DERIVATIVE FINANCIAL INSTRUMENTS Derivative Financial Instruments Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 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	22	38
Derivative Liability, Fair Value, Gross Asset	0	(1)
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	22	27
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	64
Derivative Liability	22	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	2	7
Prepayments [Member]
Derivative [Line Items]
Derivative Asset	3
Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset	1	58
Derivative Liability		2
Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset		1
Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	18	28
Other Liabilities	2
Interest Rate Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	54
Derivative Asset	0	54
Derivative Liability, Fair Value, Gross Liability	20	32
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	21	28
Derivative Liability, Fair Value, Amount Offset Against Collateral	(1)	60
Derivative Liability	20	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	2	1
Derivative Asset, Fair Value, Gross Liability	0
Derivative Asset	2	1
Derivative Liability, Fair Value, Gross Liability	0	3
Derivative Liability, Fair Value, Gross Asset	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	3
Derivative Liability	0	3
Derivative Asset, Fair Value, Amount Offset Against Collateral	2	1
Other Energy Management Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	4
Derivative Asset, Fair Value, Gross Liability	0	0
Derivative Asset	2	4
Derivative Liability, Fair Value, Gross Liability	2	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	1	1
Derivative Liability	2	2
Derivative Asset, Fair Value, Amount Offset Against Collateral	2	4
SCEG
Derivative [Line Items]
Derivative Asset	0	54
Derivative Liability	9	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
SCEG | Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	8	13
SCEG | Interest Rate Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	54
Derivative Asset	0	54
Derivative Liability, Fair Value, Gross Liability	9	15
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	9	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	15
Derivative Liability	9	15
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0	$ 54