REGULATORY MATTERS - COST OF CAPITAL & FERC (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended	36 Months Ended
	Jan. 31, 2020	Oct. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2022
Public Utilities, General Disclosures [Line Items]
Fine related to Energy Efficiency Program inquiry			$ 6		$ 0	$ 6	$ 0
California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM benchmark rate, increase (decrease) percent for trigger						1.00%
San Diego Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
FERC requirement to maintain common equity ratio, at or above (percent)			10.60%			10.60%
Base ROE			10.10%			10.10%
Additional Bps						0.50%
Additional FERC revenues		$ 12		$ 17
Fine related to Energy Efficiency Program inquiry			$ 6		$ 0	$ 6	$ 0
San Diego Gas and Electric Company [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM benchmark rate						4.498%
San Diego Gas and Electric Company [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Additional Bps						0.50%
San Diego Gas and Electric Company [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									100.00%
Weighted return on base rate (as a percent)									7.55%
San Diego Gas and Electric Company [Member] | Capital Structure, Preferred Stock [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting	6.22%
San Diego Gas and Electric Company [Member] | Capital Structure, Preferred Stock [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									2.75%
Return on rate base									6.22%
Weighted return on base rate (as a percent)									0.17%
San Diego Gas and Electric Company [Member] | Capital Structure, Long Term Debt [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									45.25%
Return on rate base									4.59%
Weighted return on base rate (as a percent)									2.08%
San Diego Gas and Electric Company [Member] | Common Equity [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity, percentage								10.05%
San Diego Gas and Electric Company [Member] | Common Equity [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									52.00%
Return on rate base									10.20%
Weighted return on base rate (as a percent)									5.30%
Southern California Gas Company [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM benchmark rate						4.029%
Southern California Gas Company [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									100.00%
Weighted return on base rate (as a percent)									7.30%
Southern California Gas Company [Member] | Capital Structure, Preferred Stock [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									2.40%
Return on rate base									6.00%
Weighted return on base rate (as a percent)									0.14%
Southern California Gas Company [Member] | Capital Structure, Long Term Debt [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									45.60%
Return on rate base									4.23%
Weighted return on base rate (as a percent)									1.93%
Southern California Gas Company [Member] | Common Equity [Member] | Forecast [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Authorized weighting									52.00%
Return on rate base									10.05%
Weighted return on base rate (as a percent)									5.23%
Energy Efficiency Program Inquiry [Member] | San Diego Gas and Electric Company [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
Reduction in revenue from inquiry			36			$ 51
After tax impact from inquiry			$ 29			$ 44