Earnings Per Share - Summary of Loss Per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 30, 2025	Mar. 31, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss attributable to Potbelly Corporation	$ (62)	$ (2,767)
Weighted average common shares outstanding-basic (in shares)	29,893	29,551
Plus: Effect of potentially dilutive stock-based compensation awards	0	0
Plus: Effect of potential warrant exercise	0	0
Weighted average common shares outstanding-diluted (in shares)	29,893	29,551
Loss per share available to common stockholders-basic (in USD per share)	$ 0.00	$ (0.09)
Loss per share available to common stockholders-diluted (in USD per share)	$ 0.00	$ (0.09)
Potentially dilutive shares that are considered anti-dilutive (in shares)	1,345	1,326
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares that are considered anti-dilutive (in shares)	817	883

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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