FAIR VALUE MEASUREMENTS - RECON OF LEVEL 3 ASSETS (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Balance at beginning of period	$ 179,000,000	$ (28,000,000)	$ (74,000,000)
Realized and unrealized gains (losses)	(184,000,000)	209,000,000	34,000,000
Allocated transmission instruments	6,000,000	10,000,000	6,000,000
Settlements	27,000,000	(12,000,000)	6,000,000
Balance at end of period	28,000,000	179,000,000	(28,000,000)
Change in unrealized gains (losses) relating to instruments still held at the end of the period	(139,000,000)	183,000,000	30,000,000
San Diego Gas and Electric Company [Member] \| Minimum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Congestion revenue rights, 2020 (price per MWh)	(3.77)
Congestion revenue rights, 2019 (price per MWh)		(8.57)
Congestion revenue rights, 2018 (price per MWh)			(7.25)
San Diego Gas and Electric Company [Member] \| Maximum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Congestion revenue rights, 2020 (price per MWh)	6.03
Congestion revenue rights, 2019 (price per MWh)		35.21
Congestion revenue rights, 2018 (price per MWh)			11.99
San Diego Gas and Electric Company [Member] \| Median [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Congestion revenue rights, 2020 (price per MWh)	(1.58)
Congestion revenue rights, 2019 (price per MWh)		(2.94)
Congestion revenue rights, 2018 (price per MWh)			$ 0.09
Level 3 [Member] \| San Diego Gas and Electric Company [Member] \| Minimum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Market electricity forward price inputs (price per MWh)	21.00	22.20
Level 3 [Member] \| San Diego Gas and Electric Company [Member] \| Maximum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Market electricity forward price inputs (price per MWh)	61.15	76.85
Level 3 [Member] \| San Diego Gas and Electric Company [Member] \| Weighted Average [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases, Sales, Issues, Settlements [Abstract]
Market electricity forward price inputs (price per MWh)	$ 37.92	$ 42.69

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Amount of unrealized gain (loss) recognized in income for derivative asset (liability) after deduction of derivative liability (asset), measured at fair value using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a derivative asset (liability) after deduction of derivative liability, measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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