Derivative Instruments And Hedging Activities Volumes related to price risk purchase derivatives (Details) - Price Risk Derivative [Member]	3 Months Ended
	Mar. 31, 2016 MMBTU bbl
Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	16,800,000
Natural Gas - long [Member] | Maturing in Next Twelve Months [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	7,200,000
Natural Gas - long [Member] | Maturing in Year Two [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	9,600,000
Other Contract [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net | bbl	975,000
Other Contract [Member] | Maturing in Next Twelve Months [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net | bbl	975,000