SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - OTHER (EXPENSE) INCOME, NET (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Income [Line Items]
Allowance for equity funds used during construction		$ 128	$ 94	$ 98
Investment gains (losses)		41	61	(6)
(Losses) gains on interest rate and foreign exchange instruments, net		(67)	34	7
Foreign currency transaction losses (gains), net		(25)	21	(6)
Non-service component of net periodic benefit cost		(102)	(132)	(35)
Fine related to Energy Efficiency Program Inquiry		(6)	0	0
Penalties related to billing practices OII		0	(8)	0
Interest on regulatory balancing accounts, net		14	14	2
Sundry, net		(31)	(7)	(2)
Total		(48)	77	58
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction		79	56	61
Non-service component of net periodic benefit cost		(20)	(20)	(6)
Fine related to Energy Efficiency Program Inquiry		(6)	0	0
Interest on regulatory balancing accounts, net		9	13	4
Sundry, net		(10)	(10)	(3)
Total		52	39	56
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction		41	34	36
Non-service component of net periodic benefit cost		(54)	(72)	(10)
Penalties related to billing practices OII	$ (8)	0	(8)	0
Interest on regulatory balancing accounts, net		5	1	(2)
Sundry, net		(20)	(10)	(9)
Total		(28)	(55)	15
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency transaction losses (gains), net		$ (42)	$ 30	$ (3)