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FINANCIAL INSTRUMENTS (Details 3) - customer
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Credit Risk    
Number of major customers 3 3
Accounts receivable | Credit risk | Major customer one    
Credit Risk    
Concentration risk (as a percent) 35.00% 36.00%
Accounts receivable | Credit risk | Major customer two    
Credit Risk    
Concentration risk (as a percent) 30.00% 29.00%
Accounts receivable | Credit risk | Major customer three    
Credit Risk    
Concentration risk (as a percent) 27.00% 25.00%