Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 41,614	$ 39,401
Cost of goods sold	22,911	20,450
Gross profit	18,703	18,951
Operating expenses:
Selling	2,384	2,018
General and administrative	4,187	4,229
Research and development	1,095	1,338
Operating Expenses, Total	7,666	7,585
Operating income	11,037	11,366
Interest and dividend income	582	313
Other investment income (losses)	211	(772)
Nonoperating Income	793	(459)
Income before provision for income taxes	11,830	10,907
Provision for income taxes	(2,392)	(2,420)
Net income	$ 9,438	$ 8,487
Net income per basic share	$ 5.09	$ 4.58
Weighted average basic shares outstanding	1,853	1,852
Net income per diluted share	$ 5.07	$ 4.57
Weighted average diluted shares outstanding	1,862	1,856
Dividends per common share	$ 1.35	$ 1.2