COMMITMENTS AND CONTINGENT LIABILITIES - LEGAL PROCEEDINGS (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2024	Sep. 30, 2023
Site Contingency [Line Items]
Manufactured gas plant remediation	$ 157,813	$ 169,390
Recovery from third party of environmental remediation cost, period	7 years
Regulatory assets	$ 535,104	$ 584,830
Expended, net of recoveries
Site Contingency [Line Items]
Regulatory assets	69,200
Minimum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate	137,300
Maximum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate	$ 201,500