REGULATORY MATTERS - COST OF CAPITAL & FERC (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2020	Oct. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2021	Dec. 31, 2019	Jan. 01, 2022	Aug. 31, 2021
California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM Benchmark Rate, Variable Rate									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%
Base ROE		10.10%
Additional Bps		0.50%
Additional FERC revenues				$ 12
San Diego Gas and Electric Company [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM Benchmark Rate									4.498%
Authorized Capital Structure, Common Equity Ratio									52.00%		54.00%
Authorized Capital Structure, Authorized ROE									10.20%		10.55%
Authorized Capital Structure, Cost of Debt									4.59%		3.84%
Authorized Capital Structure, Proposed Return on Base Rate									7.55%		7.46%
Percentage below CCM benchmark rate								1.17%
San Diego Gas and Electric Company [Member] | California Public Utilities Commission [Member] | Forecast [Member]
Public Utilities, General Disclosures [Line Items]
Authorized Capital Structure, Authorized ROE										9.62%
San Diego Gas and Electric Company [Member] | California Public Utilities Commission [Member] | Energy Efficiency Program Inquiry [Member]
Public Utilities, General Disclosures [Line Items]
Equity losses on investment			$ 36			$ 51
Litigation fines					$ 6		$ 6
Loss contingency, loss in period, after tax			$ 29			$ 44
San Diego Gas and Electric Company [Member] | Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Additional FERC revenues				$ 17
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%
Southern California Gas Company [Member] | California Public Utilities Commission [Member]
Public Utilities, General Disclosures [Line Items]
CCM Benchmark Rate									4.029%