OTHER FINANCIAL DATA - PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 29	$ 27	$ 57	$ 55
Interest cost	37	40	74	80
Expected return on assets	(40)	(41)	(80)	(83)
Prior service cost (credit)	2	3	5	6
Actuarial loss (gain)	8	7	16	13
Regulatory adjustment	(29)	(28)	(41)	(56)
Total net periodic benefit cost	7	8	31	15
Contributions by employer			28
Expected contributions in current fiscal year	174		174
Pension benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	8	15	15
Interest cost	10	11	19	21
Expected return on assets	(13)	(13)	(24)	(25)
Prior service cost (credit)	1	1	1	1
Actuarial loss (gain)	2	2	4	5
Regulatory adjustment	(7)	(8)	(14)	(15)
Total net periodic benefit cost	0	1	1	2
Contributions by employer			2
Expected contributions in current fiscal year	32		32
Pension benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	18	18	36	35
Interest cost	24	25	48	50
Expected return on assets	(25)	(27)	(51)	(52)
Prior service cost (credit)	2	2	4	4
Actuarial loss (gain)	4	2	8	5
Regulatory adjustment	(22)	(20)	(27)	(41)
Total net periodic benefit cost	1	0	18	1
Contributions by employer			17
Expected contributions in current fiscal year	90		90
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	6	11	11
Interest cost	11	11	20	22
Expected return on assets	(17)	(18)	(33)	(35)
Prior service cost (credit)	0	0	0	0
Actuarial loss (gain)	0	0	(1)	0
Regulatory adjustment	2	2	4	4
Total net periodic benefit cost	1	1	1	2
Contributions by employer			1
Expected contributions in current fiscal year	8		8
Other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	2
Interest cost	2	2	4	4
Expected return on assets	(4)	(2)	(7)	(5)
Prior service cost (credit)	1	1	2	2
Actuarial loss (gain)	0	(1)	0	(1)
Regulatory adjustment	(1)	(1)	(2)	(2)
Total net periodic benefit cost	0	0	0	0
Contributions by employer			0
Expected contributions in current fiscal year	4		4
Other postretirement benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	7	7
Interest cost	8	9	15	17
Expected return on assets	(13)	(14)	(26)	(28)
Prior service cost (credit)	0	(1)	(1)	(2)
Actuarial loss (gain)	(1)	0	(1)	0
Regulatory adjustment	3	3	6	6
Total net periodic benefit cost	0	$ 0	0	$ 0
Contributions by employer			0
Expected contributions in current fiscal year	$ 1		$ 1