Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Fair value measurements
Cash and cash equivalents	$ 46,628	$ 105,840	$ 96,617
Fair value measured on a recurring basis
Fair value measurements
Cash and cash equivalents	46,628	105,840	96,617
Available for sale securities	262,057	241,407	223,410
Trading securities	72,480	89,736	83,867
Total assets measured at fair value	381,430	437,533	405,365
Fair value measured on a recurring basis \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	165	426	717
Fair value measured on a recurring basis \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	100	124	754
Fair value measured on a recurring basis \| Level 1
Fair value measurements
Cash and cash equivalents	46,628	105,840	96,617
Available for sale securities	748	1,282	2,616
Trading securities	56,964	76,196	70,879
Total assets measured at fair value	104,440	183,442	170,866
Fair value measured on a recurring basis \| Level 1 \| Commodity futures contracts
Fair value measurements
Derivative instruments, net	100	124	754
Fair value measured on a recurring basis \| Level 2
Fair value measurements
Available for sale securities	261,309	240,125	220,794
Trading securities	15,516	13,540	12,988
Total assets measured at fair value	276,990	254,091	234,499
Fair value measured on a recurring basis \| Level 2 \| Foreign currency forward contracts
Fair value measurements
Derivative instruments, net	$ 165	$ 426	$ 717

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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