SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - ASSET RETIREMENT OBLIGATION AND SPENT NUCLEAR FUEL (Details) - USD ($) $ in Millions		1 Months Ended					12 Months Ended
	Apr. 18, 2016	Oct. 31, 2017	May 31, 2017	Feb. 28, 2017	Sep. 30, 2016	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	[1]	Dec. 31, 2015	[1]
Jointly Owned Utility Plant Interests [Line Items]
Decrease in nuclear decommissioning balancing account							$ (108)	$ (198)		$ (586)
San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Decommissioning liability							607
Cost study estimate decommissioning escalated							1,000
Decrease in nuclear decommissioning balancing account							$ (56)	$ (35)		$ (474)
San Diego Gas and Electric Company [Member] | Total Ownership [Member]
Jointly Owned Utility Plant Interests [Line Items]
Damages awarded to other party	$ 162			$ 43
Damages sought		$ 58			$ 56
San Diego Gas and Electric Company [Member] | San Onofre Nuclear Generating Station (SONGS) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Damages awarded to other party			$ 9			$ 32
Damages sought		$ 12
Decrease in regulatory asset						(23)
Decrease in nuclear decommissioning balancing account						(8)
Decrease in SONGS O&M cost balancing account						$ (1)

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