AFFILIATED TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Canadys Refined Coal [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	$ 7.6		$ 7.6		$ 16.0
Equity Method Investment, Ownership Percentage	40.00%		40.00%
Related Party Transaction, Purchases from Related Party	$ 47.5	$ 41.8	$ 144.9	$ 138.6
Sales to Affiliates	47.2	41.6	144.0	137.8
Due to Related Parties	7.7		7.7		16.1
Energy Marketing [Member]
Related Party Transaction [Line Items]
Due to Affiliate, Current	10.7		10.7		8.8
Cost of Natural Gas Purchases	35.3	34.8	93.4	83.1
SCANA Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	78.1	$ 80.4	233.6	$ 236.4
Accounts Payable, Related Parties, Current	45.3		45.3		63.5
SCEG
Related Party Transaction [Line Items]
Due to Affiliate, Current	96.0		96.0		122.0
Due from Affiliate, Current	$ 8.0		$ 8.0		$ 16.0

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