ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Third-party customers	$ 197,166	$ 203,068
Less: allowance for bad debts and credit notes	(8,548)	(9,697)
Total accounts receivable	188,618	193,371
Accounts Receivable, Credit Loss Expense (Reversal)	$ (2,500)	$ 800	$ 1,900