Interim Financial Information (Schedule Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interim Financial Information [Abstract]
Net sales	$ 94,909	$ 78,006	$ 71,745	$ 63,850	$ 85,611	$ 81,653	$ 79,227	$ 76,826	$ 308,510	$ 323,317	$ 333,633
Gross Profit	20,910	23,847	14,676	12,492	20,464	15,697	19,445	20,277	71,925	75,883	87,234
Earnings from continuing operations	11,724	14,712	8,153	5,951	11,879	6,240	10,776	10,994	40,540	39,889	43,314
Earnings (loss) from discontinued operations, net of tax		1,677	3		(71)	131	(1)	(8)	1,680	51	9,645
Net earnings	$ 11,724	$ 16,389	$ 8,156	$ 5,951	$ 11,808	$ 6,371	$ 10,775	$ 10,986	$ 42,220	$ 39,940	$ 52,959
Earnings from continuing operations per share, basic and diluted	$ 1.67	$ 2.09	$ 1.16	$ 0.85	$ 1.69	$ 0.89	$ 1.54	$ 1.57	$ 5.77	$ 5.69	$ 6.20
Earnings (loss) from discontinued operations per share, net of tax, basic and diluted		0.24			(0.01)	0.02			0.24	0.01	1.38
Net earnings per share	$ 1.67	$ 2.33	$ 1.16	$ 0.85	$ 1.68	$ 0.91	$ 1.54	$ 1.57	$ 6.01	$ 5.70	$ 7.58
Revenue recognized that was previously included in contract liability		$ 9,412