Risk Management, Derivative Instruments And Hedging Activities (Underlying Notional Amounts For Derivative Instruments Accounted For At Fair Value) (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2012 MWh dth T	Dec. 31, 2011 MWh T dth
Electricity-energy (Gigawatt-hours)	10,751,000,000	14,118,000,000
Emission allowances: NOX (in tons)	3,000	9,000
Natural gas (in decatherms)	30,000,000	40,000,000
Duke Energy Ohio [Member]
Electricity-energy (Gigawatt-hours)	6,773,000,000	14,655,000,000
Emission allowances: NOX (in tons)	3,000	9,000
Natural gas (in decatherms)	21,000,000	2,000,000