Derivative Instruments And Hedging Activities Notional Contracts by Derivative Type (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
economic hedges by derivative type [Line Items]
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss) before Taxes	$ 5.1
Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	45,600,000
Gasoline And Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	535,000
Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	45,600,000
Commodity WCS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,362,500
Commodity Price Swap WTS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,960,000
Commodity WTI Long [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	234,000
Commodity WTI short [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,178,000
Forward Contracts [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	540,000
Commodity Gasoline [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	125,000
WTI Crude Oil [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	8,340,000
Ultra Low Sulfur Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	8,340,000
Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	45,600,000
Future [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	540,000
Maturing in 2013 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	7,200,000
Maturing in 2013 [Member] | Gasoline And Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	535,000
Maturing in 2013 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	7,200,000
Maturing in 2013 [Member] | Commodity WCS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,362,500
Maturing in 2013 [Member] | Commodity Price Swap WTS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,960,000
Maturing in 2013 [Member] | Commodity WTI Long [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	234,000
Maturing in 2013 [Member] | Commodity WTI short [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,178,000
Maturing in 2013 [Member] | Forward Contracts [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	540,000
Maturing in 2013 [Member] | Commodity Gasoline [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	125,000
Maturing in 2013 [Member] | WTI Crude Oil [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	7,975,000
Maturing in 2013 [Member] | Ultra Low Sulfur Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	7,975,000
Maturing in 2013 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	7,200,000
Maturing in 2013 [Member] | Future [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	540,000
Maturing in 2014 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2014 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2014 [Member] | WTI Crude Oil [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	365,000
Maturing in 2014 [Member] | Ultra Low Sulfur Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	365,000
Maturing in 2014 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2015 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2015 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2015 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2016 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2016 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2016 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2017 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2017 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000
Maturing in 2017 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	9,600,000