Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net income	$ 10,806	$ 8,399
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	3,171	2,804
Amortization of bond premiums	83	61
Provision for losses on accounts receivable, net of adjustments	123	(59)
Provision for excess and obsolete inventories	137	41
Share-based compensation	948	438
Excess tax benefits from stock options exercised and restricted stock awards vested	(745)	(1,098)
(Gain) loss on disposal of assets	(8)	5
Foreign currency transaction (gain) loss	(48)	70
Interest income on note receivable	(7)	(8)
Deferred income taxes	(1,030)	(443)
Changes in assets and liabilities:
Accounts receivable	7,900	4,286
Income taxes	6,734	1,286
Inventories	(4,117)	(6,969)
Prepaid expenses and other	(1,950)	(301)
Accounts payable	(3,129)	(1,316)
Deferred revenue	110	64
Accrued liabilities and donations	(3,730)	(2,925)
Net cash provided by operating activities	15,248	4,335
Investing Activities
Capital expenditures	(7,332)	(3,587)
Proceeds from sale of property, plant and equipment	8	0
Maturities of certificates of deposits	1,200	2,638
Maturities of investments	1,700	8,445
Proceeds from called investments	505	504
Principal payments from note receivable	13	14
Net cash (used in) provided by investing activities	(3,906)	8,014
Financing Activities
Stock options exercised	709	1,082
Excess tax benefits from stock options exercised and restricted stock awards vested	745	1,098
Repurchase of stock	(3,456)	(2,955)
Net cash used in financing activities	(2,002)	(775)
Net increase in cash and cash equivalents	9,340	11,574
Cash and cash equivalents, beginning of period	7,908	21,952
Cash and cash equivalents, end of period	$ 17,248	$ 33,526