Amount of the cost of borrowed funds accounted for as interest expense for debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Line of credit facility, discretionary amount available

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Long-Term Debt (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
Long-Term Debt (Narrative) (Details) - USD ($)	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Line of Credit Facility [Line Items]
Interest Expense, Debt	$ 8,000	$ 10,000	$ 27,000	$ 43,000
Revolving Credit Facility [Member] \| Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	30,000,000.0		30,000,000.0
Line of Credit Facility, Remaining Borrowing Capacity	24,100,000		24,100,000
Line of Credit [Member] \| Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Line of credit facility, discretionary amount available	70,000,000.0		70,000,000.0
Letter of Credit [Member] \| Wells Fargo Bank, N.A. [Member]
Line of Credit Facility [Line Items]
Amount of facility borrowed	$ 5,900,000		$ 5,900,000