SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - NARRATIVE (Details) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	Mar. 13, 2017	Apr. 30, 2016	Oct. 31, 2015	Dec. 31, 2017	Feb. 28, 2017	Dec. 31, 2016	[1]
Jointly Owned Utility Plant Interests [Line Items]
Nuclear plant closure regulatory asset, current				$ 325		$ 348
Nuclear plant closure regulatory asset, noncurrent				1,517		3,414
Nuclear decommissioning trusts				$ 1,033		1,026
Litigation settlement payable	$ 118
Percent of arbitration expenses awarded	95.00%
Settlement payable net of arbitration expense	$ 60
Period of environmental exit				10 years
SONGS mitigation costs remaining		$ 4,400
San Onofre Nuclear Generating Station (SONGS) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Insurance recovery			$ 400
San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Nuclear plant closure regulatory asset, current				$ 316		340
Nuclear plant closure regulatory asset, noncurrent				451		2,012
Nuclear decommissioning trusts				1,033		$ 1,026
Decommissioning liability				607
Cost study estimate decommissioning escalated				$ 1,000
Litigation settlement payable	24
Arbitration expense	12
Settlement payable net of arbitration expense	12
Legal fees	11
Litigation settlement amount allocated to ratepayers and shareholders	$ 1
Percentage of environmental exit costs incurred				20.00%
SONGS mitigation costs remaining		$ 899		$ 24
Nuclear decommissioning trust authorized recovery amount				362	$ 60
San Diego Gas and Electric Company [Member] | Nuclear Plant Closure [Member]
Jointly Owned Utility Plant Interests [Line Items]
Regulatory asset threshold to cease rate recovery				775
Receivable for nuclear plant closure				152
Nuclear plant closure regulatory asset, current				32
Nuclear plant closure regulatory asset, noncurrent				$ 120
San Diego Gas and Electric Company [Member] | San Onofre Nuclear Generating Station (SONGS) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership percentage				20.00%
Portion of weighted average return on preferred stock included in nuclear plant return on ratebase				50.00%
Insurance recovery			$ 80
Recovery allocation percentage			5.00%
Ratepayers [Member] | San Onofre Nuclear Generating Station (SONGS) [Member]
Jointly Owned Utility Plant Interests [Line Items]
Amount funded to customers through Energy Resource Recovery Account			$ 75

[1] Reflects reclassifications to conform to current year presentation, which we discuss in Note 1.