Gran Tierra Energy (GTE) 10-Q 1 Nov 18 2018 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	GRAN TIERRA ENERGY INC.
Entity Central Index Key	1,273,441
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		391,347,284
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Entity Emerging Growth	false
Entity Small Business	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
EXPENSES
Operating	$ 29,511	$ 21,931	$ 78,019	$ 60,547
Workover	13,106	5,390	25,922	17,919
Transportation	7,505	6,038	21,024	19,472
Depletion, depreciation and accretion (Note 3)	51,630	35,279	137,698	93,968
General and administrative (Note 3)	13,811	8,651	37,173	26,876
Severance	1,004	1,164	2,015	1,164
Equity tax	0	0	0	1,224
Foreign exchange (gain) loss	(888)	(1,271)	94	779
Financial instruments (gain) loss (Note 10)	(4,874)	1,675	6,840	(5,211)
Interest expense (Note 5)	7,404	3,989	20,274	10,415
EXPENSES	118,209	82,846	329,059	227,153
LOSS ON SALE	0	0	(292)	(9,076)
INTEREST INCOME	725	301	2,121	954
INCOME BEFORE INCOME TAXES (Note 3)	57,634	21,223	149,562	59,280
INCOME TAX EXPENSE (RECOVERY)
Current (Note 8)	19,108	4,333	36,224	13,522
Deferred (Note 8)	(36,769)	13,760	(118)	36,664
INCOME TAX EXPENSE (RECOVERY)	(17,661)	18,093	36,106	50,186
NET AND COMPREHENSIVE INCOME	$ 75,295	$ 3,130	$ 113,456	$ 9,094
NET INCOME (LOSS) PER SHARE - BASIC (in dollars per share)	$ 0.19	$ 0.01	$ 0.29	$ 0.02
NET INCOME (LOSS) PER SHARE - DILUTED (in dollars per share)	$ 0.18	$ 0.01	$ 0.28	$ 0.02
WEIGHTED AVERAGE SHARES OUTSTANDING - BASIC (Note 6) (in shares)	391,209,589	394,771,194	391,185,636	397,439,007
WEIGHTED AVERAGE SHARES OUTSTANDING - DILUTED (Note 6) (in shares)	427,947,959	394,774,953	427,416,964	397,450,637
Oil and Gas Service
OIL AND NATURAL GAS SALES (Notes 3 and 7)	$ 175,118	$ 103,768	$ 476,792	$ 294,555

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents (Note 11)	$ 130,158	$ 12,326
Restricted cash and cash equivalents (Note 11)	1,228	11,787
Accounts receivable	64,616	45,353
Investment (Note 10)	37,608	25,055
Taxes receivable	70,256	40,831
Other current assets	14,153	9,893
Total Current Assets	318,019	145,245
Oil and Gas Properties (using the full cost method of accounting)
Proved	804,204	629,081
Unproved	441,275	464,948
Total Oil and Gas Properties	1,245,479	1,094,029
Other capital assets	2,901	5,195
Total Property, Plant and Equipment (Note 3)	1,248,380	1,099,224
Other Long-Term Assets
Deferred tax assets	58,901	57,310
Investment (Note 10)	17,623	19,147
Other long-term assets (Note 11)	5,133	6,112
Goodwill (Note 3)	102,581	102,581
Total Other Long-Term Assets	184,238	185,150
Total Assets	1,750,637	1,429,619
Current Liabilities
Accounts payable and accrued liabilities	164,885	126,199
Derivatives (Note 10)	17,688	21,151
Taxes payable	9,759	9,324
Equity compensation award liability (Note 10)	16,534	295
Total Current Liabilities	208,866	156,969
Long-Term Liabilities
Long-term debt (Notes 5 and 10)	398,989	256,542
Deferred tax liabilities	28,470	28,417
Asset retirement obligation	38,877	31,241
Equity compensation award liability (Note 10)	14,648	11,135
Other long-term liabilities	9,257	8,980
Total Long-Term Liabilities	490,241	336,315
Contingencies (Note 9)
Shareholders’ Equity
Common Stock (Note 6) (391,339,489 and 385,191,042 shares of Common Stock and nil and 6,111,665 exchangeable shares, par value $0.001 per share, issued and outstanding as at September 30, 2018, and December 31, 2017, respectively)	10,295	10,295
Additional paid in capital	1,328,983	1,327,244
Deficit	(287,748)	(401,204)
Total Shareholders’ Equity	1,051,530	936,335
Total Liabilities and Shareholders’ Equity	$ 1,750,637	$ 1,429,619

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common Stock, shares issued (in shares)	391,339,489	385,191,042
Common Stock, Shares, Outstanding	391,339,489	385,191,042
Exchangeable shares, shares issued (in shares)		6,111,665
Exchangeable shares, shares outstanding (in shares)		6,111,665
Common Stock and exchangeable shares, par value (in dollars per share)	$ 0.001	$ 0.001

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities
Net income	$ 113,456	$ 9,094
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation and accretion (Note 3)	137,698	93,968
Deferred tax (recovery) expense	(118)	36,664
Stock-based compensation (Note 6)	20,477	4,935
Amortization of debt issuance costs (Note 5)	2,329	1,868
Cash settlement of restricted share units	(360)	(534)
Unrealized foreign exchange gain	(133)	(304)
Financial instruments loss (gain) (Note 10)	6,840	(5,211)
Cash settlement of financial instruments (Note 10)	(26,169)	1,518
Cash settlement of asset retirement obligation	(456)	(462)
Loss on sale	292	9,076
Net change in assets and liabilities from operating activities (Note 11)	(40,652)	(28,105)
Net cash provided by operating activities	213,204	122,507
Investing Activities
Additions to property, plant and equipment (Note 3)	(258,551)	(175,719)
Property acquisitions (Note 4)	(20,100)	(30,410)
Net proceeds from sale of Brazil business unit	0	34,481
Changes in non-cash investing working capital	32,638	16,047
Net cash used in investing activities	(246,013)	(155,601)
Financing Activities
Proceeds from bank debt, net of issuance costs (Note 5)	4,988	115,264
Repayment of bank debt (Note 5)	(153,000)	(85,000)
Proceeds from exercise of stock options (Note 6)	1,408	0
Repurchase of shares of Common Stock (Note 6)	(1,314)	(10,000)
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)	288,087	0
Net cash provided by financing activities	140,169	20,264
Foreign exchange loss on cash, cash equivalents and restricted cash and cash equivalents	(402)	(1,060)
Net increase (decrease) in cash, cash equivalents and restricted cash and cash equivalents	106,958	(13,890)
Cash, cash equivalents and restricted cash and cash equivalents, beginning of period (Note 11)	26,678	43,267
Cash, cash equivalents and restricted cash and cash equivalents, end of period (Note 11)	$ 133,636	$ 29,377

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Share Capital	Additional Paid in Capital	Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment for accounting change related to tax reorganizations				$ 124,476
Balance, beginning of period at Dec. 31, 2016		$ 10,303	$ 1,342,656	(493,972)
Increase (Decrease) in Stockholders' Equity
Issuance of Common Stock		0
Repurchase of Common Stock (Note 6)		(4)	(9,996)
Exercise of stock options (Note 6)			0
Stock-based compensation (Note 6)			1,903
Net income	$ 9,094			9,094
Balance, end of period at Sep. 30, 2017	984,460	10,299	1,334,563	(360,402)
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment for accounting change related to tax reorganizations				0
Balance, beginning of period at Dec. 31, 2017		10,295	1,327,244	(401,204)
Increase (Decrease) in Stockholders' Equity
Issuance of Common Stock		1
Repurchase of Common Stock (Note 6)		(1)	(1,313)
Exercise of stock options (Note 6)			1,407
Stock-based compensation (Note 6)			1,645
Net income	113,456			113,456
Balance, end of period at Sep. 30, 2018	$ 1,051,530	$ 10,295	$ 1,328,983	$ (287,748)

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Gran Tierra Energy Inc., a Delaware corporation (the “Company” or “Gran Tierra”), is a publicly traded company focused on oil and natural gas exploration and production in Colombia.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
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, 2017 , included in the Company’s 2017 Annual Report on Form 10-K, filed with the SEC on February 27, 2018 . The Company’s significant accounting policies are described in Note 2 of the consolidated financial statements which are included in the Company’s 2017 Annual Report on Form 10-K and are the same policies followed in these interim unaudited condensed consolidated financial statements, except as noted below. The Company has evaluated all subsequent events through to the date these interim unaudited condensed consolidated financial statements were issued. Recently Adopted Accounting Pronouncements Revenue from Contracts with Customers The Company adopted Accounting Standard Codification ("ASC") 606 Revenue from Contracts with Customers with a date of initial application of January 1, 2018 in accordance with the modified retrospective approach without using the practical expedients. Except for providing enhanced disclosures about the Company's revenue transactions, the application of ASC 606 did not have an impact on the Company’s consolidated financial position, results of operations or cash flows. a) Significant Accounting Policy The Company's revenue relates to oil and natural gas sales in Colombia. The Company recognizes revenue when it transfers control of the product to a customer. This generally occurs at the time the customer obtains legal title to the product and when it is physically transferred to the delivery point agreed with the customer. Payment terms are generally within three business days following delivery of an invoice to the customer. Revenue is recognized based on the consideration specified in contracts with customers. Revenue represents the Company's share and is recorded net of royalty payments to governments and other mineral interest owners. The Company evaluates its arrangement with third parties and partners to determine if the Company acts as a principal or an agent. In making this evaluation, management considers if the Company obtains control of the product delivered, which is indicated by the Company having the primary responsibility for the delivery of the product, having ability to establish prices or having inventory risk. If the Company acts in the capacity of an agent rather than as a principal in transaction, then the revenue is recognized on a net-basis, only reflecting the fee realized by the Company from the transaction. Tariffs, tolls and fees charged to other entities for use of pipelines owned by the Company are evaluated by management to determine if these originate from contracts with customers or from incidental arrangements. In the comparative period, revenue from the production of oil and natural gas was recognized when the customer took title and assumed the risks and rewards of ownership, prices were fixed or determinable, the sale was evidenced by a contract and collection of the revenue was reasonably assured. b) Significant Judgments When determining if the Company acted as a principal or as an agent in transactions, management determines if the Company obtains control of the product. As part of this assessment, management considers detailed criteria for revenue recognition set out in ASC 606. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2016-01 addressed certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016-01 was effective for annual reporting periods and interim reporting periods within those annual reporting periods, beginning after December 15, 2017. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure. In February 2018, the FASB issued ASU 2018-03, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2018-03 clarified certain aspects of the guidance in ASU 2016-01. ASU 2018-03 is effective for annual reporting periods beginning after December 15, 2017 and interim reporting periods within those annual reporting periods beginning after June 15, 2018. Early adoption is permitted upon adoption of ASU 2016-01.The amendments should be applied retrospectively with a cumulative-effect adjustment to the effective date of ASU 2016-01. The Company early adopted this update on January 1, 2018. The implementation of this update did not impact the Company’s consolidated financial position, results of operations or cash flows or disclosure. Recently Issued but Not Yet Adopted Accounting Pronouncements Leases In January 2018, the FASB issued ASU 2018-01, "Land Easement Practical Expedient for Transition to Topic 842". ASU 2018-01 provides an optional transition practical expedient that, if elected, would not require an organization to reconsider their accounting for existing or expired land easements that were not previously accounted for as leases under Topic 840. The effective date and transition requirements for the amendment are the same as the effective date and transition requirements in ASU 2016-02. The Company is planning to adopt ASU 2018-01 upon transition to ASU 2016-02 "Leases". The Company has completed an assessment of its contract inventory, identified contracts which meet the definition of a lease and is currently determining the value of right-of-use lease assets and lease liabilities and transition adjustments. The Company expects to use practical expedients available for land easements and short-term leases and will apply the guidance of ASU 2016-02 using a modified retrospective transition approach. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement". ASU 2018-13 will modify certain fair value measurements disclosure requirements. ASU 2018-13 will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. The disclosure amendments on changes in unrealized gains and losses, and disclosure requirements for significant unobservable inputs used to develop Level 3 fair value measurements, should be applied prospectively. All other amendments in ASU 2018-13 should be applied retrospectively. Early adoption is permitted. The application of ASU 2018-13 will not impact the Company’s consolidated financial position, results of operations or cash flows. Intangibles - Goodwill and Other - Internal-use Software In August 2018, the FASB issued ASU 2018-15, "Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract". ASU 2018-15 clarifies requirements for capitalization of software development costs and requires that a hosting arrangement that is a service contract to be capitalized and expensed over the term of the hosting arrangement. ASU 2018-15 will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. The provisions of this amendment should be applied retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently assessing the impact this update will have on its consolidated financial position, results of operations, cash flows, and disclosure.

Segment and Geographic Reportin

Segment and Geographic Reporting	9 Months Ended
	Sep. 30, 2018
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. Commencing 2018, the Company has one reportable segment based on geographic organization, Colombia. Prior to the sale of the Company's Brazil business unit effective June 30, 2017 and Peru business unit effective December 18, 2017, Brazil and Peru were reportable segments. The "All Other" category represents the Company’s corporate activities, Mexico activities and Brazil and Peru activities until the date of sale. The following tables present information on the Company’s reportable segments and other activities: Three Months Ended September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 175,118 $ — $ 175,118 Depletion, depreciation and accretion 51,416 214 51,630 General and administrative expenses 7,370 6,441 13,811 Income (loss) before income taxes 63,797 (6,163 ) 57,634 Segment capital expenditures 101,453 10 101,463 Three Months Ended September 30, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 103,768 $ — $ 103,768 Depletion, depreciation and accretion 33,388 1,891 35,279 General and administrative expenses 5,500 3,151 8,651 Income (loss) before income taxes 31,276 (10,053 ) 21,223 Segment capital expenditures 70,606 1,088 71,694 Nine Months Ended September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 476,792 $ — $ 476,792 Depletion, depreciation and accretion 135,980 1,718 137,698 General and administrative expenses 20,876 16,297 37,173 Income (loss) before income taxes 175,977 (26,415 ) 149,562 Segment capital expenditures 257,771 780 258,551 Nine Months Ended September 30, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 286,137 $ 8,418 $ 294,555 Depletion, depreciation and accretion 88,453 5,515 93,968 General and administrative expenses 15,561 11,315 26,876 Income (loss) before income taxes 90,018 (30,738 ) 59,280 Segment capital expenditures 168,881 6,838 175,719 As at September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,246,979 $ 1,401 $ 1,248,380 Goodwill 102,581 — 102,581 All other assets 226,733 172,943 399,676 Total Assets $ 1,576,293 $ 174,344 $ 1,750,637 As at December 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,096,833 $ 2,391 $ 1,099,224 Goodwill 102,581 — 102,581 All other assets 176,980 50,834 227,814 Total Assets $ 1,376,394 $ 53,225 $ 1,429,619

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment On August 6, 2018, the Company acquired a working interest ("WI") in the VMM-2 block in the Middle Magdalena Valley Basin for cash consideration of $17.0 million , of which $ 6.2 million was allocated to proved properties. On June 20, 2018, the Company acquired the remaining WI in the Alea 1848-A and 1947-C Blocks in the Putumayo Basin for cash consideration of $3.1 million . Subsequent to September 30, 2018, the Company acquired the remaining 45% WI in the PUT-1 Block in the Putumayo Basin for cash consideration of $28.1 million .

Debt and Debt Issuance Costs

Debt and Debt Issuance Costs	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt and Debt Issuance Costs	Debt and Debt Issuance Costs The Company's debt at September 30, 2018 and December 31, 2017 was as follows: (Thousands of U.S. Dollars) As at September 30, 2018 As at December 31, 2017 Senior notes $ 300,000 $ — Convertible notes 115,000 115,000 Revolving credit facility — 148,000 Unamortized debt issuance costs (16,011 ) (6,458 ) Long-term debt $ 398,989 $ 256,542 Senior Notes On February 15, 2018 , Gran Tierra Energy International Holdings Ltd. ("GTEIH"), an indirect, wholly owned subsidiary of the Company, issued $300 million of 6.25% Senior Notes due 2025 (the "Senior Notes"). The Senior Notes are fully and unconditionally guaranteed by the Company and certain subsidiaries of the Company that guarantee its revolving credit facility. Net proceeds from the sale of the Senior Notes were $288.1 million , after deducting the initial purchasers' discounts and commission and the offering expenses payable by the Company. The Senior Notes bear interest at a rate of 6.25% per year, payable semi-annually in arrears on February 15 and August 15 of each year, beginning on August 15, 2018 . The Senior Notes will mature on February 15, 2025 , unless earlier redeemed or repurchased. Before February 15, 2022 , GTEIH may, at its option, redeem all or a portion of the Senior Notes at 100% of the principal amount plus accrued and unpaid interest and a make-whole premium. Thereafter, the Company may redeem all or a portion of the Senior Notes plus accrued and unpaid interest applicable to the date of the redemption at the following redemption prices: 2022 - 103.125% ; 2023 - 101.563% ; 2024 and thereafter - 100% . Interest Expense The following table presents total interest expense recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 2018 2017 Contractual interest and other financing expenses $ 6,588 $ 3,346 $ 17,945 $ 8,547 Amortization of debt issuance costs 816 643 2,329 1,868 $ 7,404 $ 3,989 $ 20,274 $ 10,415

Share Capital

Share Capital	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Capital	Share Capital On May 1, 2018, Gran Tierra Exchangeco Inc., a wholly-owned subsidiary of the Company, announced that it had established a redemption date of July 5, 2018 in respect of all of its outstanding exchangeable shares. Effective July 5, 2018, all remaining outstanding exchangeable shares of record on July 4, 2018 were acquired for purchase consideration of one share of Gran Tierra common stock for each exchangeable share, and on July 9, 2018, the Company retired and canceled one share of Special A Voting Stock and one share of Special B Voting Stock, which held voting rights in connection with those exchangeable shares. As a result, no shares of Special A Voting Stock and Special B Voting Stock remain outstanding. Shares of Common Stock Exchangeable Shares of Gran Tierra Exchangeco Inc. Exchangeable Shares of Gran Tierra Goldstrike Inc. Balance, December 31, 2017 385,191,042 4,422,776 1,688,889 Options exercised 541,394 — — Shares repurchased and canceled (504,612 ) — — Exchange of exchangeable shares 6,111,665 (4,422,776 ) (1,688,889 ) Balance, September 30, 2018 391,339,489 — — On March 7, 2018 , the Company announced that it intended to implement a share repurchase program (the “2018 Program”) through the facilities of the Toronto Stock Exchange ("TSX") and eligible alternative trading platforms in Canada. Under the 2018 Program, the Company is able to purchase at prevailing market prices up to 19,269,732 shares of Common Stock, representing approximately 5.00% of the issued and outstanding shares of Common Stock as of March 8, 2018 . Shares purchased pursuant to 2018 Program will be canceled. The 2018 Program will expire on March 11, 2019 , or earlier if the 5.00% share maximum is reached. Equity Compensation Awards The following table provides information about p erformance stock units (“PSUs”), deferred share units (“DSUs”), restricted stock units (“RSUs”) and stock option activity for the nine months ended September 30, 2018 : PSUs DSUs RSUs Stock Options Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Stock Options Weighted Average Exercise Price/Stock Option ($) Balance, December 31, 2017 6,131,951 455,768 122,090 8,960,692 3.65 Granted 3,660,422 182,607 — 2,049,930 2.54 Exercised — — (120,268 ) (541,394 ) 2.60 Forfeited (618,735 ) — (1,822 ) (656,847 ) 4.69 Expired — — — (621,854 ) 6.55 Balance, September 30, 2018 9,173,638 638,375 — 9,190,527 3.20 Stock-based compensation expense for the three and nine months ended September 30, 2018 , was $10.3 million and $20.5 million , respectively, and was primarily recorded in general and administrative ("G&A") expenses (three and nine months ended September 30, 2017 - $1.8 million and $4.9 million , respectively). At September 30, 2018 , there was $24.2 million ( December 31, 2017 - $13.7 million ) of unrecognized compensation cost related to unvested PSUs and stock options which is expected to be recognized over a weighted average period of 1.7 years. Net Income per Share Basic net income per share is calculated by dividing net income 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 similarly calculated except that the common shares outstanding for the period is increased using the treasury stock method to reflect the potential dilution that could occur if outstanding stock awards were vested at the end of the applicable period plus potentially issuable shares on conversion of the convertible notes. Anti-dilutive shares represent potentially dilutive securities that are excluded from the computation of diluted income or loss per share as their impact would be anti-dilutive. Weighted Average Shares Outstanding Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted average number of common and exchangeable shares outstanding 391,209,589 394,771,194 391,185,636 397,439,007 Shares issuable pursuant to stock options 6,509,385 61,325 4,295,964 187,150 Shares assumed to be purchased from proceeds of stock options (5,585,408 ) (57,566 ) (3,879,029 ) (175,520 ) Shares issuable pursuant to convertible notes 35,814,393 — 35,814,393 — Weighted average number of diluted common and exchangeable shares outstanding 427,947,959 394,774,953 427,416,964 397,450,637 For the three and nine months ended September 30, 2018 , 3,198,865 and 5,436,667 options, respectively, (three and nine months ended September 30, 2017 - 9,259,811 and 9,744,747 options, respectively), on a weighted average basis, were excluded from the diluted income per share calculation as the options were anti-dilutive. Shares issuable upon conversion of the 5.00% Convertible Notes due 2021 ("Convertible Notes") were dilutive and included in the diluted income per share calculation. For the three and nine months ended September 30, 2018 , the numerator used in the computation of diluted earnings per share included net income for the period adjusted for interest after tax on convertible debentures and amortization of debt issuance costs of $1.7 million and $5.2 million , respectively.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Most of the Company's revenues are from oil sales at prices which reflect the blended prices received upon shipment by the purchaser at defined sales points or are defined by contract relative to ICE Brent and adjusted for Vasconia crude, quality and transportation discounts each month. For the three and nine months ended September 30, 2018 , 100% (three and nine months ended September 30, 2017 - 100% ) of the Company's revenue resulted from oil sales. During the three and nine months ended September 30, 2018 , quality and transportation discounts were 13% and 14% respectively, of the ICE Brent price (three and nine months ended September 30, 2017 - 21% and 22% , respectively). During the three and nine months ended September 30, 2018 , the Company's production was sold primarily to two major customers in Colombia (three and nine months ended September 30, 2017 - three ). As at September 30, 2018 , accounts receivable included $8.9 million of accrued sales revenue related to September 2018 production ( December 31, 2017 - $11.1 million related to December 31, 2017 production).

Taxes

Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Taxes	Taxes The Company's effective tax rate was 24% in the nine months ended September 30, 2018 , compared with 85% in the comparative period in 2017 . Current income tax expense was higher in the nine months ended September 30, 2018 , compared with the corresponding period in 2017 , primarily as a result of higher taxable income in Colombia. The deferred income tax recovery of $0.1 million for the nine months ended September 30, 2018 was primarily due to the impact of the release of a portion of the valuation allowance in Colombia, partially offset by the excess tax depreciation compared with accounting depreciation in Colombia. For the nine months ended September 30, 2018 , the difference between the effective tax rate of 24% and the 21% U.S. statutory rate was primarily due to the impact of foreign taxes, which was partially offset by a decrease in the valuation allowance and other permanent differences. For the comparative period in 2017 , the 85% effective tax rate differed from the U.S. statutory rate of 35% primarily due to the impact of foreign taxes and an increase in the valuation allowance, which were partially offset by other permanent differences. The Tax Cuts and Jobs Act (the "Act") was enacted in the US on December 22, 2017. The Act reduced the US federal corporate income tax rate to 21% from 35% , required companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and created new taxes on certain foreign-sourced earnings. In 2017, the Company recorded provisional amounts for the enactment-date effects of the Act that included adjusting deferred tax assets (before valuation allowance), by applying the guidance in SAB 118, because it had not yet completed its enactment-date accounting for these effects. In the period ended September 30, 2018, the Company filed its US Federal 2017 tax return, whereby the provisional amounts recorded in 2017 were finalized and closed. The changes to the 2017 enactment-date provisional amounts resulted in a $9.4 million increased Foreign Tax Credit carryover balance, which was fully offset by a corresponding increase in the related valuation allowance.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies The Agencia Nacional de Hidrocarburos (National Hydrocarbons Agency) ("ANH") and Gran Tierra are engaged in ongoing discussions regarding the interpretation of whether certain transportation and related costs are eligible to be deducted in the calculation of an additional royalty (the "HPR royalty"). Based on the Company's understanding of the ANH's position, the estimated compensation which would be payable if the ANH’s interpretation is correct could be up to $53.7 million as at September 30, 2018 . At this time no amount has been accrued in the interim unaudited condensed consolidated financial statements as Gran Tierra does not consider it probable that a loss will be incurred. In addition to the above, the Company has a number of other lawsuits and claims pending. Although the outcome of these other lawsuits and disputes cannot be predicted with certainty, the Company 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 associated with these lawsuits and claims as they are incurred or become probable and determinable. Letters of credit and other credit support At September 30, 2018 , the Company had provided letters of credit and other credit support totaling $78.3 million ( December 31, 2017 - $76.0 million ) as security relating to work commitment guarantees contained in exploration contracts and other capital or operating requirements.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurement	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurement	Financial Instruments and Fair Value Measurement Financial Instruments At September 30, 2018 , the Company’s financial instruments recognized in the balance sheet consisted of: cash and cash equivalents; restricted cash and cash equivalents; accounts receivable; investments; derivatives, accounts payable and accrued liabilities, long-term debt and equity compensation award liability. Fair Value Measurement The fair value of certain investments, derivatives and equity compensation awards (PSU and DSU) liabilities are remeasured at the estimated fair value at the end of each reporting period. The fair value of the short-term portion of the Company's investment in PetroTal Corp. ("PetroTal") (formerly Sterling Resources Ltd.) was estimated using quoted prices from Canadian public markets, including the TSX Venture Exchange and alternative trading platforms, at September 30, 2018 and the foreign exchange rate at that time. The fair value of the long-term portion of the investment restricted by escrow conditions was estimated using observable and unobservable inputs; factors that were evaluated included quoted market prices, precedent comparable transactions, risk-free rate, measures of market risk volatility, estimates of the Company's and PetroTal's costs of capital and quotes from third parties. The fair value of commodity price and foreign currency derivatives is estimated based on various factors, including quoted market prices in active markets and quotes from third parties. The Company also performs an internal valuation to ensure the reasonableness of third party quotes. In consideration of counterparty credit risk, the Company assessed the possibility of whether the counterparty to the derivative would default by failing to make any contractually required payments. Additionally, the Company considers that it is of substantial credit quality and has the financial resources and willingness to meet its potential repayment obligations associated with the derivative transactions. The fair value of the PSU liability was estimated based on option pricing model using inputs such as quoted market prices in an active market, and PSU performance factors. The fair value of the DSU liabilities was estimated based on quoted market prices in an active market. The fair value of the Company's investment in PetroTal, derivatives and PSU and DSU liabilities at September 30, 2018 , and December 31, 2017 , was as follows: (Thousands of U.S. Dollars) As at September 30, 2018 As at December 31, 2017 Investment in PetroTal shares - current and long-term $ 55,231 $ 44,202 Foreign currency derivative asset 100 302 $ 55,331 $ 44,504 Commodity price derivative liability $ 17,688 $ 21,151 Equity compensation award liability - current and long-term 31,182 11,430 $ 48,870 $ 32,581 The following table presents gains or losses on financial instruments recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 2018 2017 Commodity price derivative loss (gain) $ 929 $ 2,489 $ 20,384 $ (3,759 ) Foreign currency derivatives loss (gain) 525 (814 ) (1,499 ) (1,452 ) Investment gain (6,328 ) — (12,045 ) — Financial instruments (gain) loss $ (4,874 ) $ 1,675 $ 6,840 $ (5,211 ) Investment gain for the three and nine months ended September 30, 2018 , related to the fair value gain on the PetroTal shares Gran Tierra received or subscribed for in connection with the sale of its Peru business unit in December 2017. For the three and nine months ended September 30, 2018 , this investment gain was unrealized. Financial instruments not recorded at fair value include the Senior Notes and the Convertible Notes. At September 30, 2018 , the carrying amounts of the Senior Notes and the Convertible Notes were $288.9 million and $111.8 million , respectively, which represented the aggregate principal amount less unamortized debt issuance costs, and the fair values were $293.8 million and $153.3 million , respectively. The fair value of long-term restricted cash and cash equivalents and the revolving credit facility approximated their carrying value because interest rates are variable and reflective of market rates. The fair values of other financial instruments approximate their carrying amounts due to the short-term maturity of these 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. At September 30, 2018 , the fair value of the current portion of the investment and DSU liability was determined using Level 1 inputs, the fair value of derivatives and PSUs was determined using Level 2 inputs and the fair value of the long-term portion of the investment restricted by escrow conditions was determined using Level 3 inputs. The table below presents the fair value of the long-term portion of the investment: Nine Months Ended Year Ended (Thousands of U.S. Dollars) September 30, 2018 December 31, 2017 Opening balance, investment - long-term $ 19,147 $ — Acquisition — 19,091 Transfer from long-term (Level 3) to current (Level 1) (4,787 ) — Unrealized valuation gain 5,332 56 Unrealized foreign exchange loss (2,069 ) — Closing balance, investment - long-term $ 17,623 $ 19,147 The Company uses available market data and valuation methodologies to estimate the fair value of debt. The fair value of debt is the estimated amount the Company would have to pay a third party to assume the debt, including a credit spread for the difference between the issue rate and the period end market rate. The credit spread is the Company’s default or repayment risk. The credit spread (premium or discount) is determined by comparing the Company’s Senior Notes, Convertible Notes and revolving credit facility to new issuances (secured and unsecured) and secondary trades of similar size and credit statistics for both public and private debt. The disclosure above regarding the fair value of the Convertible Notes was determined using Level 2 inputs based on the indicative pricing published by certain third-party services or trading levels of the Convertible Notes, which are not listed on any securities exchange or quoted on an inter-dealer automated quotation system. The disclosure in the paragraph above regarding the fair value of cash and restricted cash and cash equivalents, revolving credit facility and Senior Notes was based on Level 1 inputs. The Company’s non-recurring fair value measurements include asset retirement obligations. The fair value of an asset retirement obligation is measured by reference to the expected future cash outflows required to satisfy the retirement obligation discounted at the Company’s credit-adjusted risk-free interest rate. The significant level 3 inputs used to calculate such liabilities include estimates of costs to be incurred, the Company’s credit-adjusted risk-free interest rate, inflation rates and estimated dates of abandonment. Accretion expense is recognized over time as the discounted liabilities are accreted to their expected settlement value, while the asset retirement cost is amortized over the estimated productive life of the related assets. Commodity Price Derivatives The Company utilizes commodity price derivatives to manage the variability in cash flows associated with the forecasted sale of its oil production, reduce commodity price risk and provide a base level of cash flow in order to assure it can execute at least a portion of its capital spending. At September 30, 2018 , the Company had outstanding commodity price derivative positions as follows: Period and type of instrument Volume, Reference Sold Swap ($/bbl, Weighted Average) Purchased Call ($/bbl, Weighted Average) Swaps: October 1, to December 31, 2018 5,000 ICE Brent $ 55.90 n/a Participating Swaps: October 1, to December 31, 2018 5,000 ICE Brent $ 52.50 $ 56.11 The Company does not have any outstanding commodity price derivative positions relating to 2019. Foreign Currency Derivatives The Company utilizes foreign currency derivatives to manage the variability in cash flows associated with the Company's forecasted Colombian peso ("COP") denominated expenses. At September 30, 2018 , the Company had outstanding foreign currency derivative positions as follows: Period and type of instrument Amount Hedged U.S. Dollar Equivalent of Amount Hedged (Thousands of U.S. Dollars) (1) Reference Purchased Call Sold Put (COP, Weighted Average) Collars: October 1, 2018 to December 31, 2018 43,500 14,636 COP 3,000 3,107 (1) At September 30, 2018 foreign exchange rate.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following table provides a reconciliation of cash, cash equivalents and restricted cash and cash equivalents with the Company's interim unaudited condensed consolidated balance sheet that sum to the total of the same such amounts shown in the interim unaudited condensed consolidated statements of cash flows: (Thousands of U.S. Dollars) As at September 30, As at December 31, 2018 2017 2017 2016 Cash and cash equivalents $ 130,158 $ 15,125 $ 12,326 $ 25,175 Restricted cash and cash equivalents - current 1,228 3,920 11,787 8,322 Restricted cash and cash equivalents - long-term (included in other long-term assets) 2,250 10,332 2,565 9,770 $ 133,636 $ 29,377 $ 26,678 $ 43,267 Net changes in assets and liabilities from operating activities were as follows: Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 Accounts receivable and other long-term assets $ (35,934 ) $ 8,356 Derivatives 21,645 — Inventory (3,375 ) (28 ) Prepaids 489 3,080 Accounts payable and accrued and other long-term liabilities 5,380 5,951 Taxes receivable and payable (28,857 ) (45,464 ) Net changes in assets and liabilities from operating activities $ (40,652 ) $ (28,105 ) The following table provides additional supplemental cash flow disclosures: Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 Non-cash investing activities: Net liabilities related to property, plant and equipment, end of period $ 100,790 $ 68,018

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Recently Adopted Accounting Pronouncements/Recently Issued but Not Yet Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Revenue from Contracts with Customers The Company adopted Accounting Standard Codification ("ASC") 606 Revenue from Contracts with Customers with a date of initial application of January 1, 2018 in accordance with the modified retrospective approach without using the practical expedients. Except for providing enhanced disclosures about the Company's revenue transactions, the application of ASC 606 did not have an impact on the Company’s consolidated financial position, results of operations or cash flows. a) Significant Accounting Policy The Company's revenue relates to oil and natural gas sales in Colombia. The Company recognizes revenue when it transfers control of the product to a customer. This generally occurs at the time the customer obtains legal title to the product and when it is physically transferred to the delivery point agreed with the customer. Payment terms are generally within three business days following delivery of an invoice to the customer. Revenue is recognized based on the consideration specified in contracts with customers. Revenue represents the Company's share and is recorded net of royalty payments to governments and other mineral interest owners. The Company evaluates its arrangement with third parties and partners to determine if the Company acts as a principal or an agent. In making this evaluation, management considers if the Company obtains control of the product delivered, which is indicated by the Company having the primary responsibility for the delivery of the product, having ability to establish prices or having inventory risk. If the Company acts in the capacity of an agent rather than as a principal in transaction, then the revenue is recognized on a net-basis, only reflecting the fee realized by the Company from the transaction. Tariffs, tolls and fees charged to other entities for use of pipelines owned by the Company are evaluated by management to determine if these originate from contracts with customers or from incidental arrangements. In the comparative period, revenue from the production of oil and natural gas was recognized when the customer took title and assumed the risks and rewards of ownership, prices were fixed or determinable, the sale was evidenced by a contract and collection of the revenue was reasonably assured. b) Significant Judgments When determining if the Company acted as a principal or as an agent in transactions, management determines if the Company obtains control of the product. As part of this assessment, management considers detailed criteria for revenue recognition set out in ASC 606. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2016-01 addressed certain aspects of recognition, measurement, presentation and disclosure of financial instruments. ASU 2016-01 was effective for annual reporting periods and interim reporting periods within those annual reporting periods, beginning after December 15, 2017. The implementation of this update did not impact on the Company’s consolidated financial position, results of operations or cash flows or disclosure. In February 2018, the FASB issued ASU 2018-03, "Recognition and Measurement of Financial Assets and Financial Liabilities". ASU 2018-03 clarified certain aspects of the guidance in ASU 2016-01. ASU 2018-03 is effective for annual reporting periods beginning after December 15, 2017 and interim reporting periods within those annual reporting periods beginning after June 15, 2018. Early adoption is permitted upon adoption of ASU 2016-01.The amendments should be applied retrospectively with a cumulative-effect adjustment to the effective date of ASU 2016-01. The Company early adopted this update on January 1, 2018. The implementation of this update did not impact the Company’s consolidated financial position, results of operations or cash flows or disclosure. Recently Issued but Not Yet Adopted Accounting Pronouncements Leases In January 2018, the FASB issued ASU 2018-01, "Land Easement Practical Expedient for Transition to Topic 842". ASU 2018-01 provides an optional transition practical expedient that, if elected, would not require an organization to reconsider their accounting for existing or expired land easements that were not previously accounted for as leases under Topic 840. The effective date and transition requirements for the amendment are the same as the effective date and transition requirements in ASU 2016-02. The Company is planning to adopt ASU 2018-01 upon transition to ASU 2016-02 "Leases". The Company has completed an assessment of its contract inventory, identified contracts which meet the definition of a lease and is currently determining the value of right-of-use lease assets and lease liabilities and transition adjustments. The Company expects to use practical expedients available for land easements and short-term leases and will apply the guidance of ASU 2016-02 using a modified retrospective transition approach. Fair Value Measurements In August 2018, the FASB issued ASU 2018-13, "Changes to the Disclosure Requirements for Fair Value Measurement". ASU 2018-13 will modify certain fair value measurements disclosure requirements. ASU 2018-13 will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. The disclosure amendments on changes in unrealized gains and losses, and disclosure requirements for significant unobservable inputs used to develop Level 3 fair value measurements, should be applied prospectively. All other amendments in ASU 2018-13 should be applied retrospectively. Early adoption is permitted. The application of ASU 2018-13 will not impact the Company’s consolidated financial position, results of operations or cash flows. Intangibles - Goodwill and Other - Internal-use Software In August 2018, the FASB issued ASU 2018-15, "Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract". ASU 2018-15 clarifies requirements for capitalization of software development costs and requires that a hosting arrangement that is a service contract to be capitalized and expensed over the term of the hosting arrangement. ASU 2018-15 will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2019. The provisions of this amendment should be applied retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently assessing the impact this update will have on its consolidated financial position, results of operations, cash flows, and disclosure.

Segment and Geographic Report_2

Segment and Geographic Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Information on Reportable Segments and Other Activities	The following tables present information on the Company’s reportable segments and other activities: Three Months Ended September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 175,118 $ — $ 175,118 Depletion, depreciation and accretion 51,416 214 51,630 General and administrative expenses 7,370 6,441 13,811 Income (loss) before income taxes 63,797 (6,163 ) 57,634 Segment capital expenditures 101,453 10 101,463 Three Months Ended September 30, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 103,768 $ — $ 103,768 Depletion, depreciation and accretion 33,388 1,891 35,279 General and administrative expenses 5,500 3,151 8,651 Income (loss) before income taxes 31,276 (10,053 ) 21,223 Segment capital expenditures 70,606 1,088 71,694 Nine Months Ended September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 476,792 $ — $ 476,792 Depletion, depreciation and accretion 135,980 1,718 137,698 General and administrative expenses 20,876 16,297 37,173 Income (loss) before income taxes 175,977 (26,415 ) 149,562 Segment capital expenditures 257,771 780 258,551 Nine Months Ended September 30, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Oil and natural gas sales $ 286,137 $ 8,418 $ 294,555 Depletion, depreciation and accretion 88,453 5,515 93,968 General and administrative expenses 15,561 11,315 26,876 Income (loss) before income taxes 90,018 (30,738 ) 59,280 Segment capital expenditures 168,881 6,838 175,719
Schedule of Long-lived Assets by Geographical Area	As at September 30, 2018 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,246,979 $ 1,401 $ 1,248,380 Goodwill 102,581 — 102,581 All other assets 226,733 172,943 399,676 Total Assets $ 1,576,293 $ 174,344 $ 1,750,637 As at December 31, 2017 (Thousands of U.S. Dollars) Colombia All Other Total Property, plant and equipment $ 1,096,833 $ 2,391 $ 1,099,224 Goodwill 102,581 — 102,581 All other assets 176,980 50,834 227,814 Total Assets $ 1,376,394 $ 53,225 $ 1,429,619

Debt and Debt Issuance Costs (T

Debt and Debt Issuance Costs (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Debt	The Company's debt at September 30, 2018 and December 31, 2017 was as follows: (Thousands of U.S. Dollars) As at September 30, 2018 As at December 31, 2017 Senior notes $ 300,000 $ — Convertible notes 115,000 115,000 Revolving credit facility — 148,000 Unamortized debt issuance costs (16,011 ) (6,458 ) Long-term debt $ 398,989 $ 256,542
Schedule of Interest Expense Recognized	The following table presents total interest expense recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 2018 2017 Contractual interest and other financing expenses $ 6,588 $ 3,346 $ 17,945 $ 8,547 Amortization of debt issuance costs 816 643 2,329 1,868 $ 7,404 $ 3,989 $ 20,274 $ 10,415

Share Capital (Tables)

Share Capital (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Common Stock	Shares of Common Stock Exchangeable Shares of Gran Tierra Exchangeco Inc. Exchangeable Shares of Gran Tierra Goldstrike Inc. Balance, December 31, 2017 385,191,042 4,422,776 1,688,889 Options exercised 541,394 — — Shares repurchased and canceled (504,612 ) — — Exchange of exchangeable shares 6,111,665 (4,422,776 ) (1,688,889 ) Balance, September 30, 2018 391,339,489 — —
Schedule of PSU, DSU, RSU and Stock Option Activity	The following table provides information about p erformance stock units (“PSUs”), deferred share units (“DSUs”), restricted stock units (“RSUs”) and stock option activity for the nine months ended September 30, 2018 : PSUs DSUs RSUs Stock Options Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Share Units Number of Outstanding Stock Options Weighted Average Exercise Price/Stock Option ($) Balance, December 31, 2017 6,131,951 455,768 122,090 8,960,692 3.65 Granted 3,660,422 182,607 — 2,049,930 2.54 Exercised — — (120,268 ) (541,394 ) 2.60 Forfeited (618,735 ) — (1,822 ) (656,847 ) 4.69 Expired — — — (621,854 ) 6.55 Balance, September 30, 2018 9,173,638 638,375 — 9,190,527 3.20
Schedule of Weighted Average Shares Outstanding	Weighted Average Shares Outstanding Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted average number of common and exchangeable shares outstanding 391,209,589 394,771,194 391,185,636 397,439,007 Shares issuable pursuant to stock options 6,509,385 61,325 4,295,964 187,150 Shares assumed to be purchased from proceeds of stock options (5,585,408 ) (57,566 ) (3,879,029 ) (175,520 ) Shares issuable pursuant to convertible notes 35,814,393 — 35,814,393 — Weighted average number of diluted common and exchangeable shares outstanding 427,947,959 394,774,953 427,416,964 397,450,637

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurement (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Derivatives and RSU, PSU and DSU Liabilities	The fair value of the Company's investment in PetroTal, derivatives and PSU and DSU liabilities at September 30, 2018 , and December 31, 2017 , was as follows: (Thousands of U.S. Dollars) As at September 30, 2018 As at December 31, 2017 Investment in PetroTal shares - current and long-term $ 55,231 $ 44,202 Foreign currency derivative asset 100 302 $ 55,331 $ 44,504 Commodity price derivative liability $ 17,688 $ 21,151 Equity compensation award liability - current and long-term 31,182 11,430 $ 48,870 $ 32,581
Schedule of Gains or Losses on Financial Instruments Recognized	The following table presents gains or losses on financial instruments recognized in the accompanying interim unaudited condensed consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 2018 2017 Commodity price derivative loss (gain) $ 929 $ 2,489 $ 20,384 $ (3,759 ) Foreign currency derivatives loss (gain) 525 (814 ) (1,499 ) (1,452 ) Investment gain (6,328 ) — (12,045 ) — Financial instruments (gain) loss $ (4,874 ) $ 1,675 $ 6,840 $ (5,211 )
Schedule of Fair Value of Long-term Investments	The table below presents the fair value of the long-term portion of the investment: Nine Months Ended Year Ended (Thousands of U.S. Dollars) September 30, 2018 December 31, 2017 Opening balance, investment - long-term $ 19,147 $ — Acquisition — 19,091 Transfer from long-term (Level 3) to current (Level 1) (4,787 ) — Unrealized valuation gain 5,332 56 Unrealized foreign exchange loss (2,069 ) — Closing balance, investment - long-term $ 17,623 $ 19,147
Schedule of Commodity Price Derivative Positions and Commodity Foreign Currency Contracts	At September 30, 2018 , the Company had outstanding commodity price derivative positions as follows: Period and type of instrument Volume, Reference Sold Swap ($/bbl, Weighted Average) Purchased Call ($/bbl, Weighted Average) Swaps: October 1, to December 31, 2018 5,000 ICE Brent $ 55.90 n/a Participating Swaps: October 1, to December 31, 2018 5,000 ICE Brent $ 52.50 $ 56.11
Schedule of Outstanding Foreign Currency Derivative Positions	At September 30, 2018 , the Company had outstanding foreign currency derivative positions as follows: Period and type of instrument Amount Hedged U.S. Dollar Equivalent of Amount Hedged (Thousands of U.S. Dollars) (1) Reference Purchased Call Sold Put (COP, Weighted Average) Collars: October 1, 2018 to December 31, 2018 43,500 14,636 COP 3,000 3,107 (1) At September 30, 2018 foreign exchange rate.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash and cash equivalents with the Company's interim unaudited condensed consolidated balance sheet that sum to the total of the same such amounts shown in the interim unaudited condensed consolidated statements of cash flows: (Thousands of U.S. Dollars) As at September 30, As at December 31, 2018 2017 2017 2016 Cash and cash equivalents $ 130,158 $ 15,125 $ 12,326 $ 25,175 Restricted cash and cash equivalents - current 1,228 3,920 11,787 8,322 Restricted cash and cash equivalents - long-term (included in other long-term assets) 2,250 10,332 2,565 9,770 $ 133,636 $ 29,377 $ 26,678 $ 43,267
Schedule of Net Changes in Assets and Liabilities	Net changes in assets and liabilities from operating activities were as follows: Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 Accounts receivable and other long-term assets $ (35,934 ) $ 8,356 Derivatives 21,645 — Inventory (3,375 ) (28 ) Prepaids 489 3,080 Accounts payable and accrued and other long-term liabilities 5,380 5,951 Taxes receivable and payable (28,857 ) (45,464 ) Net changes in assets and liabilities from operating activities $ (40,652 ) $ (28,105 )
Schedule of Additional Supplemental Cash Flow Disclosures	The following table provides additional supplemental cash flow disclosures: Nine Months Ended September 30, (Thousands of U.S. Dollars) 2018 2017 Non-cash investing activities: Net liabilities related to property, plant and equipment, end of period $ 100,790 $ 68,018

Significant Accounting Polici_3

Significant Accounting Policies (Details)	9 Months Ended
	Sep. 30, 2018day
Accounting Policies [Abstract]
Payment terms, number of days	3

Segment and Geographic Report_3

Segment and Geographic Reporting - Schedule of Information on Reportable Segments and Other Activities (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)segment	Sep. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Depletion, depreciation and accretion	$ 51,630	$ 35,279	$ 137,698	$ 93,968
General and administrative expenses	13,811	8,651	37,173	26,876
Income (loss) before income taxes	57,634	21,223	149,562	59,280
Segment capital expenditures	101,463	71,694	258,551	175,719
Reportable Segments | Colombia
Segment Reporting Information [Line Items]
Depletion, depreciation and accretion	51,416	33,388	135,980	88,453
General and administrative expenses	7,370	5,500	20,876	15,561
Income (loss) before income taxes	63,797	31,276	175,977	90,018
Segment capital expenditures	101,453	70,606	257,771	168,881
All Other
Segment Reporting Information [Line Items]
Depletion, depreciation and accretion	214	1,891	1,718	5,515
General and administrative expenses	6,441	3,151	16,297	11,315
Income (loss) before income taxes	(6,163)	(10,053)	(26,415)	(30,738)
Segment capital expenditures	10	1,088	780	6,838
Oil and Gas Service
Segment Reporting Information [Line Items]
Oil and natural gas sales	175,118	103,768	476,792	294,555
Oil and Gas Service | Reportable Segments | Colombia
Segment Reporting Information [Line Items]
Oil and natural gas sales	175,118	103,768	476,792	286,137
Oil and Gas Service | All Other
Segment Reporting Information [Line Items]
Oil and natural gas sales	$ 0	$ 0	$ 0	$ 8,418

Segment and Geographic Report_4

Segment and Geographic Reporting - Schedule of Long-lived Assets by Geographical Area (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property, plant and equipment	$ 1,248,380	$ 1,099,224
Goodwill	102,581	102,581
All other assets	399,676	227,814
Total Assets	1,750,637	1,429,619
Reportable Segments | Colombia
Segment Reporting Information [Line Items]
Property, plant and equipment	1,246,979	1,096,833
Goodwill	102,581	102,581
All other assets	226,733	176,980
Total Assets	1,576,293	1,376,394
All Other
Segment Reporting Information [Line Items]
Property, plant and equipment	1,401	2,391
Goodwill	0	0
All other assets	172,943	50,834
Total Assets	$ 174,344	$ 53,225

Property, Plant and Equipment (

Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Millions	Nov. 01, 2018	Aug. 06, 2018	Jun. 20, 2018
Property, Plant and Equipment [Line Items]
Payments to acquire oil and gas property			$ 3.1
Middle Magdalena Valley Basin
Property, Plant and Equipment [Line Items]
Payments to acquire oil and gas property		$ 17
PUT-1 Block In The Putumayo Basin | Subsequent Event
Property, Plant and Equipment [Line Items]
Payments to acquire oil and gas property	$ 28.1
Business acquisition, percentage of working interests acquired	45.00%
Proved Oil and Gas Properties | Middle Magdalena Valley Basin
Property, Plant and Equipment [Line Items]
Payments to acquire oil and gas property		$ 6.2

Debt and Debt Issuance Costs -

Debt and Debt Issuance Costs - Schedule of Debt (Details) - USD ($)	Sep. 30, 2018	Feb. 15, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (16,011,000)		$ (6,458,000)
Long-term debt	398,989,000		256,542,000
Convertible notes
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	115,000,000		115,000,000
Revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	0		148,000,000
Senior Notes Unsecured 6.25% | Senior notes
Debt Instrument [Line Items]
Convertible senior notes and revolving credit facility	$ 300,000,000	$ 300,000,000	$ 0

Debt and Debt Issuance Costs _2

Debt and Debt Issuance Costs - Narrative (Details) - USD ($)	Feb. 15, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Line of Credit Facility [Line Items]
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)		$ 288,087,000	$ 0
Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Long-term debt, gross	$ 300,000,000	$ 300,000,000		$ 0
Debt instrument, interest rate, stated percentage	6.25%	6.25%
Proceeds from issuance of Senior Notes, net of issuance costs (Note 5)	$ 288,100,000
Prior to February 15th, 2022 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	100.00%
2022 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	103.125%
2023 | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	101.563%
2024 and thereafter | Senior Notes Unsecured 6.25% | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	100.00%

Debt and Debt Issuance Costs _3

Debt and Debt Issuance Costs - Schedule of Interest Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Contractual interest and other financing expenses	$ 6,588	$ 3,346	$ 17,945	$ 8,547
Amortization of debt issuance costs	816	643	2,329	1,868
Total interest expense recognized	$ 7,404	$ 3,989	$ 20,274	$ 10,415

Share Capital - Additional Info

Share Capital - Additional Information (Details) - shares	Jul. 09, 2018	Jul. 05, 2018	Mar. 08, 2018	Mar. 07, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business combination consideration transferred equity interests issued and issuable number of shares for each share of acquired entity shares		1
The 2018 Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under the 2018 Program (up to) (in shares)				19,269,732
Shares authorized representing issued and outstanding shares of Common Stock (as a percent)			5.00%
Special A Voting Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, cancelled	1
Preferred stock, shares outstanding	0
Special B Voting Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, cancelled	1
Preferred stock, shares outstanding	0

Share Capital - Schedule of Com

Share Capital - Schedule of Common Stock (Details)	9 Months Ended
	Sep. 30, 2018shares
Increase (Decrease) in Common Stock
Beginning balance (in shares)	385,191,042
Options exercised (in shares)	541,394
Ending balance (in shares)	391,339,489
Shares of Common Stock
Increase (Decrease) in Common Stock
Beginning balance (in shares)	385,191,042
Options exercised (in shares)	541,394
Shares repurchased and canceled (in shares)	504,612
Exchange of exchangeable shares (in shares)	6,111,665
Ending balance (in shares)	391,339,489
Shares of Common Stock | Exchangeable Shares of Gran Tierra Exchangeco Inc.
Increase (Decrease) in Common Stock
Beginning balance (in shares)	4,422,776
Options exercised (in shares)	0
Shares repurchased and canceled (in shares)	0
Exchange of exchangeable shares (in shares)	(4,422,776)
Ending balance (in shares)	0
Shares of Common Stock | Exchangeable Shares of Gran Tierra Goldstrike Inc.
Increase (Decrease) in Common Stock
Beginning balance (in shares)	1,688,889
Options exercised (in shares)	0
Shares repurchased and canceled (in shares)	0
Exchange of exchangeable shares (in shares)	(1,688,889)
Ending balance (in shares)	0

Share Capital - Schedule of PSU

Share Capital - Schedule of PSU, DSU, RSU and Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Number of Outstanding Stock Options
Beginning Balance (in shares)	8,960,692
Granted (in shares)	2,049,930
Exercised (in shares)	(541,394)
Forfeited (in shares)	(656,847)
Expired (in shares)	(621,854)
Ending Balance (in shares)	9,190,527
Weighted Average Exercise Price/Stock Option ($)
Beginning balance (in dollars per share) | $ / shares	$ 3.65
Granted (in dollars per share) | $ / shares	2.54
Exercised (in dollars per share) | $ / shares	2.60
Forfeited (in dollars per share) | $ / shares	4.69
Expired (in dollars per share) | $ / shares	(6.55)
Ending balance (in dollars per share) | $ / shares	$ 3.20
PSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	6,131,951
Granted (in shares)	3,660,422
Exercised (in shares)	0
Forfeited (in shares)	(618,735)
Expired (in shares)	0
Ending Balance (in shares)	9,173,638
DSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	455,768
Granted (in shares)	182,607
Exercised (in shares)	0
Forfeited (in shares)	0
Expired (in shares)	0
Ending Balance (in shares)	638,375
RSUs
Number of Outstanding Share Units
Beginning Balance (in shares)	122,090
Granted (in shares)	0
Exercised (in shares)	(120,268)
Forfeited (in shares)	(1,822)
Expired (in shares)	0
Ending Balance (in shares)	0

Share Capital - Equity Compensa

Share Capital - Equity Compensation Awards (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 24.2		$ 24.2		$ 13.7
Weighted average period for recognition			1 year 8 months 12 days
General and administrative (G&A) expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10.3	$ 1.8	$ 20.5	$ 4.9

Share Capital - Schedule of Wei

Share Capital - Schedule of Weighted Average Shares Outstanding (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted average number of common and exchangeable shares outstanding (in shares)	391,209,589	394,771,194	391,185,636	397,439,007
Shares issuable pursuant to stock options (in shares)	6,509,385	61,325	4,295,964	187,150
Shares assumed to be purchased from proceeds of stock options (in shares)	(5,585,408)	(57,566)	(3,879,029)	(175,520)
Shares issuable pursuant to convertible notes (in shares)	35,814,393	0	35,814,393	0
Weighted average number of diluted common and exchangeable shares outstanding (in shares)	427,947,959	394,774,953	427,416,964	397,450,637

Share Capital - Weighted Averag

Share Capital - Weighted Average Shares Outstanding (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Convertible debt interest and amortized debt issuance costs	$ 1.7		$ 5.2
Convertible notes | Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	5.00%		5.00%
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted income (loss) per share calculation (in shares)	3,198,865	9,259,811	5,436,667	9,744,747

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Concentration Risk [Line Items]
Variable adjustment for transportation, location, quality, and other elements, percentage	13.00%	21.00%	14.00%	22.00%
Accrued sales revenue	$ 8.9		$ 8.9		$ 11.1
Product Concentration Risk | Revenue from Contract with Customer
Concentration Risk [Line Items]
Concentration risk, percentage	99.95432%	99.68006%	100.00%	100.00%

Taxes (Details)

Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective tax rate			24.00%	85.00%
Deferred tax (recovery) expense	$ (36,769)	$ 13,760	$ (118)	$ 36,664
Tax cuts and jobs act of 2017, foreign tax credit carryforward, increase	$ 9,400		$ 9,400

Contingencies (Details)

Contingencies (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Letters of credit and other credit support provided	$ 78,300,000	$ 76,000,000
Pending Litigation Royalty, Transportation and Related Costs
Loss Contingencies [Line Items]
Estimated compensation which would be payable if the ANH's interpretation is correct	53,700,000
Amount accrued	$ 0

Financial Instruments and Fai_3

Financial Instruments and Fair Value Measurement - Schedule of Fair Value of Derivatives and RSU, PSU and DSU Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Investment in PetroTal shares - current and long-term	$ 55,231	$ 44,202
Assets, fair value disclosure	55,331	44,504
PSU, DSU and RSU liability - current and long-term	31,182	11,430
Liabilities, fair value disclosure	48,870	32,581
Foreign currency derivative asset
Derivatives, Fair Value [Line Items]
Foreign currency derivative asset	100	302
Commodity Hedge
Derivatives, Fair Value [Line Items]
Commodity price derivative liability	$ 17,688	$ 21,151

Financial Instruments and Fai_4

Financial Instruments and Fair Value Measurement - Schedule of Gains or Losses on Financial Instruments Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Investment gain	$ (6,328)	$ 0	$ (12,045)	$ 0
Financial instruments (gain) loss	(4,874)	1,675	6,840	(5,211)
Commodity price derivative loss (gain)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative (loss) gain	929	2,489	20,384	(3,759)
Foreign currency derivatives loss (gain)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative (loss) gain	$ 525	$ (814)	$ (1,499)	$ (1,452)

Financial Instruments and Fai_5

Financial Instruments and Fair Value Measurement - Narrative (Details) $ in Millions	Sep. 30, 2018USD ($)
Carrying amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value disclosure	$ 288.9
Value of the notes	111.8
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value disclosure	293.8
Value of the notes	$ 153.3

Financial Instruments and Fai_6

Financial Instruments and Fair Value Measurement - Rollforward of Level 3 Financial Asset (Details) - Equity Securities - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance, investment - long-term	$ 19,147	$ 0
Acquisition	0	19,091
Transfer from long-term (Level 3) to current (Level 1)	(4,787)	0
Unrealized valuation gain	5,332	56
Unrealized foreign exchange loss	(2,069)	0
Closing balance, investment - long-term	$ 17,623	$ 19,147

Financial Instruments and Fai_7

Financial Instruments and Fair Value Measurement - Schedule of Commodity Price Derivative Positions and Commodity Foreign Currency Contracts (Details) - Commodity Hedge	9 Months Ended
	Sep. 30, 2018$ / bblbbl
Commodity Foreign Currency Contract, Swap April 1 To December 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (in barrels of oil per day) | bbl	5,000
Commodity Foreign Currency Contract, Swap April 1 To December 31, 2018 | Purchased | Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	55.90
Participating Swaps: October 1, to December 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (in barrels of oil per day) | bbl	5,000
Participating Swaps: October 1, to December 31, 2018 | Purchased | Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	52.50
Participating Swaps: October 1, to December 31, 2018 | Purchased | Call
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Floor price (in dollars per barrel)	56.11

Financial Instruments and Fai_8

Financial Instruments and Fair Value Measurement - Schedule of Outstanding Foreign Currency Derivative Positions (Details) - Collars: October 1, 2018 to December 31, 2018 $ in Thousands, $ in Millions	Sep. 30, 2018COP ($)$ / collar	Sep. 30, 2018USD ($)$ / collar
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount hedged	$ 43,500	$ 14,636
Purchased | Call
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Purchased call (in COP per collar)	3,000	3,000
Sold | Put
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Sold put (in COP per collar)	3,107	3,107

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Reconciliation of Cash, Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 130,158	$ 12,326	$ 15,125	$ 25,175
Restricted cash and cash equivalents - current	1,228	11,787	3,920	8,322
Restricted cash and cash equivalents - long-term (included in other long-term assets)	2,250	2,565	10,332	9,770
Cash, cash equivalents and restricted cash and cash equivalents	$ 133,636	$ 26,678	$ 29,377	$ 43,267

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information - Schedule of Net Changes in Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Accounts receivable and other long-term assets	$ (35,934)	$ 8,356
Derivatives	21,645	0
Inventory	(3,375)	(28)
Prepaids	489	3,080
Accounts payable and accrued and other long-term liabilities	5,380	5,951
Taxes receivable and payable	(28,857)	(45,464)
Net changes in assets and liabilities from operating activities	$ (40,652)	$ (28,105)

Supplemental Cash Flow Inform_5

Supplemental Cash Flow Information - Schedule of Additional Supplemental Cash Flow Disclosures (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Net liabilities related to property, plant and equipment, end of period	$ 100,790	$ 68,018