Derivative Instruments And Hedging Activities (Outstanding Energy Commodity Contracts Employed As Cash Flow Hedges) (Details)	Dec. 31, 2011	Dec. 31, 2010
Natural Gas (One Million British Thermal Units (MMBtu)) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		8,597,106
Electricity (Megawatt Hours (MWh)) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	614,560	2,677,640
Electricity Capacity (MW-Days) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount		34,730
Electricity (Mwh) [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	614,560	2,517,200