Income Taxes (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets, Net of Valuation Allowance, Current Classification [Abstract]
Deferred Compensation Plans	$ 38,559,000				$ 0				$ 38,559,000	$ 0
Alternative Minimum Tax Credit Carryforward	93,316,000				0				93,316,000	0
Foreign Net Operating Loss	47,786,000				49,865,000				47,786,000	49,865,000
Foreign Valuation Allowance	(35,536,000)				(30,247,000)				(35,536,000)	(30,247,000)
Other	3,687,000				0				3,687,000	0
Total Net Current Deferred Income Tax Assets	147,812,000				19,618,000				147,812,000	19,618,000
Deferred tax assets net noncurrent classification [Abstract]
Foreign Oil and Gas Exploration and Development Costs Deducted for Tax Under Book Depreciation, Depletion and Amortization	(57,569,000)				(141,643,000)				(57,569,000)	(141,643,000)
Foreign Net Operating Loss	443,010,000				487,876,000				443,010,000	487,876,000
Foreign Valuation Allowances	(380,104,000)				(349,704,000)				(380,104,000)	(349,704,000)
Foreign Other	1,506,000				4,096,000				1,506,000	4,096,000
Total Net Noncurrent Deferred Income Tax Assets	6,843,000				625,000				6,843,000	625,000
Deferred tax liabilities net current classification [Abstract]
Commodity Hedging Contracts	0				166,109,000				0	166,109,000
Deferred Compensation Plans	0				(48,207,000)				0	(48,207,000)
Accrued Expenses and Liabilities	0				(5,643,000)				0	(5,643,000)
Other	0				(1,516,000)				0	(1,516,000)
Total Net Current Deferred Income Tax Liabilities	0				110,743,000				0	110,743,000
Deferred tax liabilities net noncurrent classification [Abstract]
Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	5,299,817,000				7,634,297,000				5,299,817,000	7,634,297,000
Non-Producing Leasehold Costs	(53,026,000)				(44,236,000)				(53,026,000)	(44,236,000)
Seismic Costs Capitalized for Tax	(162,240,000)				(158,157,000)				(162,240,000)	(158,157,000)
Equity Awards	(140,663,000)				(127,541,000)				(140,663,000)	(127,541,000)
Capitalized Interest	98,242,000				97,739,000				98,242,000	97,739,000
Alternative Minimum Tax Credit Carryforward	(685,189,000)				(793,126,000)				(685,189,000)	(793,126,000)
Undistributed Foreign Earnings	258,403,000				249,861,000				258,403,000	249,861,000
Other	(27,442,000)				(35,891,000)				(27,442,000)	(35,891,000)
Total Net Noncurrent Deferred Income Tax Liabilities	4,587,902,000				6,822,946,000				4,587,902,000	6,822,946,000
Total Net Deferred Income Tax Liabilities	4,433,247,000				6,913,446,000				4,433,247,000	6,913,446,000
Income Before Income Taxes [Abstract]
United States									(6,840,119,000)	5,161,232,000	$ 3,268,727,000
Foreign									(81,437,000)	(165,917,000)	168,159,000
Income (Loss) Before Income Taxes	(398,826,000)	$ (6,274,921,000)	$ (11,478,000)	$ (236,331,000)	1,148,593,000	$ 1,715,120,000	$ 1,100,813,000	$ 1,030,789,000	(6,921,556,000)	4,995,315,000	3,436,886,000
Current income tax provision [Abstract]
Federal									21,719,000	269,326,000	207,777,000
State									9,404,000	22,835,000	22,856,000
Foreign									54,143,000	82,721,000	134,379,000
Total									85,266,000	374,882,000	365,012,000
Deferred income tax provision [Abstract]
Federal									(2,362,926,000)	1,608,706,000	915,994,000
State									(127,444,000)	29,056,000	26,305,000
Foreign									8,063,000	67,184,000	(67,534,000)
Total									(2,482,307,000)	1,704,946,000	874,765,000
Income Tax Provision									$ (2,397,041,000)	$ 2,079,828,000	$ 1,239,777,000
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)									1.11%	0.68%	0.93%
Income Tax Provision Related to Foreign Operations (in hundredths)									(1.31%)	(0.12%)	0.23%
Canadian Divestiture (in hundredths)									0.00%	(3.46%)	0.00%
Undistributed Foreign Earnings (in hundredths)									0.00%	4.94%	0.00%
Foreign Valuation Allowances (in hundredths)									0.00%	6.47%	0.00%
Foreign Oil and Gas Impairments (in hundredths)									0.00%	(1.90%)	0.00%
Other (in hundredths)									(0.17%)	0.03%	(0.09%)
Effective Income Tax Rate (in hundredths)									34.63%	41.64%	36.07%
Valuation Allowance [Abstract]
Beginning Balance				$ 463,018,000				$ 223,599,000	$ 463,018,000	$ 223,599,000	$ 199,743,000
Increase									146,602,000	392,729,000	43,422,000
Decrease									(4,315,000)	(1,424,000)	(4,967,000)
Other									(99,178,000)	(151,886,000)	(14,599,000)
Ending Balance	506,127,000				$ 463,018,000				506,127,000	$ 463,018,000	$ 223,599,000
Unrecognized tax benefits balance	0								0
Foreign subsidiaries' undistributed earnings	2,000,000,000								2,000,000,000
Balance of State net operating loss expected to be carried forward									1,700,000,000
Alternative minimum tax credits utilized									4,000,000
AMT Paid In Years Prior To Prior Reporting Period									779,000,000
Tax net operating loss incurred in United Kingdom in current year									153,000,000
Balance of tax net operating loss incurred in the United Kingdom in prior years									764,000,000
Unrecognized tax benefits interest or penalties	0								0
Federal and state deferred income taxes	$ 258,000,000								$ 258,000,000