Risk Management, Derivative Instruments And Hedging Activities (Underlying Notional Amounts For Derivative Instruments Accounted For At Fair Value) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Risk Management, Derivative Instruments And Hedging Activities [Abstract]
Electricity-energy (Gigawatt-hours)	18,476	[1]	14,118	[1]
Emission allowances: NOX (in tons)	4,000		9,000
Natural gas (in decatherms)	38,000,000		40,000,000

[1] Amounts at Duke Energy Ohio include intercompany positions that are eliminated at Duke Energy.