v3.10.0.1
DERIVATIVE FINANCIAL INSTRUMENTS (CREDIT RISK) (Details 3) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Gain (Loss) on Derivatives      
Interest Rate Cash Flow Hedge Ineffectiveness is Immaterial insignificant insignificant insignificant
Derivative, Credit Risk Related Contingent Features [Abstract]      
Collateral Already Posted, Aggregate Fair Value $ 24.3 $ 28.9  
Additional collateral required to be posted to counterparties if all underlying contingent features were fully triggered 0.5 4.8  
Aggregate fair value of all derivative instruments with contingent provisions that are in a net liability position 24.8 33.7  
Cash collateral requested from counterparty 0.0 53.5  
Derivative, net asset position 0.0 53.5  
Letter of Credit Available Commodity Derivatives,asset position   1.2  
Commodity Derivative, net asset position $ 1.7 $ 4.0  
SCE&G      
Gain (Loss) on Derivatives      
Interest Rate Cash Flow Hedge Ineffectiveness is Immaterial insignificant insignificant insignificant
Derivative, Credit Risk Related Contingent Features [Abstract]      
Collateral Already Posted, Aggregate Fair Value $ 11.0 $ 10.1  
Additional collateral required to be posted to counterparties if all underlying contingent features were fully triggered 0.2 4.6  
Aggregate fair value of all derivative instruments with contingent provisions that are in a net liability position 11.2 14.7  
Cash collateral requested from counterparty 0.0 53.5  
Derivative, net asset position 0.0 53.5  
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Deferred in Regulatory Accounts Effective Portion, Net 64.0 (32.0) $ (34.0)
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | SCE&G      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Deferred in Regulatory Accounts Effective Portion, Net 64.0 (32.0) (34.0)
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 (2.0) (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 (2.0) (3.0)  
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 115.0 (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 0.0 (173.0) (2.0)
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     (2.0)
Interest Rate Contract [Member] | Cash Flow Hedging [Member] | SCE&G      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Deferred in Regulatory Accounts Effective Portion, Net 1.0 (2.0) 0.0
Interest Rate Contract [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]      
Gain (Loss) on Derivatives      
Derivative Instruments, Gain (Loss) Deferred in Regulatory Accounts Effective Portion, Net $ 1.0 $ (2.0) $ 0.0