Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 92,418	$ 102,450	$ 81,678
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	37,857	31,848	24,665
Non-cash deferred revenue	(1,709)	(4,887)	(25,822)
Restructuring expenses			1,138
Unrealized gain on investment in equity securities	(13,023)
Increase in inventory reserve	6,967	4,892	7,885
Stock based compensation	4,094	8,914	7,766
Deferred income tax provision	(2,057)	7,186	8,556
Toll tax	(2,105)	2,105
Other	134	581	160
Changes in assets and liabilities:
Trade receivables	(62,183)	40,651	(5,120)
Contract assets	20,916
Inventories	(7,658)	(13,283)	(23,679)
Prepaid expenses and other current assets	14,927	(8,123)	(729)
Accounts payable and other current liabilities	(2,307)	(20,114)	12,056
Deferred revenue and advance payments	3,238	985	41,962
Other non-current assets and liabilities	(2,666)	(5,608)	(3,961)
Discontinued operations:
Non-current liabilities	1,055	2,858	7,517
Net cash used in discontinued operations	(916)	(1,440)	(516)
Net cash provided by operating activities	86,982	149,015	133,556
Cash flows from investing activities:
Capital expenditures	(62,598)	(52,143)	(49,714)
Proceeds from sale of assets			13
Proceeds from sale of business		2,836
Acquisition of business and equity investment, net of cash acquired	(424,244)		(24,275)
Net cash used in investing activities	(486,842)	(49,307)	(73,976)
Cash flows from financing activities:
Borrowings	325,000
Repayments	(25,000)		(30,000)
Proceeds from stock options exercised	14,041	4,781	4,941
Debt issuance costs			(2,515)
Net cash provided by/(used in) financing activities	314,041	4,781	(27,574)
Effect of exchange rate changes on cash and cash equivalents	(1,613)	4,654	(1,839)
Net (decrease)/increase in cash and cash equivalents	(87,432)	109,143	30,167
Cash and cash equivalents at beginning of year	183,284	74,141	43,974
Cash and cash equivalents at end of year	95,852	183,284	74,141
Supplemental disclosure:
Interest paid, net of capitalized interest	4,923	1,270	425
Income taxes paid, net of refunds received	$ 15,671	$ 45,744	$ 18,210