XML 103 R61.htm IDEA: XBRL DOCUMENT v3.8.0.1
Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details)
Mcf in Millions, $ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2018
USD ($)
GWh
Mcf
Dec. 31, 2017
USD ($)
GWh
Mcf
Commodity Contracts [Member] | Electricity [Member]    
Derivative [Line Items]    
Notional amount, energy measure, in gigawatt-hours | GWh 16 34
Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Mcf 765 770
Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 1,187 $ 1,587
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount 660 660
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount 527 927
Variable Interest Entity, Primary Beneficiary [Member] | Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount $ 660 $ 660
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Mcf 110 105
Duke Energy Carolinas [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount   $ 400
Duke Energy Carolinas [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]    
Derivative [Line Items]    
Notional amount   $ 400
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Mcf 179 183
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 | Mcf 149 133
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 | Mcf 30 50
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] | 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 16 34
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Mcf 2 2
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]    
Derivative [Line Items]    
Notional amount, volume, in millions of decatherms | Mcf 474 480