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REGULATORY MATTERS (Details) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2017 | Sep. 30, 2017
Regulated Operations [Abstract] |  |
Remaining recovery period for certain regulatory assets for which no return on investment during recovery period is provided (in years) | 20 years |
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided (in years) |  | 15 years

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- Definition Remaining Recovery Period of Certain Regulatory Assets for which No Return on Investment During Recovery Period is Provided + References No definition available. + Details
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- Definition Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 55 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82849221&loc=d3e44360-110383 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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