FAIR VALUE MEASUREMENTS, INCLUDING DERIVATIVES (Details 2) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 6,728.9	$ 6,632.9
Long-term Debt, Fair Value	7,220.1	7,399.7
SCEG
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	5,259.0	5,163.3
Long-term Debt, Fair Value	$ 5,649.1	$ 5,790.3
Nuclear Fuel [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Level 3 fair value measurements	40.2