GENERAL INFORMATION AND OTHER FINANCIAL DATA - OTHER (EXPENSE) INCOME, NET (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Income [Line Items]
Allowance for equity funds used during construction	$ 38	$ 31
Investment gains	9	(37)
Losses on interest rate and foreign exchange instruments, net	(30)	(153)
Foreign currency transaction gains (losses), net	(19)	(123)
Non-service component of net periodic benefit credit	29	26
Interest on regulatory balancing accounts, net	1	2
Sundry, net	7	0
Total	35	(254)
Foreign currency transaction losses, net	(19)	(123)
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	23	21
Non-service component of net periodic benefit credit	9	8
Interest on regulatory balancing accounts, net	1	2
Sundry, net	2	0
Total	35	31
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	12	8
Non-service component of net periodic benefit credit	28	25
Sundry, net	(1)	(3)
Total	39	30
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency transaction losses, net	$ (23)	$ (149)