COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Environmental
Goal For Reduced Carbon Dioxide Emissions From 2005 Levels By 2030 Under Clean Air Act		32.00%
Nuclear Generation
Change in Retail Electric Rates Approved Under BLRA		$ 1,800,000,000
Asset Impairment Charges		210,000,000
Guaranty Fee Income		2,200,000,000
Other Receivables, Gross, Current		1,016,000,000
Guaranty Assets		83,000,000
Impairment of Retained Interest	$ 6.2
Summer Station New Units [Domain]
Nuclear Generation
Guaranty Fee Income		2,200,000,000
Other Receivables, Gross, Current		1,847,000,000
SCEG
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
Federal Limit on Public Liability Claims from Nuclear Incident Approximate		13,400,000,000
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
EMANI Maximum Retrospective Premium Assessment		1,900,000
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		45,400,000
NEIL Maximum Insurance Coverage to Nuclear Facility for Property Damage and Outage Costs		2,750,000,000
Environmental
Environmental Remediation Costs Recognized in Regulatory Assets		$ 24,700,000
Number of MGP decommissioned sites that contain residues of byproduct chemicals		4
Number Of States Required To Reduce Emissions Under CSAPR		28
Site Contingency MGP Estimated Environmental Remediation Costs		$ 9,900,000
Nuclear Generation
Estimate of aggregate amount of subcontractor and vendor liens filed		166,000,000
Asset Impairment Charges		210,000,000
EPC Contract Amendment, Fixed Price Option, Price For New Nuclear Construction After June 2015		3,345,000,000
Guaranty Fee Income		1,200,000,000
Monetization of guaranty settlement		1,000,000,000
Unrecovered nuclear project costs post impairment after Toshiba Settlement offset		3,500,000,000
Guaranty Assets		83,000,000
November 2016 SCPSC Approved Project Costs above SCPSC 2015 order		831,000,000
Total New Nuclear Project Cost Nov 2016, excludes AFC and escalation		6,800,000,000
Total New Nuclear Project Cost 2016, including AFC and escalation		7,700,000,000
Public Utilities, Authorized Allowable Return on Common Equity, Percentage				10.50%
Summer Station New Units and Transmission Assets [Domain]
Nuclear Generation
Guaranty Assets		150,000,000
SCEG
Nuclear Generation
Guaranty Assets		82,500,000
Summer Station New Units [Domain]
Nuclear Generation
jointly owned utility plant ownership, construction financing cost		$ 3,800,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share		55.00%
Estimate of aggregate amount of subcontractor and vendor liens filed		$ 302,000,000
Unrecovered nuclear project costs post impairment		4,500,000,000
Nuclear Production Tax Credits		1,400,000,000
EPC Contract Amendment, Fixed Price Option, Price For New Nuclear Construction After June 2015		$ 6,082,000,000
Scenario, Forecast [Member] | SCEG
Nuclear Generation
Public Utilities, Authorized Allowable Return on Common Equity, Percentage			10.25%
Summer Station New Units [Domain]
Nuclear Generation
Change in Retail Electric Rates Approved Under BLRA			$ 445,000,000