RATE AND OTHER REGULATORY MATTERS (Details 3) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2014	Jun. 30, 2015	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2013
Regulatory Liabilities [Line Items]
Regulatory Assets, Noncurrent			$ 1,884.0	$ 1,823.0
Regulatory Liabilities			859.0	$ 814.0
SCEG
Regulatory Liabilities [Line Items]
Public Utilities, Percent Increase (Decrease) in Retail Natural Gas Rates				0.60%
Storm Damage Reserve Applied To Offset Net Lost Margin Related To DSM	$ 5.0
Regulatory Assets, Noncurrent			1,808.0	$ 1,745.0
Public Utilities Increase (Decrease) in Retail Electric Rates Approved under BLRA			$ 65.0	66.0	$ 67.2
Public Utilities, Authorized Allowable Return on Common Equity, Percentage		11.00%	11.00%
Demand Side Management Program Costs, Noncurrent			$ 32.0			$ 15.4	$ 16.9
Regulatory Liabilities			641.0	610.0
Annual Storm Damage Costs not offset by Amounts Recovered through Electric Rates			2.5
Amount Allowed to be Recovered through Electric Rates to Offset Incremental Storm Damage Costs			100.0
Asset Retirement Obligation Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			729.0	703.0
Asset Retirement Obligation Costs [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities			520.0	505.0
Storm damage reserve [Member]
Regulatory Liabilities [Line Items]
Storm Damage Reserve Applied To Offset Net Lost Margin Related To DSM				5.0
Regulatory Liabilities			6.0	6.0
Annual Storm Damage Costs not offset by Amounts Recovered through Electric Rates			2.5
Amount Allowed to be Recovered through Electric Rates to Offset Incremental Storm Damage Costs			100.0
Storm damage reserve [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities			6.0	6.0
Deferred gains on interest rate derivatives [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			87.0	82.0
Deferred gains on interest rate derivatives [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities			87.0	82.0
Deferred Income Tax Charges [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			22.0	22.0
Deferred Income Tax Charges [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities			16.0	17.0
Planned major maintenance [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			12.0	0.0
Planned major maintenance [Member] | SCEG
Regulatory Liabilities [Line Items]
Regulatory Liabilities			$ 12.0	$ 0.0