Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Revenues	$ 36,164	$ 36,143	$ 74,669	$ 72,358
Cost of goods sold	18,470	18,928	38,344	37,578
Gross profit	17,694	17,215	36,325	34,780
Operating expenses:
Selling	1,864	1,664	3,612	3,400
General and administrative	4,287	3,880	8,304	7,829
Research and development	1,368	1,597	2,907	3,012
Operating Expenses, Total	7,519	7,141	14,823	14,241
Operating income	10,175	10,074	21,502	20,539
Interest income	370	85	519	208
Other income (expense), net	0	36	1	(309)
Nonoperating Income	370	121	520	(101)
Income before provision for income taxes	10,545	10,195	22,022	20,438
Provision for income taxes	(519)	(2,745)	(2,046)	(6,042)
Net income	$ 10,026	$ 7,450	$ 19,976	$ 14,396
Net income per basic share	$ 5.44	$ 4.09	$ 10.86	$ 7.9
Weighted average basic shares outstanding	1,844	1,822	1,839	1,823
Net income per diluted share	$ 5.4	$ 4.02	$ 10.76	$ 7.76
Weighted average diluted shares outstanding	1,858	1,853	1,856	1,855
Dividends per common share	$ 1.05	$ 0.9	$ 2.1	$ 1.8