FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair value measurements
Cash and cash equivalents	$ 138,960	$ 110,899
Available for sale securities	177,292	183,289
Trading securities	76,183	62,260
Fair value measured on a recurring basis
Fair value measurements
Cash and cash equivalents	138,960	110,899
Available for sale securities	177,292	183,289
Trading securities	76,183	62,260
Total assets measured at fair value	392,570	355,454
Fair value measured on a recurring basis \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	14	(407)
Fair value measured on a recurring basis \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	121	(587)
Fair value measured on a recurring basis \| Level 1
Fair value measurements
Cash and cash equivalents	138,960	110,899
Available for sale securities	3,588	3,007
Trading securities	48,260	36,753
Total assets measured at fair value	190,929	150,072
Fair value measured on a recurring basis \| Level 1 \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	121	(587)
Fair value measured on a recurring basis \| Level 2
Fair value measurements
Available for sale securities	173,704	180,282
Trading securities	27,923	25,507
Total assets measured at fair value	201,641	205,382
Fair value measured on a recurring basis \| Level 2 \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	$ 14	$ (407)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fair value of asset after deduction of liability.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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