Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenues	$ 36,625	$ 34,044	$ 108,069	$ 100,142
Cost of goods sold	18,587	17,003	55,234	51,757
Gross profit	18,038	17,041	52,835	48,385
Operating expenses:
Selling	1,440	1,530	4,642	4,596
General and administrative	4,151	3,651	12,465	10,952
Research and development	1,221	1,147	3,545	3,229
Operating Expenses, Total	6,812	6,328	20,652	18,777
Operating income	11,226	10,713	32,183	29,608
Interest income	240	310	904	1,005
Other income, net	12	0	13	0
Nonoperating Income	252	310	917	1,005
Income before provision for income taxes	11,478	11,023	33,100	30,613
Provision for income taxes	(3,793)	(3,350)	(11,332)	(9,800)
Net income	$ 7,685	$ 7,673	$ 21,768	$ 20,813
Net income per basic share	$ 3.94	$ 3.82	$ 11.08	$ 10.33
Weighted average basic shares outstanding	1,949	2,007	1,964	2,014
Net income per diluted share	$ 3.91	$ 3.81	$ 10.99	$ 10.31
Weighted average diluted shares outstanding	1,966	2,016	1,980	2,019
Dividends per common share	$ 0.75	$ 0.64	$ 2.03	$ 1.76