SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) MW	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) MW	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Reclassification Operations and Maintenance Expense	$ (2.0)		$ (6.0)
Reclassification Total Operating Expense	(2.0)		(6.0)
Reclassification Operating Income	2.0		6.0
Reclassification Other Income(Expense)	(2.0)		(6.0)
Property, Plant and Equipment, Net	267.0		267.0		$ 270.0
SCEG
Reclassification Operations and Maintenance Expense		$ (1.0)		$ (5.0)
Reclassification Total Operating Expense		(1.0)		(5.0)
Reclassification Operating Income		1.0		5.0
Reclassification Other Income(Expense)		$ (1.0)		$ (5.0)
Property, Plant and Equipment, Net	73.0		73.0		$ 71.0
Genco
Property, Plant and Equipment, Net	$ 497.0		$ 497.0
Power Generation Capacity Megawatts | MW	605		605
PSNC Energy [Member]
Percentage of natural gas inventory held by counterparties under asset management and supply service agreements (as a percent)	41.00%		41.00%		39.00%
Natural gas inventory, carrying amount	$ 9.8		$ 9.8		$ 11.5
PercentOfStorageFeesCreditedToRatePayers			75.00%