Segment Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Segment Reporting Information By Segment [Abstract]
Crude Oil and Condensate	$ 5,659,437	$ 3,838,284	$ 1,998,771
Natural Gas Liquids	727,177	779,364	462,345
Natural Gas	1,571,762	2,240,540	2,420,099
Gains on Mark-to-Market Commodity Derivative Contracts	393,744	626,053	61,912
Gathering, Processing and Marketing	3,096,694	2,115,792	909,680
Gains on Asset Dispositions, Net	192,660	492,909	223,538
Other, Net	41,162	33,173	23,551
Net Operating Revenues (2)	11,682,636	10,126,115	6,099,896
Depreciation, Depletion and Amortization	3,169,703	2,516,381	1,941,926
Operating Income (Loss)	1,479,797	2,113,309	523,319
Interest Income	8,771	1,019	823
Other Income (Expense)	5,724	5,834	13,420
Net Interest Expense	213,552	210,363	129,586
Income (Loss) Before Income Taxes	1,280,740	1,909,799	407,976
Income Tax Provision (Benefit)	710,461	818,676	247,322
Additions to Oil and Gas Properties, Excluding Dry Hole Costs	6,720,346	6,241,167	5,138,126
Total Property, Plant and Equipment, Net	23,337,681	21,288,824	18,680,900
Total Assets	27,336,578	24,838,797	21,624,233
Percentage of revenues used to determine significant purchasers	10.00%
United States [Member]
Schedule of Segment Reporting Information By Segment [Abstract]
Crude Oil and Condensate	5,383,612	3,458,248	1,700,770
Natural Gas Liquids	713,497	762,730	448,647
Natural Gas	951,463	1,593,964	1,778,823
Gains on Mark-to-Market Commodity Derivative Contracts	393,744	626,053	61,912
Gathering, Processing and Marketing	3,091,281	2,115,768	909,660
Gains on Asset Dispositions, Net	166,201	475,878	196,774
Other, Net	40,780	32,329	19,886
Net Operating Revenues (2)	10,740,578	9,064,970	5,116,472
Depreciation, Depletion and Amortization	2,780,563	2,131,706	1,539,240
Operating Income (Loss)	2,233,911	2,252,508	787,422
Interest Income	8,343	436	152
Other Income (Expense)	(12,455)	(6,480)	(3,905)
Net Interest Expense	242,138	214,360	112,226
Income (Loss) Before Income Taxes	1,987,661	2,032,104	671,443
Income Tax Provision (Benefit)	707,401	732,362	255,945
Additions to Oil and Gas Properties, Excluding Dry Hole Costs	6,198,267	5,790,590	4,491,897
Total Property, Plant and Equipment, Net	21,560,998	18,711,774	15,747,808
Total Assets	24,523,072	21,313,158	17,762,533
Canada [Member]
Schedule of Segment Reporting Information By Segment [Abstract]
Crude Oil and Condensate	221,556	264,895	178,349
Natural Gas Liquids	13,680	16,634	13,698
Natural Gas	86,361	178,324	285,369
Gains on Mark-to-Market Commodity Derivative Contracts	0	0	0
Gathering, Processing and Marketing	0	0	0
Gains on Asset Dispositions, Net	26,459	17,033	23,112
Other, Net	367	258	(31)
Net Operating Revenues (2)	348,423	477,144	500,497
Depreciation, Depletion and Amortization	223,689	260,084	315,849
Operating Income (Loss)	(1,065,434)	(459,520)	(516,874)
Interest Income	123	342	387
Other Income (Expense)	(8,689)	(2,375)	2,067
Net Interest Expense	6,589	23,085	34,350
Income (Loss) Before Income Taxes	(1,080,589)	(484,638)	(548,770)
Income Tax Provision (Benefit)	(134,745)	(125,474)	(146,495)
Additions to Oil and Gas Properties, Excluding Dry Hole Costs	302,851	259,634	446,626
Total Property, Plant and Equipment, Net	877,996	1,760,066	2,189,961
Total Assets	1,202,031	2,131,949	2,598,412
Trinidad [Member]
Schedule of Segment Reporting Information By Segment [Abstract]
Crude Oil and Condensate	50,708	112,554	117,605
Natural Gas Liquids	0	0	0
Natural Gas	514,322	442,589	330,247
Gains on Mark-to-Market Commodity Derivative Contracts	0	0	0
Gathering, Processing and Marketing	5,413	24	20
Gains on Asset Dispositions, Net	0	(2)	3,652
Other, Net	15	586	3,696
Net Operating Revenues (2)	570,458	555,751	455,220
Depreciation, Depletion and Amortization	147,062	107,141	71,085
Operating Income (Loss)	371,876	383,992	312,128
Interest Income	125	101	120
Other Income (Expense)	20,482	18,755	14,022
Net Interest Expense	238	0	448
Income (Loss) Before Income Taxes	392,245	402,848	325,822
Income Tax Provision (Benefit)	140,468	204,698	140,934
Additions to Oil and Gas Properties, Excluding Dry Hole Costs	49,376	132,159	134,198
Total Property, Plant and Equipment, Net	535,405	627,794	595,970
Total Assets	1,012,727	1,085,664	954,391
Other International [Member]
Schedule of Segment Reporting Information By Segment [Abstract]
Crude Oil and Condensate	3,561	2,587	2,047
Natural Gas Liquids	0	0	0
Natural Gas	19,616	25,663	25,660
Gains on Mark-to-Market Commodity Derivative Contracts	0	0	0
Gathering, Processing and Marketing	0	0	0
Gains on Asset Dispositions, Net	0	0	0
Other, Net	0	0	0
Net Operating Revenues (2)	23,177	28,250	27,707
Depreciation, Depletion and Amortization	18,389	17,450	15,752
Operating Income (Loss)	(60,556)	(63,671)	(59,357)
Interest Income	180	140	164
Other Income (Expense)	6,386	(4,066)	1,236
Net Interest Expense	(35,413)	(27,082)	(17,438)
Income (Loss) Before Income Taxes	(18,577)	(40,515)	(40,519)
Income Tax Provision (Benefit)	(2,663)	7,090	(3,062)
Additions to Oil and Gas Properties, Excluding Dry Hole Costs	169,852	58,784	65,405
Total Property, Plant and Equipment, Net	363,282	189,190	147,161
Total Assets	$ 598,748	$ 308,026	$ 308,897