Share Capital (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share Capital [Abstract]
Authorized share capital (in shares)	595,000,002
Common stock-authorized (in shares)	570,000,000
Common stock-par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock-authorized (in shares)	25,000,000
Preferred stock-par value (in dollars per share)	$ 0.001
Special voting stock-authorized (in shares)	2
Special voting stock-par value (in dollars per share)	$ 0.001
Outstanding share capital-common voting shares (in shares)	262,304,249	240,440,830
Common voting shares per exchangeable share (in shares)	1
Votes per common stock	1
Weighted Average Exercise Price per share [Abstract]
Weighted Average Exercise Price of Options, beginning balance (in dollars per share)	$ 3.49
Weighted Average Exercise Price of Options Granted (in dollars per share)	$ 7.94
Weighted Average Exercise Price of Options Exercised (in dollars per share)	$ (2.70)
Weighted Average Exercise Price of Options Vested (in dollars per share)	$ 0
Weighted Average Exercise Price of Options Forfeited (in dollars per share)	$ (6.70)
Weighted Average Exercise Price of Options, ending balance (in dollars per share)	$ 4.90	$ 3.49
Weighted Average Grant-Date Fair Value per share [Abstract]
Weighted Average Grant-Date Fair Value Price of Options, beginning balance (in dollars per share)	$ 2.68
Weighted Average Grant-Date Fair Value Price of Options Granted (in dollars per share)	$ 4.84
Weighted Average Grant-Date Fair Value Price of Options Vested (in dollars per share)	$ (2.26)
Weighted Average Grant-Date Fair Value Price of Options Forfeited (in dollars per share)	$ (4.06)
Weighted Average Grant-Date Fair Value Price of Options, ending balance (in dollars per share)	$ 4.22	$ 2.68
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	12,864,002
Weighted Average Exercise Price (in dollars per share)	$ 4.90
Weighted Average Expiry Years (in years)	7.7
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	6,648,806
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 2.89
Weighted Average Expiry Years/Exercisable Options (in years)	6.6
Fair value valuation assumptions [Abstract]
Dividend yield (per share)	0.00%	0.00%	0.00%
Volatility-minimum (in hundredths)	75.00%	84.00%	94.00%
Volatility-maximum (in hundredths)	81.00%	90.00%	98.00%
Weighted average volatility	80.00%	89.00%	96.00%
Risk-free interest rate-minimum (in hundredths)	0.40%	0.20%	0.40%
Risk-free interest rate-maximum (in hundredths)	1.40%	0.50%	0.60%
Weighted average risk-free interest rate (in hundredths)	1.20%	0.30%	0.50%
Expected term, minimum (in years)	4
Expected term, maximum (in years)	6
Expected term (in years)	3	3	3
Weighted average number of shares outstanding [Abstract]
Weighted average number of common and exchangeable shares outstanding (in shares)	273,491,564	253,697,076	241,258,568
Shares issuable pursuant to warrants (in shares)	2,708,183	3,750,781	9,503,818
Shares issuable pursuant to stock options (in shares)	5,143,498	7,402,966	5,797,322
Shares to be purchased from proceeds of stock options (in shares)	(56,243)	(545,992)	(2,969,605)
Weighted average number of diluted common and exchangeable shares outstanding (in shares)	281,287,002	264,304,831	253,590,103
0.50 to 2.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	1,195,837
Weighted Average Exercise Price (in dollars per share)	$ 1.12
Weighted Average Expiry Years (in years)	4.6
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	1,195,837
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 1.12
Weighted Average Expiry Years/Exercisable Options (in years)	4.6
2.01 to 3.50 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	4,310,250
Weighted Average Exercise Price (in dollars per share)	$ 2.47
Weighted Average Expiry Years (in years)	6.8
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	4,128,583
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 2.47
Weighted Average Expiry Years/Exercisable Options (in years)	6.8
3.51 to 5.50 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	621,666
Weighted Average Exercise Price (in dollars per share)	$ 4.52
Weighted Average Expiry Years (in years)	8.3
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	283,332
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 4.47
Weighted Average Expiry Years/Exercisable Options (in years)	7.8
5.51 to 7.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	3,132,753
Weighted Average Exercise Price (in dollars per share)	$ 5.94
Weighted Average Expiry Years (in years)	8.4
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	897,721
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 5.90
Weighted Average Expiry Years/Exercisable Options (in years)	8.2
7.01 to 8.40 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options (in shares)	3,603,496
Weighted Average Exercise Price (in dollars per share)	$ 8.23
Weighted Average Expiry Years (in years)	9.1
Exercisable Options [Abstract]
Number of Exercisable Options (in shares)	143,333
Weighted Average Exercise Price/Exercisable Options (in dollars per share)	$ 7.67
Weighted Average Expiry Years/Exercisable Options (in years)	7.2
Stock Options [Member]
Stock Options [Abstract]
Number of shares of common stock available for issuance initially approved under program ( in shares)	18,000,000
Number of shares of common stock available for issuance (in shares)	23,306,100
Common shares each option permits the holder to purchase (in shares)	1
Vesting period (in years)	3 Y
Term of options, in service (in years)	10 Y
Common shares issued (in shares)	1,695,049
Stock Options exercised (in shares)	1,695,049	2,895,553	1,391,028
Number of Outstanding Options [Roll Forward]
Stock Options, beginning balance (in shares)	10,943,058
Stock Options granted (in shares)	4,215,996
Stock Options exercised (in shares)	(1,695,049)	(2,895,553)	(1,391,028)
Stock Options vested (in shares)	0
Stock Options forfeited (in shares)	(600,003)
Stock Options, ending balance (in shares)	12,864,002	10,943,058
Income (loss) per share [Abstract]
Anti-dilutive securities excluded from the diluted income per share calculations	3,726,999	290,000	1,080,000
Weighted Average Grant-Date Fair Value per share [Abstract]
Weighted average grant date fair value for options granted (in dollars per share)	$ 4.84	$ 3.36	2.43
Weighted average grant date fair value for options vested (in dollars per share)	$ 2.26	$ 1.61	1.38
Fair value of shares vested	$ 6.6	$ 5.1	4.7
Aggregate intrinsic value of options outstanding	14.7	49.9	39.0
Closing stock price (in dollars per share)	$ 4.80	$ 8.05	5.73
Intrinsic value of options exercised	6.2	12.8	2.9
Stock based compensation expense	13.7	8.5	5.6
Stock based compensation - capitalized as part of exploration and development costs	1.0	0.5	0.3
Unrecognized compensation cost	11.7	6.1	5.4
Unvested stock options-expected recognition period (in years)	3
Aggregate intrinsic value of options exercisable	14.2	49.4	19.8
Stock Options [Member] | General and Administrative Expense [Member]
Weighted Average Grant-Date Fair Value per share [Abstract]
Stock based compensation expense	11.4	7.2	4.5
Stock Options [Member] | Other Operating Expense [Member]
Weighted Average Grant-Date Fair Value per share [Abstract]
Stock based compensation expense	1.3	0.8	0.8
Nonvested Stock Options [Member]
Stock Options [Abstract]
Stock Options exercised (in shares)	0
Number of Outstanding Options [Roll Forward]
Stock Options, beginning balance (in shares)	5,516,691
Stock Options granted (in shares)	4,215,996
Stock Options exercised (in shares)	0
Stock Options vested (in shares)	(2,940,822)
Stock Options forfeited (in shares)	(576,669)
Stock Options, ending balance (in shares)	6,215,196
Petrolifera [Member]
Share Capital [Abstract]
Common stock-par value (in dollars per share)	$ 0.001
Warrants [Abstract]
Replacement Warrants issued in business acquisition (in shares)	4,125,036
Gran Tierra Goldstrike Inc [Member]
Share Capital [Abstract]
Outstanding share capital-exchangeable shares (in shares)	7,811,112
Gran Tierra Exchangeco Inc [Member]
Share Capital [Abstract]
Outstanding share capital-exchangeable shares (in shares)	8,512,707
Warrants [Member]
Warrants [Abstract]
Warrants outstanding	6,298,230
Common shares (on exercise of warrants outstanding)	3,149,115
Exercise price per share (in dollars per share)	$ 1.05
Warrants expiration date range start	Jun. 20, 2012
Warrants expiration date range end	Jun. 30, 2012
Common shares issued-exercise of warrants (in shares)	735,817	11,127,527
Warrants exercised (in shares)	1,471,634	15,109,116
Warrants exercised to purchase common shares-assumed on acquisition of Solana (in shares)		7,145,938
Common shares issued on the exercise of warrants-assumed on acquisition of Solana (in shares)		7,145,938
Market price on exercise of warrant acquired through acquisition of Solana		$ 14.4