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Income Taxes - Additional Information (Detail) (USD $)
 3 Months Ended
Dec. 30, 2012
Dec. 28, 2014
Dec. 29, 2013
Income Tax [Line Items]      
Net operating loss deferred tax assets   $ 336,000us-gaap_DeferredTaxAssetsOperatingLossCarryforwards $ 583,000us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
Prepaid income taxes   1,900,000us-gaap_PrepaidTaxes 500,000us-gaap_PrepaidTaxes
Benefit to release full valuation allowance against deferred tax assets 16,900,000pbpb_DeferredTaxBenefitOnReleaseOfValuationAllowance    
State Tax [Member]      
Income Tax [Line Items]      
Net operating loss carryforwards   5,500,000us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= pbpb_StateTaxMember		  
Net operating loss deferred tax assets   $ 336,000us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= pbpb_StateTaxMember