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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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