Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets (Liabilities), Net of Valuation Allowance, Current Classification [Abstract]
Commodity Hedging Contracts		$ 22,206				$ 0				$ 22,206	$ 0
Deferred Compensation Plans		43,984				38,559				43,984	38,559
Alternative Minimum Tax Credit Carryforward		84,426				93,316				84,426	93,316
Foreign Net Operating Loss		37,251				47,786				37,251	47,786
Deferred Tax Liability, Net of Valuation Allowance		(28,097)				(35,536)				(28,097)	(35,536)
Accrued Expenses and Liabilities		13,754				0				13,754	0
Other		(4,137)				3,687				(4,137)	3,687
Total Net Current Deferred Income Tax Assets		169,387				147,812				169,387	147,812
Deferred Tax Assets (Liabilities) Net Noncurrent Classification [Abstract]
Foreign Oil and Gas Exploration and Development Costs Deducted for Tax Under Book Depreciation, Depletion and Amortization		(39,852)				(57,569)				(39,852)	(57,569)
Foreign Net Operating Loss		314,899				443,010				314,899	443,010
Foreign Valuation Allowances		(268,499)				(380,104)				(268,499)	(380,104)
Foreign Other		438				1,506				438	1,506
Total Net Noncurrent Deferred Income Tax Assets		6,986				6,843				6,986	6,843
Deferred tax (assets) liabilities net noncurrent classification [Abstract]
Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization		5,899,533				5,299,817				5,899,533	5,299,817
Non-Producing Leasehold Costs		(64,898)				(53,026)				(64,898)	(53,026)
Seismic Costs Capitalized for Tax		(161,920)				(162,240)				(161,920)	(162,240)
Equity Awards		(139,787)				(140,663)				(139,787)	(140,663)
Capitalized Interest		86,504				98,242				86,504	98,242
Alternative Minimum Tax Credit Carryforward		(673,205)				(685,189)				(673,205)	(685,189)
Undistributed Foreign Earnings		280,099				258,403				280,099	258,403
Total Net Noncurrent Deferred Income Tax Liabilities		5,188,640				4,587,902				5,188,640	4,587,902
Deferred Tax and Other Assets, Noncurrent		(37,686)				(27,442)				(37,686)	(27,442)
Deferred Tax Liabilities, Net		5,012,267				4,433,247				5,012,267	4,433,247
Income Before Income Taxes [Abstract]
United States										(1,520,573)	(6,840,119)	$ 5,161,232
Foreign										(36,932)	(81,437)	(165,917)
Income (Loss) Before Income Taxes		(194,010)	$ (272,250)	$ (380,277)	$ (710,968)	(398,826)	$ (6,274,921)	$ (11,478)	$ (236,331)	(1,557,505)	(6,921,556)	4,995,315
Current income tax provision (benefit) [Abstract]
Federal										11,567	21,719	269,326
State										(8,369)	9,404	22,835
Foreign										51,189	54,143	82,721
Total										54,387	85,266	374,882
Deferred income tax provision (benefit) [Abstract]
Federal										(532,979)	(2,362,926)	1,608,706
State										4,876	(127,444)	29,056
Foreign										12,897	8,063	67,184
Total										(515,206)	(2,482,307)	1,704,946
Income Tax Provision (Benefit)										$ (460,819)	$ (2,397,041)	$ 2,079,828
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)										0.15%	1.11%	0.68%
Income Tax Provision Related to Foreign Operations (in hundredths)										(1.23%)	(1.31%)	(0.12%)
Income Tax Provision Related to Trinidad Operations (in hundredths)										(3.71%)	0.00%	0.00%
Canadian Divestiture (in hundredths)										0.00%	0.00%	(3.46%)
Undistributed Foreign Earnings (in hundredths)										0.00%	0.00%	4.94%
Foreign Valuation Allowances (in hundredths)										0.00%	0.00%	6.47%
Foreign Oil and Gas Impairments (in hundredths)										0.00%	0.00%	(1.90%)
Other (in hundredths)										(0.62%)	(0.17%)	0.03%
Effective Income Tax Rate (in hundredths)										29.59%	34.63%	41.64%
Valuation Allowance [Abstract]
Beginning Balance					$ 506,127				$ 463,018	$ 506,127	$ 463,018	$ 223,599
Increase	[1]									37,221	146,602	392,729
Decrease	[2]									(12,667)	(4,315)	(1,424)
Other	[3]									(147,460)	(99,178)	(151,886)
Ending Balance		383,221				$ 506,127				383,221	$ 506,127	$ 463,018
Unrecognized tax benefits balance		36,000								36,000
Unrecognized tax benefit earnings impact		2,000								2,000
Foreign subsidiaries' undistributed earnings		2,000,000								2,000,000
Balance of State net operating loss expected to be carried forward										1,600,000
Alternative minimum tax credits utilized										21,000
AMT Paid In Years Prior To Prior Reporting Period										758,000
Tax net operating loss incurred in United Kingdom in current year										38,000
Balance of tax net operating loss incurred in the United Kingdom in prior years										740,000
Unrecognized tax benefits interest or penalties		2,000								2,000
Federal and state deferred income taxes		$ 280,000								$ 280,000

[1] Increase in valuation allowance related to the generation of tax net operating losses and other deferred tax assets.

[2] Decrease in valuation allowance associated with adjustments to certain deferred tax assets and their related allowance.

[3] Represents dispositions/revisions/foreign exchange rate variances and the effect of statutory income tax rate changes.