Risk Management Activities (Details) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Crude Oil and Natural Gas Derivative Contracts [Member]	Dec. 31, 2010 Crude Oil and Natural Gas Derivative Contracts [Member]	Dec. 31, 2011 Foreign Currency Swap [Member]	Dec. 31, 2010 Foreign Currency Swap [Member]	Dec. 31, 2012 Natural Gas Derivative Contracts January [Member]	Dec. 31, 2012 Natural Gas Derivative Contracts - February - December [Member]	Dec. 31, 2014 Natural Gas Derivative Contracts January - December [Member]	Dec. 31, 2013 Natural Gas Derivative Contracts January - December [Member]	Dec. 31, 2012 Crude Oil Derivative Contracts January - June [Member]	Dec. 31, 2012 Crude Oil Dervative Contracts July - December [Member]
Notes To Financial Statements [Abstract]
Gains on Mark-to-Market Commodity Derivative Contracts	$ (626,053,000)	$ (61,912,000)	$ (431,757,000)
Realized Gains (Losses)	180,701,000	7,033,000	1,277,584,000
Assets from Price Risk Management Activities	450,730,000	48,153,000		451,000,000	51,000,000
Liabilities from Price Risk Management Activities	0	28,339,000		0	30,000,000
Other Assets	35,000,000	20,000,000
Other Liabilities		1,000,000
Derivative [Line Items]
Volume (MMBtud)								525000	525000	150000	150000
Volume (Bbld)												34000	17000
Volumes (MMBtud) - Derivative Contracts									425,000	150,000	150,000
Average Price ($/MMBtu) - Derivative Contracts									5.44	4.79	4.79
Weighted Average Price ($/Bbl)												104.95	103.59
Derivative Weighted Average Price Natural Gas ($/MMBtu)								5.44	5.44	4.79	4.79
Principal amount of notes issued by Canadian subsidiary, whose exchange rate is hedged by foreign currency swap transaction	150,000,000
Volumes (Bbld) - Derivative Contacts													17,000
Average Price ($/Bbl) - Derivative Contracts													106.31
Derivatives, Fair Value [Line Items]
Derivatives Assets, Current	450,730,000	48,153,000		451,000,000	51,000,000
Other Assets	0	2,000,000		35,000,000	18,000,000
Derivative Liabilities, Current	0	28,339,000		0	30,000,000
Other Liabilities	3,000,000	0				53,000,000	55,000,000
Receivable Major Customer Percentage	10.00%	13.00%
Interest Rate Cash Flow Hedges [Abstract]
Interest Rate Swap, Notional Amount	350,000,000
Interest Rate Swap, at Fair Value	(3,000,000)	2,000,000
After-tax net impact from interest rate swap	(3,000,000)	1,000,000
Fair Value Of The Foreign Currency Swap	(52,000,000)	(55,000,000)
After-Tax Impact Other Comprehensive Income Increase (Decrease) From The Foreign Currency Swap Transaction	$ (1,000,000)	$ 3,000,000	$ 5,000,000