FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair value measurements
Available for sale securities	$ 171,596	$ 164,183
Trading securities	60,520	67,995
Fair value measured on a recurring basis
Fair value measurements
Cash and cash equivalents	96,314	119,145
Available for sale securities	171,596	164,183
Trading securities	60,520	67,995
Total assets measured at fair value	328,541	352,950
Fair value measured on a recurring basis \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	79	(119)
Fair value measured on a recurring basis \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	32	1,746
Fair value measured on a recurring basis \| Level 1
Fair value measurements
Cash and cash equivalents	96,314	119,145
Available for sale securities	1,200	2,419
Trading securities	60,520	67,995
Total assets measured at fair value	158,066	191,305
Fair value measured on a recurring basis \| Level 1 \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	32	1,746
Fair value measured on a recurring basis \| Level 2
Fair value measurements
Available for sale securities	170,396	161,764
Total assets measured at fair value	170,475	161,645
Fair value measured on a recurring basis \| Level 2 \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	$ 79	$ (119)

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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