SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - AFFILIATES REVENUE AND COST OF SALES (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) MW	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Related Party Transaction [Line Items]
Related party revenue	$ 64	$ 43	$ 25
Related party cost of sales	46	47	72
San Diego Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related party revenue	5	8	7
Related party cost of sales	73	71	64
Southern California Gas Company [Member]
Related Party Transaction [Line Items]
Related party revenue	$ 64	$ 74	$ 76
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	0.13%
Maximum [Member] \| Federal Funds Rate [Member] \| California Utilities [Member]
Related Party Transaction [Line Items]
Variable percentage rate	0.20%

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