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Debt and Credit Facilities - Additional Information (Detail) - USD ($) |  |  |  | 3 Months Ended
--- | --- | --- | --- | ---
Feb. 26, 2021 | Aug. 10, 2020 | Aug. 07, 2019 | Mar. 28, 2021 | Mar. 29, 2020
CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Minimum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, maturity date | Mar. 31, 2022 |  |  |  |
CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, maturity date | Jan. 31, 2023 |  |  |  |
JPMorgan Chase Bank, N.A. [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Commitment fee, percentage |  |  | 0.20% |  |
Revolving Credit Facility [Member] | JPMorgan Chase Bank, N.A. [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Credit facility agreement, expiration date |  |  | Jul. 31, 2022 |  |
Credit facility agreement, maximum principal amount |  |  | $ 40,000,000 |  |
Revolving Credit Facility [Member] | JPMorgan Chase Bank, N.A. [Member] | Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Credit facility agreement, future increases |  |  | $ 20,000,000 |  |
Paycheck Protection Program Loan [Member] | CARES Act Of 2020 [Member] | Potbelly Sandwich Works, LLC [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Loan maturity period |  | 5 years |  |  |
Credit facility agreement, interest rate |  | 1.00% |  |  |
Paycheck Protection Program Loan [Member] | Harvest Small Business Finance L L C | Commercial Loan [Member] | Potbelly Sandwich Works, LLC [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Loan amount |  | $ 10,000,000.0 |  |  |
Paycheck Protection Program Loan [Member] | Harvest Small Business Finance L L C | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Credit facility agreement, amount outstanding |  |  |  | $ 2,800,000 | $ 39,800,000
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Minimum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Credit facility agreement, future increases | $ 40,000,000 |  |  |  |
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Maximum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Credit facility agreement, future increases | $ 25,000,000 |  |  |  |
Eurodollar Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt instrument, increase in interest rate | 5.00% |  |  |  |
CBFR Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt instrument, increase in interest rate | 2.75% |  |  |  |

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition Incremental percentage increase (decrease) in the stated rate on a debt instrument. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Average amount borrowed under the credit facility during the period. + References No definition available. + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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- Definition Date the credit facility terminates, in CCYY-MM-DD format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Amount of increase (decrease) of the credit facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(f)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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