FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair value measurements
Cash and cash equivalents	$ 110,899	$ 96,314
Available for sale securities	183,289	171,596
Trading securities	62,260	60,520
Fair value measured on a recurring basis
Fair value measurements
Cash and cash equivalents	110,899	96,314
Available for sale securities	183,289	171,596
Trading securities	62,260	60,520
Total assets measured at fair value	355,454	328,541
Fair value measured on a recurring basis \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	(407)	79
Fair value measured on a recurring basis \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	(587)	32
Fair value measured on a recurring basis \| Level 1
Fair value measurements
Cash and cash equivalents	110,899	96,314
Available for sale securities	3,000	1,200
Trading securities	62,260	60,520
Total assets measured at fair value	175,572	158,066
Fair value measured on a recurring basis \| Level 1 \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	(587)	32
Fair value measured on a recurring basis \| Level 2
Fair value measurements
Available for sale securities	180,289	170,396
Total assets measured at fair value	179,882	170,475
Fair value measured on a recurring basis \| Level 2 \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	$ (407)	$ 79

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

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