COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments and contingencies
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 31,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		270,000,000
Public Utilities, Property, Plant and Equipment, Amount of Acquisition Adjustments	$ 180,000,000	180,000,000
Sales and Excise Tax Payable	410,000,000	410,000,000
Utilities Operating Loss, Impairment, Net of Taxes		2,700,000	$ 690,000,000
Costs Not to Be Recovered Under Merger Agreement		180,000,000
Regulatory Request to Lower Revenues		445,000,000
Utilities Operating Expense, Impairments	0	3,600,000	1,118,000,000
Remaining Impairment Loss		4,900,000,000
Remaining Impairment Loss, Net of Tax		3,700,000,000
Long-term Line of Credit	1,800,000,000	1,800,000,000
Customer Refundable Fees, Refund Payments, Post Merger		$ 109,300,000
SCPSC Order Percentage Reduction Of Total Fuel Cost Component Of Retail Electric Rates To Reflect Lower Projected Fuel Costs And Eliminate Over-Collection Balances		5.00%
Costs Not to Be Recovered, Post Merger	2,000,000,000	$ 2,000,000,000
Long-term Debt, Current Maturities	568,000,000	568,000,000	727,000,000
Short-term borrowings	517,000,000	517,000,000	350,000,000
Impairment Cost, Additional Liabilities, Post Merger		1,700,000,000
Impairment Cost, Additional Liabilities, Post Merger, Net of Tax	1,000,000,000	1,000,000,000
Unrecovered Nuclear Project Costs	842,000,000	842,000,000
Customer Fees, Refunds Payments, Additional Liability	2,000,000,000	2,000,000,000
Monetization Settlement Exceeding Costs Incurred, Post Merger	1,000,000,000	1,000,000,000
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery		0.035
Guaranty Fee Income		2,200,000,000
Asset Impairment Charges		4,000,000
Monetization Settlement Exceeding Costs Incurred		1,997,000,000
Estimate of aggregate amount of subcontractor and vendor liens filed		290,000,000
Estimated Litigation Liability	75,000,000	75,000,000
Operating Leases, Future Minimum Payments Due	11,000,000	$ 11,000,000
Environmental
Goal For Reduced Carbon Dioxide Emissions From 2005 Levels By 2030 Under Clean Air Act		32.00%
Summer Station Unit 2 and Unit 3 [Domain]
Commitments and contingencies
Customer Refundable Fees, Refund Payments, Post Merger		$ 1,300,000,000
Debt Instrument, Periodic Payment, Interest		318,000,000
Short-term borrowings	517,000,000	517,000,000
SCEG
Commitments and contingencies
Regulatory Request to Lower Revenues		2,100,000,000
Utilities Operating Expense, Impairments		4,000,000
Long-term Line of Credit	1,200,000,000	1,200,000,000
Long-term Debt, Current Maturities	564,000,000	564,000,000	723,000,000
Short-term borrowings	457,000,000	457,000,000	$ 252,000,000
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery		1,300,000
Guarantee Settlement Receipts		1,200,000,000
Asset Impairment Charges		4,000,000
Monetization Settlement Exceeding Costs Incurred		1,098,000,000
Estimate of aggregate amount of subcontractor and vendor liens filed		33,000,000
Operating Leases, Future Minimum Payments Due	3,000,000	3,000,000
Nuclear Insurance
Maximum liability assessment per reactor for each nuclear incident		127,300,000
Maximum Insurance Coverage For Each Nuclear Plant by ANI	450,000,000	450,000,000
Federal Limit on Public Liability Claims from Nuclear Incident Approximate		13,100,000,000
Maximum Federal Limit on Public Liability Claims Per Reactor for Each Year		18,900,000
Maximum Federal Limit on Public Liability Claims per Reactor for each Nuclear Incident at 2/3		84,800,000
Maximum Federal Limit on Public Liability Claims Per Incident for Each Year		$ 12,600,000
Inflation adjustment period for nuclear insurance		5
NEIL Maximum Insurance Coverage To Nuclear Facility For Property Damage And Outage Costs From Non-Nuclear Event		$ 2,330,000,000
NEIL Maximum Insurance Coverage of Accidental Property Damage	2,750,000,000	2,750,000,000
EMANI Maximum Retrospective Premium Assessment		2,000,000
EMANI Maximum Insurance Coverage for Summer Station Unit 1 For Property Damage And Outage Costs From Non-Nuclear Event		415,000,000
NEIL Maximum Prosepective Insurance Premium Per Nuclear Incident		23,400,000
NEIL Maximum Insurance Coverage to Nuclear Facility for Property Damage and Outage Costs	2,750,000,000	2,750,000,000
Environmental
Environmental Remediation Costs Recognized in Regulatory Assets	$ 23,900,000	$ 23,900,000
Number of MGP decommissioned sites that contain residues of byproduct chemicals	4	4
Number Of States Required To Reduce Emissions Under CSAPR	28	28
Site Contingency MGP Estimated Environmental Remediation Costs		$ 9,800,000
SCEG | SCEG
Commitments and contingencies
Debt Instrument, Periodic Payment, Interest		238,000,000
Short-term borrowings	$ 457,000,000	457,000,000
Summer Station Unit 2 and Unit 3 [Domain]
Commitments and contingencies
Estimate of aggregate amount of subcontractor and vendor liens filed		$ 60,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share	55.00%	55.00%