Income Taxes Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Deferred tax assets:
Inventories	$ 3,428	$ 3,336
Retirement benefits	1,190	1,394
State net operating losses	3,305	3,362
Federal net operating losses	556	715
State tax credit carryforwards	1,688	1,688
Federal tax credit carryforwards	4,413	4,282
Allowances for bad debts, claims and discounts	2,024	1,978
Other	5,196	4,039
Total deferred tax assets	21,800	20,794
Valuation allowance	(15,443)	(13,264)
Net deferred tax assets	6,357	7,530
Deferred tax liabilities:
Property, plant and equipment	6,448	7,621
Total deferred tax liabilities	6,448	7,621
Net deferred tax liability	$ (91)	$ (91)