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Debt and Credit Facilities (Narrative) (Details) - USD ($)
May 10, 2018
Mar. 31, 2018
Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Facility size   $ 8,000,000,000
Revolving Credit Facility [Member] | Subsequent Event [Member]    
Debt Instrument [Line Items]    
Line of Credit Facility, Expiration Date Mar. 16, 2023  
Three Year Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Facility size   1,000,000,000.0
Long-term Line of Credit   500,000,000
Duke Energy Carolinas [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Facility size   1,550,000,000
Duke Energy Carolinas [Member] | USDOJ [Member] | North Carolina Ash Basins [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Minimum Master Credit Facility Balance Required   250,000,000
Duke Energy Progress [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Facility size   1,250,000,000
Duke Energy Progress [Member] | USDOJ [Member] | North Carolina Ash Basins [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Minimum Master Credit Facility Balance Required   $ 250,000,000