RATE AND OTHER REGULATORY MATTERS (Details 3) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%	35.00%
Regulatory Liabilities	$ 3,040.0		$ 3,059.0
SCEG
Regulatory Liabilities [Line Items]
Refund to Customer Related to Tax Act	61.0
Regulatory Liabilities	2,635.0		2,667.0
PSNC Energy [Member]
Regulatory Liabilities [Line Items]
Refund to Customer Related to Tax Act	10.1
Settlement Proceeds [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,098.0		1,095.0
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,075.0		1,076.0
Deferred Income Tax Charge [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities	916.0		914.0
Asset Retirement Obligation Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	775.0		757.0
Asset Retirement Obligation Costs [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities	539.0		527.0
Deferred gains on interest rate derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	77.0		131.0
Deferred gains on interest rate derivatives [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities	77.0		131.0
Other Regulatory Liability [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	15.0
Other Regulatory Liability [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 5.0		$ 0.0