FAIR VALUE MEASUREMENTS - RECON OF LEVEL 3 ASSETS (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) $ / MWh	Mar. 31, 2020 USD ($) $ / MWh	Dec. 31, 2020 USD ($) $ / MWh
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 69	$ 28	$ 28
Realized and unrealized losses	(2)	(5)
Settlements	(5)	(7)
Ending balance	62	16	69
Change in unrealized gains (losses) relating to instruments still held at the end of the period	(1)	(6)
Sempra LNG [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Change in unrealized gains (losses) relating to instruments still held at the end of the period	2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	3
Realized and unrealized gains	2
Settlements	(2)
Ending balance	3		3
Sempra LNG [Member] | Other current assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Ending balance	7
Sempra LNG [Member] | Deferred Credits and Other [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Ending balance	4
San Diego Gas and Electric Company [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	69	28	28
Realized and unrealized losses	(2)	(5)
Settlements	(5)	(7)
Ending balance	62	16	$ 69
Change in unrealized gains (losses) relating to instruments still held at the end of the period	$ (1)	$ (6)
Level 3 [Member] | San Diego Gas and Electric Company [Member] | Minimum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Congestion revenue rights (in dollars per MWH) | $ / MWh	(1.81)		(3.77)
Market electricity forward price inputs ( in dollars per MWH) | $ / MWh	20.60	16.51
Level 3 [Member] | San Diego Gas and Electric Company [Member] | Maximum [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Congestion revenue rights (in dollars per MWH) | $ / MWh	14.11		6.03
Market electricity forward price inputs ( in dollars per MWH) | $ / MWh	117.00	52.45
Level 3 [Member] | San Diego Gas and Electric Company [Member] | Weighted Average [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Congestion revenue rights (in dollars per MWH) | $ / MWh	(0.12)		(1.58)
Market electricity forward price inputs ( in dollars per MWH) | $ / MWh	46.46	35.41