RATE AND OTHER REGULATORY MATTERS (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Rate Matters [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%		35.00%	35.00%
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery	$ 0.035
Asset Retirement Obligation Costs [Member]
Rate Matters [Line Items]
Regulatory Noncurrent Asset Amortization Period	107 years
Environmental Restoration Costs [Member]
Rate Matters [Line Items]
MPG environmental remediation	17
SCEG
Rate Matters [Line Items]
SCPSC Order, Recovery Of Projected DER Program Costs	$ 29,300,000
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery	1,300,000
SCPSC Order, Annual DSM Program Rate Rider Recovery Amount	33,000,000
SCEG | Pension costs, electric [Member]
Rate Matters [Line Items]
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	2,000,000
SCEG | Pension costs, gas [Member]
Rate Matters [Line Items]
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	$ 1,000,000
PSNC Energy
Rate Matters [Line Items]
MPG environmental remediation	6.9
Pipeline integrity mgmt annual revenue requirement approved by NCUC	$ 14,700,000	$ 700,000	$ 1,900,000