CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 210,061	$ 184,213	$ 133,372
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	24,815	19,968	15,217
Amortization of intangibles	17,459	21,994	21,969
Amortization of premium and discount on investments, net	(6,461)	(373)	(4,960)
Impairment of minority investments	6,962	0	0
Stock-based compensation to employees	28,380	34,871	26,631
Stock-based compensation to Board of Directors and Scientific Advisory Board	1,566	1,404	1,647
Deferred income tax (benefit) expense	(26,946)	1,748	(4,446)
Retirement plan expense	5,276	8,875	5,656
Decrease (increase) in assets:
Accounts receivable	14,975	(25,378)	(21,809)
Inventory	(49,060)	(42,569)	(27,638)
Other current assets	(24,843)	(202)	1,200
Other assets	25,971	(32,369)	(17,251)
Increase (decrease) in liabilities:
Accounts payable and accrued expenses	3,338	1,902	(8,305)
Other current liabilities	20,917	2,105	2,683
Deferred revenue	(93,203)	(5,220)	17,439
Other liabilities	(32,392)	20,136	7,387
Net cash provided by operating activities	126,815	191,105	148,792
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(42,497)	(43,161)	(27,991)
Purchase of intangibles	(4,709)	(394)	(60)
Purchases of investments	(701,993)	(642,180)	(604,153)
Proceeds from sale and maturity of investments	468,456	227,984	1,023,460
Net cash (used in) provided by investing activities	(280,743)	(457,751)	391,256
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	1,570	1,507	1,176
Payment of withholding taxes related to stock-based compensation to employees	(9,209)	(14,949)	(14,394)
Cash dividends paid	(56,996)	(37,931)	(28,445)
Net cash used in financing activities	(64,635)	(51,373)	(41,663)
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(218,563)	(318,019)	498,385
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	311,993	630,012	131,627
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 93,430	$ 311,993	$ 630,012