Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 205,226	$ 291,018	$ 275,026
Gross profit	74,139	73,398	20,261
Selling, general, and administrative expenses
Compensation expense	3,028	3,809	4,153
Other expense	1,904	1,936	1,986
Related party expense	707	690	576
Research and development expenses	3,191	3,524	3,659
Total operating expenses	8,830	9,959	10,374
Income from operations	65,309	63,439	9,887
Interest and dividend income	10,050	9,183	7,809
Interest expense	(173)	(173)	(172)
Gain (loss) on marketable securities	4,619	(12,011)	(687)
Other expense	(10)	(261)	(188)
Other income (expense)	14,486	(3,262)	6,762
Income before income taxes	79,795	60,177	16,649
Income tax (benefit) provision	(8,386)	7,019	(6,862)
Net income	$ 88,181	$ 53,158	$ 23,511
Earnings per common share
Earnings per common share, basic (in dollars per share)	$ 2.02	$ 1.22	$ 0.54
Earnings per common share, diluted (in dollars per share)	$ 2.02	$ 1.22	$ 0.54
Weighted average shares outstanding
Weighted average shares outstanding, basic (in shares)	43,743,243	43,725,333	43,676,171
Weighted average shares outstanding, diluted (in shares)	43,744,676	43,731,192	43,685,579
Net income	$ 88,181	$ 53,158	$ 23,511
Other comprehensive income (loss) from unrealized net gains (losses) on available-for-sale debt securities	400	(229)	7,535
Income tax effect	(84)	49	(2,642)
Total unrealized gains (losses), net of tax	316	(180)	4,893
Comprehensive income	88,497	52,978	28,404
Non-related Parties [Member]
Revenue	202,048	286,949	273,144
Cost of goods sold	107,028	191,859	224,329
Non-related Parties [Member] | Shipping and Handling [Member]
Cost of goods sold	6,933	6,075	3,750
Related Parties [Member]
Revenue	3,178	4,069	1,882
Cost of goods sold	16,945	19,495	26,526
Related Parties [Member] | Shipping and Handling [Member]
Cost of goods sold	$ 181	$ 191	$ 160