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Employee Benefit Plans (Employee Savings Plans)(Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Jan. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   $ 169.0 $ 159.0 $ 143.0
Employee Savings Plans [Abstract]        
Matching contribution percentage   100.00%    
Eligible pay percentage   6.00%    
Additional contribution percentage for employees not participating in defined pension plans   4.00%    
Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   $ 155.0 302.0  
Duke Energy Carolinas [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   57.0 54.0 47.0
Duke Energy Carolinas [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   43.0 91.0  
Progress Energy [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   50.0 48.0 43.0
Progress Energy [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   43.0 83.0  
Duke Energy Progress [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   35.0 34.0 30.0
Duke Energy Progress [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   24.0 42.0  
Duke Energy Florida [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   15.0 13.0 14.0
Duke Energy Florida [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   20.0 40.0  
Duke Energy Ohio [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   3.0 3.0 3.0
Duke Energy Ohio [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   5.0 8.0  
Duke Energy Indiana [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Contribution Plan, Cost Recognized   8.0 7.0 $ 7.0
Duke Energy Indiana [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Employer contributions   $ 9.0 $ 19.0  
Piedmont Natural Gas [Member]        
Employee Savings Plans [Abstract]        
Eligible pay percentage   5.00%    
Additional contribution percentage for employees not participating in defined pension plans   4.00%    
Piedmont Natural Gas [Member] | Pension Plan [Member]        
Employee Savings Plans [Abstract]        
Eligible pay percentage   4.00%    
Piedmont Natural Gas [Member] | Pension Plan [Member] | Subsequent Event [Member]        
Employee Savings Plans [Abstract]        
Employer contributions $ 2.2