Derivative Instruments And Hedging Activities (Outstanding Energy Commodity Contracts Employed As Cash Flow Hedges) (Details)	Sep. 30, 2011	Dec. 31, 2010
Forecasted Purchases Hedges [Member] | Natural Gas (One Million British Thermal Units (MMBtu)) [Member]
Derivative, Nonmonetary Notional Amount		8,597,106
Forecasted Purchases Hedges [Member] | Electricity (Megawatt Hours (MWh)) [Member]
Derivative, Nonmonetary Notional Amount	1,879,840	2,677,640
Forecasted Purchases Hedges [Member] | Electricity Capacity (MW-Days) [Member]
Derivative, Nonmonetary Notional Amount		34,730
Forecasted Sales Hedges [Member] | Electricity (Mwh) [Member]
Derivative, Nonmonetary Notional Amount	991,840	2,517,200