EMPLOYEE BENEFIT PLANS - AMOUNTS EXPECTED TO BE RECOGNIZED IN NET PERIODIC BENEFIT COST (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2021 USD ($)
Pension
Regulatory Assets
Net actuarial loss	$ 5,843
Prior service cost (credit)	102
Total	5,945
Accumulated Other Comprehensive Income (Loss)
Net actuarial loss	2,902
Prior service cost (credit)	0
Total	2,902
OPEB
Regulatory Assets
Net actuarial loss	4,577
Prior service cost (credit)	(133)
Total	4,444
Accumulated Other Comprehensive Income (Loss)
Net actuarial loss	1,107
Prior service cost (credit)	(11)
Total	$ 1,096