Derivative and Hedging (Interest Rate Risk) (Details) (Interest Rate Contracts [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Derivative [Line Items]
Notional amount	$ 791		$ 832
Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount	764	[1]	798	[1]
Duke Energy Ohio [Member]
Derivative [Line Items]
Notional amount	27		27
Duke Energy Ohio [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount		[1]		[1]
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount	27		34
Not Designated as Hedging Instrument [Member] | Duke Energy Ohio [Member]
Derivative [Line Items]
Notional amount	27		27
Variable Interest Entity, Primary Beneficiary [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount	$ 552		$ 584

[1] In May 2013, the PUCO approved a Duke Energy Ohio settlement agreement that provides for a net annual increase in electric distribution revenues beginning in May 2013. This rate increase impacts Regulated Utilities.