DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE IMPACT ON INCOME (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings			$ 44	$ 142	[1]
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI	$ 31	$ 17	173	(37)
Pretax gain (loss) reclassified from AOCI into earnings	8	2	5	(13)
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Expense [Member] | Interest rate and foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI	16	14	57	22
Pretax gain (loss) reclassified from AOCI into earnings	0	0	1	4
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Income, Net [Member] | Interest rate and foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) reclassified from AOCI into earnings	11	0	11	0
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Equity Earnings [Member] | Interest rate and foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI	20	(2)	123	(57)
Pretax gain (loss) reclassified from AOCI into earnings	(3)	0	(8)	(9)
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Revenues: Energy- Related Businesses [Member] | Foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI	(5)	5	(7)	(5)
Pretax gain (loss) reclassified from AOCI into earnings	0	2	1	1
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Revenues: Energy- Related Businesses [Member] | Commodity contracts not subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI			0	3
Pretax gain (loss) reclassified from AOCI into earnings			0	(9)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	97	60	104	163
Not Designated as Hedging Instrument [Member] | Other Income, Net [Member] | Foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	28	4	35	101
Not Designated as Hedging Instrument [Member] | Equity Earnings [Member] | Foreign exchange instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	0	1	0	1
Not Designated as Hedging Instrument [Member] | Revenues: Energy- Related Businesses [Member] | Commodity contracts not subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	9	(3)	0	27
Not Designated as Hedging Instrument [Member] | Operation and Maintenance [Member] | Commodity contracts not subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	0	0	0	(1)
Not Designated as Hedging Instrument [Member] | Cost of Electric Fuel and Purchased Power [Member] | Commodity contracts subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	62	59	70	36
Not Designated as Hedging Instrument [Member] | Cost of Natural Gas [Member] | Commodity contracts subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	(2)	(1)	(1)	(1)
San Diego Gas and Electric Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings			1	1	[1]
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Expense [Member] | Interest rate instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) recognized in OCI	0	0	1	(2)
Pretax gain (loss) reclassified from AOCI into earnings	(2)	(3)	(6)	(9)
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Cost of Electric Fuel and Purchased Power [Member] | Commodity contracts subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	62	59	70	36
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	(2)	0	(1)	(1)
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Operation and Maintenance [Member] | Commodity contracts not subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	0	1	0	0
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Cost of Natural Gas [Member] | Commodity contracts subject to rate recovery [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gain (loss) on derivatives recognized in earnings	$ (2)	$ (1)	$ (1)	$ (1)

[1] As adjusted for the retrospective adoption of ASU 2016-15 and ASU 2016-18, which we discuss in Note 2.