Property, Plant and Equipment (Details) (USD $)	12 Months Ended			36 Months Ended	60 Months Ended	12 Months Ended				12 Months Ended							36 Months Ended	72 Months Ended	12 Months Ended			36 Months Ended	72 Months Ended	12 Months Ended			36 Months Ended	72 Months Ended	12 Months Ended			36 Months Ended	72 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2010	Dec. 31, 2011 Santa Victoria Block Farm out interest [Member]	Dec. 31, 2010 Argentina Blow-out Preventer [Member]	Dec. 31, 2011 Argentina Blow-out Preventer [Member]	Dec. 31, 2011 Garibay Block [Member]	Dec. 31, 2011 Guachiria Norte, Guachiria, Guachiria Sur Blocks [Member]	Dec. 31, 2010 Guachiria Norte, Guachiria, Guachiria Sur Blocks [Member]	Dec. 31, 2009 Guachiria Norte, Guachiria, Guachiria Sur Blocks [Member]	Dec. 31, 2011 Participating Interest In Four Blocks In Brazil [Member]	Dec. 31, 2011 Colombia [Member]	Dec. 31, 2010 Colombia [Member]	Dec. 31, 2009 Colombia [Member]	Dec. 31, 2008 Colombia [Member]	Dec. 31, 2011 Colombia [Member]	Dec. 31, 2011 Argentina [Member]	Dec. 31, 2010 Argentina [Member]	Dec. 31, 2009 Argentina [Member]	Dec. 31, 2008 Argentina [Member]	Dec. 31, 2011 Argentina [Member]	Dec. 31, 2011 Peru [Member]	Dec. 31, 2010 Peru [Member]	Dec. 31, 2009 Peru [Member]	Dec. 31, 2008 Peru [Member]	Dec. 31, 2011 Peru [Member]	Dec. 31, 2011 Brazil [Member]	Dec. 31, 2010 Brazil [Member]	Dec. 31, 2009 Brazil [Member]	Dec. 31, 2008 Brazil [Member]	Dec. 31, 2011 Brazil [Member]	Dec. 31, 2011 Proved Oil and Gas Properties [Member]	Dec. 31, 2010 Proved Oil and Gas Properties [Member]	Dec. 31, 2011 Unproved - Oil and Gas Properties [Member]	Dec. 31, 2010 Unproved - Oil and Gas Properties [Member]	Dec. 31, 2011 Oil and Natural Gas Properties [Member]	Dec. 31, 2010 Oil and Natural Gas Properties [Member]	Dec. 31, 2011 Furniture and Fixtures and Leasehold Improvements [Member]	Dec. 31, 2010 Furniture and Fixtures and Leasehold Improvements [Member]	Dec. 31, 2011 Computer Equipment [Member]	Dec. 31, 2010 Computer Equipment [Member]	Dec. 31, 2011 Automobiles [Member]	Dec. 31, 2010 Automobiles [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 1,616,082,000	$ 1,067,548,000			$ 1,067,548,000																													$ 1,181,503,000	$ 777,262,000	$ 417,868,000	$ 278,753,000	$ 1,599,371,000	$ 1,056,015,000	$ 6,973,000	$ 5,233,000	$ 8,443,000	$ 5,521,000	$ 1,295,000	$ 779,000
Accumulated DD&A	(561,240,000)	(340,524,000)			(340,524,000)																													(562,521,000)	(334,858,000)	0	0	(562,521,000)	(334,858,000)	(4,002,000)	(2,831,000)	(4,174,000)	(2,358,000)	(543,000)	(477,000)
Net book value	1,044,842,000	727,024,000			727,024,000																													618,982,000	442,404,000	417,868,000	278,753,000	1,036,850,000	721,157,000	2,971,000	2,402,000	4,269,000	3,163,000	752,000	302,000
Ceiling test impairment loss			1,900,000				23,600,000												25,700,000					42,000,000
Impairment loss associated with abandonment of the Valle Morado sidetrack operations		17,900,000
Depreciation, depletion and amortization	163,500,000	140,000,000	134,000,000
Impairment loss resulting from decrease in reserves combined with higher forecasted operating costs to produce remaining proved reserves		5,700,000
Cost Center Unproved assets	417,900,000	278,800,000			278,800,000									274,800,000	228,800,000			274,800,000	57,000,000	9,400,000			57,000,000	33,700,000	28,200,000			33,700,000	52,400,000	12,400,000			52,400,000
Acquisition costs														76,346,000	0	0	159,045,000	235,391,000	45,015,000	0	0	0	45,015,000	23,423,000	2,000,000	0	0	25,423,000	22,891,000	12,395,000	0	0	35,286,000
Exploration costs														19,233,000	12,427,000	3,311,000	487,000	35,458,000	181,000	683,000	163,000	229,000	1,256,000	7,389,000	301,000	372,000	189,000	8,251,000	17,155,000	0	0	0	17,155,000
Development costs														3,929,000	0	0	0	3,929,000	5,683,000	5,021,000	0	0	10,704,000	0	0	0	0	0	0				0
Total oil and natural gas properties not subject to depletion	221,245,000	32,827,000	3,846,000	159,950,000	417,868,000
Capitalized G&A, including stock-based compensation	14,353,000	5,585,000	2,230,000		5,585,000									7,996,000	4,127,000	1,600,000		7,996,000	3,189,000	1,171,000	1,083,000		3,189,000	1,183,000	287,000	30,000		1,183,000	1,985,000	0	0		1,985,000
Capitalized stock-based compensation	956,000	458,000	315,000		458,000									456,000	308,000	198,000		456,000	266,000	150,000	117,000		266,000	0	0	0		0	234,000	0	0		234,000
Acquistion Of Oil Gas Property Plant And Equipment [Line Items]
Participation in Oil and Gas property description													On August 26, 2010, the Company entered into an agreement to acquire a 70 participating interest in four blocks in Brazil. With the exception of one block which has a producing well, the remaining blocks are unproved properties. The agreement was effective September 1, 2010, subject to regulatory approvals, and the transaction was completed on June 15, 2011. Purchase consideration was 40.1 million and was recorded in All other capital expenditure in 2011 and 2010. The 70 share of all benefits and costs with respect to the period between the effective date and the completion of the transaction were an adjustment to the consideration paid for the four blocks.
Participating interest (in hundredths)						50.00%							70.00%
Purchase price consideration for oil and gas property participation													40,100,000
Significant Acquisitions and Disposals [Line Items]
Sale of Interest, aggregate consideration						3,300,000		1,200,000	6,400,000	7,000,000
Initial cash payment										4,000,000
Monthly installments receivable										15
Monthly installment amount receivable										200,000
Sale of Interest, net proceeds											$ 1,600,000	$ 5,400,000
Percentage of royalty interest retained (in hundredths)										10.00%
Percentage of costs for previously acquired seismic data designed to be reimbursed (in hundredths)										200.00%