Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating Activities
Net income	$ 25,147	$ 19,529
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	6,346	5,599
Amortization of bond premiums	151	106
Provision for losses on accounts receivable, net of adjustments	(42)	(102)
Provision for excess and obsolete inventories	308	59
Share-based compensation	2,043	1,281
Excess tax benefits from stock options exercised and restricted stock awards vested	(1,129)	(2,452)
Gain on disposal of assets	(20)	(25)
Foreign currency transaction (gain) loss	(48)	53
Interest income on note receivable	(14)	(16)
Deferred income taxes	(1,851)	(563)
Changes in assets and liabilities:
Accounts receivable	(8,417)	(1,286)
Income taxes	5,162	1,636
Inventories	(1,934)	(9,623)
Prepaid expenses and other	(550)	(446)
Accounts payable	1,848	(1,030)
Deferred revenue	220	136
Accrued liabilities and donations	1,252	(867)
Net cash provided by operating activities	28,472	11,989
Investing Activities
Capital expenditures	(15,825)	(9,304)
Proceeds from sale of property, plant and equipment	1	30
Payments to Acquire Other Investments	4,112	0
Maturities of certificates of deposits	6,000	4,658
Payments to Acquire Held-to-maturity Securities	9,782	0
Maturities of investments	3,801	9,201
Proceeds from called investments	1,010	504
Principal payments from note receivable	26	28
Net cash (used in) provided by investing activities	(18,881)	5,117
Financing Activities
Proceeds from Lines of Credit	761	0
Repayments of Lines of Credit	761	0
Stock options exercised	1,255	2,534
Excess tax benefits from stock options exercised and restricted stock awards vested	1,129	2,452
Repurchase of stock	(7,674)	(6,444)
Net cash used in financing activities	(5,290)	(1,458)
Net increase in cash and cash equivalents	4,301	15,648
Cash and cash equivalents, beginning of period	7,908	21,952
Cash and cash equivalents, end of period	$ 12,209	$ 37,600