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Commitments and Contingencies (Narrative) (Details)
gal in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Feb. 28, 2014
T
gal
Sep. 30, 2017
USD ($)
plant
claim
Sep. 30, 2017
USD ($)
plant
claim
Dec. 31, 2016
USD ($)
Mar. 31, 2014
USD ($)
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   $ 83,000,000 $ 83,000,000 $ 98,000,000  
Progress Energy Merger Shareholder Litigation [Member]          
Valuation and Qualifying Accounts [Abstract]          
Proceeds from Legal Settlements   $ 20,000,000      
Coal Ash Insurance Coverage Litigation [Member]          
Valuation and Qualifying Accounts [Abstract]          
Number of NC and SC Plants with Ash Basins | plant   15 15    
NCDEQ State Enforcement Actions [Member]          
Valuation and Qualifying Accounts [Abstract]          
Number of Plants with No Disputed Facts | plant   7 7    
Number of NC Plants with Ash Basins | plant   14 14    
Number of Plants with Disputed Facts | plant   7 7    
Groundwater Contamination Claims [Member]          
Valuation and Qualifying Accounts [Abstract]          
Goodwill Payment   $ 5,000 $ 5,000    
Water Bill Stipend Period     25 years    
Duke Energy Carolinas [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   23,000,000 $ 23,000,000 23,000,000  
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   19,000,000 19,000,000    
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member]          
Valuation and Qualifying Accounts [Abstract]          
Asbestos-related injuries and damages reserves   486,000,000 486,000,000 512,000,000  
Reinsurance retention policy, excess retention, amount reinsured     797,000,000    
Probable insurance recoveries   $ 570,000,000 $ 570,000,000 587,000,000  
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Non-Malignant Asbestos Claim [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss contingency, pending claims, number | claim   120 120    
Asbestos-related injuries and damages reserves   $ 29,000,000 $ 29,000,000    
Duke Energy Carolinas [Member] | Asbestos-related Injuries and Damages Claims [Member] | Malignant Asbestos Claim [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss contingency, pending claims, number | claim   57 57    
Asbestos-related injuries and damages reserves   $ 16,000,000 $ 16,000,000    
Duke Energy Carolinas [Member] | Minimum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]          
Valuation and Qualifying Accounts [Abstract]          
Coal ash released, in tons | T 30,000        
Basin water released, in gallons | gal 24        
Duke Energy Carolinas [Member] | Maximum [Member] | North Carolina Ash Basins [Member] | Dan River [Member]          
Valuation and Qualifying Accounts [Abstract]          
Coal ash released, in tons | T 39,000        
Basin water released, in gallons | gal 27        
Progress Energy [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   56,000,000 56,000,000 59,000,000  
Duke Energy Progress [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   13,000,000 13,000,000 14,000,000  
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   4,000,000 4,000,000    
Duke Energy Florida [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual   28,000,000 28,000,000 28,000,000  
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]          
Valuation and Qualifying Accounts [Abstract]          
Gain Contingency, Unrecorded Amount   54,000,000 54,000,000    
Loss Contingency, Damages Sought, Original Amount   482,000,000 482,000,000   $ 510,000,000
Loss Contingency, Damages Awarded, Value     30,000,000    
Gain Contingency, Dismissed Amount   54,000,000 54,000,000    
Loss contingency, damages sought, value     424,000,000    
Loss Contingency Damages Awarded and Interest, Value     34,000,000    
Duke Energy Florida [Member] | MGP Cost Recovery Action [Member]          
Valuation and Qualifying Accounts [Abstract]          
Gain Contingency, Unrecorded Amount   $ 43,000,000 $ 43,000,000    
Duke Energy Ohio [Member]          
Valuation and Qualifying Accounts [Abstract]          
Loss Contingency Accrual       $ 4,000,000