CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ (43,609)	$ (90,419)	$ (157,957)
Adjustments to reconcile net loss to net cash provided by operating activities:
Stock-based compensation	25,778	26,476	21,736
Depreciation expense and amortization of operating leases' right of use assets	28,951	23,507	10,745
Amortization of intangible assets	18,413	17,058	29,341
Non-cash interest expense and amortization of convertible debt issuance costs	7,243	6,854	9,243
Deferred income taxes	685	(1,816)	79,954
Non-cash restructuring	0	0	670
Loss on divestiture	0	7,439	0
Loss on equity investment	747	696	67
Gain from sale of marketable equity security	0	0	(291)
Gain from sale of assets held for sale	0	0	(1,266)
(Gain) loss from disposal of property, plant and equipment	(77)	157	395
Change in fair value of earn-out liability	(1,800)	0	0
Change in operating assets and liabilities, net of effects of acquisitions and divestiture:
Accounts receivable	16,136	4,994	(24,933)
Unbilled receivables	160,116	151,513	145,164
Prepaid expenses and other assets	2,042	4,064	(4,084)
Inventories	(4,380)	(3,353)	(1,856)
Accounts payable	(2,176)	2,934	(2,268)
Accrued salaries and benefits and other liabilities	3,353	7,135	(3,221)
Income taxes payable	(17,852)	(15,925)	(14,550)
Deferred revenue	(1,486)	(3,497)	228
Operating lease liabilities	(6,625)	(9,282)	0
Net cash provided by operating activities	185,459	128,535	87,117
Cash flows from investing activities:
Purchases of property, plant and equipment	(29,728)	(6,472)	(10,762)
Acquisition of intangible assets	0	0	350
Purchases of marketable securities	(898,957)	(657,433)	(282,117)
Maturities of marketable securities	817,834	507,385	223,079
Proceeds from sale of marketable securities	21,588	6,758	0
Proceeds from divestiture, net of cash disposed	0	76,039	0
Proceeds from sale of assets held for sale	0	0	3,754
Proceeds from sale of property and property, plant and equipment	0	29	10
Settlement of working capital adjustment from disposal of business	(1,131)	0	0
Proceeds from sale of equity security	0	0	1,350
Investment in privately-held companies	0	(1,000)	(3,000)
Acquisition of businesses, net of cash acquired	0	(66,780)	0
Net cash used in investing activities	(90,394)	(141,474)	(68,036)
Cash flows from financing activities:
Repayment of senior convertible notes	0	0	(81,207)
Proceeds received from issuance of common stock under employee stock plans	11,487	15,104	11,402
Payments under Installment	(13,201)	(8,379)	0
Principal payments against financing lease obligation	0	0	(1,080)
Repurchase and retirement of common stock, including prepayment under accelerated share repurchase program	(50,069)	0	(50,033)
Payments Related to Tax Withholding for Share-based Compensation	(9,403)	(7,023)	(6,766)
Net cash used in financing activities	(61,186)	(298)	(127,684)
Effect of exchange rate changes on cash and cash equivalents	106	(497)	(989)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	33,985	(13,734)	(109,592)
Cash, cash equivalents and restricted cash at beginning of year	102,518	116,252	225,844
Cash, cash equivalents and restricted cash at end of year	136,503	102,518	116,252
Cash paid during the period for:
Interest	2,372	2,372	3,044
Income taxes, net of refunds	21,312	17,835	23,581
Non-cash investing and financing activities:
Property, plant and equipment received and accrued in accounts payable and other accrued liabilities	$ 20,952	$ 29,844	$ 8,225