Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net income	$ 10,217	$ 11,551
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	3,638	3,171
Amortization of bond premiums	16	83
Provision for losses on accounts receivable, net of adjustments	184	123
Provision for excess and obsolete inventories	60	137
Share-based compensation	1,645	948
Gain on disposal of assets	(1)	(8)
Foreign currency transaction gain	(5)	(48)
Interest income on note receivable	(7)	(7)
Deferred	720	(1,030)
Changes in assets and liabilities:
Accounts receivable	(1,560)	7,900
Income taxes	3,230	5,989
Inventories	(8,696)	(4,117)
Prepaid expenses and other	(313)	(1,950)
Accounts payable	1,736	(3,129)
Deferred revenue	78	110
Accrued liabilities and donations	(776)	(3,730)
Net cash provided by operating activities	10,166	15,993
Investing Activities
Capital expenditures	(6,071)	(7,332)
Proceeds from sale of property, plant and equipment	7	8
Maturities of certificates of deposits	2,392	1,200
Maturities of investments	6,928	1,700
Proceeds from called investments	0	505
Principal payments from note receivable	13	13
Net cash provided by (used in) investing activities	3,269	(3,906)
Financing Activities
Stock options exercised	898	709
Repurchase of stock	(6,303)	(3,276)
Employee taxes paid by withholding shares	(560)	(180)
Net cash used in financing activities	(5,965)	(2,747)
Net increase in cash and cash equivalents	7,470	9,340
Cash and cash equivalents, beginning of period	24,153	7,908
Cash and cash equivalents, end of period	$ 31,623	$ 17,248