Consolidated Statements Of Comprehensive Income - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements Of Comprehensive Income [Abstract]
Net sales	$ 333,633,000	$ 341,905,000	$ 355,649,000
Cost of sales	246,399,000	256,243,000	266,216,000
Gross profit	87,234,000	85,662,000	89,433,000
Selling and general expenses	22,900,000	22,429,000	21,735,000
Intangibles amortization	2,630,000	721,000	5,173,000
Operating profit	61,704,000	62,512,000	62,525,000
Other income	3,581,000	810,000	397,000
Earnings from continuing operations before provision for income taxes	65,285,000	63,322,000	62,922,000
Provision for income taxes from continuing operations	21,971,000	21,407,000	20,760,000
Earnings (loss) from continuing operations	43,314,000	41,915,000	42,162,000
Earnings (loss) from discontinued operations, net of tax	9,645,000	2,649,000	(1,666,000)
Net earnings	$ 52,959,000	$ 44,564,000	$ 40,496,000
Weighted average shares outstanding:
Basic and diluted	6,989	6,970	6,951
Earnings (loss) per share, basic and diluted:
From continuing operations	$ 6.20	$ 6.01	$ 6.07
From discontinued operations	1.38	0.38	(0.24)
Net earnings per share	$ 7.58	$ 6.39	$ 5.83
Other comprehensive loss, net of tax:
Unrealized loss on available-for-sale securities	$ (39,000)	$ (38,000)	$ (6,000)
Comprehensive income	$ 52,920,000	$ 44,526,000	$ 40,490,000