Income Taxes (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Tax Assets, Net of Valuation Allowance, Current Classification [Abstract]
Commodity Hedging Contracts	$ 0				$ 29,582,000				$ 0	$ 29,582,000
Deferred Compensation Plans	0				42,296,000				0	42,296,000
Net Operating Loss	0				96,616,000				0	96,616,000
Alternative Minimum Tax Credit Carryforward	0				72,297,000				0	72,297,000
Foreign Net Operating Loss	49,865,000				0				49,865,000	0
Foreign Valuation Allowance	(30,247,000)				0				(30,247,000)	0
Other	0				3,815,000				0	3,815,000
Total Net Current Deferred Income Tax Assets	19,618,000				244,606,000				19,618,000	244,606,000
Deferred tax assets net noncurrent classification [Abstract]
Foreign Oil and Gas Exploration and Development Costs Deducted for Tax Under Book Depreciation, Depletion and Amortization	(141,643,000)				(112,346,000)				(141,643,000)	(112,346,000)
Foreign Net Operating Loss	487,876,000				369,257,000				487,876,000	369,257,000
Foreign Valuation Allowances	(349,704,000)				(183,122,000)				(349,704,000)	(183,122,000)
Foreign Other	4,096,000				4,179,000				4,096,000	4,179,000
Total Net Noncurrent Deferred Income Tax Assets	625,000				77,968,000				625,000	77,968,000
Deferred tax liabilities net current classification [Abstract]
Commodity Hedging Contracts	166,109,000				0				166,109,000	0
Deferred Compensation Plans	(48,207,000)				0				(48,207,000)	0
Accrued Expenses and Liabilities	(5,643,000)				0				(5,643,000)	0
Other	(1,516,000)				0				(1,516,000)	0
Total Net Current Deferred Income Tax Liabilities	110,743,000				0				110,743,000	0
Deferred tax liabilities net noncurrent classification [Abstract]
Oil and Gas Exploration and Development Costs Deducted for Tax Over Book Depreciation, Depletion and Amortization	7,634,297,000				6,287,541,000				7,634,297,000	6,287,541,000
Non-Producing Leasehold Costs	(44,236,000)				(50,581,000)				(44,236,000)	(50,581,000)
Seismic Costs Capitalized for Tax	(158,157,000)				(136,964,000)				(158,157,000)	(136,964,000)
Equity Awards	(127,541,000)				(122,665,000)				(127,541,000)	(122,665,000)
Capitalized Interest	97,739,000				101,006,000				97,739,000	101,006,000
Alternative Minimum Tax Credit Carryforward	(793,126,000)				(557,352,000)				(793,126,000)	(557,352,000)
Undistributed Foreign Earnings	249,861,000				0				249,861,000	0
Other	(35,891,000)				1,369,000				(35,891,000)	1,369,000
Total Net Noncurrent Deferred Income Tax Liabilities	6,822,946,000				5,522,354,000				6,822,946,000	5,522,354,000
Total Net Deferred Income Tax Liabilities	6,913,446,000				5,199,780,000				6,913,446,000	5,199,780,000
Income Before Income Taxes [Abstract]
United States									5,161,232,000	3,268,727,000	1,988,105,000
Foreign									(165,917,000)	168,159,000	(707,365,000)
Income (Loss) Before Income Taxes	1,148,593,000	1,715,120,000	1,100,813,000	1,030,789,000	919,082,000	721,555,000	1,035,230,000	761,019,000	4,995,315,000	3,436,886,000	1,280,740,000
Current income tax provision [Abstract]
Federal									269,326,000	207,777,000	242,674,000
State									22,835,000	22,856,000	22,573,000
Foreign									82,721,000	134,379,000	152,276,000
Total									374,882,000	365,012,000	417,523,000
Deferred income tax provision [Abstract]
Federal									1,608,706,000	915,994,000	454,173,000
State									29,056,000	26,305,000	632,000
Foreign									67,184,000	(67,534,000)	(161,867,000)
Total									1,704,946,000	874,765,000	292,938,000
Income Tax Provision									2,079,828,000	1,239,777,000	710,461,000
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)									0.68%	0.93%	1.18%
Income Tax Provision Related to Foreign Operations (in hundredths)									(0.12%)	0.23%	1.11%
Canadian Divestiture (in hundredths)									(3.46%)	0.00%	0.00%
Undistributed Foreign Earnings (in hundredths)									4.94%	0.00%	0.00%
Foreign Valuation Allowances (in hundredths)									6.47%	0.00%	10.57%
Foreign Oil and Gas Impairments (in hundredths)									(1.90%)	0.00%	6.90%
Other (in hundredths)									0.03%	(0.09%)	0.71%
Effective Income Tax Rate (in hundredths)									41.64%	36.07%	55.47%
Additional income tax provision related to valuation allowances recorded to reduce value of foreign deferred tax assets	463,000,000				224,000,000				463,000,000	224,000,000	200,000,000
Unrecognized tax benefits balance	0								0
Foreign subsidiaries' undistributed earnings	1,800,000,000								1,800,000,000
Regular tax net operating loss utilized									940,000,000
Balance of State net operating loss expected to be carried forward									1,600,000,000
Tax benefit reflected in additional paid-in-capital due to current year utilization of net operating losses	29,000,000								29,000,000
Alternative minimum tax paid									196,000,000
AMT Paid In Years Prior To Prior Reporting Period									597,000,000
Tax net operating loss incurred in United Kingdom in current year									246,000,000
Balance of tax net operating loss incurred in the United Kingdom in prior years									548,000,000
Unrecognized tax benefits interest or penalties	0								0
Federal and state deferred income taxes	$ 250,000,000								$ 250,000,000