SAN ONOFRE NUCLEAR GENERATING STATION (Details) - USD ($) $ in Millions			9 Months Ended
	Jul. 26, 2018	Mar. 13, 2017	Sep. 30, 2018	Jan. 31, 2018	Dec. 31, 2017	[1]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount awarded		$ 118.0
Percent of arbitration expenses reduction of award		95.00%
Settlement amount net of arbitration expense		$ 60.0
Regulatory asset threshold to cease rate recovery			$ 775.0
Regulatory asset, current			92.0		$ 325.0
Regulatory asset, noncurrent			$ 1,469.0		1,517.0
Anticipated term of dismantlement work			10 years
San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount awarded		24.0
Settlement amount net of arbitration expense		12.0
Arbitration expense		12.0
Legal costs		11.0
Litigation settlement amount allocated to ratepayers and shareholders		$ 1.0
Regulatory asset threshold to cease rate recovery			$ 152.0
Regulatory asset, current			77.0		316.0
Regulatory asset, noncurrent			$ 399.0		$ 451.0
Percent of dismantlement work expense			20.00%
Authorized recovery amount, nuclear decommissioning trust funding			$ 362.0	$ 60.0
San Diego Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Jointly Owned Utility Plant Interests [Line Items]
Regulatory asset			152.0
Regulatory asset, current			59.0
Regulatory asset, noncurrent			$ 93.0
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%
SONGS Outage [Member] | Jointly Owned Nuclear Power Plant [Member]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount payable	$ 12.5
SONGS Outage [Member] | Jointly Owned Nuclear Power Plant [Member] | San Diego Gas and Electric Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Settlement amount payable	$ 2.5

[1] Derived from audited financial statements.