Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Cash flows from operating activities:
Net income (loss)	$ 25,791	$ (18,329)	$ 19,436
Net (income) loss from discontinued operations	0	35,655	(30,569)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	19,406	18,851	22,529
Stock-based compensation	29,137	26,461	18,969
Deferred income taxes	(1,379)	2,459	21,119
Provision for excess and obsolete inventory	3,878	2,904	2,866
Other	29	116	46
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	26,500	(43,055)	(23,121)
Inventories	4,504	(85,064)	34,336
Prepaid expenses and other assets	(1,654)	(12,114)	4,604
Accounts payable	(56,614)	45,503	(432)
Accrued employee compensation	(11,642)	7,145	(5,278)
Other accrued liabilities	(16,603)	15,589	15,109
Deferred revenue	(3,354)	5,759	2,440
Income taxes payable	(4,474)	(16,939)	18,293
Net cash provided by (used in) continuing operating activities	13,525	(15,059)	100,347
Net cash used in discontinued operating activities	0	(88,152)	(12,823)
Net cash provided by (used in) operating activities	13,525	(103,211)	87,524
Cash flows from investing activities:
Purchases of short-term investments	(1,617)	(81,814)	(136,556)
Proceeds from maturities of short-term investments	70,790	137,058	135,549
Purchases of property and equipment	(14,230)	(12,251)	(10,140)
Purchases of long-term investments	(5,484)	(1,091)	(4,400)
Proceeds from sale of long-term investments	0	624	0
Payments made in connection with business acquisitions, net of cash acquired	0	(14,352)	0
Net cash provided by (used in) continuing investing activities	49,459	28,174	(15,547)
Net cash used in discontinued investing activities	0	(71,363)	(4,271)
Net cash provided by (used in) investing activities	49,459	(43,189)	(19,818)
Cash flows from financing activities:
Repurchases of common stock	(75,946)	(30,000)	(113,161)
Restricted stock unit withholdings	(6,521)	(8,065)	(6,415)
Proceeds from exercise of stock options	5,027	6,841	9,508
Proceeds from issuance of common stock under employee stock purchase plan	3,617	5,554	4,764
Net cash used in continuing financing activities	(73,823)	(25,670)	(105,304)
Net cash provided by discontinued financing activities	0	170,247	0
Net cash provided by (used in) financing activities	(73,823)	144,577	(105,304)
Net decrease in cash and cash equivalents	(10,839)	(1,823)	(37,598)
Cash and cash equivalents, at beginning of period	201,047	202,870	240,468
Cash and cash equivalents, at end of period	190,208	201,047	202,870
Supplemental Cash Flow Information:
Cash paid for income taxes	8,876	23,220	32,090
Non-cash investing and financing activities:
Change in accounts payable and other accrued liabilities relating to property and equipment additions	(4,360)	2,604	638
Fair value of contingent consideration in connection with business acquisition in other accrued liabilities	$ 0	$ 5,953	$ 0