EMPLOYEE BENEFIT PLANS - COMPONENTS OF NET PERIODIC COST (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,351	$ 2,073	$ 2,701	$ 4,146
Interest cost	3,793	2,408	7,587	4,816
Expected return on plan assets	(4,993)	(5,318)	(9,986)	(10,637)
Recognized actuarial loss	75	2,186	150	4,372
Prior service cost (credit) amortization	26	26	51	51
Net periodic benefit cost	252	1,375	503	2,748
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	618	1,076	1,236	2,152
Interest cost	2,287	1,589	4,573	3,178
Expected return on plan assets	(1,681)	(1,894)	(3,361)	(3,788)
Recognized actuarial loss	0	1,421	0	2,842
Prior service cost (credit) amortization	0	(36)	0	(72)
Net periodic benefit cost	$ 1,224	$ 2,156	$ 2,448	$ 4,312