Consolidated Statements Of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Consolidated Statements Of Comprehensive Income [Abstract]
Net sales	$ 81,653	$ 70,614	$ 237,706	$ 218,029
Cost of sales	65,956	51,722	182,287	161,451
Gross profit	15,697	18,892	55,419	56,578
Selling and general expenses	5,829	5,729	17,611	16,907
Intangibles amortization	5	1,479	2,166	1,851
Impairment of long-lived assets	3,021		3,021
Operating profit	6,842	11,684	32,621	37,820
Other income	1,189	792	3,081	2,722
Earnings from continuing operations before provision for income taxes	8,031	12,476	35,702	40,542
Provision for income taxes from continuing operations	1,791	4,138	7,692	13,290
Earnings from continuing operations	6,240	8,338	28,010	27,252
Earnings (loss) from discontinued operations, net of tax	131	(6)	122	8,947
Net earnings	$ 6,371	$ 8,332	$ 28,132	$ 36,199
Weighted average shares outstanding:
Basic and diluted	7,007	6,991	7,004	6,987
Earnings per share, basic and diluted:
From continuing operations	$ 0.89	$ 1.19	$ 4.00	$ 3.90
From discontinued operations	0.02	0.00	0.02	1.28
Net earnings per share	$ 0.91	$ 1.19	$ 4.02	$ 5.18
Other comprehensive income, net of tax:
Unrealized gain (loss) on available-for-sale securities	$ (31)	$ 12	$ 34	$ 35
Comprehensive income	$ 6,340	$ 8,344	$ 28,166	$ 36,234
Cash dividends declared and paid per common share	$ 0.00	$ 0.00	$ 6.00	$ 5.50