EMPLOYEE BENEFIT PLANS - AMOUNTS EXPECTED TO BE RECOGNIZED IN NET PERIODIC BENEFIT COST (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2019 USD ($)
Pension
Regulatory Assets
Net actuarial loss	$ 8,470
Prior service cost (credit)	102
Total	8,572
Accumulated Other Comprehensive Income (Loss)
Net actuarial loss	2,514
Prior service cost (credit)	0
Total	2,514
OPEB
Regulatory Assets
Net actuarial loss	10,055
Prior service cost (credit)	(182)
Total	9,873
Accumulated Other Comprehensive Income (Loss)
Net actuarial loss	1,407
Prior service cost (credit)	(15)
Total	$ 1,392