v3.10.0.1
RATE AND OTHER REGULATORY MATTERS RATE AND OTHER REGULATORY MATTERS (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
PSNC Energy Rate Case Application, Increase Amount                 $ 0.18
Public Utilities, Approved Rate Increase (Decrease), Percentage             3.20%    
SCPSC Order Reduction Of Total Fuel Cost Component Of Retail Electric Rates To Reflect Lower Projected Fuel Costs And Eliminate Over-Collection Balances             $ 2,000,000,000    
Deferred Revenue, Refund Payments             2,039,000,000    
Customer Refundable Fees, Alternative Plan over 20 yrs             1,032,000,000    
Customer Refundable Fees, Alternative Plan             1,007,000,000    
Refundable Gas Costs   $ 2,450,000         2,450,000    
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Charitable Contributions, Amount             1,000,000    
SCPSC Order, Recovery Of Projected DER Program Costs             29,300,000    
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery           $ 35,400,000 $ 1,300,000    
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent         35.00%   21.00% 35.00%  
Refund to Customer Related to Tax Act             $ 73,700,000    
Change in Retail Electric Rates Approved Under BLRA             2,768,000,000   $ 64,400,000
Public Utilities, Approved Return on Equity, Percentage           10.00%     10.50%
SCE&G                  
Demand Side Management Program Costs, Noncurrent   33,000,000   $ 37,000,000   $ 30,300,000 33,000,000 $ 37,000,000 $ 37,600,000
SCPSC Order Reduction Of Total Fuel Cost Component Of Retail Electric Rates To Reflect Lower Projected Fuel Costs And Eliminate Over-Collection Balances             31,000,000   61,000,000
SCPSC Order, Recovery Of Projected DER Program Costs               16,500,000 6,900,000
SCPSC Order for Increase of Total Fuel Cost Component of Retail Electric Rates to produce a projected under recovery               61,000,000  
Carrying costs on deferred income tax assets               18,800,000 $ 14,000,000
SCPSC Order, Approx Annual pension rider decrease amount               11,900,000  
Refund to Customer Related to Tax Act           67,000,000 $ 100,000,000    
PSNC Energy [Member]                  
Customer Credits, Alternative Plan over 3 yrs           $ 1,250,000      
PSNC Energy Rate Case Application, Increase Amount               $ 19,100,000  
Public Utilities, Approved Rate Increase (Decrease), Percentage               4.39%  
Pipeline integrity mgmt annual revenue requirement approved by NCUC $ 1,700,000 $ 1,100,000 $ 14,700,000 $ 700,000 $ 1,900,000        
Asset Retirement Obligation Costs [Member]                  
Regulatory Asset, Amortization Period             106 years    
Revenue Subject to Refund [Member] | SCE&G                  
Refund to Customer Related to Tax Act             $ 3,700,000    
Revenue Subject to Refund [Member] | PSNC Energy [Member]                  
Refund to Customer Related to Tax Act             $ 15,400,000