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Organization and Other Matters - Additional Information (Detail)
 3 Months Ended
Mar. 28, 2021
Shop
Subsidiary
JointVenture
Nature Of Business And Basis Of Presentation [Line Items]  
Number of shops franchisees operate 45
Number of wholly owned subsidiaries | Subsidiary 7
Number of joint ventures | JointVenture 7
Minimum [Member]  
Nature Of Business And Basis Of Presentation [Line Items]  
Number of shops Potbelly Corporation owns or operates 399
Ownership interest rate 51.00%
Maximum [Member]  
Nature Of Business And Basis Of Presentation [Line Items]  
Ownership interest rate 80.00%