Long-Term Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Interest Expense, Debt [Abstract]
Interest expense	$ 8	$ 8	$ 24	$ 27

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

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Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration