SAN ONOFRE NUCLEAR GENERATING STATION (Details) - USD ($) $ in Millions		3 Months Ended
	Mar. 13, 2017	Mar. 31, 2018	Jan. 31, 2018	Dec. 31, 2017	[1]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount awarded	$ 118
Percent of arbitration expenses reduction of award	95.00%
Settlement amount net of arbitration expense	$ 60
Regulatory asset threshold to cease rate recovery		$ 775
Regulatory asset, current		241		$ 325
Regulatory asset, noncurrent		$ 1,597		1,517
Anticipated term of dismantlement work		10 years
Nuclear decommissioning trusts		$ 1,017		1,033
San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount awarded	24
Settlement amount net of arbitration expense	12
Arbitration expense	12
Legal costs	11
Litigation settlement amount allocated to ratepayers and shareholders	$ 1
Regulatory asset, current		233		316
Regulatory asset, noncurrent		$ 483		451
Percent of dismantlement work expense		20.00%
Nuclear decommissioning trusts		$ 1,017		$ 1,033
Authorized recovery amount, nuclear decommissioning trust funding		362	$ 60
San Diego Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Jointly Owned Utility Plant Interests [Line Items]
Regulatory asset		153
Regulatory asset, current		42
Regulatory asset, noncurrent		$ 111
Jointly Owned Nuclear Power Plant [Member] | San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, proportionate ownership share		20.00%

[1] Derived from audited financial statements.