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DERIVATIVE FINANCIAL INSTRUMENTS (CREDIT RISK) (Details 3) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Derivative, Credit Risk Related Contingent Features [Abstract]      
Collateral Already Posted, Aggregate Fair Value $ 28.9 $ 29.2  
Additional collateral required to be posted to counterparties if all underlying contingent features were fully triggered 4.8 21.1  
Aggregate fair value of all derivative instruments with contingent provisions that are in a net liability position 33.7 50.3  
Cash collateral requested from counterparty 53.5 62.9  
Derivative, net asset position 53.5 62.9  
Letter of Credit Available Commodity Derivatives,asset position 1.2 1.5  
Commodity Derivative, net asset position 4.0 9.0  
SCE&G      
Derivative, Credit Risk Related Contingent Features [Abstract]      
Collateral Already Posted, Aggregate Fair Value 10.1 9.2  
Additional collateral required to be posted to counterparties if all underlying contingent features were fully triggered 4.6 21.1  
Aggregate fair value of all derivative instruments with contingent provisions that are in a net liability position 14.7 30.3  
Cash collateral requested from counterparty 53.5 62.0  
Derivative, net asset position 53.5 62.0  
Interest Rate Contract [Member] | Interest Expense [Member] | Not Designated as Hedging Instrument [Member]      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income (3.0)    
Interest Rate Contract [Member] | Interest Expense [Member] | Not Designated as Hedging Instrument [Member] | SCE&G      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income (3.0) (2.0)  
Interest Rate Contract [Member] | Operating Expense [Member] | Not Designated as Hedging Instrument [Member]      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income (173.0)    
Interest Rate Contract [Member] | Operating Expense [Member] | Not Designated as Hedging Instrument [Member] | SCE&G      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income $ (173.0)    
Interest Rate Contract [Member] | Other Nonoperating Income (Expense) [Member] | Not Designated as Hedging Instrument [Member]      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income   $ (2.0) $ 5.0
Interest Rate Contract [Member] | Other Nonoperating Income (Expense) [Member] | Not Designated as Hedging Instrument [Member] | SCE&G      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Reclassified from Deferred Accounts into Income     $ 5.0