EMPLOYEE BENEFIT PLANS - ASSUMED HCCTR (Details) - OPEB - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
HCCTR	6.60%	6.90%	7.60%
Ultimate HCCTR	4.50%	4.50%	4.50%
Effect of a 1 percentage point increase in the HCCTR on:
Year-end benefit obligation	$ 26,710	$ 43,217	$ 49,106
Total service and interest cost	2,544	2,959	2,799
Effect of a 1 percentage point decrease in the HCCTR on:
Year-end benefit obligation	(21,853)	(34,669)	(38,844)
Total service and interest costs	$ (1,966)	$ (2,253)	$ (2,151)