OTHER COMPREHENSIVE INCOME (LOSS) - Amounts Reclassified from AOCI (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	$ 29,073			$ 34,480			$ 96,102	$ 54,360
Tax benefit (expense)	(12,366)			(12,649)			(32,783)	(21,022)
Net income	16,707	$ 17,112	$ 29,500	21,831	$ 895	$ 10,612	63,319	33,338
Pension and other defined benefit plans | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	(1,573)			(1,045)			(4,719)	(3,137)
Cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	(413)			556			(2,812)	1,550
Accumulated other comprehensive income (loss), attributable to parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	(1,986)			(489)			(7,531)	(1,587)
Tax benefit (expense)	417			102			1,582	333
Net income	$ (1,569)			$ (387)			$ (5,949)	$ (1,254)