Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 36,063	$ 30,136
Short-term investments	24,176	35,468
Accounts receivable	18,269	17,076
Inventories	32,503	29,354
Prepaid expenses and other current assets	2,919	3,199
Total Current Assets	113,930	115,233
Long-term investments	22,208	9,136
Property, plant and equipment	174,322	167,080
Less accumulated depreciation and amortization	104,750	100,711
Property plant and equipment net	69,572	66,369
Other assets and deferred charges:
Patents	1,718	1,778
Goodwill	9,730	9,730
Other	1,624	1,534
Prepaid Expense and Other Assets, Noncurrent, Total	13,072	13,042
Total assets	218,782	203,780
Current liabilities:
Accounts payable and accrued liabilities	9,738	8,876
Accrued income and other taxes	593	746
Total Current Liabilities	10,331	9,622
Line of credit
Other non-current liabilities	10,394	9,770
Stockholders' equity:
Common stock, par value $0.10 per share; authorized 10,000 shares, issued 3,420 shares	342	342
Paid-in capital	49,635	48,730
Accumulated other comprehensive loss	0	(1,215)
Retained earnings	279,807	268,194
Treasury shares,1,567 at June 30, 2018 and 1,568 at December 31, 2017, at cost	(131,727)	(131,663)
Total stockholders' equity	198,057	184,388
Total liabilities and stockholders' equity	$ 218,782	$ 203,780