Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net income	$ 38,084	$ 45,329
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,837	17,157
Amortization of premium (discount) on marketable securities	1,690	520
Write-down for excess and obsolete inventories, net	1,834	1,550
Stock-based compensation expense	8,152	7,698
Allowance for doubtful accounts	(728)	80
Change in fair value of business acquisition liabilities	(263)	258
Change in deferred income taxes	(2,994)	(808)
(Gain)/loss on disposal of assets, net	115	103
Payment of business acquisition related liabilities	(743)
(Increase)/decrease in:
Accounts receivable	(1,614)	(20,346)
Inventories	(17,939)	(3,997)
Prepaid expenses and other assets	547	4,516
Increase/(decrease) in:
Accounts payable	4,160	4,212
Accrued expenses and other liabilities	(15,428)	(4,783)
Income taxes payable/receivable	12,980	12,081
Net cash provided by/(used in) operating activities	44,690	63,570
Cash flows from investing activities:
Purchases of marketable securities	(142,145)	(185,110)
Maturities of marketable securities	106,549	39,850
Sales of marketable securities	42,673	33,818
Purchases of property and equipment	(19,971)	(13,672)
Acquisition of businesses, net of cash acquired, and purchases of intangible and other assets	(1,000)
Net cash provided by/(used in) investing activities	(13,894)	(125,114)
Cash flows from financing activities:
Payment of business acquisition liabilities	(1,699)	(1,537)
Proceeds from exercise of stock options	7,746	9,101
Net cash provided by/(used in) financing activities	6,047	7,564
Effect of foreign exchange rates on cash	(123)	(569)
Net increase in cash and cash equivalents	36,720	(54,549)
Cash and cash equivalents at beginning of period	193,069	239,397
Cash and cash equivalents at end of period	229,789	184,848
Supplemental disclosures of cash flow information:
Income taxes paid	572	570
Purchases of property and equipment included in accounts payable and accrued expenses	$ 4,105	$ 2,620