Derivatives and Hedging (Notional Amounts of Derivative Instruments) (Details) Mcf in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) GWh Mcf	Dec. 31, 2016 USD ($) GWh Mcf	Aug. 31, 2016 USD ($)
Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 1,587	$ 1,677
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	660	750
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 927	$ 927
Commodity Contracts [Member] | Electricity [Member]
Derivative [Line Items]
Notional amount, energy measure, in gigawatt-hours | GWh	34	147
Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	770	890
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 660	$ 750
Piedmont Natural Gas [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Loss on Interest Rate Derivative Instruments Not Designated as Hedging Instruments		190
Piedmont Natural Gas [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount			$ 1,400
Duke Energy Carolinas [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	400	400
Duke Energy Carolinas [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 400	$ 400
Duke Energy Carolinas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	105	91
Progress Energy [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 500	$ 500
Progress Energy [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 500	$ 500
Progress Energy [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	183	269
Duke Energy Progress [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Progress [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Progress [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	133	118
Duke Energy Florida [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 250	$ 250
Duke Energy Florida [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [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	50	151
Duke Energy Ohio [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	$ 27	$ 27
Duke Energy Ohio [Member] | Interest Rate Contract [Member] | Not Designated as Hedging Instrument [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	34	147
Duke Energy Indiana [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	2	1
Piedmont Natural Gas [Member] | Commodity Contracts [Member] | Natural Gas [Member]
Derivative [Line Items]
Notional amount, volume in millions of decatherms | Mcf	480	529
Commercial Renewables [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		$ 300
Commercial Renewables [Member] | 4YearInterestRateContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		81
Commercial Renewables [Member] | 18YearInterestRateContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount		$ 219