Risk Management, Derivative Instruments And Hedging Activities (Underlying Notional Amounts For Derivative Instruments Accounted For At Fair Value) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Risk Management, Derivative Instruments And Hedging Activities [Abstract]
Electricity-energy (Gigawatt-hours)	14,118	8,200
Electricity-capacity (Gigawatt-months)		58
Emission allowances: SO2 (in tons)		8,000
Emission allowances: NOX (in tons)	9,000
Natural gas (in decatherms)	40,000,000	37,000,000