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Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details)
Bcf in Millions, $ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2016
USD ($)
GWh
Bcf
Dec. 31, 2015
USD ($)
GWh
Bcf
Derivative [Line Items]    
Undesignated Commodity Contracts Latest Expiration Year 2048  
Commodity Contracts [Member] | Electricity [Member]    
Derivative [Line Items]    
Notional amount, energy measure, in gigawatt-hours | GWh 183 70
Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Bcf 470 398
Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 3,027 $ 2,527
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount 700 700
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount 2,327 1,827
Variable Interest Entity, Primary Beneficiary [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount 497 $ 497
Piedmont Natural Gas [Member]    
Derivative [Line Items]    
Notional amount 1,400  
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments 93  
Piedmont Natural Gas [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Derivative, Contract Entered Into During The Period, Notional Amount 500  
Notional amount $ 1,400  
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Bcf 92 66
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 400 $ 400
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 400 $ 400
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Bcf 378 332
Progress Energy [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 500 $ 500
Progress Energy [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 500 $ 500
Duke Energy Progress [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Bcf 131 117
Duke Energy Progress [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 250 $ 250
Duke Energy Progress [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 250 $ 250
Duke Energy Florida [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Bcf 247 215
Duke Energy Florida [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 250 $ 250
Duke Energy Florida [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 250 $ 250
Duke Energy Ohio [Member] | Commodity Contracts [Member] | Electricity [Member]    
Derivative [Line Items]    
Notional amount, energy measure, in gigawatt-hours | GWh 144 34
Duke Energy Ohio [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 27 $ 27
Duke Energy Ohio [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 27 $ 27
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Electricity [Member]    
Derivative [Line Items]    
Notional amount, energy measure, in gigawatt-hours | GWh 39 36