OTHER COMPREHENSIVE INCOME (LOSS) - Amounts Reclassified from AOCI (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total gain (loss)	$ 2,929		$ 9,684		$ 19,880	$ 23,649
Tax benefit (expense)	(2,034)		(3,194)		(8,373)	(8,406)
Net income (loss)	895	$ 10,612	(1,156)	$ 8,753	11,507	7,597
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)	(1,046)		(225)		(2,092)	(451)
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)	1,050		310		994	992
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)	4		85		(1,098)	541
Tax benefit (expense)	(1)		(18)		231	(114)
Net income (loss)	$ 3		$ 67		$ (867)	$ 427