POSTRETIREMENT BENEFITS - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 4,556	$ 5,264	$ 5,175
Expected return on plan assets	(4,323)	(3,364)	(5,027)
Amortization of actuarial loss	208	266	667
Net periodic cost	$ 441	$ 2,166	$ 815
Weighted-average assumptions used to determine net periodic pension cost during the period:
Discount rate	4.90%	5.80%	5.40%
Expected return on plan assets	4.00%	3.30%	5.00%