v3.10.0.1
EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Details 5) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   $ 2.0 $ 0.0 $ 0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax   $ (2.0) 0.0 1.0
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate   5.00%    
Defined Contribution Plan, Maximum Percentage of Employer Contribution for up to Six Percent of Participant Contribution   100.00%    
Defined Contribution Plan, Maximum Percentage of Participant Contribution Eligible for Employer Contribution Match   6.00%    
Defined Contribution Plan, Cost   $ 24.1 27.9 27.5
Pension Plan, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   4.5 (1.0) 0.6
Amortization of deferred employee benefit plan costs reclassified to net income, net of tax   (0.5) (0.6) (0.6)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax   0.0 0.0 (0.1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax   4.0 (1.6) (0.1)
Defined Benefit Plan, Service Cost   21.0 21.7 20.7
Defined Benefit Plan, Interest Cost   34.1 37.4 39.4
Defined Benefit Plan, Expected Return (Loss) on Plan Assets   (56.7) (54.7) (55.9)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)   0.5 1.6 3.9
Defined Benefit Plan, Amortization of Gain (Loss)   12.8 16.3 14.8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)   $ 11.7 $ 22.3 $ 22.9
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate   3.71% 4.22% 4.68%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets   7.00% 7.25% 7.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   3.00% 3.00% 3.00%
Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   $ (2.4) $ 1.1 $ 0.8
Amortization of deferred employee benefit plan costs reclassified to net income, net of tax   0.0 (0.1) 0.0
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax   0.0 0.0 0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax   (2.4) 1.0 0.8
Defined Benefit Plan, Service Cost   4.6 4.5 4.4
Defined Benefit Plan, Interest Cost   10.1 11.5 12.1
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)   0.0 0.0 0.3
Defined Benefit Plan, Amortization of Gain (Loss)   0.7 1.0 0.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)   $ 15.4 $ 17.0 $ 17.3
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate   3.74% 4.30% 4.78%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   3.00% 3.00% 3.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year   7.00% 6.60% 7.00%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate   5.00% 5.00% 5.00%
SCE&G        
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   $ 0.0 $ 0.0 $ 0.0
Amortization of deferred employee benefit plan costs reclassified to net income, net of tax   $ 0.0 (1.0) 0.0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets   7.00%    
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate   5.00%    
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year   insignificant    
Defined Contribution Plan, Maximum Percentage of Employer Contribution for up to Six Percent of Participant Contribution   100.00%    
Defined Contribution Plan, Maximum Percentage of Participant Contribution Eligible for Employer Contribution Match   6.00%    
Defined Contribution Plan, Cost   $ 19.6 23.4 22.9
SCE&G | Pension Plan, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   1.4 0.3 0.0
Amortization of deferred employee benefit plan costs reclassified to net income, net of tax   (0.1) (0.1) (0.1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax   1.3 0.2 (0.1)
Defined Benefit Plan, Service Cost   17.1 18.1 16.9
Defined Benefit Plan, Interest Cost   29.0 31.9 33.4
Defined Benefit Plan, Expected Return (Loss) on Plan Assets   (48.1) (46.7) (47.4)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)   0.4 1.4 3.4
Defined Benefit Plan, Amortization of Gain (Loss)   10.9 13.9 12.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)   $ 9.3 $ 18.6 $ 18.8
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate   3.71% 4.22% 4.68%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets   7.00% 7.25% 7.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   3.00% 3.00% 3.00%
SCE&G | Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax   $ (1.0) $ 0.5 $ 0.3
Amortization of deferred employee benefit plan costs reclassified to net income, net of tax   0.0 0.0 0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax   (1.0) 0.5 0.3
Defined Benefit Plan, Service Cost   3.6 3.7 3.6
Defined Benefit Plan, Interest Cost   8.0 9.5 9.9
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)   0.0 0.0 0.3
Defined Benefit Plan, Amortization of Gain (Loss)   0.6 0.8 0.4
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)   $ 12.2 $ 14.0 $ 14.2
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate   3.74% 4.30% 4.78%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   3.00% 3.00% 3.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year   7.00% 6.60% 7.00%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate   5.00% 5.00% 5.00%
Scenario, Forecast [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets 7.00%      
Scenario, Forecast [Member] | Pension Plan, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Amortization of Net Gains (Losses) $ 0.8      
Defined benefit plan, future amortization of gain or loss from regulatory assets 14.7      
Defined benefit plan, future amortization of prior service cost (credit) from regulatory assets 0.3      
Defined benefit plan, amount to be amortized from regulatory assets next year 15.0      
Scenario, Forecast [Member] | Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Amortization of Net Gains (Losses) 0.0      
Defined benefit plan, future amortization of gain or loss from regulatory assets 0.0      
Defined benefit plan, future amortization of prior service cost (credit) from regulatory assets 0.0      
Defined benefit plan, amount to be amortized from regulatory assets next year 0.0      
Scenario, Forecast [Member] | SCE&G | Pension Plan, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Defined benefit plan, future amortization of gain or loss from regulatory assets 12.9      
Defined benefit plan, future amortization of prior service cost (credit) from regulatory assets 0.3      
Defined benefit plan, amount to be amortized from regulatory assets next year 13.2      
Scenario, Forecast [Member] | SCE&G | Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined benefit plan, future amortization of gain or loss from regulatory assets 0.0      
Defined benefit plan, future amortization of prior service cost (credit) from regulatory assets 0.0      
Defined benefit plan, amount to be amortized from regulatory assets next year $ 0.0