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COMMITMENTS AND CONTINGENT LIABILITIES - LEGAL PROCEEDINGS (Details) | 9 Months Ended |
--- | --- | ---
Jun. 30, 2018 USD ($) site | Sep. 30, 2017 USD ($)
Site Contingency [Line Items] |  |
Number of MGP sites | site | 5 |
Recovery of expenditures, including carrying costs, rolling period approved by the BPU | 7 years |
Regulatory assets | $ 348,079,000 | $ 375,919,000
Manufactured gas plant remediation | 140,821,000 | 149,000,000
Minimum |  |
Site Contingency [Line Items] |  |
Product liability contingency, loss exposure in excess of accrual, best estimate | 117,600,000 |
Loss contingency, estimate of possible loss | 600,000 |
Maximum |  |
Site Contingency [Line Items] |  |
Product liability contingency, loss exposure in excess of accrual, best estimate | 205,200,000 |
Loss contingency, estimate of possible loss | 3,200,000 |
Expended, net of recoveries |  |
Site Contingency [Line Items] |  |
Regulatory assets | 29,647,000 | 28,547,000
Liability for future expenditures |  |
Site Contingency [Line Items] |  |
Regulatory assets | 140,821,000 | $ 149,000,000
RAC |  |
Site Contingency [Line Items] |  |
Public utilities, approved rate, amount | 9,400,000 |
Public utilities, requested rate, amount | $ 7,000,000 |

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