DERIVATIVE FINANCIAL INSTRUMENTS Derivative Financial Instruments Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4	$ 59
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	4	59
Derivative Liability, Fair Value, Gross Liability	29	38
Derivative Liability, Fair Value, Gross Asset	0	(1)
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	27	27
Derivative Liability, Fair Value, Amount Offset Against Collateral	2	64
Derivative Liability	29	37
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	4	59
Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability	4	7
Prepayments [Member]
Derivative [Line Items]
Derivative Liability	2
Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset	3	58
Derivative Liability		2
Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset	1	1
Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	23	28
Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	54
Derivative Asset	0	54
Derivative Liability, Fair Value, Gross Liability	25	32
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	26	28
Derivative Liability, Fair Value, Amount Offset Against Collateral	(1)	60
Derivative Liability	25	32
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	54
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Asset, Fair Value, Gross Liability	0
Derivative Asset	1	1
Derivative Liability, Fair Value, Gross Liability	1	3
Derivative Liability, Fair Value, Gross Asset	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	1	3
Derivative Liability	1	3
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	1
Other Energy Management Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3	4
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	3	4
Derivative Liability, Fair Value, Gross Liability	3	3
Derivative Liability, Fair Value, Gross Asset	0	(1)
Derivative, Collateral, Right to Reclaim Cash	1	1
Derivative Liability, Fair Value, Amount Offset Against Collateral	2	1
Derivative Liability	3	2
Derivative Asset, Fair Value, Amount Offset Against Collateral	3	4
SCEG
Derivative [Line Items]
Derivative Asset	0	54
Derivative Liability	11	15
SCEG | Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability	1	2
SCEG | Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset		54
SCEG | Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset	0	0
SCEG | Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	10	13
SCEG | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	54
Derivative Asset	0	54
Derivative Liability, Fair Value, Gross Liability	11	15
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	11	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	15
Derivative Liability	11	15
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0	$ 54