CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 39,839	$ 49,970
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	6,496	5,627
Amortization of intangibles	2,891	5,498
Amortization of premium and discount on investments, net	(3,597)	(271)
Stock-based compensation to employees	3,992	6,085
Stock-based compensation to Board of Directors and Scientific Advisory Board	423	430
Deferred income tax benefit	(5,936)	(1,380)
Retirement plan expense, net of benefit payments	782	1,359
Decrease (increase) in assets:
Accounts receivable	(13)	2,692
Inventory	8,975	(9,080)
Other current assets	8,598	(8,172)
Other assets	5,515	9,488
Increase (decrease) in liabilities:
Accounts payable and accrued expenses	(24,116)	(4,261)
Other current liabilities	12,874	5,807
Deferred revenue	(8,616)	(13,568)
Other liabilities	(486)	2,384
Net cash provided by operating activities	47,621	52,608
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(9,098)	(10,751)
Purchases of intangibles	(51)	(12)
Purchases of investments	(65,207)	(24,915)
Proceeds maturity of investments	115,031	50,240
Net cash used in investing activities	40,675	14,562
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	518	403
Payment of withholding taxes related to stock-based compensation to employees	(7,181)	(7,896)
Cash dividends paid	(16,769)	(14,246)
Net cash used in financing activities	(23,432)	(21,739)
INCREASE IN CASH AND CASH EQUIVALENTS	64,864	45,431
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	93,430	311,993
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 158,294	$ 357,424