Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Cash flows from operating activities:
Net income (loss)	$ 58,293	$ 25,791	$ (18,329)
Net loss from discontinued operations	0	0	35,655
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	18,931	19,406	18,851
Stock-based compensation	30,505	29,137	26,461
Gain/loss on investments, net	6,222	224	861
Deferred income taxes	(9,386)	(1,379)	2,459
Provision for excess and obsolete inventory	7,872	3,878	2,904
Change in fair value of contingent consideration	(2,928)	(25)	0
Other	74	(170)	(745)
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	(59,885)	26,500	(43,055)
Inventories	55,505	4,504	(85,064)
Prepaid expenses and other assets	4,833	(1,654)	(12,114)
Accounts payable	9,744	(56,614)	45,503
Accrued employee compensation	15,718	(11,642)	7,145
Other accrued liabilities	28,194	(16,603)	15,589
Deferred revenue	8,112	(3,354)	5,759
Income taxes payable	9,346	(4,474)	(16,939)
Net cash provided by (used in) continuing operating activities	181,150	13,525	(15,059)
Net cash used in discontinued operating activities	0	0	(88,152)
Net cash provided by (used in) operating activities	181,150	13,525	(103,211)
Cash flows from investing activities:
Purchases of short-term investments	(305)	(1,617)	(81,814)
Proceeds from maturities of short-term investments	290	70,790	137,058
Purchases of property and equipment	(10,296)	(14,230)	(12,251)
Purchases of long-term investments	(6,525)	(5,484)	(1,091)
Proceeds from sale of long-term investments	0	0	624
Payments made in connection with business acquisitions, net of cash acquired	0	0	(14,352)
Net cash provided by (used in) continuing investing activities	(16,836)	49,459	28,174
Net cash used in discontinued investing activities	0	0	(71,363)
Net cash provided by (used in) investing activities	(16,836)	49,459	(43,189)
Cash flows from financing activities:
Repurchases of common stock	(23,800)	(75,946)	(30,000)
Restricted stock unit withholdings	(5,090)	(6,521)	(8,065)
Proceeds from exercise of stock options	16,950	5,027	6,841
Proceeds from issuance of common stock under employee stock purchase plan	3,878	3,617	5,554
Net cash used in continuing financing activities	(8,062)	(73,823)	(25,670)
Net cash provided by discontinued financing activities	0	0	170,247
Net cash provided by (used in) financing activities	(8,062)	(73,823)	144,577
Net increase (decrease) in cash and cash equivalents	156,252	(10,839)	(1,823)
Cash and cash equivalents, at beginning of period	190,208	201,047	202,870
Cash and cash equivalents, at end of period	346,460	190,208	201,047
Supplemental Cash Flow Information:
Cash paid for income taxes	8,218	8,876	23,220
Non-cash investing and financing activities:
Change in accounts payable and other accrued liabilities relating to property and equipment additions	846	(4,360)	2,604
Fair value of contingent consideration in connection with business acquisition in other accrued liabilities	$ 0	$ 0	$ 5,953