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COMMITMENTS AND CONTINGENT LIABILITIES - LEGAL PROCEEDINGS (Details) - USD ($) $ in Thousands			9 Months Ended
	Sep. 09, 2020	Sep. 08, 2020	Jun. 30, 2021	Sep. 30, 2020
Site Contingency [Line Items]
Manufactured gas plant remediation			$ 136,874	$ 150,590
Recovery from third party of environmental remediation cost, period			7 years
Regulatory assets			$ 537,185	$ 527,459
Expended, net of recoveries
Site Contingency [Line Items]
Regulatory assets			44,300
RAC
Site Contingency [Line Items]
Approved rate, amount	$ 9,700	$ 8,500
Minimum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate			143,100
Maximum
Site Contingency [Line Items]
Product liability contingency, loss exposure in excess of accrual, best estimate			$ 181,700

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