Derivative Instruments And Hedging Activities Volumes related to price risk purchase derivatives (Details) - Price Risk Derivative [Member]	6 Months Ended
	Jun. 30, 2016 MMBTU bbl
Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	14,400,000
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 | MMBTU	4,800,000
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 | MMBTU	9,600,000
Forward Contracts [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	75,000
Forward Contracts [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	75,000
Other Contract [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	275,000
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	275,000