ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Third-party customers	$ 168,805	$ 149,957
Less: allowance for bad debts and credit notes	(9,902)	(8,586)
Total accounts receivable	158,903	141,371
Provision for Doubtful Accounts	$ 1,900	$ 3,700	$ 2,300