Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred tax assets net current classification [Abstract]
Commodity Hedging Contracts	$ 0	$ (7,141,000)
Deferred Compensation Plans	(28,346,000)	13,216,000
Other	0	3,185,000
Total Net Current Deferred Income Tax Assets	0	9,260,000
Deferred tax assets net noncurrent classification [Abstract]
United Kingdom Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	(57,850,000)	(16,611,000)
United Kingdom Net Operating Loss	62,477,000	17,329,000
United Kingdom Other	314,000	226,000
Total Net Noncurrent Deferred Income Tax Assets	4,941,000	944,000
Deferred tax liabilities net current classification [Abstract]
Commodity Hedging Contracts	158,302,000	0
Deferred Compensation Plans	(28,346,000)	13,216,000
Timing Differences Associated With Different Year-ends in Foreign Jurisdictions	6,251,000	41,027,000
Other	(218,000)	676,000
Total Net Current Deferred Income Tax Assets	135,989,000	41,703,000
Deferred tax liabilities net noncurrent classification [Abstract]
Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	5,485,436,000	4,373,110,000
Non-Producing Leasehold Costs	(66,926,000)	(78,846,000)
Seismic Costs Capitalized for Tax	(111,862,000)	(92,901,000)
Equity Awards	(120,852,000)	(99,447,000)
Capitalized Interest	106,265,000	94,957,000
Net Operating Loss	(1,152,386,000)	(498,893,000)
Alternative Minimum Tax Credit Carryforward	(298,350,000)	(214,873,000)
Other	25,894,000	18,599,000
Total Net Noncurrent Deferred Income Tax Liabilities	3,867,219,000	3,501,706,000
Total Net Deferred Income Tax Liabilities	3,998,267,000	3,533,205,000
Income Before Income Taxes [Abstract]
United States	2,156,147,000	646,495,000	784,248,000
Foreign	(246,348,000)	(238,519,000)	87,763,000
Total	1,909,799,000	407,976,000	872,011,000
Current income tax provision [Abstract]
Federal	94,244,000	17,154,000	95,194,000
State	1,083,000	(1,642,000)	8,783,000
Foreign	224,049,000	155,565,000	47,015,000
Total	319,376,000	171,077,000	150,992,000
Deferred income tax provision [Abstract]
Federal	608,181,000	190,602,000	166,045,000
State	40,321,000	60,619,000	31,580,000
Foreign	(149,202,000)	(174,976,000)	(23,233,000)
Total	499,300,000	76,245,000	174,392,000
Income Tax Provision	818,676,000	247,322,000	325,384,000
Effective income tax rate [Abstract]
Statutory Federal Income Tax Rate (in hundredths)	35.00%	35.00%	35.00%
State Income Tax, Net of Federal Benefit (in hundredths)	1.41%	9.39%	3.00%
Income Tax Provision Related to Foreign Operations (in hundredths)	0.88%	(0.03%)	(1.40%)
Income Tax Provision Related to Trinidad Operations (in hundredths)	3.37%	6.26%	0.60%
Canadian Shallow Natural Gas Impairments (in hundredths)	1.85%	9.49%	0.00%
Other (in hundredths)	0.36%	0.51%	0.11%
Effective Income Tax Rate (in hundredths)	42.87%	60.62%	37.31%
Change in Canadian Federal and Provincial Statutory Tax Rates and Other Canadian Adjustments (in hundredths)	27.00%
Unrecognized tax benefits balance	33,000,000
Foreign subsidiaries' undistributed earnings	2,300,000,000
Regular tax net operating loss	1,800,000,000	1,400,000,000
Tax benefit reflected in APIC	23,000,000	17,000,000
Alternative minimum tax paid	104,000,000
AMT paid in years prior to current reporting period	194,000,000
Foreign tax net operating loss	71,000,000	30,000,000
Statutory Federal Income Tax Rate (in hundredths)	35.00%	35.00%	35.00%
State Income Tax Net Operating Losses	$ 700,000,000
Increase in the statutory income tax rate applying to oil and gas activities	50% to 62%
Increase in a statutory deduction	6% to 10%