GENERAL INFORMATION AND OTHER FINANCIAL DATA - OTHER (EXPENSE) INCOME, NET (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Income [Line Items]
Allowance for equity funds used during construction	$ 34	$ 25	$ 96	$ 69
Investment gains	16	9	9	46
Gains (losses) on interest rate and foreign exchange instruments, net	19	(17)	(129)	7
Foreign currency transaction gains (losses), net	15	(13)	(95)	(2)
Non-service component of net periodic benefit (cost) credit	(48)	(13)	(45)	(19)
Fine related to Energy Efficiency Program inquiry	(6)	0	(6)	0
Penalties related to billing practices OII	0	0	0	(8)
Interest on regulatory balancing accounts, net	0	4	13	9
Sundry, net	(1)	(2)	(6)	1
Total	29	(7)	(163)	103
Foreign currency translation gain (loss)			(95)	(2)
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	21	15	61	42
Non-service component of net periodic benefit (cost) credit	(18)	0	(15)	8
Fine related to Energy Efficiency Program inquiry	(6)	0	(6)	0
Interest on regulatory balancing accounts, net	0	4	8	10
Sundry, net	1	0	(1)	0
Total	(2)	19	47	60
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	11	9	29	25
Non-service component of net periodic benefit (cost) credit	(15)	(5)	(3)	9
Penalties related to billing practices OII	0	0	0	(8)
Interest on regulatory balancing accounts, net	0	0	5	(1)
Sundry, net	(3)	(3)	(10)	(7)
Total	(7)	$ 1	21	18
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency translation gain (loss)	$ 15		$ (120)	$ (17)