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FINANCIAL INSTRUMENTS - Concentration of credit risk (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of detailed information about financial instruments [line items]      
Percentage of entity's revenue 86.30%    
Concentration risk, percentage 26.10% 32.00% 28.90%
United States of America      
Disclosure of detailed information about financial instruments [line items]      
Percentage of entity's revenue 73.30%    
One Customer      
Disclosure of detailed information about financial instruments [line items]      
Percentage of entity's revenue 11.20% 11.30% 10.20%