SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - AFFILIATES REVENUE AND COST OF SALES (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) MW	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Related party revenue	$ 37	$ 52	$ 64
Related party cost of sales	45	50	46
Interest Income, Related Party	56	74	62
Interest Expense, Related Party	14	2	2
San Diego Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related party revenue	6	6	5
Related party cost of sales	79	74	73
Southern California Gas Company [Member]
Related Party Transaction [Line Items]
Related party revenue	88	69	64
Related party cost of sales	$ 0	$ 8	$ 0
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%
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

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