DERIVATIVE FINANCIAL INSTRUMENTS Derivative Financial Instruments Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 63	$ 90
Derivative Asset, Fair Value, Gross Liability	(3)	(4)
Derivative Asset	60	86
Derivative Liability, Fair Value, Gross Liability	78	67
Derivative Liability, Fair Value, Gross Asset	(3)	(3)
Derivative, Collateral, Right to Reclaim Securities	(7)	(9)
Derivative, Collateral, Right to Reclaim Cash	(31)	(29)
Derivative Liability, Fair Value, Amount Offset Against Collateral	37	26
Derivative Liability	75	64
Derivative, Collateral, Obligation to Return Securities	(7)	(9)
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	53	77
Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability	45	35
Prepayments [Member]
Derivative [Line Items]
Derivative Asset	1	9
Derivative Liability	1
Other Current Assets [Member]
Derivative [Line Items]
Derivative Asset	2	5
Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset	57	72
Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	29	29
Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	56	71
Derivative Asset	56	71
Derivative Liability, Fair Value, Gross Liability	72	58
Derivative, Collateral, Right to Reclaim Securities	(7)	(9)
Derivative, Collateral, Right to Reclaim Cash	(30)	(29)
Derivative Liability, Fair Value, Amount Offset Against Collateral	35	20
Derivative Liability	72	58
Derivative, Collateral, Obligation to Return Securities	(7)	(9)
Derivative Asset, Fair Value, Amount Offset Against Collateral	49	62
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	9
Derivative Asset, Fair Value, Gross Liability	(1)
Derivative Asset	1	9
Derivative Liability, Fair Value, Gross Liability	2	0
Derivative Liability, Fair Value, Gross Asset	(1)
Derivative Liability, Fair Value, Amount Offset Against Collateral	1	0
Derivative Liability	1	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	9
Other Energy Management Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5	10
Derivative Asset, Fair Value, Gross Liability	(2)	(4)
Derivative Asset	3	6
Derivative Liability, Fair Value, Gross Liability	4	9
Derivative Liability, Fair Value, Gross Asset	(2)	(3)
Derivative, Collateral, Right to Reclaim Cash	(1)
Derivative Liability, Fair Value, Amount Offset Against Collateral	1	6
Derivative Liability	2	6
Derivative Asset, Fair Value, Amount Offset Against Collateral	3	6
SCEG
Derivative [Line Items]
Derivative Asset	56	71
Derivative Liability	54	39
SCEG | Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Derivative Liability	41	28
SCEG | Other Deferred Debits and Other Assets [Member]
Derivative [Line Items]
Derivative Asset	56	71
SCEG | Other Deferred Credits and Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability	13	11
SCEG | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	56	71
Derivative Asset	56	71
Derivative Liability, Fair Value, Gross Liability	54	39
Derivative, Collateral, Right to Reclaim Securities	(7)	(9)
Derivative, Collateral, Right to Reclaim Cash	(10)	(9)
Derivative Liability, Fair Value, Amount Offset Against Collateral	37	21
Derivative Liability	54	39
Derivative, Collateral, Obligation to Return Securities	(7)	(9)
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 49	$ 62