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Employee Benefit Plans (Employee Savings Plans) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Matching contribution percentage 100.00%    
Eligible pay percentage 6.00%    
Additional contribution percentage for employees not participating in defined pension plans 4.00%    
Employer contributions $ 213 $ 214 $ 213
Vesting period 3 years    
Duke Energy Carolinas      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 67 66 68
Progress Energy      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions 57 58 58
Duke Energy Progress      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions 38 38 40
Duke Energy Florida      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions 19 20 19
Duke Energy Ohio      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions 5 5 4
Duke Energy Indiana      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions 11 11 10
Piedmont      
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 13 $ 13 $ 12
Minimum | Piedmont      
Defined Benefit Plan Disclosure [Line Items]      
Additional contribution percentage for employees not participating in defined pension plans 3.00%    
Maximum | Piedmont      
Defined Benefit Plan Disclosure [Line Items]      
Additional contribution percentage for employees not participating in defined pension plans 5.00%