Discontinued Operations (Summary Of Results) (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jul. 01, 2018	Oct. 01, 2017	Jul. 02, 2017	Sep. 30, 2018	Oct. 01, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales	$ 81,653,000		$ 70,614,000		$ 237,706,000	$ 218,029,000
Cost of sales	(65,956,000)		(51,722,000)		(182,287,000)	(161,451,000)
Selling and general expenses	(5,829,000)		(5,729,000)		(17,611,000)	(16,907,000)
Gain on divestiture of business, net		$ 0				11,413,000
Other income	1,189,000		792,000		3,081,000	2,722,000
Earnings (loss) from discontinued operations, net of tax	131,000		(6,000)		122,000	8,947,000
Discontinued Operations Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales						421,000
Cost of sales	68,000		(133,000)		57,000	(618,000)
Selling and general expenses						(24,000)
Gain on divestiture of business, net		$ 0		$ 11,413,000		11,413,000
Other income						2,078,000
Earnings (loss) from discontinued operations before provision for income taxes	68,000		(133,000)		57,000	13,270,000
Provision for (benefit from) income taxes from discontinued operations	(63,000)		(127,000)		(65,000)	4,323,000
Earnings (loss) from discontinued operations, net of tax	$ 131,000		$ (6,000)		$ 122,000	$ 8,947,000