Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net income	$ 92,674	$ 86,874
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	33,764	36,287
Amortization of premium (discount) on marketable securities	3,208	1,131
Write-down for excess and obsolete inventories, net	4,068	5,000
Stock-based compensation expense	15,989	15,330
Allowance for doubtful accounts	(528)	590
Change in fair value of business acquisition liabilities	(1,390)	14,128
Change in deferred income taxes	(7,939)	(1,783)
(Gain)/loss on disposal of assets, net	200	191
Payment of business acquisition related liabilities	(1,099)
(Increase)/decrease in:
Accounts receivable	(30,224)	(25,587)
Inventories	(31,421)	(6,024)
Prepaid expenses and other assets	1,268	845
Increase/(decrease) in:
Accounts payable	12,375	2,737
Accrued expenses and other liabilities	(7,408)	3,559
Income taxes payable/receivable	(1,964)	(10,519)
Net cash provided by/(used in) operating activities	81,573	122,759
Cash flows from investing activities:
Purchases of marketable securities	(179,096)	(293,092)
Maturities of marketable securities	170,572	131,739
Sales of marketable securities	66,655	58,154
Purchases of property and equipment	(43,724)	(22,058)
Acquisition of businesses, net of cash acquired and purchases of intangible and other assets	(1,175)
Net cash provided by/(used in) investing activities	13,232	(125,257)
Cash flows from financing activities:
Payment of business acquisition liabilities	(3,553)	(3,105)
Proceeds from exercise of stock options	11,331	35,597
Repurchase of common stock	(144,493)
Net cash provided by/(used in) financing activities	(136,715)	32,492
Effect of foreign exchange rates on cash	(387)	(608)
Net increase/(decrease) in cash and cash equivalents	(42,297)	29,386
Cash and cash equivalents at beginning of period	193,069	239,397
Cash and cash equivalents at end of period	150,772	268,783
Supplemental disclosures of cash flow information:
Income taxes paid	36,696	31,597
Purchases of property and equipment included in accounts payable and accrued expenses	$ 5,019	$ 3,537