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Management of Financial Risk (Disclosure of Nature and Extent Arising from Financial Instruments - Commodity Price Risk) (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
USD ($)
$ / T
Dec. 31, 2019
USD ($)
Feb. 11, 2021
$ / T
Dec. 31, 2020
$ / gal
Dec. 31, 2020
Dec. 31, 2020
USD ($)
Entering in to Derivative Contract [Member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate quantity of zero cost collars     6,237      
Floor Price | $ / T     2,000      
Cap Price | $ / T     2,125      
Silver Commodity Type [member] | Commodity price risk [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Effect on Sales $ 1,338          
Change percentage, commodity (10.00%)          
Gold Commodity Type [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Increase (decrease) in sales due to price changes of commodity $ 3,307 $ 368        
Gold Commodity Type [member] | Commodity price risk [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Effect on Sales $ 561          
Change percentage, commodity (10.00%)          
Lead Commodity [member] | Commodity price risk [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Effect on Sales $ 195          
Change percentage, commodity (10.00%)          
Zinc Commodity [member] | Entering in to Derivative Contract [Member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate quantity of zero cost collars         12,300  
Floor Price | $ / T 2,600          
Cap Price | $ / T 2,900          
Zinc Commodity [member] | Commodity price risk [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Effect on Sales $ 253          
Change percentage, commodity (10.00%)          
Heating Oil Commodity [Member] | Entering in to Derivative Contract [Member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate quantity of zero cost collars         720,000  
Floor Price | $ / gal       1.40    
Cap Price | $ / gal       1.6150    
Heating Oil Commodity [Member] | Entering in to Derivative Contract [Member] | Swap contract [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate forward- swap       1.52 720,000  
Jet Fuel Commodity [Member] | Entering in to Derivative Contract [Member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate quantity of zero cost collars         1,680,000  
Floor Price | $ / gal       1.30    
Cap Price | $ / gal       1.4775    
Jet Fuel Commodity [Member] | Entering in to Derivative Contract [Member] | Swap contract [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Aggregate forward- swap       1.438 1,680,000  
Non-Revolving Credit Facility [Member] | Interest rate risk [member]            
Disclosure of nature and extent of risks arising from financial instruments [line items]            
Borrowing capacity           $ 40,000