CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenues	$ 143,487	$ 145,733	$ 140,762
Cost of Goods Sold	75,857	74,752	72,244
Gross Profit	67,630	70,981	68,518
Operating Expenses:
Selling	6,611	6,043	6,210
General and administrative	15,319	16,082	16,205
Research and development	6,574	6,346	5,286
Operating Expenses, Total	28,504	28,471	27,701
Operating Income	39,126	42,510	40,817
Interest Income	448	771	1,191
Other Income (Expense), net	(308)	(2,411)	13
Income before Provision for Income Taxes	39,266	40,870	42,021
Provision for Income Taxes	(11,685)	(11,945)	(14,213)
Net Income	$ 27,581	$ 28,925	$ 27,808
Net Income Per Basic Share	$ 15.12	$ 15.67	$ 14.20
Weighted Average Basic Shares Outstanding	1,824	1,846	1,958
Net Income Per Diluted Share	$ 14.85	$ 15.47	$ 14.08
Weighted Average Diluted Shares Outstanding	1,857	1,870	1,975
Dividends Per Common Share	$ 3.90	$ 3.30	$ 2.78