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

Derivative warrant liabilities - Private placement offering narrative (Details)

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Derivative warrant liabilities - Private placement offering narrative (Details) - USD ($)
12 Months Ended
Feb. 14, 2014
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of classes of share capital [line items]        
Proceeds from exercise of derivative warrants   $ 6,989,000 $ 0  
Private Placement Offering Feb 14 2014        
Disclosure of classes of share capital [line items]        
Number of warrants exercised     0  
Warrants        
Disclosure of classes of share capital [line items]        
Number of warrants outstanding   1,691,000 5,261,000 5,261,000
Number of warrants exercised   1,172,000    
Warrants | Private Placement Offering Feb 14 2014        
Disclosure of classes of share capital [line items]        
Net proceeds from commons shared issued $ 52,000,000      
Number of units issued 18,919,404      
Share issuance, price per share (in dollars per share) $ 2.7485      
Private placement, number of shares per Unit 0.25      
Warrant exercise period 5 years      
Exercise price, price per unit (in dollars per share) $ 3.2204 $ 3.2204    
Proceeds from exercise of derivative warrants   $ 1,493,000    
Number of warrants outstanding   0 1,738,000 1,738,000
Number of cashless warrants exercised (in shares)   1,274,000    
Number of warrants exercised   464,000    
Increase (decrease) through exercise of share purchase warrants   $ 5,920,000    
Revaluation of derivative warrant liability   $ 363,000    
Derivative warrant liabilities (note 10)     $ 6,272,000  
Common shares        
Disclosure of classes of share capital [line items]        
Number of shares issued   111,798,000 85,500,000 84,052,000
Common shares | Private Placement Offering Feb 14 2014        
Disclosure of classes of share capital [line items]        
Number of shares issued, warrants exercised, cashless   687,000    
Number of shares issued   464,000    
Common units | Common shares | Private Placement Offering Feb 14 2014        
Disclosure of classes of share capital [line items]        
Private placement, number of shares per Unit 1