v3.8.0.1
Earnings (Loss) Per Share - Summary of Earnings (Loss) Per Share Calculation (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 24, 2017
Sep. 25, 2016
Sep. 24, 2017
Sep. 25, 2016
Earnings (Loss) Per Share [Line Items]        
Net income (loss) attributable to Potbelly Corporation $ (240) $ 1,795 $ 305 $ 6,256
Weighted average common shares outstanding-basic 24,959,023 25,240,374 25,030,951 25,772,846
Plus: Effect of potential stock options exercise   533,249 770,965 514,257
Plus: Effect of potential warrant exercise   56,347 55,167 54,810
Weighted average common shares outstanding-diluted 24,959,023 25,829,970 25,857,083 26,341,913
Income (loss) per share available to common stockholders-basic $ (0.01) $ 0.07 $ 0.01 $ 0.24
Income (loss) per share available to common stockholders-diluted $ (0.01) $ 0.07 $ 0.01 $ 0.24
Common Share Options [Member]        
Earnings (Loss) Per Share [Line Items]        
Potentially dilutive shares that are considered anti-dilutive 4,012,073 1,233,294 1,151,317 1,236,599