Consolidated Statements Of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Cash flows from operating activities:
Net income (loss)	$ (18,329)	$ 19,436	$ 75,851
Net (income) loss from discontinued operations	35,655	(30,569)	(5,539)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	18,851	22,529	29,932
Purchase premium amortization/discount accretion on investments, net	(745)	46	167
Stock-based compensation	26,461	18,969	17,141
Income tax impact associated with stock option exercises	0	0	2,160
Gains /charges related to long-term investments	861	0	0
Deferred income taxes	2,459	21,119	869
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	(43,055)	(23,121)	23,132
Inventories	(82,160)	37,202	(12,648)
Prepaid expenses and other assets	(12,114)	4,604	8,691
Accounts payable	45,503	(432)	9,816
Accrued employee compensation	7,145	(5,278)	3,701
Other accrued liabilities	15,589	15,109	(17,766)
Deferred revenue	5,759	2,440	(4,560)
Income taxes payable	(16,939)	18,293	3,870
Net cash provided by (used in) continuing operating activities	(15,059)	100,347	134,817
Net cash used in discontinued operating activities	(88,152)	(12,823)	(16,636)
Net cash provided by (used in) operating activities	(103,211)	87,524	118,181
Cash flows from investing activities:
Purchases of short-term investments	(81,814)	(136,556)	(144,271)
Proceeds from maturities of short-term investments	137,058	135,549	115,291
Purchases of property and equipment	(12,251)	(10,140)	(10,231)
Purchases of long-term investments	(1,091)	(4,400)	0
Proceeds from sale of long-term investments	624	0	0
Payments made in connection with business acquisitions, net of cash acquired	(14,352)	0	0
Net cash provided by (used in) continuing investing activities	28,174	(15,547)	(39,211)
Net cash used in discontinued investing activities	(71,363)	(4,271)	(9,548)
Net cash used in investing activities	(43,189)	(19,818)	(48,759)
Cash flows from financing activities:
Repurchases of common stock	(30,000)	(113,161)	(38,252)
Restricted stock unit withholdings	(8,065)	(6,415)	(4,686)
Proceeds from exercise of stock options	6,841	9,508	28,147
Proceeds from issuance of common stock under employee stock purchase plan	5,554	4,764	3,892
Net cash used in continuing financing activities	(25,670)	(105,304)	(10,899)
Net cash provided by discontinued financing activities	170,247	0	0
Net cash provided by (used in) financing activities	144,577	(105,304)	(10,899)
Net increase (decrease) in cash and cash equivalents	(1,823)	(37,598)	58,523
Cash and cash equivalents, at beginning of year	202,870	240,468	181,945
Cash and cash equivalents, at end of year		202,870	240,468
Cash and cash equivalents, at end of year	201,047	202,727
Cash paid for income taxes	23,220	32,090	35,149
Non-cash Investing And Financing Activities [Abstract]
Additions to property and equipment included in accounts payable and other accrued liabilities	2,604	638	744
Estimated fair value of contingent consideration in connection with business acquisition in other accrued liabilities	$ 5,953	$ 0	$ 0