CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 279,881	$ 176,186	$ 203,865
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	43,774	42,661	45,589
Depreciation of property, plant, and equipment	16,616	22,139	21,527
Gain (Loss) on Disposition of Property Plant Equipment	33	1,817	324
Amortization of intangible assets	3,667	4,364	3,373
Intangible asset impairment charges	0	19,571	0
Excess and Obsolete Inventory Charges	2,573	9,908	5,296
Operating Lease, Impairment Loss	0	3,427	0
Amortization of discounts or premiums on investments	4,887	1,274	(618)
Realized gain on sale of investments	(236)	(4,119)	(1,452)
Revaluation of contingent consideration	0	(114)	(1,401)
Change in deferred income taxes	(3,118)	(3,353)	(94,866)
Accounts receivable	(4,503)	(21,285)	16,807
Unbilled revenue	1,637	(848)	3,530
Inventories	(54,920)	(10,319)	17,841
Prepaid expenses and other current assets	(32,342)	(9,909)	7,405
Accounts payable	27,828	(1,688)	1,633
Accrued expenses	16,861	24,542	(8,938)
Accrued income taxes	(6,401)	(22,973)	25,266
Deferred revenue and customer deposits	14,417	6,571	3,875
Other	3,411	4,548	4,255
Net cash provided by operating activities	314,065	242,400	253,311
Cash flows from investing activities:
Purchases of investments	(668,053)	(922,867)	(1,031,642)
Maturities and sales of investments	430,969	1,104,605	1,062,962
Purchases of property, plant, and equipment	(15,455)	(13,303)	(21,745)
Business acquisitions	0	1,004	(166,911)
Net cash provided by (used in) investing activities	(252,539)	169,439	(157,336)
Cash flows from financing activities:
Net proceeds from issuance of common stock under stock plans	63,292	125,715	64,581
Repurchase of common stock	(161,652)	(51,036)	(61,690)
Payment of dividends	(43,263)	(390,508)	(35,124)
Payment of Chiaro contingent consideration	0	(1,039)	0
Net cash used in financing activities	(141,623)	(316,868)	(32,233)
Effect of foreign exchange rate changes on cash and cash equivalents	(2,815)	2,671	(523)
Net change in cash and cash equivalents	(82,912)	97,642	63,219
Cash and cash equivalents at beginning of year	269,073	171,431	108,212
Cash and cash equivalents at end of year	$ 186,161	$ 269,073	$ 171,431