SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR INSURANCE (Details) - San Diego Gas and Electric Company [Member] - USD ($) $ in Millions	Apr. 05, 2018	Mar. 31, 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
Maximum premium assessment under nuclear property damage insurance		10.4
Maximum nuclear property insurance terrorism coverage		$ 3,240.0
Subsequent Event [Member]
Schedule Of Nuclear Insurance [Line Items]
Spent nuclear fuel storage insurance	$ 500.0