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Earnings Per Share - Schedule of the Calculation of Weighted Average Common Shares Outstanding for Basic and Diluted Earnings per Share Available to Common Stockholders (Detail) (USD $)
 3 Months Ended 9 Months Ended
Sep. 29, 2013
Sep. 23, 2012
Sep. 29, 2013
Sep. 23, 2012
Calculation of undistributed (loss) for basic and diluted shares:        
Net income attributable to Potbelly Corporation $ 2,165,000 $ 2,548,000 $ 4,941,000 $ 5,571,000
Less: Dividend declared to common and preferred stockholders (49,854,000)   (49,854,000)  
Less: Accretion of redeemable convertible preferred stock to maximum redemption value (4,796,000) (5,545,000) (15,097,000) (13,887,000)
Undistributed loss for basic and diluted shares (52,485,000) (2,997,000) (60,010,000) (8,316,000)
Allocation of undistributed (loss) to participating securities:        
Undistributed (loss) income (52,485) (2,997) (60,010) (8,316)
Weighted average common shares outstanding-basic 4,268,953 3,972,873 4,250,819 3,972,873
Plus: Effect of potential stock options exercise            
Plus: Effect of potential warrant exercise            
Weighted average common shares outstanding-diluted 4,268,953 3,972,873 4,250,819 3,972,873
Income (loss) per share available to common stockholders-basic $ (12.29) $ (0.75) $ (14.12) $ (2.09)
Income (loss) per share available to common stockholders-diluted $ (12.29) $ (0.75) $ (14.12) $ (2.09)
Common Share Options [Member]
        
Allocation of undistributed (loss) to participating securities:        
Potentially dilutive shares that are considered anti-dilutive 4,744,664 4,446,049 4,744,664 4,446,049
Common Stock [Member]
        
Allocation of undistributed (loss) to participating securities:        
Undistributed (loss) income $ (52,485) $ (2,997) $ (60,010) $ (8,316)
Warrant [Member]
        
Allocation of undistributed (loss) to participating securities:        
Potentially dilutive shares that are considered anti-dilutive 241,704 378,996 241,704 378,996