Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets net noncurrent classification [Abstract]
Foreign Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	$ 25,592,000	$ (57,850,000)
Foreign Net Operating Loss	164,829,000	62,477,000
Foreign Other	1,607,000	314,000
Foreign Valuation Allowances	(134,792,000)	0
Total Net Noncurrent Deferred Income Tax Assets	57,236,000	4,941,000
Deferred tax liabilities net current classification [Abstract]
Commodity Hedging Contracts	57,754,000	158,302,000
Deferred Compensation Plans	(35,715,000)	(28,346,000)
Timing Differences Associated With Different Year-ends in Foreign Jurisdictions	2,762,000	6,251,000
Other	(1,963,000)	(218,000)
Total Net Current Deferred Income Tax Liabilities	22,838,000	135,989,000
Deferred tax liabilities net noncurrent classification [Abstract]
Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	5,300,115,000	5,485,436,000
Non-Producing Leasehold Costs	(61,512,000)	(66,926,000)
Seismic Costs Capitalized for Tax	(125,026,000)	(111,862,000)
Equity Awards	(116,666,000)	(120,852,000)
Capitalized Interest	102,677,000	106,265,000
Net Operating Loss	(308,154,000)	(1,152,386,000)
Alternative Minimum Tax Credit Carryforward	(476,505,000)	(298,350,000)
Other	12,467,000	25,894,000
Total Net Noncurrent Deferred Income Tax Liabilities	4,327,396,000	3,867,219,000
Total Net Deferred Income Tax Liabilities	4,292,998,000	3,998,267,000
Income Before Income Taxes [Abstract]
United States	1,988,105,000	2,156,147,000	646,495,000
Foreign	(707,365,000)	(246,348,000)	(238,519,000)
Income Before Income Taxes	1,280,740,000	1,909,799,000	407,976,000
Current income tax provision [Abstract]
Federal	242,674,000	94,244,000	17,154,000
State	22,573,000	1,083,000	(1,642,000)
Foreign	152,276,000	224,049,000	155,565,000
Total	417,523,000	319,376,000	171,077,000
Deferred income tax provision [Abstract]
Federal	454,173,000	608,181,000	190,602,000
State	632,000	40,321,000	60,619,000
Foreign	(161,867,000)	(149,202,000)	(174,976,000)
Total	292,938,000	499,300,000	76,245,000
Income Tax Provision	710,461,000	818,676,000	247,322,000
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)	1.18%	1.41%	9.39%
Income Tax Provision Related to Foreign Operations (in hundredths)	1.38%	0.88%	(0.03%)
Income Tax Provision Related to Trinidad Operations (in hundredths)	(0.27%)	3.37%	6.26%
Canadian Valuation Allowances (in hundredths)	10.57%	0.00%	0.00%
Canadian Shallow Natural Gas Impairments (in hundredths)	6.90%	1.85%	9.49%
Other (in hundredths)	0.71%	0.36%	0.51%
Effective Income Tax Rate (in hundredths)	55.47%	42.87%	60.62%
Unrecognized tax benefits balance	33,000,000
Foreign subsidiaries' undistributed earnings	2,500,000,000
Regular tax net operating loss utilized	939,000,000
Balance of federal net operating loss expected to be carried forward	932,000,000
Balance of federal net operating loss generated in 2011	444,000,000
Balance of federal net operating loss generated in 2010	488,000,000
State Income Tax Net Operating Losses	800,000,000
Tax benefit reflected in additional paid-in-capital due to current year utilization of net operating losses	11,000,000
Additional tax benefit to be reflected in additional paid-in-capital due to future utilization of net operating losses	29,000,000
Alternative minimum tax paid	187,000,000
AMT Paid In Years Prior To Prior Reporting Period	289,000,000
Tax net operating loss incurred in United Kingdom in current year	159,000,000
Balance of tax net operating loss incurred in the United Kingdom in prior years	$ 104,000,000