Derivative Instruments And Hedging Activities Volumes related to price risk purchase derivatives (Details)	3 Months Ended
	Mar. 31, 2015 MMBTU
Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	26,400,000
WTI Crude Oil [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	3,300,000
Ultra Low Sulfur Diesel [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	3,300,000
Forward Contracts [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	1,760,000
Future [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	625,000
Maturing in Next Twelve Months [Member] | Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	7,200,000
Maturing in Next Twelve Months [Member] | WTI Crude Oil [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	3,300,000
Maturing in Next Twelve Months [Member] | Ultra Low Sulfur Diesel [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	3,300,000
Maturing in Next Twelve Months [Member] | Forward Contracts [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	1,760,000
Maturing in Next Twelve Months [Member] | Future [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Price Risk Fair Value Hedge Derivative, at Fair Value, Net	625,000
Maturing in Year Two [Member] | Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	9,600,000
Maturing in Year Three [Member] | Natural Gas - long [Member]
Price Risk Derivatives for Future Purchases Notional Contract Volumes [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	9,600,000