CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	Sep. 30, 2017 USD ($) counterparty
Concentration Risk [Line Items]
Number of large counterparties for which credit risk is disclosed \| counterparty	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	$ 17.9
Net receivable amount	8.9
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	58.2
Net receivable amount	55.8
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	23.8
Net receivable amount	$ 23.1

Net carrying value as of the balance sheet date of receivables. Net carrying value can include contractual netting arrangements.

No definition available.

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- Definition

Number of large counterparties in terms of net accounts receivable exposure for which credit risk is reported.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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