Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenues	$ 37,381	$ 36,625	$ 113,361	$ 108,069
Cost of goods sold	18,997	18,587	57,668	55,234
Gross profit	18,384	18,038	55,693	52,835
Operating expenses:
Selling	1,322	1,440	4,525	4,642
General and administrative	3,926	4,151	12,196	12,465
Research and development	1,563	1,221	4,792	3,545
Operating Expenses, Total	6,811	6,812	21,513	20,652
Operating income	11,573	11,226	34,180	32,183
Interest income	131	240	636	904
Other income, net	0	12	0	13
Nonoperating Income	131	252	636	917
Income before provision for income taxes	11,704	11,478	34,816	33,100
Provision for income taxes	(3,905)	(3,793)	(11,941)	(11,332)
Net income	$ 7,799	$ 7,685	$ 22,875	$ 21,768
Net income per basic share	$ 4.25	$ 3.94	$ 12.34	$ 11.08
Weighted average basic shares outstanding	1,836	1,949	1,853	1,964
Net income per diluted share	$ 4.19	$ 3.91	$ 12.19	$ 10.99
Weighted average diluted shares outstanding	1,860	1,966	1,876	1,980
Dividends per common share	$ 0.9	$ 0.75	$ 2.4	$ 2.03