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SAN ONOFRE NUCLEAR GENERATING STATION (Details) - USD ($)
$ in Millions
6 Months Ended
Jul. 26, 2018
Mar. 13, 2017
Jun. 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     337.0   $ 325.0
Regulatory asset, noncurrent     $ 1,644.0   1,517.0
Anticipated term of dismantlement work     10 years    
Nuclear decommissioning trusts     $ 1,022.0   1,033.0
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     327.0   316.0
Regulatory asset, noncurrent     $ 463.0   451.0
Percent of dismantlement work expense     20.00%    
Nuclear decommissioning trusts     $ 1,022.0   $ 1,033.0
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     154.0    
Regulatory asset, current     52.0    
Regulatory asset, noncurrent     $ 102.0    
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%    
Subsequent Event [Member] | SONGS Outage [Member] | Jointly Owned Nuclear Power Plant [Member]          
Jointly Owned Utility Plant Interests [Line Items]          
Settlement amount payable $ 12.5        
Subsequent Event [Member] | 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.