Annual reports filed by certain Canadian issuers pursuant to Section 15(d) and Rule 15d-4

Derivative warrant liabilities - Assumptions used to estimate fair value of derivative warrant liability (Details)

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Derivative warrant liabilities - Assumptions used to estimate fair value of derivative warrant liability (Details)
12 Months Ended
Dec. 31, 2018
USD ($)
year
$ / shares
Dec. 31, 2017
USD ($)
year
$ / shares
Disclosure of classes of share capital [line items]    
Annualized volatility 55.00% 74.00%
Risk-free interest rate 2.04% 1.31%
Life of warrants in years 4 6.6
Expected dividend as percentage, warrants options granted 0.00% 0.00%
February 14, 2014 Warrants | Warrants    
Disclosure of classes of share capital [line items]    
Annualized volatility 45.00% 48.00%
Risk-free interest rate 2.56% 1.76%
Life of warrants in years | year 0.12 1.12
Expected dividend as percentage, warrants options granted 0.00% 0.00%
Market price (in dollars per share) | $ $ 6.82 $ 4.53
Fair value per Warrant (in dollars per share) | $ / shares $ 3.61 $ 1.64
Bought Deal Public Offering | Warrants    
Disclosure of classes of share capital [line items]    
Annualized volatility 55.00% 55.00%
Risk-free interest rate 2.45% 2.08%
Life of warrants in years | year 2.99 3.99
Expected dividend as percentage, warrants options granted 0.00% 0.00%
Market price (in dollars per share) | $ $ 6.82 $ 4.53
Fair value per Warrant (in dollars per share) | $ / shares $ 4.39 $ 2.54