CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenues	$ 145,733	$ 140,762	$ 131,993
Cost of Goods Sold	74,752	72,244	68,931
Gross Profit	70,981	68,518	63,062
Operating Expenses:
Selling	6,043	6,210	6,218
General and administrative	16,082	16,205	14,612
Research and development	6,346	5,286	4,288
Operating Expenses, Total	28,471	27,701	25,118
Operating Income	42,510	40,817	37,944
Interest Income	771	1,191	1,313
Other Income (Expense), net	(2,411)	13	8
Income before Provision for Income Taxes	40,870	42,021	39,265
Provision for Income Taxes	(11,945)	(14,213)	(12,683)
Net Income	$ 28,925	$ 27,808	$ 26,582
Net Income Per Basic Share	$ 15.67	$ 14.20	$ 13.22
Weighted Average Basic Shares Outstanding	1,846	1,958	2,010
Net Income Per Diluted Share	$ 15.47	$ 14.08	$ 13.18
Weighted Average Diluted Shares Outstanding	1,870	1,975	2,017
Dividends Per Common Share	$ 3.30	$ 2.78	$ 2.40