COMMITMENTS AND CONTINGENT LIABILITIES - LEGAL PROCEEDINGS (Details) - USD ($) $ in Thousands				9 Months Ended
	Apr. 12, 2023	Mar. 23, 2022	Apr. 07, 2021	Jun. 30, 2023	Sep. 30, 2022
Site Contingency [Line Items]
Manufactured gas plant remediation				$ 123,070	$ 127,060
Recovery from third party of environmental remediation cost, period				7 years
Regulatory assets				$ 528,114	$ 500,666
Expended, net of recoveries
Site Contingency [Line Items]
Regulatory assets				63,800
RAC
Site Contingency [Line Items]
Approved rate, amount	$ 15,400	$ 11,700	$ 11,100
Interim rate increase (decrease), amount	$ 3,700
Minimum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate				110,800
Maximum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate				$ 167,100