OTHER COMPREHENSIVE INCOME (LOSS) - Amounts Reclassified from AOCI (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	$ 27,860		$ 2,929		$ 67,029	$ 19,880
Tax benefit (expense)	(10,748)		(2,034)		(20,417)	(8,373)
Net income	17,112	$ 29,500	895	$ 10,612	46,612	11,507
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)		(1,046)		(3,146)	(2,092)
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)	(1,741)		1,050		(2,399)	994
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)	(3,314)		4		(5,545)	(1,098)
Tax benefit (expense)	696		(1)		1,165	231
Net income	$ (2,618)		$ 3		$ (4,380)	$ (867)