GENERAL INFORMATION AND OTHER FINANCIAL DATA - PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges		$ 13	$ 7	$ 22
Amortization of:
Settlement charges		13	7	22
Pension benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges	$ 0	13	7	22
Defined Benefit Plan Disclosure [Line Items]
Service cost	36	31	109	97
Interest cost	28	32	84	97
Expected return on assets	(44)	(41)	(130)	(126)
Amortization of:
Prior service cost (credit)	3	3	8	9
Actuarial loss (gain)	12	9	34	26
Settlement charges	0	13	7	22
Net periodic benefit cost (credit)	35	47	112	125
Regulatory adjustments	73	37	66	31
Total expense recognized	108	84	178	156
Pension benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	7	26	23
Interest cost	6	7	18	22
Expected return on assets	(11)	(12)	(36)	(37)
Amortization of:
Prior service cost (credit)	0	1	0	2
Actuarial loss (gain)	1	1	2	3
Net periodic benefit cost (credit)	5	4	10	13
Regulatory adjustments	21	22	30	28
Total expense recognized	26	26	40	41
Pension benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	20	73	64
Interest cost	19	22	59	66
Expected return on assets	(27)	(27)	(85)	(81)
Amortization of:
Prior service cost (credit)	2	2	6	6
Actuarial loss (gain)	8	6	27	19
Net periodic benefit cost (credit)	25	23	80	74
Regulatory adjustments	52	15	36	3
Total expense recognized	77	38	116	77
Other postretirement benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Settlement charges	0	0	0	0
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5	17	14
Interest cost	7	8	21	24
Expected return on assets	(14)	(14)	(44)	(41)
Amortization of:
Prior service cost (credit)	(1)	(1)	(2)	(2)
Actuarial loss (gain)	(3)	(2)	(7)	(7)
Settlement charges	0	0	0	0
Net periodic benefit cost (credit)	(5)	(4)	(15)	(12)
Regulatory adjustments	5	4	15	12
Total expense recognized	0	0	0	0
Other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	4	3
Interest cost	1	2	4	5
Expected return on assets	(2)	(3)	(7)	(8)
Amortization of:
Prior service cost (credit)	0	0	0	0
Actuarial loss (gain)	(1)	(1)	(2)	(2)
Net periodic benefit cost (credit)	0	(1)	(1)	(2)
Regulatory adjustments	0	1	1	2
Total expense recognized	0	0	0	0
Other postretirement benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	3	13	10
Interest cost	5	7	16	19
Expected return on assets	(12)	(11)	(36)	(32)
Amortization of:
Prior service cost (credit)	(1)	(1)	(2)	(2)
Actuarial loss (gain)	(2)	(1)	(5)	(5)
Net periodic benefit cost (credit)	(5)	(3)	(14)	(10)
Regulatory adjustments	5	3	14	10
Total expense recognized	$ 0	$ 0	$ 0	$ 0