COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended				9 Months Ended		12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments and contingencies
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 31,000,000
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		3,700,000,000	$ 2,700,000					$ 690,000,000
Impairment loss write off		3,960,000,000
Regulatory Request to Lower Revenues	$ 279,000,000				445,000,000
Utilities Operating Expense, Impairments		0	$ 3,600,000	$ 210,000,000	4,000,000	$ 210,000,000		1,118,000,000
Remaining Impairment Loss		5,000,000,000
Long-term Line of Credit		1,800,000,000			1,800,000,000
Costs Not to Be Recovered, Alternate Merger Plan		2,300,000,000			$ 2,300,000,000
Estimated Percentage Reduction Of Total Fuel Cost Component Of Retail Electric Rates To Reflect Lower Projected Fuel Costs And Eliminate Over-Collection Balances					14.00%
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%
Long-term Debt, Current Maturities		18,000,000			$ 18,000,000			727,000,000
Short-term borrowings		314,000,000			314,000,000			350,000,000
Impairment Cost, Additional Liabilities, Post Merger					1,700,000,000
Transmission Assets related to BLRA Capital Costs		376,000,000			376,000,000
Impairment Cost, Additional Liabilities, Post Merger Utility Plant Alternative Plan					86,000,000
Customer Fees, Refunds Payments, Additional Liability Alternative Plan		1,880,000,000			1,880,000,000
Impairment Cost, Additional Liabilities, Post Merger Utility Plant					86,000,000
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
Guarantee Settlement Receipts					2,200,000,000
Asset Impairment Charges					4,000,000	210,000,000
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		9,000,000			9,000,000
Summer Station Unit 2 and Unit 3 [Domain]
Commitments and contingencies
Customer Refundable Fees, Refund Payments, Post Merger					1,300,000,000
Customer Refundable Fees, Alternative Plan					1,910,000,000
Customer Refundable Fees, Alternative Plan over 20 yrs					1,000,000,000
Customer Credits, Alternative Plan over 10 yrs					880,000,000
Debt Instrument, Periodic Payment, Interest					335,000,000
Short-term borrowings		314,000,000			314,000,000
Impairment Cost, Additional Liabilities, Post Merger					800,000,000
Unrecovered Nuclear Project Costs		4,140,000,000			4,140,000,000
Impairment Cost, Additional Liabilities, Post Merger Alternative Plan					1,368,000,000
SCEG
Commitments and contingencies
Regulatory Request to Lower Revenues					2,100,000,000
Utilities Operating Expense, Impairments				$ 210,000,000	4,000,000	210,000,000
Long-term Line of Credit		1,200,000,000			1,200,000,000
Long-term Debt, Current Maturities		14,000,000			14,000,000			723,000,000
Short-term borrowings		173,000,000			173,000,000			$ 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	$ 210,000,000
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		$ 23,600,000			$ 23,600,000
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					$ 9,600,000
Environmental Exit Costs, Reasonably Possible Additional Loss					8,000,000
SCEG | SCEG
Commitments and contingencies
Debt Instrument, Periodic Payment, Interest					255,000,000
Short-term borrowings		$ 173,000,000			173,000,000
Summer Station Unit 2 and Unit 3 [Domain]
Commitments and contingencies
Transmission Assets related to BLRA Capital Costs		$ 365,000,000			365,000,000
Estimate of aggregate amount of subcontractor and vendor liens filed					$ 60,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share		55.00%			55.00%
Summer Station Unit 2 and Unit 3 [Domain]
Commitments and contingencies
Impairment Cost, Additional Liabilities, Post Merger, Net of Tax	$ 1,000,000,000						$ 1,000,000,000
Impairment Cost, Additional Liabilities, Post Merger Alternate Plan							$ 2,300,000,000