DEBT - Borrowing Under Term Loan (Details) - Texas Capital Bank, National Association (TCB) - Revolving Credit Facility - Credit Agreement - USD ($)	Mar. 28, 2021	Dec. 27, 2020
Debt Instrument [Line Items]
Long-Term Debt, Gross, Initial Borrowing	$ 3,925,000	$ 4,300,000
Debt Instrument, Interest Rate, Effective Percentage for Initial Borrowing Amount	2.36%	2.15%
Long-Term Debt, Gross, Second Borrowing Amount	$ 24,625,000	$ 24,625,000
Debt Instrument, Interest Rate, Effective Percentage for Second Borrowing Amount	2.39%	2.39%
Long-term debt, less current portion	$ 28,550,000	$ 28,925,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant