Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 44,294	$ 39,403
Adjustments to reconcile net income to cash flows:
Depreciation and amortization	17,717	16,320
Non-cash deferred revenue	(2,972)	(12,232)
Increase in inventory reserve	5,950	3,561
Stock based compensation	5,189	3,837
Deferred income tax provision	7,838	9,162
Other	265	(139)
Changes in assets and liabilities:
Trade receivables	44,213	38,102
Inventories	(40,088)	(52,542)
Prepaid expenses and other current assets	(2,144)	(569)
Accounts payable and other current liabilities	(11,462)	13,842
Deferred revenue and advance payments	39,363	25,340
Other non-current assets and liabilities	(2,764)	(2,978)
Discontinued operations:
Non-current liabilities	6,748
Net cash used in discontinued operations	(312)	(1,062)
Net cash provided by operating activities	111,835	80,045
Cash flows from investing activities:
Capital expenditures	(37,706)	(39,706)
Proceeds from sale of assets	13	2,282
Other		(56)
Net cash used in investing activities	(37,693)	(37,480)
Cash flows from financing activities:
Repayment of debt	(30,000)	(30,000)
Proceeds from stock options exercised	2,116	2,959
Debt issuance costs	(2,515)
Other	2,958	861
Net cash used in financing activities	(27,441)	(26,180)
Effect of exchange rate changes on cash and cash equivalents	61	(1,721)
Net increase in cash and cash equivalents	46,762	14,664
Cash and cash equivalents at beginning of period	43,974	45,518
Cash and cash equivalents at end of period	$ 90,736	$ 60,182