Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net income	$ 4,260	$ 10,217
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	4,129	3,638
Amortization of bond premiums	5	16
Provision for losses on accounts receivable, net of adjustments	(11)	184
Provision for excess and obsolete inventories	101	60
Share-based compensation	1,724	1,645
(Gain) loss on disposal of assets	(7)	(1)
Foreign currency transaction gain	3	(5)
Interest income on note receivable	9	(7)
Deferred	420	720
Changes in assets and liabilities:
Accounts receivable	(2,897)	(1,560)
Income taxes	(5,673)	3,230
Inventories	3,447	(8,696)
Prepaid expenses and other	(712)	(313)
Accounts payable	9,833	1,736
Deferred revenue	37	78
Accrued liabilities and donations	(3,924)	(776)
Net cash provided by operating activities	10,744	10,166
Investing Activities
Capital expenditures	(8,451)	(6,071)
Cash paid in business combination	(6,000)	0
Proceeds from sale of property, plant and equipment	6	7
Investment in certificates of deposits	(4,320)	0
Maturities of certificates of deposits	1,200	2,392
Purchases of investments held to maturity	(7,495)	0
Maturities of investments	4,230	6,928
Proceeds from called investments	395	0
Principal payments from note receivable	14	13
Net cash (used in) provided by investing activities	(20,421)	3,269
Financing Activities
Stock options exercised	1,340	898
Repurchase of stock	(4,379)	(6,303)
Employee taxes paid by withholding shares	(568)	(560)
Net cash used in financing activities	(3,607)	(5,965)
Net (decrease) increase in cash and cash equivalents	(13,284)	7,470
Cash and cash equivalents, beginning of period	21,457	24,153
Cash and cash equivalents, end of period	$ 8,173	$ 31,623