AFFILIATED TRANSACTIONS -SCEG (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	$ 75.6	$ 73.1
Canadys Refined Coal [Member]
Related Party Transaction [Line Items]
Equity Method Investment, Ownership Percentage	40.00%
Related Party Transaction, Purchases from Related Party	$ 52.8	70.1
Sales to Affiliate	52.5	69.7
Related Party Tax Expense, Due from Affiliates, Current	15.2	12.8
Related Party Tax Expense, Due to Affiliates, Current	15.3	12.9
Carolina Gas Transmission [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party			$ 3.4
Energy Marketing [Member]
Related Party Transaction [Line Items]
Due to Affiliate, Current	4.0		7.5
Cost of Natural Gas Purchases	22.4	$ 34.6
SCEG
Related Party Transaction [Line Items]
Due to Affiliate, Current	116.0		113.0
Due from Affiliate, Current	15.0		22.0
Accounts Payable, Related Parties, Current	$ 48.1		$ 57.0

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Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Cost of natural gas purchased and associated transportation and storage costs during the period.

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Amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership, due within 1 year (or 1 business cycle).

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Amount of payable due to an entity that is affiliated with the reporting entity by means of direct or indirect ownership. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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