RATE AND OTHER REGULATORY MATTERS (Details 2) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Regulatory Assets
Asset Impairment Charges		$ 4.0	$ 210.0
Regulatory Liability, Noncurrent		3,040.0		$ 3,059.0
Regulatory Assets, Noncurrent		5,739.0		5,580.0
SCEG
Regulatory Assets
Asset Impairment Charges		4.0	$ 210.0
Regulatory Liability, Noncurrent		2,635.0		2,667.0
Regulatory Assets, Noncurrent		5,623.0		5,476.0
PSNC Energy [Member]
Regulatory Assets
Pipeline integrity mgmt annual revenue requirement approved by NCUC	$ 14.7
Pipeline integrity management costs, amount deferred pending future approval of rate recovery		$ 44.9
MPG environmental remediation		4.2
Pipeline integrity management costs, amount recovering beginning November 2016		$ 4.1
Settlement Proceeds [Member] | Summer Station Unit 2 and Unit 3 [Domain]
Regulatory Assets
Regulatory Liability, Noncurrent		1,098.0		1,095.0
Settlement Proceeds [Member] | SCEG
Regulatory Assets
Regulatory Liability, Noncurrent		1,098.0		1,095.0
Deferred Income Tax Charge [Member]
Regulatory Assets
Regulatory Liability, Noncurrent		1,075.0		1,076.0
Deferred Income Tax Charge [Member] | SCEG
Regulatory Assets
Regulatory Liability, Noncurrent		916.0		914.0
Asset Retirement Obligation Costs [Member]
Regulatory Assets
Regulatory Liability, Noncurrent		775.0		757.0
Asset Retirement Obligation Costs [Member] | SCEG
Regulatory Assets
Regulatory Liability, Noncurrent		539.0		527.0
Deferred gains on interest rate derivatives [Member]
Regulatory Assets
Regulatory Liability, Noncurrent		77.0		131.0
Deferred gains on interest rate derivatives [Member] | SCEG
Regulatory Assets
Regulatory Liability, Noncurrent		77.0		131.0
Other Regulatory Liability [Member]
Regulatory Assets
Regulatory Liability, Noncurrent		15.0
Other Regulatory Liability [Member] | SCEG
Regulatory Assets
Regulatory Liability, Noncurrent		5.0		0.0
Unrecovered nuclear project costs post impairment [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		$ 4,140.0		3,976.0
Unrecovered nuclear project costs post impairment [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent				3,976.0
Asset Retirement Obligation Costs [Member]
Regulatory Assets
Regulatory Asset, Amortization Period		107 years
Regulatory Assets, Noncurrent		$ 448.0		434.0
Asset Retirement Obligation Costs [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		423.0		410.0
Pension Costs [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		282.0		305.0
Pension Costs [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		254.0		273.0
Deferred Losses On Interest Rate Derivatives [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		446.0		456.0
Deferred Losses On Interest Rate Derivatives [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		446.0		456.0
unrecovered plant [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		96.0		105.0
unrecovered plant [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		96.0		105.0
Demand Side Management programs [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		$ 57.0		59.0
Demand Side Management programs [Member] | SCEG
Regulatory Assets
Regulatory Asset, Amortization Period		5 years
Regulatory Assets, Noncurrent		$ 57.0		59.0
Pipeline integrity management costs [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		67.0		51.0
Pipeline integrity management costs [Member] | SCEG
Regulatory Assets
Pipeline integrity management costs, annual amortization amount		1.9
Regulatory Assets, Noncurrent		$ 9.0		8.0
Environmental Restoration Costs [Member]
Regulatory Assets
MPG environmental remediation		17
Regulatory Assets, Noncurrent		$ 28.0		30.0
Environmental Restoration Costs [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		24.0		25.0
Storm Costs [Member]
Regulatory Assets
Regulatory Assets, Noncurrent		29.0		24.0
Storm Costs [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		$ 29.0		24.0
Other Regulatory Assets [Member]
Regulatory Assets
Regulatory Asset Recovery Assessments		2047
Regulatory Assets, Noncurrent		$ 135.0		140.0
Other Regulatory Assets [Member] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		134.0		$ 140.0
Deferred transmission operating costs [Member] [Domain]
Regulatory Assets
Regulatory Assets, Noncurrent		11.0
Deferred transmission operating costs [Member] [Domain] | SCEG
Regulatory Assets
Regulatory Assets, Noncurrent		$ 11.0