SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - AFFILIATES REVENUE AND COST OF SALES (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Related Party Transaction [Line Items]
Related party revenue	$ 43	$ 25	$ 26
Related party cost of sales	47	72	107
San Diego Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related party revenue	8	7	10
Related party cost of sales	71	64	49
Southern California Gas Company [Member]
Related Party Transaction [Line Items]
Related party revenue	$ 74	$ 76	$ 75
Energia Sierra Juarez Wind Project [Member] \| San Diego Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Power purchase agreement term	20 years
Generating capacity (in mw) \| MW	155
Minimum [Member] \| Federal Funds Rate [Member] \| California Utilities [Member]
Related Party Transaction [Line Items]
Variable percentage rate	13.00%
Maximum [Member] \| Federal Funds Rate [Member] \| California Utilities [Member]
Related Party Transaction [Line Items]
Variable percentage rate	20.00%

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999

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