SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - NUCLEAR INSURANCE (Details) - San Diego Gas and Electric Company [Member] - USD ($) $ in Millions	Jan. 10, 2018	Jan. 09, 2018	Jan. 05, 2018	Jan. 04, 2018	Dec. 31, 2017
Public Utilities, General Disclosures [Line Items]
Maximum required nuclear liability insurance available					$ 450.0
Maximum secondary financial protection available					13,000.0
Maximum required company contribution if nuclear liability loss occurs					50.9
Annual maximum required company contribution if nuclear liability loss occurs					7.6
Federal nuclear property damage insurance, minimum required					1,060.0
Federal nuclear property damage insurance premium assessment					10.4
Maximum nuclear property insurance terrorism coverage					$ 3,240.0
Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Maximum required nuclear liability insurance available			$ 100.0	$ 450.0
Federal nuclear property damage insurance, minimum required	$ 50.0	$ 1,060.0