REGULATORY MATTERS (FERC Compliance) (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
FERC Refund Orders [Member]
Public Utilities, General Disclosures [Line Items]
Transmission Service Agreement time value refunds recorded	$ 22

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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Balance Type:	debit
Period Type:	duration