Gran Tierra Energy (GTE) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2013	Nov. 06, 2013
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'GRAN TIERRA ENERGY INC.	'
Entity Central Index Key	'0001273441	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	272,193,233
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Retained Earnings (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
REVENUE AND OTHER INCOME	'	'	'	'
Oil and natural gas sales	$188,974	$168,616	$561,935	$438,406
Interest income	684	317	1,904	1,628
Total revenue and other income	189,658	168,933	563,839	440,034
EXPENSES	'	'	'	'
Operating	35,588	36,295	108,505	88,115
Depletion, depreciation, accretion and impairment (Note 4)	58,875	45,044	180,309	137,982
General and administrative	14,673	12,896	37,840	46,394
Foreign exchange loss (gain)	1,880	-1,315	-15,329	27,867
Other loss (Note 8)	0	0	4,400	0
Total expenses	111,016	92,920	315,725	300,358
INCOME BEFORE INCOME TAXES	78,642	76,013	248,114	139,676
Income tax expense (Note 7)	-45,585	-31,408	-109,361	-82,280
NET INCOME AND COMPREHENSIVE INCOME	33,057	44,605	138,753	57,396
RETAINED EARNINGS, BEGINNING OF PERIOD	390,369	197,805	284,673	185,014
RETAINED EARNINGS, END OF PERIOD	$423,426	$242,410	$423,426	$242,410
NET INCOME PER SHARE — BASIC (in dollars per share)	$0.12	$0.16	$0.49	$0.20
NET INCOME PER SHARE — DILUTED (in dollars per share)	$0.12	$0.16	$0.49	$0.20
WEIGHTED AVERAGE SHARES OUTSTANDING - BASIC (Note 5)	283,092,224	281,695,212	282,687,871	280,387,484
WEIGHTED AVERAGE SHARES OUTSTANDING - DILUTED (Note 5)	286,026,519	284,605,162	285,820,007	283,968,384

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$353,064	$212,624
Restricted cash	3,819	1,404
Accounts receivable	143,915	119,844
Inventory (Note 4)	16,404	33,468
Taxes receivable	6,069	39,922
Prepaids	5,365	4,074
Deferred tax assets (Note 7)	2,090	2,517
Total Current Assets	530,726	413,853
Oil and Gas Properties (using the full cost method of accounting)	'	'
Proved	790,193	813,247
Unproved	435,082	383,414
Total Oil and Gas Properties	1,225,275	1,196,661
Other capital assets	9,101	8,765
Total Property, Plant and Equipment (Note 4)	1,234,376	1,205,426
Other Long-Term Assets	'	'
Restricted cash	3,305	1,619
Deferred tax assets (Note 7)	2,076	1,401
Taxes receivable	14,608	1,374
Other long-term assets	6,746	6,621
Goodwill	102,581	102,581
Total Other Long-Term Assets	129,316	113,596
Total Assets	1,894,418	1,732,875
Current Liabilities	'	'
Accounts payable	70,783	102,263
Accrued liabilities	79,934	66,418
Taxes payable	88,757	22,339
Deferred tax liabilities (Note 7)	1,643	337
Asset retirement obligation (Note 6)	0	28
Total Current Liabilities	241,117	191,385
Long-Term Liabilities	'	'
Deferred tax liabilities (Note 7)	183,925	225,195
Equity tax payable (Note 7)	0	3,562
Asset retirement obligation (Note 6)	20,388	18,264
Other long-term liabilities	9,015	3,038
Total Long-Term Liabilities	213,328	250,059
Contingencies (Note 8)	'	'
Shareholders’ Equity	'	'
Common Stock (Note 5) (271,872,896 and 268,482,445 shares of Common Stock and 11,278,855 and 13,421,488 exchangeable shares, par value $0.001 per share, issued and outstanding as at September 30, 2013 and December 31, 2012, respectively)	10,020	7,986
Additional paid in capital	1,006,527	998,772
Retained earnings	423,426	284,673
Total Shareholders’ Equity	1,439,973	1,291,431
Total Liabilities and Shareholders’ Equity	$1,894,418	$1,732,875

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]	'	'
Common shares, par value (in dollars per share)	$0.00	$0.00
Common shares, issued	271,872,896	268,482,445
Common shares, outstanding	271,872,896	268,482,445
Exchangeable shares, issued	11,278,855	13,421,488
Exchangeable shares, outstanding	11,278,855	13,421,488

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating Activities	'	'	'	'
Net income	'	'	$138,753	$57,396
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'	'
Depletion, depreciation, accretion and impairment	58,875	45,044	180,309	137,982
Deferred tax recovery (Note 7)	'	'	-23,791	-8,855
Stock-based compensation (Note 5)	'	'	6,113	9,854
Unrealized foreign exchange (gain) loss	'	'	-16,853	14,072
Cash settlement of asset retirement obligation	'	'	-927	-404
Equity tax	'	'	-3,345	-3,534
Other loss (Note 8)	0	0	4,400	0
Net change in assets and liabilities from operating activities	'	'	'	'
Accounts receivable and other long-term assets	'	'	-26,284	-96,656
Inventory	'	'	12,366	-9,769
Prepaids	'	'	-1,291	1,087
Accounts payable and accrued and other liabilities	'	'	-7,593	-25,960
Taxes receivable and payable	'	'	87,230	-59,281
Net cash provided by operating activities	'	'	349,087	15,932
Investing Activities	'	'	'	'
Increase in restricted cash	'	'	-4,101	-21,704
Additions to property, plant and equipment	'	'	-267,642	-222,119
Proceeds from oil and gas properties (Note 4)	'	'	59,621	0
Net cash used in investing activities	'	'	-212,122	-243,823
Financing Activities	'	'	'	'
Proceeds from issuance of shares of Common Stock (Note 5)	'	'	3,475	3,797
Net cash provided by financing activities	'	'	3,475	3,797
Net increase (decrease) in cash and cash equivalents	'	'	140,440	-224,094
Cash and cash equivalents, beginning of period	'	'	212,624	351,685
Cash and cash equivalents, end of period	353,064	127,591	353,064	127,591
Cash	296,520	99,442	296,520	99,442
Term deposits	56,544	28,149	56,544	28,149
Supplemental cash flow disclosures:	'	'	'	'
Cash paid for income taxes	'	'	38,978	140,069
Non-cash investing activities:	'	'	'	'
Non-cash net assets and liabilities related to property, plant and equipment, end of period	$65,645	$33,961	$65,645	$33,961

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Shareholders' Equity (USD $)	Total	Share Capital [Member]	Additional Paid-in Capital [Member]	Warrants [Member]	Retained Earnings [Member]
In Thousands, unless otherwise specified
Balance, beginning of period at Dec. 31, 2011	'	$7,510	$980,014	$1,780	$185,014
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'
Issue of shares of Common Stock (Note 5)	'	476	2,902	'	'
Exercise of warrants	'	'	1,590	-1,590	'
Expiry of warrants	'	'	190	-190	'
Exercise of stock options (Note 5)	'	'	960	'	'
Stock-based compensation (Note 5)	'	'	13,116	'	'
Net income	'	'	'	'	99,659
Balance, end of period at Dec. 31, 2012	1,291,431	7,986	998,772	0	284,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'
Issue of shares of Common Stock (Note 5)	'	2,034	0	'	'
Exercise of warrants	'	'	0	0	'
Expiry of warrants	'	'	0	0	'
Exercise of stock options (Note 5)	'	'	1,441	'	'
Stock-based compensation (Note 5)	'	'	6,314	'	'
Net income	138,753	'	'	'	138,753
Balance, end of period at Sep. 30, 2013	$1,439,973	$10,020	$1,006,527	$0	$423,426

Description_of_Business

Description of Business	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Description of Business	'
	Description of Business
	Gran Tierra Energy Inc., a Nevada corporation (the “Company” or “Gran Tierra”), is a publicly traded oil and gas company engaged in the acquisition, exploration, development and production of oil and natural gas properties. The Company’s principal business activities are in Colombia, Argentina, Peru and Brazil.

Significant_Accounting_Policie

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Significant Accounting Policies	'
	Significant Accounting Policies
	These interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). The information furnished herein reflects all normal recurring adjustments that are, in the opinion of management, necessary for the fair presentation of results for the interim periods.
	The note disclosure requirements of annual consolidated financial statements provide additional disclosures to that required for interim unaudited condensed consolidated financial statements. Accordingly, these interim unaudited condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements as at and for the year ended December 31, 2012, included in the Company’s 2012 Annual Report on Form 10-K, filed with the Securities and Exchange Commission (“SEC”) on February 26, 2013.
	The Company’s significant accounting policies are described in Note 2 of the consolidated financial statements which are included in the Company’s 2012 Annual Report on Form 10-K and are the same policies followed in these interim unaudited condensed consolidated financial statements, except as disclosed below. The Company has evaluated all subsequent events through to the date these interim unaudited condensed consolidated financial statements were issued.
	Restricted Stock Units
	In May 2013, the Company's Board of Directors determined that the Company will annually grant time-vested restricted stock units ("RSUs") to officers, employees and consultants. RSUs entitle the holder to receive, at the option of the Company, either the underlying number of shares of the Company's Common Stock upon vesting of such shares or a cash payment equal to the value of the underlying shares. The Company expects its practice will be to settle RSUs in cash and, therefore, RSUs are accounted for as liability instruments. Compensation expense for RSUs granted is based on the estimated fair value, which is determined using the closing share price, at each reporting date, and the expense, net of estimated forfeitures, is recognized over the requisite service period using the accelerated method, with a corresponding change to liabilities. An adjustment is made to compensation expense for any difference between the estimated forfeitures and the actual forfeitures related to vested awards. Additionally, the Company will continue to grant options to purchase shares of Common Stock to certain directors, officers, employees and consultants. Stock-based compensation expense relating to RSUs and stock options is capitalized as part of oil and natural gas properties or expensed as part of operating expenses or general and administrative (“G&A”) expenses, as appropriate.
	Recently Issued Accounting Pronouncements
	Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is fixed at the Reporting Date
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013- 04, “Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is fixed at the Reporting Date”. The ASU provides guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of this update include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The implementation of this update is not expected to materially impact the Company’s consolidated financial position, results of operations or cash flows.
	Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists
	In July 2013, the FASB issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists". The ASU provides guidance on the financial statement presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The implementation of this update is not expected to materially impact the Company’s consolidated financial position, results of operations or cash flows.

Segment_and_Geographic_Reporti

Segment and Geographic Reporting	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Segment and Geographic Reporting	'
	Segment and Geographic Reporting
	The Company is primarily engaged in the exploration and production of oil and natural gas. The Company’s reportable segments are Colombia, Argentina, Peru and Brazil based on geographic organization. The level of activity in Peru and Brazil was not significant at September 30, 2013, or December 31, 2012; however, the Company has separately disclosed its results of operations in Peru and Brazil as reportable segments. The All Other category represents the Company’s corporate activities.
	The accounting policies of the reportable segments are the same as those described in Note 2. The Company evaluates reportable segment performance based on income or loss before income taxes.
	The following tables present information on the Company’s reportable segments and other activities:
		Three Months Ended September 30, 2013
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	164,241	$	18,149		$	—		$	6,584		$	—		$	188,974
	Interest income	111		164			—			281			128			684
	Depletion, depreciation, accretion and impairment	46,821		7,606			73			4,129			246			58,875
	Depletion, depreciation, accretion and impairment - per unit of production	27.48		30.51			—			59.72			—			29.12
	Income (loss) before income taxes	89,214		(4,164		)	(1,404		)	(337		)	(4,667		)	78,642
	Segment capital expenditures (1)	$	39,608	$	8,159		$	11,063		$	(22,500	)	$	289		$	36,619
		Three Months Ended September 30, 2012
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	145,610	$	22,332		$	—		$	674		$	—		$	168,616
	Interest income	171		10			—			40			96			317
	Depletion, depreciation, accretion and impairment	35,255		9,165			68			305			251			45,044
	Depletion, depreciation, accretion and impairment - per unit of production	24.46		26.6			—			40.35			—			25.12
	Income (loss) before income taxes	79,915		1,777			(847		)	(1,170		)	(3,662		)	76,013
	Segment capital expenditures	$	35,880	$	11,568		$	11,204		$	2,838		$	300		$	61,790
		Nine Months Ended September 30, 2013
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	488,577	$	54,620		$	—		$	18,738		$	—		$	561,935
	Interest income	415		710			27			292			460			1,904
	Depletion, depreciation, accretion and impairment	141,141		22,986			272			15,143			767			180,309
	Depletion, depreciation, accretion and impairment - per unit of production	27.58		27.79			—			75.74			—			29.35
	Income (loss) before income taxes	275,353		(6,183		)	(4,984		)	(3,663		)	(12,409		)	248,114
	Segment capital expenditures (1)	$	118,758	$	12,424		$	59,911		$	12,021		$	528		$	203,642
		Nine Months Ended September 30, 2012
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	376,261	$	59,183		$	—		$	2,962		$	—		$	438,406
	Interest income	598		96			15			607			312			1,628
	Depletion, depreciation, accretion and impairment	90,625		23,080			1,174			22,379			724			137,982
	Depletion, depreciation, accretion and impairment - per unit of production	24.96		24.54			—			708.76			—			29.98
	Income (loss) before income taxes	182,516		2,568			(4,147		)	(24,467		)	(16,794		)	139,676
	Segment capital expenditures	$	98,476	$	28,412		$	43,866		$	44,536		$	695		$	215,985
	(1) In the third quarter of 2013, segment capital expenditures in Brazil are net of proceeds of $54.0 million relating to termination of a farm-in agreement. Additionally, segment capital expenditures for the nine months ended September 30, 2013, are net of proceeds of $4.1 million relating to the Company's assumption of the remaining 50% working interest in the Santa Victoria Block in Argentina and $1.5 million relating to the Company's sale of its 15% working interest in the Mecaya Block in Colombia (Note 4).
		As at September 30, 2013
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Property, plant and equipment	$	822,522	$	128,799		$	155,579		$	124,418		$	3,058		$	1,234,376
	Goodwill	102,581		—			—			—			—			102,581
	Other assets	267,186		37,320			18,285			50,555			184,115			557,461
	Total Assets	$	1,192,289	$	166,119		$	173,864		$	174,973		$	187,173		$	1,894,418
		As at December 31, 2012
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Property, plant and equipment	$	840,027	$	138,768		$	95,940		$	127,394		$	3,297		$	1,205,426
	Goodwill	102,581		—			—			—			—			102,581
	Other assets	222,220		47,038			10,880			8,498			136,232			424,868
	Total Assets	$	1,164,828	$	185,806		$	106,820		$	135,892		$	139,529		$	1,732,875
	The Company’s revenues are derived principally from uncollateralized sales to customers in the oil and natural gas industry. The concentration of credit risk in a single industry affects the Company’s overall exposure to credit risk because customers may be similarly affected by changes in economic and other conditions.
	In the nine months ended September 30, 2013, the Company had two significant customers in Colombia: Ecopetrol S.A. ("Ecopetrol") and one other customer, which accounted for 52% and 29%, respectively, of the Company's consolidated oil and natural gas sales. For the three months ended September 30, 2013, these customers accounted for 56% and 28%, respectively, of the Company's consolidated oil and natural gas sales. In the nine months ended September 30, 2012, the Company had one significant customer in Colombia: Ecopetrol. For the three and nine months ended September 30, 2012, sales to Ecopetrol accounted for 71% and 77%, respectively, of the Company's consolidated oil and natural gas sales. For the three months ended September 30, 2012, the Company had an additional short-term significant customer , which accounted for 13% of the Company's revenues during the period.

Property_Plant_and_Equipment_a

Property, Plant and Equipment and Inventory	9 Months Ended
	Sep. 30, 2013
Property, Plant and Equipment [Abstract]	'
Property, Plant and Equipment and Inventory	'
	Property, Plant and Equipment and Inventory
	Property, Plant and Equipment
		As at September 30, 2013							As at December 31, 2012
	(Thousands of U.S. Dollars)	Cost		Accumulated			Net book value		Cost		Accumulated			Net book value
				depletion,							depletion,
				depreciation							depreciation
				and							and
				impairment							impairment
	Oil and natural gas properties
	Proved	$	1,710,788	$	(920,595	)	$	790,193	$	1,562,477	$	(749,230	)	$	813,247
	Unproved	435,082		—			435,082		383,414		—			383,414
		2,145,870		(920,595		)	1,225,275		1,945,891		(749,230		)	1,196,661
	Furniture and fixtures and leasehold improvements	8,215		(6,203		)	2,012		7,575		(5,093		)	2,482
	Computer equipment	14,018		(7,458		)	6,560		10,971		(5,248		)	5,723
	Automobiles	1,352		(823		)	529		1,376		(816		)	560
	Total Property, Plant and Equipment	$	2,169,455	$	(935,079	)	$	1,234,376	$	1,965,813	$	(760,387	)	$	1,205,426
	Depletion and depreciation expense on property, plant and equipment for the three months ended September 30, 2013, was $59.1 million (three months ended September 30, 2012 - $43.0 million) and for the nine months ended September 30, 2013, was $172.7 million (nine months ended September 30, 2012 - $120.8 million). A portion of depletion and depreciation expense was recorded as inventory in each period and adjusted for inventory changes.
	In the second quarter of 2013, the Company recorded a ceiling test impairment loss of $2.0 million in the Company's Brazil cost center as a result of lower realized prices and increased operating costs.
	In the first quarter of 2012, the Company recorded a ceiling test impairment loss in the Company’s Brazil cost center of $20.2 million. This impairment loss resulted from the recognition of $23.8 million of capital expenditures in relation to the Block BM-CAL-10 farm-out agreement in the first quarter of 2012. On February 17, 2012, in accordance with the terms of the farm-out agreement for Block BM-CAL-10 in Brazil, the Company gave notice to its joint venture partner that it would not enter into and assume its share of the work obligations of the second exploration period of the block. As a result, the farm-out agreement terminated and the Company did not receive any interest in this block. Pursuant to the farm-out agreement, the Company was obligated to make payment for a certain percentage of the costs relating to Block BM-CAL-10, which relate primarily to a well that was drilled during the term of the farm-out agreement. The notice of withdrawal was a trigger for payment of amounts that would otherwise have been due if the farm-out agreement had closed and the Company had acquired a working interest.
	In the second quarter of 2013, the Company assumed its partner's 50% working interest in the Santa Victoria Block in Argentina and received cash consideration of $4.1 million from its partner, comprising the balance owing for carry consideration and compensation for the second exploration phase work commitment. The Company also received proceeds of $1.5 million relating to a sale of its 15% working interest in the Mecaya Block in Colombia.
	During the third quarter of 2013, the Company received a net payment of $54.0 million (before income taxes) from a third party in connection with termination of a farm-in agreement in the Recôncavo Basin relating to Block REC-T-129, Block REC-T-142, Block REC-T-155 and Block REC-T-224.
	The Company successfully bid on three blocks in the 2013 Brazil Bid Round administered by Brazil's Agência Nacional de Petróleo, Gás Natural e Biocombustíveis ("ANP") and, in the third quarter of 2013, paid a signature bonus of $14.4 million upon finalization of the concession agreement.
	In Brazil, the exploration phase of the concession agreements on Blocks REC-T-129, REC-T-142 and REC-T-155 is due to expire on November 24, 2013; however, under the concession agreements the Company is able and has submitted an application to the ANP for extension of the exploration phase of these blocks. Additionally, the exploration phase of the concession agreement on Block REC-T-224 is due to expire on December 11, 2013, but we plan to apply for an extension of the exploration phase of this block. At September 30, 2013, unproved properties included $59.6 million relating to these four blocks. Management assessed these blocks for impairment at September 30, 2013 and concluded no impairment had occurred.
	In Argentina, Rio Negro Province has enacted legislation that changes the royalty regime associated with concession agreement extensions. The Company is negotiating concession agreement extensions and royalty rates for its Puesto Morales, Puesto Morales Este, Rinconada Norte and Rinconada Sur Blocks and expects that royalty rates in Rio Negro Province will likely increase and a bonus payment, not determinable at this time, may be payable for the concession agreement extensions.
	The amounts of G&A expenses and stock-based compensation capitalized in each of the Company's cost centers were as follows:
		Nine Months Ended September 30, 2013
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru		Brazil		Total
	Capitalized G&A, including stock-based compensation	$	14,746	$	2,896		$	5,981	$	5,813	$	29,436
	Capitalized stock-based compensation	$	794	$	171		$	571	$	566	$	2,102
		Nine Months Ended September 30, 2012
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru		Brazil		Total
	Capitalized G&A, including stock-based compensation	$	9,279	$	3,480		$	3,670	$	2,653	$	19,082
	Capitalized stock-based compensation	$	376	$	275		$	—	$	216	$	867
	Unproved oil and natural gas properties consist of exploration lands held in Colombia, Argentina, Peru and Brazil. As at September 30, 2013, the Company had $163.0 million (December 31, 2012 - $175.9 million) of unproved assets in Colombia, $39.5 million (December 31, 2012 - $42.3 million) of unproved assets in Argentina, $154.6 million (December 31, 2012 - $95.1 million) of unproved assets in Peru, and $78.0 million (December 31, 2012 - $70.1 million) of unproved assets in Brazil for a total of $435.1 million (December 31, 2012 - $383.4 million). These properties are being held for their exploration value and are not being depleted pending determination of the existence of proved reserves. Gran Tierra will continue to assess the unproved properties over the next several years as proved reserves are established and as exploration dictates whether or not future areas will be developed. The Company expects that approximately 62% of costs not subject to depletion at September 30, 2013, will be transferred to the depletable base within the next five years and the remainder in the next five to 10 years.
	Inventory
	At September 30, 2013, oil and supplies inventories were $14.6 million and $1.8 million, respectively (December 31, 2012 - $31.2 million and $2.3 million, respectively).

Share_Capital

Share Capital	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share Capital	'
	Share Capital
	The Company’s authorized share capital consists of 595,000,002 shares of capital stock, of which 570 million are designated as Common Stock, par value $0.001 per share, 25 million are designated as Preferred Stock, par value $0.001 per share, and two shares are designated as special voting stock, par value $0.001 per share.
	As at September 30, 2013, outstanding share capital consists of 271,872,896 shares of Common Stock of the Company, 6,744,728 exchangeable shares of Gran Tierra Exchangeco Inc., (the "Exchangeco exchangeable shares") and 4,534,127 exchangeable shares of Gran Tierra Goldstrike Inc. (the "Goldstrike exchangeable shares"). The redemption date of the Exchangeco exchangeable shares was previously established as November 14, 2013 (or at an earlier date under certain specified circumstances). However, pursuant to resolutions of the board of directors of Gran Tierra Exchangeco Inc., effective October 25, 2013, the redemption date for the Exchangeco exchangeable shares was extended to such later date as may be established by the board of directors of Gran Tierra Exchangeco Inc. at its discretion. The redemption date of the Goldstrike exchangeable shares was previously established as November 10, 2013. However, pursuant to resolutions of the board of directors of Gran Tierra Goldstrike Inc., effective October 31, 2013, the redemption date for the Goldstrike exchangeable shares was extended to such later date as may be established by the board of directors of Gran Tierra Goldstrike Inc. at its discretion. During the nine months ended September 30, 2013, 1,247,818 shares of Common Stock were issued upon the exercise of stock options, 452,950 shares of Common Stock were issued upon the exchange of the Exchangeco exchangeable shares and 1,689,683 shares of Common Stock were issued upon the exchange of the Goldstrike exchangeable shares.
	The holders of shares of Common Stock are entitled to one vote for each share on all matters submitted to a stockholder vote and are entitled to share in all dividends that the Company’s board of directors, in its discretion, declares from legally available funds. The holders of Common Stock have no pre-emptive rights, no conversion rights, and there are no redemption provisions applicable to the shares.
	The Exchangeco exchangeable shares were issued upon acquisition of Solana Resources Limited. The Goldstrike exchangeable shares were issued upon the business combination between Gran Tierra Energy Inc., an Alberta corporation, and Goldstrike, Inc., which is now the Company. Holders of exchangeable shares have substantially the same rights as holders of shares of Common Stock. Each exchangeable share is exchangeable into one share of Common Stock of the Company.
	Restricted Stock Units and Stock Options
	In May 2013, the Company issued RSUs and stock options, which will vest as to 1/3 of the awards on each of March 1, 2014, March 1, 2015 and March 1, 2016. The term of options granted starting May 2013 is five years or three months after the grantee’s end of service to the Company, whichever occurs first. Options granted prior to May 2013 continue to have a term of ten years or three months after the grantee’s end of service to the Company, whichever occurs first. Once an RSU is vested, it is immediately settled and considered to be at the end of its term.
	The following table provides information about long-term incentive plan ("LTIP") activity for the nine months ended September 30, 2013:
		RSUs			Options
		Number of Outstanding Share Units			Number of Outstanding Options			Weighted Average Exercise Price $/Option
	Balance, December 31, 2012	—			15,399,662			5.11
	Granted	939,365			2,066,935			6.27
	Exercised	—			(1,247,818	)		(2.79	)
	Forfeited	(21,655	)		(284,835	)		(6.17	)
	Expired	—			(102,593	)		(6.57	)
	Balance, September 30, 2013	917,710			15,831,351			5.42
	For the nine months ended September 30, 2013, 1,247,818 shares of Common Stock were issued for cash proceeds of $3.5 million upon the exercise of 1,247,818 stock options (nine months ended September 30, 2012 - $3.8 million).
	The weighted average grant date fair value for options granted in the three months ended September 30, 2013, was $2.34 (three months ended September 30, 2012 - $2.62) and for the nine months ended September 30, 2013, was $2.62 (nine months ended September 30, 2012 - $3.36). As a result of the change in the term of stock options to five years for stock options granted starting May 2013, the weighted average volatility used in the Black-Scholes option pricing model was reduced to 43% for the three months ended September 30, 2013 and 53% for the nine months ended September 30, 2013, from 75% for the year ended December 31, 2012, resulting in a lower grant date fair value per share than in prior periods.
	The amounts recognized for stock-based compensation were as follows:
	(Thousands of U.S. Dollars)		Three Months Ended September 30,								Nine Months Ended September 30,
			2013				2012				2013			2012
	Compensation costs for stock options		$	2,132			$	3,268			$	6,314		$	10,721
	Compensation costs for RSUs		1,282				—				1,901			—
			3,414				3,268				8,215			10,721
	Less: stock-based compensation costs capitalized		(1,717		)		(336		)		(2,102		)	(867		)
	Total stock-based compensation expense		$	1,697			$	2,932			$	6,113		$	9,854
	Of the total compensation expense for the three months ended September 30, 2013, $1.3 million (three months ended September 30, 2012 - $2.6 million) was recorded in G&A expenses and $0.4 million (three months ended September 30, 2012 – $0.3 million) was recorded in operating expenses. Of the total compensation expense for the nine months ended September 30, 2013, $5.3 million (nine months ended September 30, 2012 – $8.9 million) was recorded in G&A expenses and $0.8 million (nine months ended September 30, 2012 – $0.9 million) was recorded in operating expenses.
	At September 30, 2013, there was $11.3 million (December 31, 2012 - $8.2 million) of unrecognized compensation cost related to unvested LTIP units which is expected to be recognized over a weighted average period of 2.1 years.
	Net income per share
	Basic net income per share is calculated by dividing net income attributable to common shareholders by the weighted average number of shares of Common Stock and exchangeable shares issued and outstanding during each period. Diluted net income per share is calculated by adjusting the weighted average number of shares of Common Stock and exchangeable shares outstanding for the dilutive effect, if any, of share equivalents. The Company uses the treasury stock method to determine the dilutive effect. This method assumes that all Common Stock equivalents have been exercised at the beginning of the period (or at the time of issuance, if later), and that the funds obtained thereby were used to purchase shares of Common Stock of the Company at the volume weighted average trading price of shares of Common Stock during the period.
			Three Months Ended September 30,						Nine Months Ended September 30,
			2013			2012			2013			2012
	Weighted average number of common and exchangeable shares outstanding		283,092,224			281,695,212			282,687,871			280,387,484
	Shares issuable pursuant to warrants		—			—			—			235,582
	Shares issuable pursuant to stock options		12,428,489			5,643,730			10,823,968			5,947,880
	Shares assumed to be purchased from proceeds of stock options		(9,494,194	)		(2,733,780	)		(7,691,832	)		(2,602,562	)
	Weighted average number of diluted common and exchangeable shares outstanding		286,026,519			284,605,162			285,820,007			283,968,384
	For the three months ended September 30, 2013, 3,472,472 options (three months ended September 30, 2012 - 9,957,585 options) were excluded from the diluted income per share calculation as the options were anti-dilutive. For the nine months ended September 30, 2013, 5,584,732 options (nine months ended September 30, 2012 - 9,808,758 options) were excluded from the diluted income per share calculation as the options were anti-dilutive.

Asset_Retirement_Obligation

Asset Retirement Obligation	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation [Abstract]	'
Asset Retirement Obligation	'
	Asset Retirement Obligation
	Changes in the carrying amounts of the asset retirement obligation associated with the Company’s oil and natural gas properties were as follows:
		Nine Months Ended			Year Ended
	(Thousands of U.S. Dollars)	September 30, 2013			31-Dec-12
	Balance, beginning of year	$	18,292		$	12,669
	Settlements	(2,068		)	(404		)
	Liability incurred	1,397			5,190
	Liability assumed in a business combination	—			410
	Foreign exchange	(23		)	45
	Accretion	918			998
	Revisions in estimated liability	1,872			(616		)
	Balance, end of period	$	20,388		$	18,292
	Asset retirement obligation - current	$	—		$	28
	Asset retirement obligation - long-term	20,388			18,264
	Balance, end of period	$	20,388		$	18,292
	For the nine months ended September 30, 2013, settlements included cash payments of $0.9 million with the balance in accounts payable and accrued liabilities at September 30, 2013. Revisions to estimated liabilities relate primarily to changes in estimates of asset retirement costs and include, but are not limited to, revisions of estimated inflation rates, changes in property lives and the expected timing of settling the asset retirement obligation. At September 30, 2013, the fair value of assets that are legally restricted for purposes of settling the asset retirement obligation was $1.9 million (December 31, 2012 - $1.3 million).

Taxes

Taxes	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Taxes	'
	Taxes
	The income tax expense reported differs from the amount computed by applying the U.S. statutory rate to income before income taxes for the following reasons:
		Nine Months Ended September 30,
	(Thousands of U.S. Dollars)	2013			2012
	Income (loss) before income taxes
	United States	$	(8,488	)	$	(7,942	)
	Foreign	256,602			147,618
		248,114			139,676
		35		%	35		%
	Income tax expense expected	86,840			48,887
	Foreign currency translation adjustments	(7,649		)	8,025
	Impact of foreign taxes	1,908			2,716
	Stock-based compensation	1,943			3,277
	Increase in valuation allowance	22,700			9,304
	Branch and other foreign loss pick-up	(2,013		)	(4,358		)
	Non-deductible third party royalty in Colombia	8,812			9,951
	Other permanent differences	(3,180		)	4,478
	Total income tax expense	$	109,361		$	82,280
	Current income tax expense
	United States	$	813		$	778
	Foreign	132,339			90,357
		133,152			91,135
	Deferred income tax recovery
	United States	—			—
	Foreign	(23,791		)	(8,855		)
		(23,791		)	(8,855		)
	Total income tax expense	$	109,361		$	82,280
		As at
	(Thousands of U.S. Dollars)	September 30, 2013			31-Dec-12
	Deferred Tax Assets
	Tax benefit of operating loss carryforwards	$	53,693		$	51,920
	Tax basis in excess of book basis	44,500			22,519
	Foreign tax credits and other accruals	30,550			30,926
	Tax benefit of capital loss carryforwards	4,835			4,779
	Deferred tax assets before valuation allowance	133,578			110,144
	Valuation allowance	(129,412		)	(106,226		)
		$	4,166		$	3,918
	Deferred tax assets - current	$	2,090		$	2,517
	Deferred tax assets - long-term	2,076			1,401
		4,166			3,918
	Deferred tax liabilities - current	(1,643		)	(337		)
	Deferred tax liabilities - long-term	(183,925		)	(225,195		)
		(185,568		)	(225,532		)
	Net Deferred Tax Liabilities	$	(181,402	)	$	(221,614	)
	As at September 30, 2013, the Company had operating loss carryforwards of $233.7 million (December 31, 2012 - $213.1 million) and capital loss carryforwards of $32.6 million (December 31, 2012 – $35.9 million) before valuation allowance. Of these operating loss carryforwards and capital loss carryforwards, $233.8 million (December 31, 2012 - $215.2 million) were losses generated by the foreign subsidiaries of the Company. In certain jurisdictions, the operating loss carryforwards expire between 2014 and 2033 and the capital loss carryforwards expire between 2014 and 2017, while certain other jurisdictions allow operating losses to be carried forward indefinitely.
	As at September 30, 2013, the total amount of Gran Tierra’s unrecognized tax benefit was approximately $19.8 million (December 31, 2012 - $21.8 million), a portion of which, if recognized, would affect the Company’s effective tax rate. To the extent interest and penalties may be assessed by taxing authorities on any underpayment of income tax, such amounts have been accrued and are classified as a component of income taxes in the consolidated statement of operations.
	Changes in the Company's unrecognized tax benefit are as follows:
		Nine Months Ended September 30,
		2013			2012
	(Thousands of U.S. Dollars)
	Unrecognized tax benefit at beginning of period	$	21,800		$	20,500
	Changes for positions relating to prior year	(2,000		)	—
	Unrecognized tax benefit at end of period	$	19,800		$	20,500
	The Company and its subsidiaries file income tax returns in the U.S. and certain other foreign jurisdictions. The Company is potentially subject to income tax examinations for the tax years 2005 through 2012 in certain jurisdictions. The Company does not anticipate any material changes to the unrecognized tax benefit disclosed above within the next twelve months.
	The equity tax liability at September 30, 2013, and December 31, 2012, includes a Colombian tax of 6% on a legislated measure and was calculated based on the Company’s Colombian segment’s balance sheet equity for tax purposes at January 1, 2011. The tax is payable in eight semi-annual installments over four years, but was expensed in the first quarter of 2011 at the commencement of the four-year period. The equity tax liability also partially related to an equity tax liability assumed upon the 2011 acquisition of Petrolifera Petroleum Limited.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Contingencies	'
	Contingencies
	Gran Tierra Energy Colombia, Ltd. and Petrolifera Petroleum Exploration (Colombia) Ltd (collectively “GTEC”) and Ecopetrol, the contracting parties of the Guayuyaco Association Contract, are engaged in a dispute regarding the interpretation of the procedure for allocation of oil produced and sold during the long-term test of the Guayuyaco-1 and Guayuyaco-2 wells, prior to GTEC's purchase of the companies originally involved in the dispute. There has been no agreement between the parties, and Ecopetrol filed a lawsuit in the Contravention Administrative Tribunal in the District of Cauca (the "Tribunal") regarding this matter. During the first quarter of 2013, the Tribunal ruled in favor of Ecopetrol and awarded Ecopetrol 44,025 bbl of oil. GTEC has filed an appeal of the ruling to the Supreme Administrative Court (Consejo de Estado) in a second instance procedure. During the nine months ended September 30, 2013, based on market oil prices in Colombia, Gran Tierra accrued $4.4 million in the condensed consolidated financial statements in relation to this dispute.
	Gran Tierra’s production from the Costayaco field is subject to an additional royalty that applies when cumulative gross production from a commercial field is greater than 5 MMbbl. This additional royalty is calculated on the difference between a trigger price defined by the Agencia Nacional de Hidrocarburos (National Hydrocarbons Agency) (“ANH”) and the sales price. The ANH has requested that the additional compensation be paid with respect to production from wells relating to the Moqueta discovery and has initiated a non-compliance procedure under the Chaza Contract. The Moqueta discovery is not located in the Costayaco Exploitation Area. Further, Gran Tierra views the Costayaco field and the Moqueta discovery as two clearly separate and independent hydrocarbon accumulations. Therefore, it is Gran Tierra’s view that it is clear that, pursuant to the Chaza Contract, the additional compensation payments are only to be paid with respect to production from the Moqueta wells when the accumulated oil production from any new Exploitation Area created with respect to the Moqueta discovery exceeds 5 MMbbl. Discussions with the ANH have not resolved this issue and Gran Tierra has initiated the dispute resolution process and filed an arbitration claim. As at September 30, 2013, total cumulative production from the Moqueta field was 1.9 MMbbl. The estimated compensation which would be payable on cumulative production to date if the ANH’s interpretation is successful is $31.7 million. At this time, no amount has been accrued in the condensed consolidated financial statements nor deducted from the Company's reserves as Gran Tierra does not consider it probable that a loss will be incurred.
	Additionally, the ANH and Gran Tierra Colombia are engaged in discussions regarding the interpretation of whether certain transportation and related costs are eligible to be deducted in the calculation of the additional royalty. Discussions with the ANH are ongoing. As at September 30, 2013, the estimated compensation which would be payable if the ANH’s interpretation is successful is $23.4 million. At this time, no amount has been accrued in the condensed consolidated financial statements as Gran Tierra does not consider it probable that a loss will be incurred.
	Gran Tierra has several lawsuits and claims pending. Although the outcome of these lawsuits and disputes cannot be predicted with certainty, Gran Tierra believes the resolution of these matters would not have a material adverse effect on the Company’s consolidated financial position, results of operations or cash flows. Gran Tierra records costs as they are incurred or become probable and determinable.
	Letters of credit
	At September 30, 2013, the Company had provided promissory notes totaling $49.6 million (December 31, 2012 - $34.2 million) as security for letters of credit relating to work commitment guarantees contained in exploration contracts and other capital or operating requirements.

Financial_Instruments_Fair_Val

Financial Instruments, Fair Value Measurements and Credit Risk	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]	'
Financial Instruments, Fair Value Measurements and Credit Risk	'
	Financial Instruments, Fair Value Measurements and Credit Risk
	At September 30, 2013, the Company’s financial instruments recognized in the balance sheet consist of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued liabilities, and contingent consideration and contingent liability included in other long-term liabilities. The fair value of long-term restricted cash approximates its carrying value because interest rates are variable and reflective of market rates. Contingent consideration, which relates to the acquisition of the remaining 30% working interest in certain properties in Brazil in October 2012, was recorded on the balance sheet at the acquisition date fair value based on the consideration expected to be transferred and discounted back to present value by applying an appropriate discount rate that reflected the risk factors associated with the payment streams. The discount rate used was determined at the time of measurement in accordance with accepted valuation methods. The contingent liability which relates to a dispute with Ecopetrol (Note 8) was based on the fair value of the amount awarded. The fair value of the contingent consideration and contingent liability is being remeasured at the estimated fair value at each reporting period with the change in fair value recognized as income or expense in operating income. The fair value of the contingent consideration was $1.1 million at September 30, 2013, and December 31, 2012. The fair value of the contingent liability was $4.4 million at September 30, 2013. The fair values of other financial instruments approximate their carrying amounts due to the short-term maturity of these instruments. At September 30, 2013, and December 31, 2012, the Company held no derivative instruments.
	GAAP establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. This hierarchy consists of three broad levels. Level 1 inputs consist of quoted prices (unadjusted) in active markets for identical assets and liabilities and have the highest priority. Level 2 and 3 inputs are based on significant other observable inputs and significant unobservable inputs, respectively, and have lower priorities. The Company uses appropriate valuation techniques based on the available inputs to measure the fair values of assets and liabilities. The fair value of the contingent consideration payable in connection with the Brazil acquisition was determined using Level 3 inputs at September 30, 2013, and December 31, 2012. The disclosure in the paragraph above regarding the fair value of other financial instruments is based on Level 1 inputs.
	Credit risk arises from the potential that the Company may incur a loss if a counterparty to a financial instrument fails to meet its obligation in accordance with agreed terms. The Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and accounts receivable. The carrying value of cash and accounts receivable reflects management’s assessment of credit risk.
	At September 30, 2013, cash and cash equivalents and restricted cash included balances in savings and checking accounts, as well as term deposits and certificates of deposit, placed primarily with financial institutions with strong investment grade ratings or governments, or the equivalent in the Company’s operating areas. Any foreign currency transactions are conducted on a spot basis, with major financial institutions in the Company’s operating areas.
	Most of the Company’s accounts receivable relate to uncollateralized sales to customers in the oil and natural gas industry and are exposed to typical industry credit risks. The concentration of revenues in a single industry affects the Company’s overall exposure to credit risk because customers may be similarly affected by changes in economic and other conditions. The Company manages this credit risk by entering into sales contracts with only credit worthy entities and reviewing its exposure to individual entities on a regular basis. For the nine months ended September 30, 2013, the Company had two customers which were significant to the Colombian segment, three customers which were significant to the Argentina segment and one customer which was significant to the Brazilian segment.
	For the nine months ended September 30, 2013, 87% (nine months ended September 30, 2012 - 86%) of the Company's revenue and other income was generated in Colombia.
	Additionally, foreign exchange gains and losses mainly result from fluctuation of the U.S. dollar to the Colombian peso due to Gran Tierra’s current and deferred tax liabilities, which are monetary liabilities mainly denominated in the local currency of the Colombian foreign operations. As a result, foreign exchange gains and losses must be calculated on conversion to the U.S. dollar functional currency. A strengthening in the Colombian peso against the U.S. dollar results in foreign exchange losses, estimated at $95,000 for each one peso decrease in the exchange rate of the Colombian peso to one U.S. dollar.
	The Argentina government has imposed a number of monetary and currency exchange control measures that include restrictions on the free disposition of funds deposited with banks and tight restrictions on transferring funds abroad, with certain exceptions for transfers related to foreign trade and other authorized transactions approved by the Argentina Central Bank. The Argentina Central Bank may require prior authorization and may or may not grant such authorization for Gran Tierra's Argentina subsidiaries to make dividends or loan payments to the Company. During the three months ended June 30, 2013, the Company repatriated $11.1 million from one of its Argentina subsidiaries through loan repayments, authorized by the Argentina Central Bank. These were repayments of loan principal and as such had no withholding tax applied. At September 30, 2013, $20.3 million, or 6%, of the Company's cash and cash equivalents was deposited with banks in Argentina. We expect to use these funds for the Argentina work program and operations in 2013.

Credit_Facilities

Credit Facilities	9 Months Ended
	Sep. 30, 2013
Line of Credit Facility [Abstract]	'
Credit Facilities	'
	Credit Facilities
	At September 30, 2013, a subsidiary of Gran Tierra had a credit facility with a syndicate of banks, led by Wells Fargo Bank National Association as administrative agent. This reserve-based facility has a current borrowing base of $150 million and a maximum borrowing base of up to $300 million and is supported by the present value of the petroleum reserves of two of the Company’s subsidiaries with operating branches in Colombia and the Company's subsidiary in Brazil. Amounts drawn down under the facility bear interest at the U.S. dollar LIBOR rate plus a margin ranging between 2.25% and 3.25% per annum depending on the rate of borrowing base utilization. In addition, a stand-by fee of 0.875% per annum is charged on the unutilized balance of the committed borrowing base and is included in G&A expenses. The credit facility was entered into on August 30, 2013 and became effective on October 31, 2013 for a three-year term. Subsequent to the effective date, the Company has not drawn down any amounts under the new credit facility. Under the terms of the facility, the Company is required to maintain and was in compliance with certain financial and operating covenants. Under the terms of the credit facility, the Company cannot pay any dividends to its shareholders if it is in default under the facility and, if the Company is not in default, then it is required to obtain bank approval for any dividend payments exceeding $2 million in any fiscal year.

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2013
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	On August 7, 2012, Gran Tierra entered into a contract related to the Brazil drilling program with a company for which one of Gran Tierra’s directors is a shareholder and was a director. During the three and nine months ended September 30, 2013, $4.2 million and $11.8 million, respectively, (three and nine months ended September 30, 2012 - $nil) was incurred and capitalized under this contract. At September 30, 2013, $2.3 million (December 31, 2012 - $1.1 million) was included in accounts payable relating to this contract.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]	'
Restricted Stock Units	'
	Restricted Stock Units
	In May 2013, the Company's Board of Directors determined that the Company will annually grant time-vested restricted stock units ("RSUs") to officers, employees and consultants. RSUs entitle the holder to receive, at the option of the Company, either the underlying number of shares of the Company's Common Stock upon vesting of such shares or a cash payment equal to the value of the underlying shares. The Company expects its practice will be to settle RSUs in cash and, therefore, RSUs are accounted for as liability instruments. Compensation expense for RSUs granted is based on the estimated fair value, which is determined using the closing share price, at each reporting date, and the expense, net of estimated forfeitures, is recognized over the requisite service period using the accelerated method, with a corresponding change to liabilities. An adjustment is made to compensation expense for any difference between the estimated forfeitures and the actual forfeitures related to vested awards. Additionally, the Company will continue to grant options to purchase shares of Common Stock to certain directors, officers, employees and consultants. Stock-based compensation expense relating to RSUs and stock options is capitalized as part of oil and natural gas properties or expensed as part of operating expenses or general and administrative (“G&A”) expenses, as appropriate.
Recently Issued Accounting Pronouncements	'
	Recently Issued Accounting Pronouncements
	Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is fixed at the Reporting Date
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2013- 04, “Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation is fixed at the Reporting Date”. The ASU provides guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of this update include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The implementation of this update is not expected to materially impact the Company’s consolidated financial position, results of operations or cash flows.
	Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists
	In July 2013, the FASB issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists". The ASU provides guidance on the financial statement presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. The implementation of this update is not expected to materially impact the Company’s consolidated financial position, results of operations or cash flows.

Segment_and_Geographic_Reporti1

Segment and Geographic Reporting (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]	'
Reportable Geographic Segments	'
	The following tables present information on the Company’s reportable segments and other activities:
		Three Months Ended September 30, 2013
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	164,241	$	18,149		$	—		$	6,584		$	—		$	188,974
	Interest income	111		164			—			281			128			684
	Depletion, depreciation, accretion and impairment	46,821		7,606			73			4,129			246			58,875
	Depletion, depreciation, accretion and impairment - per unit of production	27.48		30.51			—			59.72			—			29.12
	Income (loss) before income taxes	89,214		(4,164		)	(1,404		)	(337		)	(4,667		)	78,642
	Segment capital expenditures (1)	$	39,608	$	8,159		$	11,063		$	(22,500	)	$	289		$	36,619
		Three Months Ended September 30, 2012
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	145,610	$	22,332		$	—		$	674		$	—		$	168,616
	Interest income	171		10			—			40			96			317
	Depletion, depreciation, accretion and impairment	35,255		9,165			68			305			251			45,044
	Depletion, depreciation, accretion and impairment - per unit of production	24.46		26.6			—			40.35			—			25.12
	Income (loss) before income taxes	79,915		1,777			(847		)	(1,170		)	(3,662		)	76,013
	Segment capital expenditures	$	35,880	$	11,568		$	11,204		$	2,838		$	300		$	61,790
		Nine Months Ended September 30, 2013
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	488,577	$	54,620		$	—		$	18,738		$	—		$	561,935
	Interest income	415		710			27			292			460			1,904
	Depletion, depreciation, accretion and impairment	141,141		22,986			272			15,143			767			180,309
	Depletion, depreciation, accretion and impairment - per unit of production	27.58		27.79			—			75.74			—			29.35
	Income (loss) before income taxes	275,353		(6,183		)	(4,984		)	(3,663		)	(12,409		)	248,114
	Segment capital expenditures (1)	$	118,758	$	12,424		$	59,911		$	12,021		$	528		$	203,642
		Nine Months Ended September 30, 2012
	(Thousands of U.S. Dollars, except per unit of production amounts)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Oil and natural gas sales	$	376,261	$	59,183		$	—		$	2,962		$	—		$	438,406
	Interest income	598		96			15			607			312			1,628
	Depletion, depreciation, accretion and impairment	90,625		23,080			1,174			22,379			724			137,982
	Depletion, depreciation, accretion and impairment - per unit of production	24.96		24.54			—			708.76			—			29.98
	Income (loss) before income taxes	182,516		2,568			(4,147		)	(24,467		)	(16,794		)	139,676
	Segment capital expenditures	$	98,476	$	28,412		$	43,866		$	44,536		$	695		$	215,985
	(1) In the third quarter of 2013, segment capital expenditures in Brazil are net of proceeds of $54.0 million relating to termination of a farm-in agreement. Additionally, segment capital expenditures for the nine months ended September 30, 2013, are net of proceeds of $4.1 million relating to the Company's assumption of the remaining 50% working interest in the Santa Victoria Block in Argentina and $1.5 million relating to the Company's sale of its 15% working interest in the Mecaya Block in Colombia (Note 4).
Long-lived Assets by Geographical Area	'
		As at September 30, 2013
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Property, plant and equipment	$	822,522	$	128,799		$	155,579		$	124,418		$	3,058		$	1,234,376
	Goodwill	102,581		—			—			—			—			102,581
	Other assets	267,186		37,320			18,285			50,555			184,115			557,461
	Total Assets	$	1,192,289	$	166,119		$	173,864		$	174,973		$	187,173		$	1,894,418
		As at December 31, 2012
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru			Brazil			All Other			Total
	Property, plant and equipment	$	840,027	$	138,768		$	95,940		$	127,394		$	3,297		$	1,205,426
	Goodwill	102,581		—			—			—			—			102,581
	Other assets	222,220		47,038			10,880			8,498			136,232			424,868
	Total Assets	$	1,164,828	$	185,806		$	106,820		$	135,892		$	139,529		$	1,732,875

Property_Plant_and_Equipment_a1

Property, Plant and Equipment and Inventory (Tables)	9 Months Ended
	Sep. 30, 2013
Property, Plant and Equipment [Abstract]	'
Schedule of Property, Plant and Equipment	'
	Property, Plant and Equipment
		As at September 30, 2013							As at December 31, 2012
	(Thousands of U.S. Dollars)	Cost		Accumulated			Net book value		Cost		Accumulated			Net book value
				depletion,							depletion,
				depreciation							depreciation
				and							and
				impairment							impairment
	Oil and natural gas properties
	Proved	$	1,710,788	$	(920,595	)	$	790,193	$	1,562,477	$	(749,230	)	$	813,247
	Unproved	435,082		—			435,082		383,414		—			383,414
		2,145,870		(920,595		)	1,225,275		1,945,891		(749,230		)	1,196,661
	Furniture and fixtures and leasehold improvements	8,215		(6,203		)	2,012		7,575		(5,093		)	2,482
	Computer equipment	14,018		(7,458		)	6,560		10,971		(5,248		)	5,723
	Automobiles	1,352		(823		)	529		1,376		(816		)	560
	Total Property, Plant and Equipment	$	2,169,455	$	(935,079	)	$	1,234,376	$	1,965,813	$	(760,387	)	$	1,205,426
Schedule of capitalized general and administrative expenses	'
	The amounts of G&A expenses and stock-based compensation capitalized in each of the Company's cost centers were as follows:
		Nine Months Ended September 30, 2013
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru		Brazil		Total
	Capitalized G&A, including stock-based compensation	$	14,746	$	2,896		$	5,981	$	5,813	$	29,436
	Capitalized stock-based compensation	$	794	$	171		$	571	$	566	$	2,102
		Nine Months Ended September 30, 2012
	(Thousands of U.S. Dollars)	Colombia		Argentina			Peru		Brazil		Total
	Capitalized G&A, including stock-based compensation	$	9,279	$	3,480		$	3,670	$	2,653	$	19,082
	Capitalized stock-based compensation	$	376	$	275		$	—	$	216	$	867

Share_Capital_Tables

Share Capital (Tables)	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
RSU's and Stock options outstanding	'
	The following table provides information about long-term incentive plan ("LTIP") activity for the nine months ended September 30, 2013:
		RSUs			Options
		Number of Outstanding Share Units			Number of Outstanding Options			Weighted Average Exercise Price $/Option
	Balance, December 31, 2012	—			15,399,662			5.11
	Granted	939,365			2,066,935			6.27
	Exercised	—			(1,247,818	)		(2.79	)
	Forfeited	(21,655	)		(284,835	)		(6.17	)
	Expired	—			(102,593	)		(6.57	)
	Balance, September 30, 2013	917,710			15,831,351			5.42
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan	'
	The amounts recognized for stock-based compensation were as follows:
	(Thousands of U.S. Dollars)		Three Months Ended September 30,								Nine Months Ended September 30,
			2013				2012				2013			2012
	Compensation costs for stock options		$	2,132			$	3,268			$	6,314		$	10,721
	Compensation costs for RSUs		1,282				—				1,901			—
			3,414				3,268				8,215			10,721
	Less: stock-based compensation costs capitalized		(1,717		)		(336		)		(2,102		)	(867		)
	Total stock-based compensation expense		$	1,697			$	2,932			$	6,113		$	9,854
Weighted average shares outstanding	'
			Three Months Ended September 30,						Nine Months Ended September 30,
			2013			2012			2013			2012
	Weighted average number of common and exchangeable shares outstanding		283,092,224			281,695,212			282,687,871			280,387,484
	Shares issuable pursuant to warrants		—			—			—			235,582
	Shares issuable pursuant to stock options		12,428,489			5,643,730			10,823,968			5,947,880
	Shares assumed to be purchased from proceeds of stock options		(9,494,194	)		(2,733,780	)		(7,691,832	)		(2,602,562	)
	Weighted average number of diluted common and exchangeable shares outstanding		286,026,519			284,605,162			285,820,007			283,968,384

Asset_Retirement_Obligation_Ta

Asset Retirement Obligation (Tables)	9 Months Ended
	Sep. 30, 2013
Asset Retirement Obligation [Abstract]	'
Changes in Asset Retirement Obligations	'
	Changes in the carrying amounts of the asset retirement obligation associated with the Company’s oil and natural gas properties were as follows:
		Nine Months Ended			Year Ended
	(Thousands of U.S. Dollars)	September 30, 2013			31-Dec-12
	Balance, beginning of year	$	18,292		$	12,669
	Settlements	(2,068		)	(404		)
	Liability incurred	1,397			5,190
	Liability assumed in a business combination	—			410
	Foreign exchange	(23		)	45
	Accretion	918			998
	Revisions in estimated liability	1,872			(616		)
	Balance, end of period	$	20,388		$	18,292
	Asset retirement obligation - current	$	—		$	28
	Asset retirement obligation - long-term	20,388			18,264
	Balance, end of period	$	20,388		$	18,292

Taxes_Tables

Taxes (Tables)	9 Months Ended
	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'
Income tax expense reported reconciliation to computed statutory rate	'
	The income tax expense reported differs from the amount computed by applying the U.S. statutory rate to income before income taxes for the following reasons:
		Nine Months Ended September 30,
	(Thousands of U.S. Dollars)	2013			2012
	Income (loss) before income taxes
	United States	$	(8,488	)	$	(7,942	)
	Foreign	256,602			147,618
		248,114			139,676
		35		%	35		%
	Income tax expense expected	86,840			48,887
	Foreign currency translation adjustments	(7,649		)	8,025
	Impact of foreign taxes	1,908			2,716
	Stock-based compensation	1,943			3,277
	Increase in valuation allowance	22,700			9,304
	Branch and other foreign loss pick-up	(2,013		)	(4,358		)
	Non-deductible third party royalty in Colombia	8,812			9,951
	Other permanent differences	(3,180		)	4,478
	Total income tax expense	$	109,361		$	82,280
	Current income tax expense
	United States	$	813		$	778
	Foreign	132,339			90,357
		133,152			91,135
	Deferred income tax recovery
	United States	—			—
	Foreign	(23,791		)	(8,855		)
		(23,791		)	(8,855		)
	Total income tax expense	$	109,361		$	82,280
Deferred tax assets and liabilities	'
		As at
	(Thousands of U.S. Dollars)	September 30, 2013			31-Dec-12
	Deferred Tax Assets
	Tax benefit of operating loss carryforwards	$	53,693		$	51,920
	Tax basis in excess of book basis	44,500			22,519
	Foreign tax credits and other accruals	30,550			30,926
	Tax benefit of capital loss carryforwards	4,835			4,779
	Deferred tax assets before valuation allowance	133,578			110,144
	Valuation allowance	(129,412		)	(106,226		)
		$	4,166		$	3,918
	Deferred tax assets - current	$	2,090		$	2,517
	Deferred tax assets - long-term	2,076			1,401
		4,166			3,918
	Deferred tax liabilities - current	(1,643		)	(337		)
	Deferred tax liabilities - long-term	(183,925		)	(225,195		)
		(185,568		)	(225,532		)
	Net Deferred Tax Liabilities	$	(181,402	)	$	(221,614	)
Schedule of Unrecognized Tax Benefits Roll Forward	'
	Changes in the Company's unrecognized tax benefit are as follows:
		Nine Months Ended September 30,
		2013			2012
	(Thousands of U.S. Dollars)
	Unrecognized tax benefit at beginning of period	$	21,800		$	20,500
	Changes for positions relating to prior year	(2,000		)	—
	Unrecognized tax benefit at end of period	$	19,800		$	20,500

Segment_and_Geographic_Reporti2

Segment and Geographic Reporting (Details) (USD $)	3 Months Ended			9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	$188,974		$168,616	$561,935		$438,406
Interest income	684		317	1,904		1,628
Depletion, depreciation, accretion and impairment	58,875		45,044	180,309		137,982
Depletion, depreciation, accretion and impairment - per unit of production	29.12		25.12	29.35		29.98
Income (loss) before income taxes	78,642		76,013	248,114		139,676
Segment capital expenditures	36,619	[1]	61,790	203,642	[1]	215,985
Colombia [Member]	'		'	'		'
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	164,241		145,610	488,577		376,261
Interest income	111		171	415		598
Depletion, depreciation, accretion and impairment	46,821		35,255	141,141		90,625
Depletion, depreciation, accretion and impairment - per unit of production	27.48		24.46	27.58		24.96
Income (loss) before income taxes	89,214		79,915	275,353		182,516
Segment capital expenditures	39,608	[1]	35,880	118,758	[1]	98,476
Argentina [Member]	'		'	'		'
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	18,149		22,332	54,620		59,183
Interest income	164		10	710		96
Depletion, depreciation, accretion and impairment	7,606		9,165	22,986		23,080
Depletion, depreciation, accretion and impairment - per unit of production	30.51		26.6	27.79		24.54
Income (loss) before income taxes	-4,164		1,777	-6,183		2,568
Segment capital expenditures	8,159	[1]	11,568	12,424	[1]	28,412
Peru [Member]	'		'	'		'
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	0		0	0		0
Interest income	0		0	27		15
Depletion, depreciation, accretion and impairment	73		68	272		1,174
Depletion, depreciation, accretion and impairment - per unit of production	0		0	0		0
Income (loss) before income taxes	-1,404		-847	-4,984		-4,147
Segment capital expenditures	11,063	[1]	11,204	59,911	[1]	43,866
Brazil [Member]	'		'	'		'
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	6,584		674	18,738		2,962
Interest income	281		40	292		607
Depletion, depreciation, accretion and impairment	4,129		305	15,143		22,379
Depletion, depreciation, accretion and impairment - per unit of production	59.72		40.35	75.74		708.76
Income (loss) before income taxes	-337		-1,170	-3,663		-24,467
Segment capital expenditures	-22,500	[1]	2,838	12,021	[1]	44,536
All Other [Member]	'		'	'		'
Segment Reporting Information [Line Items]	'		'	'		'
Oil and natural gas sales	0		0	0		0
Interest income	128		96	460		312
Depletion, depreciation, accretion and impairment	246		251	767		724
Depletion, depreciation, accretion and impairment - per unit of production	0		0	0		0
Income (loss) before income taxes	-4,667		-3,662	-12,409		-16,794
Segment capital expenditures	$289	[1]	$300	$528	[1]	$695
[1]	In the third quarter of 2013, segment capital expenditures in Brazil are net of proceeds of $54.0 million relating to termination of a farm-in agreement. Additionally, segment capital expenditures for the nine months ended September 30, 2013, are net of proceeds of $4.1 million relating to the Company's assumption of the remaining 50% working interest in the Santa Victoria Block in Argentina and $1.5 million relating to the Company's sale of its 15% working interest in the Mecaya Block in Colombia (Note 4).

Segment_and_Geographic_Reporti3

Segment and Geographic Reporting Assets (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	$1,234,376	$1,205,426
Goodwill	102,581	102,581
Other assets	557,461	424,868
Total Assets	1,894,418	1,732,875
Colombia [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	822,522	840,027
Goodwill	102,581	102,581
Other assets	267,186	222,220
Total Assets	1,192,289	1,164,828
Argentina [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	128,799	138,768
Goodwill	0	0
Other assets	37,320	47,038
Total Assets	166,119	185,806
Peru [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	155,579	95,940
Goodwill	0	0
Other assets	18,285	10,880
Total Assets	173,864	106,820
Brazil [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	124,418	127,394
Goodwill	0	0
Other assets	50,555	8,498
Total Assets	174,973	135,892
All Other [Member]	'	'
Segment Reporting Information [Line Items]	'	'
Property, plant and equipment	3,058	3,297
Goodwill	0	0
Other assets	184,115	136,232
Total Assets	$187,173	$139,529

Segment_and_Geographic_Reporti4

Segment and Geographic Reporting Narrative (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Concentration Risk [Line Items]	'	'	'	'
Proceeds from oil and gas properties	'	'	59,621,000	0
Colombia [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Number of significant customers	'	'	2	1
Colombia [Member] | Ecopetrol [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Sales to Ecopetrol, as a percentage of total revenue (in hundredths)	56.00%	71.00%	52.00%	77.00%
Colombia [Member] | Other Customer Number One [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Number of other significant customers	'	'	1	'
Sales to Ecopetrol, as a percentage of total revenue (in hundredths)	28.00%	'	29.00%	'
Colombia [Member] | Other Customer Number Two [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Sales to Ecopetrol, as a percentage of total revenue (in hundredths)	'	13.00%	'	'
Brazil [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Proceeds from termination of farm-in agreement	54,000,000	'	'	'
Argentina [Member] | Santa Victoria Block [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Proceeds from assumption of oil and gas property	4,100,000	'	'	'
Working interest assumed from partner	50.00%	'	'	'
Colombia [Member] | Mecaya Block [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Proceeds from oil and gas properties	1,500,000	'	'	'
Working interest sold, percentage	15.00%	'	'	'

Property_Plant_and_Equipment_a2

Property, Plant and Equipment and Inventory (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Cost	$2,169,455	$1,965,813
Accumulated depletion, depreciation and impairment	-935,079	-760,387
Total Property, Plant and Equipment (Note 4)	1,234,376	1,205,426
Unproved oil and gas property full cost accounting	435,082	383,414
Proved [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Cost	1,710,788	1,562,477
Accumulated depletion, depreciation and impairment	-920,595	-749,230
Total Property, Plant and Equipment (Note 4)	790,193	813,247
Unproved [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Accumulated depletion, depreciation and impairment	0	0
Total Property, Plant and Equipment (Note 4)	435,082	383,414
Unproved oil and gas property full cost accounting	435,082	383,414
Oil and natural gas properties depletable base under full cost accounting [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Cost	2,145,870	1,945,891
Accumulated depletion, depreciation and impairment	-920,595	-749,230
Total Property, Plant and Equipment (Note 4)	1,225,275	1,196,661
Furniture and fixtures and leasehold improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Cost	8,215	7,575
Accumulated depletion, depreciation and impairment	-6,203	-5,093
Total Property, Plant and Equipment (Note 4)	2,012	2,482
Computer equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Cost	14,018	10,971
Accumulated depletion, depreciation and impairment	-7,458	-5,248
Total Property, Plant and Equipment (Note 4)	6,560	5,723
Automobiles [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Cost	1,352	1,376
Accumulated depletion, depreciation and impairment	-823	-816
Total Property, Plant and Equipment (Note 4)	$529	$560

Amounts_Capitalized_by_Cost_Ce

Amounts Capitalized by Cost Center (Details) (USD $)	Sep. 30, 2013	Sep. 30, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Capitalized G&A, including stock-based compensation	$29,436	$19,082
Capitalized stock-based compensation	2,102	867
Colombia [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Capitalized G&A, including stock-based compensation	14,746	9,279
Capitalized stock-based compensation	794	376
Argentina [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Capitalized G&A, including stock-based compensation	2,896	3,480
Capitalized stock-based compensation	171	275
Peru [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Capitalized G&A, including stock-based compensation	5,981	3,670
Capitalized stock-based compensation	571	0
Brazil [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Capitalized G&A, including stock-based compensation	5,813	2,653
Capitalized stock-based compensation	$566	$216

Property_Plant_and_Equipment_a3

Property, Plant and Equipment and Inventory Narrative (Details) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Minimum [Member]

Maximum [Member]

Block-BM-CAL-10 [Member]

Colombia [Member]

Colombia [Member]

Colombia [Member]

Argentina [Member]

Argentina [Member]

Argentina [Member]

Peru [Member]

Peru [Member]

Brazil [Member]

Brazil [Member]

Brazil [Member]

Brazil [Member]

Brazil [Member]

Brazil [Member]

Four out of Seven Blocks Unproved Oil and Gas Properties [Member]

Mecaya Block [Member]

Santa Victoria Block [Member]

block

block

Brazil [Member]

Property, Plant and Equipment [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation and depletion

$59,100,000

$43,000,000

$172,700,000

$120,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment of oil and gas properties

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,000,000

20,200,000

'

'

'

'

Purchase consideration for oil and gas regulatory approval

'

'

'

'

'

'

'

23,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Working interest assumed from partner

'

'

'

'

'

'

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

Proceeds from assumption of oil and gas property

'

'

'

'

'

'

'

'

'

'

'

'

'

4,100,000

'

'

'

'

'

'

'

'

'

Proceeds from oil and gas properties

'

'

59,621,000

0

'

'

'

'

'

'

1,500,000

'

'

'

'

'

'

'

'

'

'

'

'

Working interest sold, percentage

'

'

'

'

'

'

'

'

'

'

15.00%

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from termination of farm-in agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

54,000,000

'

'

'

'

'

'

Number of blocks successfully bid

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

Payments for signature bonus

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

14,400,000

'

'

Unproven properties relating to four blocks

1,234,376,000

'

1,234,376,000

'

1,205,426,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

59,600,000

Number of unproved reserves blocks

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

Unproved assets by cost center

435,100,000

'

435,100,000

'

383,400,000

'

'

'

163,000,000

175,900,000

'

39,500,000

42,300,000

'

154,600,000

95,100,000

78,000,000

'

'

70,100,000

'

'

'

Costs transferred to depletable base within 5 years

62.00%

'

62.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Oil and Gas Property, Transfer of Costs to Depletable Base, Time Period

'

'

'

'

'

'5 years

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Crude oil inventories

14,600,000

'

14,600,000

'

31,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Supplies

$1,800,000

'

$1,800,000

'

$2,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Share_Capital_Stock_Options_Ou

Share Capital Stock Options Outstanding (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Number of Outstanding Options	'
Balance, December 31, 2012 (in shares)	15,399,662
Granted (in shares)	2,066,935
Exercised (in shares)	-1,247,818
Forfeited (in shares)	-284,835
Expired (in shares)	-102,593
Balance, June 30, 2013 (in shares)	15,831,351
Weighted Average Exercise Price $/Option	'
Weighted Average Exercise Price $/Option, beginning balance (in dollars per share)	$5.11
Weighted Average Exercise Price $/Option, Granted (in dollars per share)	$6.27
Weighted Average Exercise Price $/Options Exercised (in dollars per share)	($2.79)
Weighted Average Exercise Price $/Options, Forfeited (in dollars per share)	($6.17)
Weighted Average Exercise Price $/Options, Expired (in dollars per share)	($6.57)
Weighted Average Exercise Price $/Option, ending balance (in dollars per share)	$5.42
RSUs [Member]	'
Number of Outstanding Share Units	'
Balance, December 31, 2012 (in shares)	0
Granted (in shares)	939,365
Exercised (in shares)	0
Forfeited (in shares)	-21,655
Expired (in shares)	0
Balance, June 30, 2013 (in shares)	917,710

Allocation_of_Share_Based_Comp

Allocation of Share Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation cost	$3,414	$3,268	$8,215	$10,721
Less: stock-based compensation costs capitalized	-1,717	-336	-2,102	-867
Total stock-based compensation expense	1,697	2,932	6,113	9,854
Stock Options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation cost	2,132	3,268	6,314	10,721
RSUs [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Compensation cost	$1,282	$0	$1,901	$0

Weighted_Average_Shares_Detail

Weighted Average Shares (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Weighted average number of common and exchangeable shares outstanding	283,092,224	281,695,212	282,687,871	280,387,484
Shares issuable pursuant to warrants	0	0	0	235,582
Shares issuable pursuant to stock options	12,428,489	5,643,730	10,823,968	5,947,880
Shares assumed to be purchased from proceeds of stock options	-9,494,194	-2,733,780	-7,691,832	-2,602,562
Weighted average number of diluted common and exchangeable shares outstanding	286,026,519	284,605,162	285,820,007	283,968,384

Share_Capital_Narrative_Detail

Share Capital Narrative (Details) (USD $)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	31-May-13	Apr. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'	'	'
Authorized share capital	'	'	595,000,002	'	595,000,002	'	'
Common stock, authorized	'	'	570,000,000	'	570,000,000	'	'
Common shares, par value (in dollars per share)	'	'	$0.00	'	$0.00	'	$0.00
Preferred stock, authorized	'	'	25,000,000	'	25,000,000	'	'
Preferred stock, par value (in dollars per share)	'	'	$0.00	'	$0.00	'	'
Special voting stock-authorized (in shares)	'	'	2	'	2	'	'
Special voting stock-par value (in dollars per share)	'	'	$0.00	'	$0.00	'	'
Common shares, outstanding	'	'	271,872,896	'	271,872,896	'	268,482,445
Stock issued during period upon exercise of stock options (in shares)	'	'	'	'	1,247,818	'	'
Votes per common stock	'	'	'	'	1	'	'
Common voting shares per exchangeable share (in shares)	'	'	'	'	1	'	'
Stock option exercises in period (in shares)	'	'	'	'	-1,247,818	'	'
Cash received from exercise of stock options	'	'	'	'	$3,500,000	$3,800,000	'
Stock Options [Abstract]	'	'	'	'	'	'	'
Stock-based compensation expense	'	'	1,697,000	2,932,000	6,113,000	9,854,000	'
Unvested stock options recognition period	'	'	'	'	'2 years 1 month 6 days	'	'
General and Administrative Expense [Member]	'	'	'	'	'	'	'
Stock Options [Abstract]	'	'	'	'	'	'	'
Stock-based compensation expense	'	'	1,300,000	2,600,000	5,300,000	8,900,000	'
Stock Options [Member]	'	'	'	'	'	'	'
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'	'	'
Option term	'5 years	'10 years	'	'	'	'	'
Option term after leaving service of company	'3 months	'3 months	'	'	'	'	'
Weighted average volatility rate	'	'	43.00%	'	53.00%	'	75.00%
Weighted Average Grant Date Fair Value $/Option, Granted in Period	'	'	$2.34	$2.62	$2.62	$3.36	'
Stock Options [Abstract]	'	'	'	'	'	'	'
Unrecognized compensation cost related to unvested stock options	'	'	11,300,000	'	11,300,000	'	8,200,000
Earnings Per Share [Abstract]	'	'	'	'	'	'	'
Options excluded from the diluted income per share calculation	'	'	3,472,472	9,957,585	5,584,732	9,808,758	'
Stock Options [Member] | Operating Expense [Member]	'	'	'	'	'	'	'
Stock Options [Abstract]	'	'	'	'	'	'	'
Stock-based compensation expense	'	'	$400,000	$300,000	$800,000	$900,000	'
Vesting Rateable on March 1, 2014, 2015 and 2016 [Member] | RSUs [Member]	'	'	'	'	'	'	'
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'	'	'
Award vesting percentage	33.33%	'	'	'	'	'	'
Gran Tierra Exchangeco Inc [Member]	'	'	'	'	'	'	'
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'	'	'
Exchangeable shares outstanding (in shares)	'	'	6,744,728	'	6,744,728	'	'
Exchange shares issued during period	'	'	'	'	452,950	'	'
Gran Tierra Goldstrike Inc [Member]	'	'	'	'	'	'	'
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'	'	'
Exchangeable shares outstanding (in shares)	'	'	4,534,127	'	4,534,127	'	'
Exchange shares issued during period	'	'	'	'	1,689,683	'	'

Asset_Retirement_Obligation_De

Asset Retirement Obligation (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'	'
Balance, beginning of year	$18,292,000	$12,669,000	$12,669,000
Settlements	-2,068,000	'	-404,000
Liability incurred	1,397,000	'	5,190,000
Liability assumed in a business combination	0	'	410,000
Foreign exchange	-23,000	'	45,000
Accretion	918,000	'	998,000
Revisions in estimated liability	1,872,000	'	-616,000
Balance, end of period	20,388,000	'	18,292,000
Asset retirement obligation - current	0	'	28,000
Asset retirement obligation - long-term	20,388,000	'	18,264,000
Cash settlement of asset retirement obligation	-927,000	-404,000	'
Fair value of legally restricted assets	$1,900,000	'	$1,300,000

Income_Tax_Reconciliation_Deta

Income Tax Reconciliation (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income (loss) before income taxes	'	'	'	'
United States	'	'	($8,488)	($7,942)
Foreign	'	'	256,602	147,618
INCOME BEFORE INCOME TAXES	78,642	76,013	248,114	139,676
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]	'	'	'	'
Effective income tax rate	'	'	35.00%	35.00%
Income tax expense expected	'	'	86,840	48,887
Foreign currency translation adjustments	'	'	-7,649	8,025
Impact of foreign taxes	'	'	1,908	2,716
Stock-based compensation	'	'	1,943	3,277
Increase in valuation allowance	'	'	22,700	9,304
Branch and other foreign loss pick-up	'	'	-2,013	-4,358
Non-deductible third party royalty in Colombia	'	'	8,812	9,951
Other permanent differences	'	'	-3,180	4,478
Total income tax expense	45,585	31,408	109,361	82,280
Current income tax expense	'	'	'	'
United States	'	'	813	778
Foreign	'	'	132,339	90,357
Total Current income tax expense	'	'	133,152	91,135
Deferred income tax recovery	'	'	'	'
United States	'	'	0	0
Foreign	'	'	-23,791	-8,855
Total Deferred income tax expense (recovery)	'	'	($23,791)	($8,855)

Permanent_Differences_Reconcil

Permanent Differences Reconciliation (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'
Tax benefit of operating loss carryforwards	$53,693	$51,920
Tax basis in excess of book basis	44,500	22,519
Foreign tax credits and other accruals	30,550	30,926
Tax benefit of capital loss carryforwards	4,835	4,779
Deferred tax assets before valuation allowance	133,578	110,144
Valuation allowance	-129,412	-106,226
Deferred tax assets, net	4,166	3,918
Deferred tax assets - current	2,090	2,517
Deferred tax assets - long-term	2,076	1,401
Deferred tax liabilities - current	-1,643	-337
Deferred tax liabilities - long-term	-183,925	-225,195
Deferred tax liabilities, net	-185,568	-225,532
Net Deferred Tax Liabilities	($181,402)	($221,614)

Unrecognized_Tax_Benefits_Roll

Unrecognized Tax Benefits Rollforward (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'
Unrecognized tax benefit at beginning of period	$21,800	$20,500
Changes for positions relating to prior year	-2,000	0
Unrecognized tax benefit at end of period	$19,800	$20,500

Taxes_Narrative_Details

Taxes Narrative (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
		installment
Income Tax Disclosure [Abstract]	'	'	'	'	'	'
Operating loss carryforwards	'	'	$233,700,000	'	$213,100,000	'
Capital losses before valuation allowance	'	'	32,600,000	'	35,900,000	'
Net operating loss and capital loss carryforward from foreign subsidiaries	'	'	233,800,000	'	215,200,000	'
Unrecognized tax benefits	20,500,000	'	19,800,000	20,500,000	21,800,000	20,500,000
Unrecognized tax benefits income tax penalties and interest expense	$0	'	$0	$0	'	'
Equity tax rate (in hundredths)	'	'	6.00%	'	6.00%	'
Equity tax for foreign operations - Columbia, number of semi-annual installments	'	8	'	'	'	'
Equity tax for foreign operations - Columbia, assessment term (in years)	'	'4 years	'	'	'	'

Contingencies_Details

Contingencies (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			Pending Litigation Escopetrol [Member]	Pending Litigation Escopetrol [Member]	Pending Litigation Moqueta Discovery [Member]	Pending Litigation Royalty, Transportation and Related Costs [Member]
			bbl		bbl
Loss Contingencies [Line Items]	'	'	'	'	'	'
Loss Contingency, Loss in Period, Barrels of Oil	'	'	44,025	'	'	'
Value of damages sought for loss contingency	'	'	'	$4.40	$31.70	$23.40
Threshold by which additional royalty due (barrels)	'	'	'	'	5,000,000	'
Total cumulative production of oil field (barrels)	'	'	'	'	1,900,000	'
Promissory notes provided as collateral for letters of credit	$49.60	$34.20	'	'	'	'

Financial_Instruments_Fair_Val1

Financial Instruments, Fair Value Measurements and Credit Risk (Details) (USD $)

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Oct. 08, 2012

Sep. 30, 2013

Dec. 31, 2012

Colombia [Member]

Colombia [Member]

Colombia [Member]

Colombia [Member]

Argentina [Member]

Argentina [Member]

Brazil [Member]

Pending Litigation Escopetrol [Member]

Block-Brazil [Member]

Block-Brazil [Member]

Block-Brazil [Member]

customer

customer

Sales Revenue, Segment [Member]

Sales Revenue, Segment [Member]

customer

customer

Geographic Concentration Risk [Member]

Geographic Concentration Risk [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Participating interest percentage oil and gas property, remaining percentage

'

'

'

'

'

'

'

'

'

30.00%

'

'

Fair value of contingent consideration payable

'

'

'

'

'

'

'

'

'

'

$1,100,000

$1,100,000

Value of damages sought for loss contingency

'

'

'

'

'

'

'

'

4,400,000

'

'

'

Number of significant customers

'

2

1

'

'

'

3

1

'

'

'

'

Concentration risk, percentage

'

'

'

87.00%

86.00%

'

'

'

'

'

'

'

Foreign exchange losses, Colombian peso to U.S. dollar

95,000

'

'

'

'

'

'

'

'

'

'

'

Proceeds from argentinian subsidiary

'

'

'

'

'

11,100,000

'

'

'

'

'

'

Cash and cash equivalents on deposit with local Argentinian banks

'

'

'

'

'

$20,300,000

$20,300,000

'

'

'

'

'

Cash and cash equivalents on deposit with local Argentinian bank, percent

'

'

'

'

'

6.00%

6.00%

'

'

'

'

'

Credit_Facilities_Details

Credit Facilities (Details) (USD $)	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Oct. 31, 2013	Sep. 30, 2013	Sep. 30, 2013
	Subsidiary	Foreign Line of Credit [Member]	Wells Fargo Bank, N.A. [Member]	Wells Fargo Bank, N.A. [Member]	Wells Fargo Bank, N.A. [Member]	Wells Fargo Bank, N.A. [Member]
			Revolving Credit Facility [Member]	Revolving Credit Facility [Member]	Revolving Credit Facility [Member]	Revolving Credit Facility [Member]
				Colombia [Member]	Minimum [Member]	Maximum [Member]
				Foreign Line of Credit [Member]	LIBOR [Member]	LIBOR [Member]
				Subsequent Event [Member]
Line of Credit Facility [Line Items]	'	'	'	'	'	'
Current borrowing capacity	'	'	$150,000,000	'	'	'
Maximum borrowing capacity	'	'	300,000,000	'	'	'
Number of subsidiaries used as collateral for reserve based facility	2	'	'	'	'	'
Basis spread on variable rate	'	'	'	'	2.25%	3.25%
Stand-by fee on unutilized balance	'	'	0.88%	'	'	'
Term of credit facility	'	'	'	'3 years	'	'
Max dividends payment allowable	'	$2,000,000	'	'	'	'

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Related Party Transaction [Line Items]	'	'	'	'	'
Accounts payable, Brazil drilling program	$70,783,000	'	$70,783,000	'	$102,263,000
Director - Brazil drilling program related party [Member]	'	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'	'
Capitalization of Brazil drilling program	4,200,000	0	11,800,000	0	'
Accounts payable, Brazil drilling program	$2,300,000	'	$2,300,000	'	$1,100,000