OTHER FINANCIAL DATA - PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 28	$ 28
Interest cost	37	40
Expected return on assets	(40)	(42)
Prior service cost (credit)	3	3
Actuarial loss (gain)	8	6
Regulatory adjustment	(12)	(28)
Total net periodic benefit cost	24	7
Contributions by employer	26
Expected contributions in current fiscal year	181
Pension benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	7
Interest cost	9	10
Expected return on assets	(11)	(12)
Prior service cost (credit)	0	0
Actuarial loss (gain)	2	3
Regulatory adjustment	(7)	(7)
Total net periodic benefit cost	1	1
Contributions by employer	2
Expected contributions in current fiscal year	38
Pension benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	18	17
Interest cost	24	25
Expected return on assets	(26)	(25)
Prior service cost (credit)	2	2
Actuarial loss (gain)	4	3
Regulatory adjustment	(5)	(21)
Total net periodic benefit cost	17	1
Contributions by employer	17
Expected contributions in current fiscal year	90
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5
Interest cost	9	11
Expected return on assets	(16)	(17)
Prior service cost (credit)	0	0
Actuarial loss (gain)	(1)	0
Regulatory adjustment	2	2
Total net periodic benefit cost	0	1
Contributions by employer	1
Expected contributions in current fiscal year	8
Other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	2	2
Expected return on assets	(3)	(3)
Prior service cost (credit)	1	1
Actuarial loss (gain)	0	0
Regulatory adjustment	(1)	(1)
Total net periodic benefit cost	0	0
Contributions by employer	0
Expected contributions in current fiscal year	4
Other postretirement benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4
Interest cost	7	8
Expected return on assets	(13)	(14)
Prior service cost (credit)	(1)	(1)
Actuarial loss (gain)	0	0
Regulatory adjustment	3	3
Total net periodic benefit cost	0	$ 0
Contributions by employer	0
Expected contributions in current fiscal year	$ 1