INCOME - Components of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	$ 636,548	$ 610,807
Fair value of derivatives, tax	504	1,908
Pension liability, tax	11,638	26,988
Cumulative foreign currency translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	(155,251)	(151,881)
Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	(1,558)	(5,884)
Minimum pension liabilities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	(35,930)	(82,954)
Accumulated Other Comprehensive (Loss) Income (net of tax)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income	$ (192,739)	$ (240,719)