Oil and Gas Exploration and Production Industries Disclosures, Results Of Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues	$ 7,958,376	$ 6,858,188	$ 4,881,215
Other	41,162	33,173	23,551
Total	7,999,538	6,891,361	4,904,766
Exploration Costs	185,569	171,658	187,381
Dry Hole Costs	14,970	53,230	72,486
Transportation Costs	601,431	430,322	385,189
Production Costs	1,468,628	1,332,210	998,065
Impairments	1,270,735	1,031,037	725,052
Depreciation, Depletion and Amortization	3,024,514	2,393,814	1,831,023
Income (Loss) Before Income Taxes	1,433,691	1,479,090	705,570
Tax Provision (Benefit)	722,906	637,868	350,708
Results of Operations	710,785	841,222	354,862
United States [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues	7,048,572	5,814,942	3,928,240
Other	40,780	32,329	19,886
Total	7,089,352	5,847,271	3,948,126
Exploration Costs	162,152	148,199	156,252
Dry Hole Costs	1,772	30,521	30,927
Transportation Costs	591,547	421,060	372,466
Production Costs	1,264,633	1,096,955	763,769
Impairments	294,172	575,976	271,466
Depreciation, Depletion and Amortization	2,637,500	2,011,080	1,430,408
Income (Loss) Before Income Taxes	2,137,576	1,563,480	922,838
Tax Provision (Benefit)	761,459	569,153	375,855
Results of Operations	1,376,117	994,327	546,983
Canada [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues	321,597	459,853	477,416
Other	367	258	(31)
Total	321,964	460,111	477,385
Exploration Costs	13,350	10,479	17,597
Dry Hole Costs	1,570	432	14,875
Transportation Costs	7,511	5,969	9,892
Production Costs	154,509	174,973	174,667
Impairments	976,563	452,103	451,703
Depreciation, Depletion and Amortization	222,366	258,772	314,663
Income (Loss) Before Income Taxes	(1,053,905)	(442,617)	(506,012)
Tax Provision (Benefit)	(136,105)	(121,044)	(151,315)
Results of Operations	(917,800)	(321,573)	(354,697)
Trinidad [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues	565,030	555,143	447,852
Other	15	586	3,696
Total	565,045	555,729	451,548
Exploration Costs	2,262	2,520	2,277
Dry Hole Costs	0	0	5,000
Transportation Costs	1,104	1,620	1,348
Production Costs	37,792	49,318	51,125
Impairments	0	0	1,465
Depreciation, Depletion and Amortization	146,690	106,802	70,553
Income (Loss) Before Income Taxes	377,197	395,469	319,780
Tax Provision (Benefit)	119,442	202,815	140,413
Results of Operations	257,755	192,654	179,367
Other International [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Crude Oil and Condensate, Natural Gas Liquids and Natural Gas Revenues	23,177	28,250	27,707
Other	0	0	0
Total	23,177	28,250	27,707
Exploration Costs	7,805	10,460	11,255
Dry Hole Costs	11,628	22,277	21,684
Transportation Costs	1,269	1,673	1,483
Production Costs	11,694	10,964	8,504
Impairments	0	2,958	418
Depreciation, Depletion and Amortization	17,958	17,160	15,399
Income (Loss) Before Income Taxes	(27,177)	(37,242)	(31,036)
Tax Provision (Benefit)	(21,890)	(13,056)	(14,245)
Results of Operations	$ (5,287)	$ (24,186)	$ (16,791)