SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR INSURANCE (Details) - San Diego Gas and Electric Company [Member] $ in Millions	Jun. 30, 2021 USD ($)
Schedule Of Nuclear Insurance [Line Items]
Maximum nuclear liability insurance coverage	$ 450.0
Maximum secondary financial protection	110.0
Maximum nuclear liability loss coverage per incident	560.0
Nuclear property damage insurance	130.0
Federal nuclear property damage insurance, minimum required	50.0
Maximum premium assessment under nuclear property damage insurance	4.3
Maximum nuclear property insurance terrorism coverage	$ 3,240.0