SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR INSURANCE (Details) - San Diego Gas and Electric Company [Member] - USD ($) $ in Millions	Jun. 30, 2018	Apr. 05, 2018	Jan. 09, 2018	Jan. 05, 2018	Jan. 04, 2018
Schedule Of Nuclear Insurance [Line Items]
Maximum nuclear liability insurance coverage	$ 450.0			$ 100.0	$ 450.0
Maximum secondary financial protection	110.0
Annual maximum secondary financial protection contribution by company	560.0
Federal nuclear property damage insurance, minimum required	50.0		$ 1,060.0
Nuclear property damage insurance	1,500.0
Spent nuclear fuel storage insurance		$ 500.0
Maximum premium assessment under nuclear property damage insurance	10.4
Maximum nuclear property insurance terrorism coverage	$ 3,240.0