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Debt and Credit Facilities - Additional Information (Detail) - USD ($) |  |  |  |  | 1 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
Feb. 26, 2021 | Nov. 04, 2020 | Aug. 10, 2020 | Aug. 07, 2019 | Jul. 17, 2020 | May 15, 2020 | Dec. 27, 2020 | Dec. 29, 2019 | Mar. 17, 2020
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  |  | $ 55,000,000 |  |
Line of credit facility amount borrowed |  |  |  |  | $ 10,000,000.0 |  |  |  |
February 28, 2022 [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Minimum Liquidity Level |  |  |  |  |  |  | 15,000,000.0 |  |
Minimum Building Adjusted EBITDA |  |  |  |  |  |  | (18,000,000.0) |  |
February 28, 2022 [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Minimum Liquidity Level |  |  |  |  |  |  | 30,000,000.0 |  |
Minimum Building Adjusted EBITDA |  |  |  |  |  |  | 8,300,000 |  |
Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Upfront fee payable |  |  |  |  |  | 1.00% |  |  |
CARES Act Of 2020 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  |  | 33,500,000 |  |
CARES Act Of 2020 [Member] | Minimum [Member] | Fourth Credit Agreement Amendment |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrumnet estimated periodic Minimum Liquidity |  | $ 23,000.0 |  |  |  |  |  | $ 25,000.0 |
CARES Act Of 2020 [Member] | Minimum [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, maturity date | Mar. 31, 2022 |  |  |  |  |  |  |  |
CARES Act Of 2020 [Member] | Maximum [Member] | Fourth Credit Agreement Amendment |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrumnet estimated periodic Minimum Liquidity |  | $ 37,500 |  |  |  |  |  | 37,500 |
CARES Act Of 2020 [Member] | Maximum [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, maturity date | Jan. 31, 2023 |  |  |  |  |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  | 1.75% | 4.75% |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  |  |  | 5.00% |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  | 1.25% | 1.00% |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  |  |  | 1.00% |  |  |
Prime Rate [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  |  | 2.25% |  |  |  |
JPMorgan Chase Bank, N.A. [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Commitment fee, percentage |  |  |  | 0.20% |  |  |  |  |
JPMorgan Chase Bank, N.A. [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Commitment fee, percentage |  |  |  |  |  | 1.00% |  |  |
Debt instrument, elimination expansion |  |  |  |  |  | $ 20,000,000.0 |  |  |
Credit facility agreement, amount outstanding |  |  |  |  |  | 15,000,000.0 |  |  |
Line of credit facility amount borrowed |  |  |  |  |  | $ 28,000,000.0 |  |  |
JPMorgan Chase Bank, N.A. [Member] | Maximum [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, Maturity date |  |  |  |  |  | Mar. 31, 2022 |  |  |
JPMorgan Chase Bank, N.A. [Member] | Minimum [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, Maturity date |  |  |  |  |  | Jul. 31, 2022 |  |  |
JPMorgan Chase Bank, N.A. [Member] | Prime Rate [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  | 0.50% |  |  |  |  |
JPMorgan Chase Bank, N.A. [Member] | Prime Rate [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  | 0.00% |  |  |  |  |
JPMorgan Chase Bank, N.A. [Member] | Prime Rate [Member] | Minimum [Member] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  |  |  |  | 4.00% |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, maximum principal amount |  |  |  |  | $ 40,000,000.0 |  |  |  |
Credit facility agreement, future increases |  |  |  |  | 30,000,000.0 |  |  |  |
Line of credit facility amount borrowed |  |  |  |  | $ 14,500,000 |  |  |  |
Revolving Credit Facility [Member] | CARES Act Of 2020 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  |  |  |  | $ 39,800,000
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] | Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  | $ 15,000,000.0 |  |  |
Revolving Credit Facility [Member] | JPMorgan Chase Bank, N.A. [Member] | COVID 19 [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  |  |  |  | $ 39,800,000
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] | Harvest Small Business Finance [Member] | Commercial Loan [Member] | Potbelly Sandwich Works, LLC [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Loan amount |  |  | $ 10,000,000.0 |  |  |  |  |  |
Paycheck Protection Program Loan [Member] | CARES Act Of 2020 [Member] | Potbelly Sandwich Works, LLC [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, interest rate |  |  | 1.00% |  |  |  |  |  |
Loan maturity period |  |  | 5 years |  |  |  |  |  |
Paycheck Protection Program Loan [Member] | CARES Act Of 2020 [Member] | Harvest Small Business Finance [Member] | Third Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Line of credit facility amount borrowed |  |  |  |  |  |  | 10,000,000.0 |  |
Credit facility agreement, amount outstanding |  |  |  |  |  |  | $ 6,300,000 | $ 0 |
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Minimum [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, future increases | $ 40,000,000 |  |  |  |  |  |  |  |
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Maximum [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Credit facility agreement, future increases | $ 25,000,000 |  |  |  |  |  |  |  |
CBFR Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrument, increase in interest rate | 50.00% |  |  |  |  |  |  |  |
Eurodollar Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |
Debt instrument, increase in interest rate | 25.00% |  |  |  |  |  |  |  |

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