AFFILIATED TRANSACTIONS (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Advances to Affiliate	$ 71,000,000		$ 71,000,000
Canadys Refined Coal [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party	$ 8,500,000		$ 8,500,000		$ 4,900,000
Equity Method Investment, Ownership Percentage	40.00%		40.00%
Related Party Transaction, Purchases from Related Party	$ 45,200,000	$ 47,500,000	$ 122,500,000	$ 144,900,000
Sales to Affiliates	44,900,000	47,200,000	121,800,000	144,000,000
Due to Related Parties	8,500,000		8,500,000		4,900,000
Energy Marketing [Member]
Related Party Transaction [Line Items]
Due to Affiliate, Current	10,600,000		10,600,000		10,000,000
Related Party Transaction, Purchases from Related Party	35,000	35,300,000	95,000,000	93,400,000
SCANA Services [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	72,900,000	$ 78,100,000	208,300,000	$ 233,600,000
Accounts Payable, Related Parties, Current	42,800,000		42,800,000		42,000,000
SCEG
Related Party Transaction [Line Items]
Due to Affiliate, Current	259,000,000		259,000,000		102,000,000
Due from Affiliate, Current	$ 186,000,000		$ 186,000,000		$ 32,000,000