GENERAL INFORMATION AND OTHER FINANCIAL DATA - PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges	$ 7	$ 5
Amortization of:
Settlement charges	7	5
Pension benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges	7	5
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	33
Interest cost	28	32
Expected return on assets	(43)	(42)
Amortization of:
Prior service cost (credit)	3	3
Actuarial loss (gain)	11	9
Settlement charges	7	5
Net periodic benefit cost (credit)	43	40
Regulatory adjustments	(29)	(28)
Total expense recognized	14	12
Pension benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	8
Interest cost	6	7
Expected return on assets	(12)	(13)
Amortization of:
Prior service cost (credit)	0	1
Actuarial loss (gain)	0	1
Net periodic benefit cost (credit)	2	4
Regulatory adjustments	(2)	(3)
Total expense recognized	0	1
Pension benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	22
Interest cost	20	22
Expected return on assets	(28)	(27)
Amortization of:
Prior service cost (credit)	2	2
Actuarial loss (gain)	9	6
Net periodic benefit cost (credit)	28	25
Regulatory adjustments	(27)	(25)
Total expense recognized	1	0
Other postretirement benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges	0	0
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5
Interest cost	7	8
Expected return on assets	(15)	(13)
Amortization of:
Prior service cost (credit)	(1)	(1)
Actuarial loss (gain)	(2)	(3)
Settlement charges	0	0
Net periodic benefit cost (credit)	(5)	(4)
Regulatory adjustments	5	4
Total expense recognized	0	0
Other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	1	2
Expected return on assets	(2)	(3)
Amortization of:
Prior service cost (credit)	0	0
Actuarial loss (gain)	0	(1)
Net periodic benefit cost (credit)	0	(1)
Regulatory adjustments	0	1
Total expense recognized	0	0
Other postretirement benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	3
Interest cost	5	6
Expected return on assets	(12)	(10)
Amortization of:
Prior service cost (credit)	(1)	0
Actuarial loss (gain)	(1)	(2)
Net periodic benefit cost (credit)	(5)	(3)
Regulatory adjustments	5	3
Total expense recognized	$ 0	$ 0