Property, Plant and Equipment (Details) - USD ($)		3 Months Ended		9 Months Ended
	Sep. 24, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment
Gross property, plant, and equipment		$ 160,687,000		$ 160,687,000		$ 168,638,000
Less accumulated depreciation and amortization, including accumulated amortization of finance leases		(101,876,000)		(101,876,000)		(106,553,000)
Property, plant, and equipment - net		58,811,000		58,811,000		62,085,000
Depreciation		2,041,000	$ 1,940,000	6,049,000	$ 5,838,000
Impairments of property, plant, and equipment				0	$ 0
Discontinued Operations, Disposed of by Sale
Property, Plant and Equipment
Proceeds from divestiture of businesses	$ 23,902,000
Land
Property, Plant and Equipment
Gross property, plant, and equipment		6,223,000		6,223,000		6,627,000
Improvements to land and leaseholds
Property, Plant and Equipment
Gross property, plant, and equipment		15,401,000		15,401,000		17,573,000
Buildings
Property, Plant and Equipment
Gross property, plant, and equipment		26,966,000		26,966,000		27,348,000
Machinery and equipment, including equipment under finance leases
Property, Plant and Equipment
Gross property, plant, and equipment		110,821,000		110,821,000		116,175,000
Construction in progress
Property, Plant and Equipment
Gross property, plant, and equipment		$ 1,276,000		$ 1,276,000		$ 915,000