Income Taxes Components of Deferred Tax Assets and Liabilities, Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Valuation Allowance	$ 15,443	$ 13,264
Deferred Tax Liabilities, Net	91	91
Federal net operating losses	556	715
State net operating losses	3,305	3,362
Federal tax credit carryforwards	4,413	4,282
State tax credit carryforwards	1,688	$ 1,688
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 2,646
Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards and Tax Credit Carryforwards, Expiration Date	2029
Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards and Tax Credit Carryforwards, Expiration Date	2041
State Taxing Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 61,640
State Taxing Authority [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards and Tax Credit Carryforwards, Expiration Date	2020
State Taxing Authority [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards and Tax Credit Carryforwards, Expiration Date	2040