COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017	Dec. 31, 2016
Environmental
Goal For Reduced Carbon Dioxide Emissions From 2005 Levels By 2030 Under Clean Air Act		32.00%
NPDES permit renewal permit period		five
Nuclear Generation
Impairment of Retained Interest	$ 6.2
Summer Station New Units [Domain]
Nuclear Generation
Guaranty Fee Income		$ 2.2
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	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
Maximum loss for a single nuclear incident		$ 2,750,000,000
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	500,000,000	500,000,000
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	2,750,000,000
Environmental
Environmental Remediation Costs Recognized in Regulatory Assets	$ 25,000,000	$ 25,000,000
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		$ 9,900,000
Nuclear Generation
Estimate of aggregate amount of subcontractor and vendor liens filed		142,000,000
Aggregate amount of subcontractor and vendor liens paid		27,500,000
EPC Contract Amendment, Fixed Price Option, Price For New Nuclear Construction After June 2015		3,345,000,000
Guaranty Fee Income		1.2
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	6,800,000,000
Total New Nuclear Project Cost 2016, including AFC and escalation	7,700,000,000	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
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	4,900,000,000	4,900,000,000
Summer Station New Units [Domain]
Nuclear Generation
jointly owned utility plant ownership, construction financing cost	$ 3,800,000,000	$ 3,800,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share	55.00%	55.00%
Estimate of aggregate amount of subcontractor and vendor liens filed		$ 258,000,000
Aggregate amount of subcontractor and vendor liens paid		50,000,000
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%