Derivative Instruments And Hedging Activities Notional Contracts by Derivative Type (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013
economic hedges by derivative type [Line Items]
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss) before Taxes	$ 4.9
Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	43,200,000
Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	43,200,000
Commodity WCS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	3,588,000
Commodity Price Swap WTS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,472,000
Commodity WTI short [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,896,000
WTI Crude Oil [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,701,000
Ultra Low Sulfur Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,701,000
Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	43,200,000
Maturing in 2013 [Member] | Natural Gas [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	4,800,000
Maturing in 2013 [Member] | Natural Gas - long [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	4,800,000
Maturing in 2013 [Member] | Commodity WCS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	3,588,000
Maturing in 2013 [Member] | Commodity Price Swap WTS Spread [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,472,000
Maturing in 2013 [Member] | Commodity WTI short [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	1,681,000
Maturing in 2013 [Member] | WTI Crude Oil [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,336,000
Maturing in 2013 [Member] | Ultra Low Sulfur Diesel Member
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	5,336,000
Maturing in 2013 [Member] | Natural Gas - Short [Member]
economic hedges by derivative type [Line Items]
Portion Of Future Gas Production Being Hedged	4,800,000
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] | Commodity WTI short [Member]
economic hedges by derivative type [Line Items]
Derivative, Nonmonetary Notional Amount	215,000
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