FINANCIAL INSTRUMENTS - Quantitative Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial Instruments
Fair value of derivative - current assets	$ 70
Fair value of derivative - noncurrent assets	6,020	$ 19,585
Fair value of derivative - current liabilities	(852)	(1,552)
Derivatives designated as hedging instruments \| Interest rate swap
Financial Instruments
Fair value of derivative - current assets	70
Fair value of derivative - noncurrent assets	6,020	19,585
Fair value of derivative - current liabilities	(852)	(1,552)
Total derivatives designated as hedging instruments, net	$ 5,238	$ 18,033

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