REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2019	Dec. 31, 2017
Regulatory Assets, Noncurrent	$ 4,380.0		$ 5,580.0
Regulatory Liability, Noncurrent	2,789.0		3,059.0
Asset Retirement Obligation Costs [Member]
Regulatory Liability, Noncurrent	779.0		757.0
Deferred Income Tax Charge [Member]
Regulatory Liability, Noncurrent	814.0		1,076.0
Deferred gains on interest rate derivatives [Member]
Regulatory Liability, Noncurrent	77.0		131.0
Other Regulatory Liability [Member]
Regulatory Liability, Noncurrent	21.0		0.0
Unrecovered nuclear project costs post impairment [Member]
Regulatory Assets, Noncurrent	2,768.0
Demand Side Management programs [Member]
Regulatory Assets, Noncurrent	65.0		59.0
Pipeline integrity management costs [Member]
Regulatory Assets, Noncurrent	73.0		51.0
Storm Costs [Member]
Regulatory Assets, Noncurrent	35.0		24.0
Deferred transmission operating costs [Member] [Domain]
Regulatory Assets, Noncurrent	$ 15.0		0.0
Asset Retirement Obligation Costs [Member]
Regulatory Asset, Amortization Period	106 years
Regulatory Assets, Noncurrent	$ 406.0		434.0
Pension Costs [Member]
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	1.0
Regulatory Assets, Noncurrent	302.0		305.0
Deferred Losses On Interest Rate Derivatives [Member]
Regulatory Assets, Noncurrent	448.0		456.0
Canadys Refined Coal [Member]
Regulatory Assets, Noncurrent	93.0		105.0
Environmental Restoration Costs [Member]
Regulatory Assets, Noncurrent	$ 27.0		30.0
Other Regulatory Assets [Member]
Regulatory Asset Recovery Assessments	2047
Regulatory Assets, Noncurrent	$ 148.0		140.0
Summer Station Unit 2 and Unit 3 [Domain] | Settlement Proceeds [Member]
Regulatory Liability, Noncurrent	1,098.0		1,095.0
SCE&G
Regulatory Assets, Noncurrent	4,256.0		5,476.0
Regulatory Liability, Noncurrent	2,380.0		2,667.0
SCE&G | Settlement Proceeds [Member]
Regulatory Liability, Noncurrent	1,098.0		1,095.0
SCE&G | Asset Retirement Obligation Costs [Member]
Regulatory Liability, Noncurrent	541.0		527.0
SCE&G | Deferred Income Tax Charge [Member]
Regulatory Liability, Noncurrent	659.0		914.0
SCE&G | Deferred gains on interest rate derivatives [Member]
Regulatory Liability, Noncurrent	77.0		131.0
SCE&G | Other Regulatory Liability [Member]
Regulatory Liability, Noncurrent	5.0		0.0
SCE&G | Unrecovered nuclear project costs post impairment [Member]
Regulatory Assets, Noncurrent	2,768.0		3,976.0
SCE&G | Demand Side Management programs [Member]
Regulatory Assets, Noncurrent	65.0		59.0
SCE&G | Pipeline integrity management costs [Member]
Regulatory Assets, Noncurrent	9.0		8.0
Pipeline integrity management costs, annual amortization amount	3.2	$ 1.9
SCE&G | Storm Costs [Member]
Regulatory Assets, Noncurrent	35.0		24.0
SCE&G | Deferred transmission operating costs [Member] [Domain]
Regulatory Assets, Noncurrent	15.0		0.0
SCE&G | Asset Retirement Obligation Costs [Member]
Regulatory Assets, Noncurrent	380.0		410.0
SCE&G | Pension Costs [Member]
Defined Benefit Plan, Deferred Debit Attributable to Share of Regulatory Authority	2.0
Regulatory Assets, Noncurrent	272.0		273.0
SCE&G | Deferred Losses On Interest Rate Derivatives [Member]
Regulatory Assets, Noncurrent	448.0		456.0
SCE&G | Canadys Refined Coal [Member]
Regulatory Assets, Noncurrent	93.0		105.0
SCE&G | Environmental Restoration Costs [Member]
Regulatory Assets, Noncurrent	24.0		25.0
SCE&G | Other Regulatory Assets [Member]
Regulatory Assets, Noncurrent			$ 140.0
PSNC Energy [Member]
Pipeline integrity management costs, amount recovering beginning November 2016	4.1
Pipeline integrity management costs, amount deferred pending future approval of rate recovery	$ 51.3