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Commitments and Contingencies (Narrative) (Details)
gal in Millions
12 Months Ended
Sep. 23, 2016
USD ($)
Feb. 08, 2016
USD ($)
Apr. 22, 2015
USD ($)
Mar. 10, 2015
USD ($)
Dec. 31, 2017
USD ($)
plant
Claims
reactor
T
Dec. 31, 2015
USD ($)
Dec. 31, 2016
USD ($)
Mar. 31, 2014
USD ($)
Feb. 28, 2014
gal
T
Insurance [Abstract]                  
Insured public liability limit per nuclear incident         $ 13,400,000,000        
Excess nuclear liability program coverage         13,000,000,000        
Pro rata assessment for each reactor owned for each incident exceeding public liability insurance         $ 127,000,000        
Number of licensed nuclear reactors | reactor         102        
Annual payment limit to pro rata assessments         $ 19,000,000        
Industry aggregate limit         3,200,000,000        
Sublimit for non-nuclear terrorist events         $ 1,830,000,000        
Insurance Coverage Percentage Initial Weeks         100.00%        
Accidental Outage Insurance Coverage Initial Weeks         365 days        
Insurance Coverage Percentage Additional Weeks         80.00%        
Accidental Outage Insurance Coverage Additional Weeks         770 days        
Weeks of Sublimits for Accidental Outage Coverage         728 days        
Sublimit accidental outage recovery         $ 328,000,000        
Maximum Magnitude of Retroactive Premiums         10        
Maximum Period for Retroactive Premium Assessment         6 years        
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         $ 88,000,000   $ 98,000,000    
Progress Energy Merger Shareholder Litigation [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Payments for Legal Settlements     $ 25,000,000            
Litigation Settlement Covered by Insurance     $ 121,000,000            
Proceeds from Legal Settlements         $ 20,000,000        
Litigation Settlement, Amount Awarded to Other Party       $ 146,000,000          
Coal Ash Insurance Coverage Litigation [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Number of NC and SC Plants with Ash Basins | plant         15        
NCDEQ State Enforcement Actions [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Facilities with Ash Basins | plant         14        
Number of Plants with No Disputed Facts | plant         7        
Number of Plants with Disputed Facts | plant         7        
Groundwater Contamination Claims [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Goodwill Payment         $ 5,000        
Water Bill Stipend Period         25 years        
Duke Energy Carolinas [Member]                  
Insurance [Abstract]                  
Primary nuclear liability program coverage         $ 450,000,000        
Max Retroactive Premium Assessments         146,000,000        
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         30,000,000   23,000,000    
Duke Energy Carolinas [Member] | McGuire Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         1,500,000,000        
Additional nuclear accident limit         1,250,000,000        
Accidental outage insurance coverage policy limit         490,000,000        
Duke Energy Carolinas [Member] | Catawba Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         1,500,000,000        
Dedicated additional nuclear accident limit         1,250,000,000        
Additional Non Nuclear Accident Limit         750,000,000        
Accidental outage insurance coverage policy limit         $ 490,000,000        
Potential Obligation percentage         100.00%        
Duke Energy Carolinas [Member] | Oconee Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         $ 1,500,000,000        
Additional nuclear accident limit         1,250,000,000        
Additional Non Nuclear Accident Limit         750,000,000        
Accidental outage insurance coverage policy limit         434,000,000        
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Civil Penalty Assessed   $ 6,800,000              
Litigation Settlement, Amount Awarded to Other Party $ 6,000,000                
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member] | Minimum [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Estimated amount of ash released, in tons | T                 30,000
Estimated amount of ash basin water released, in gallons | gal                 24
Duke Energy Carolinas [Member] | North Carolina Ash Basins [Member] | Dan River [Member] | Maximum [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Estimated amount of ash released, in tons | T                 39,000
Estimated amount of ash basin water released, in gallons | gal                 27
Duke Energy Carolinas [Member] | Groundwater Contamination Claims [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         19,000,000        
Duke Energy Carolinas [Member] | Asbestos Issue [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Asbestos-related injuries and damages reserves         489,000,000   512,000,000    
Reinsurance retention policy, excess retention, amount reinsured         797,000,000        
Probable insurance recoveries         $ 585,000,000   587,000,000    
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Non Malignant Asbestos Claim [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Loss contingency, pending claims, number | Claims         161        
Asbestos-related injuries and damages reserves         $ 42,000,000        
Duke Energy Carolinas [Member] | Asbestos Issue [Member] | Malignant Asbestos Claim [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Loss contingency, pending claims, number | Claims         54        
Asbestos-related injuries and damages reserves         $ 16,000,000        
Progress Energy [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         55,000,000   59,000,000    
Duke Energy Progress [Member]                  
Insurance [Abstract]                  
Primary nuclear liability program coverage         450,000,000        
Max Retroactive Premium Assessments         96,000,000        
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         13,000,000   14,000,000    
Duke Energy Progress [Member] | Robinson Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         1,500,000,000        
Additional nuclear accident limit         1,250,000,000        
Accidental outage insurance coverage policy limit         378,000,000        
Duke Energy Progress [Member] | Brunswick Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         1,500,000,000        
Additional nuclear accident limit         1,250,000,000        
Accidental outage insurance coverage policy limit         462,000,000        
Duke Energy Progress [Member] | Shearon Harris Nuclear Station [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         1,500,000,000        
Additional nuclear accident limit         1,250,000,000        
Accidental outage insurance coverage policy limit         448,000,000        
Duke Energy Progress [Member] | Groundwater Contamination Claims [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         4,000,000        
Duke Energy Progress [Member] | Spent Nuclear Fuels [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Gain contingency, unrecorded amount         48,000,000        
Litigation Settlement, Amount Awarded from Other Party         $ 48,000,000        
Duke Energy Progress [Member] | Gypsum Supply Agreements [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Minimum Amount of Gypsum To Be Supplied | T         50,000        
Duke Energy Florida [Member]                  
Insurance [Abstract]                  
Primary nuclear liability program coverage         $ 450,000,000        
Max Retroactive Premium Assessments         1,000,000        
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         24,000,000   28,000,000    
Duke Energy Florida [Member] | Crystal River Unit 3 [Member]                  
Insurance [Abstract]                  
Sublimit property damage losses         50,000,000        
Duke Energy Florida [Member] | Spent Nuclear Fuels [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Gain contingency, unrecorded amount         25,000,000        
Litigation Settlement, Amount Awarded from Other Party         21,000,000        
Duke Energy Florida [Member] | Westinghouse Electric Company Litigation [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Gain contingency, unrecorded amount         54,000,000        
Loss Contingency, Damages Sought, Original Amount         482,000,000     $ 510,000,000  
Loss Contingency, Damages Awarded, Value         30,000,000        
Gain Contingency, Dismissed Amount         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]                  
Loss contingency, damages sought, value         43,000,000        
Duke Energy Ohio [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters             4,000,000    
Duke Energy Ohio [Member] | Antitrust Lawsuit [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Litigation Settlement, Amount Awarded to Other Party           $ 81,000,000      
Litigation Settlement, Expense           $ 81,000,000      
Piedmont Natural Gas [Member]                  
Valuation and Qualifying Accounts [Abstract]                  
Reserves for legal matters         $ 2,000,000   $ 2,000,000