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Decommissioning provision (Tables)
 12 Months Ended
Dec. 31, 2017
Disclosure of other provisions [abstract]  
Schedule of Changes in Decommissioning Provision
 
  
December 31,
    
December 31,
  
 
  
2017
    
2016
  
 
            
Provisions, beginning of year
  
$
3,829
    
$
4,568
  
Decommissioning costs and change in estimates
    
(66
)
    
(891
)
Accretion on decommissioning provision
    
185
      
152
  
Provisions, end of year
  
$
3,948
    
$
3,829