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Operating Leases - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 28, 2014
Option
Dec. 29, 2013
Dec. 30, 2012
Leases, Operating [Abstract]      
Initial operating lease period 10 years    
Number of renewal options under operating leases 2pbpb_OperatingLeaseNumberOfRenewals    
Operating lease rent increment term 5 years    
Operating lease period for expiration or renewal 2015 to 2029    
Letters of credit in lieu of rent deposits $ 0.6us-gaap_LettersOfCreditOutstandingAmount $ 0.6us-gaap_LettersOfCreditOutstandingAmount $ 0.6us-gaap_LettersOfCreditOutstandingAmount
Letters of credit annual fee percentage 1.50%pbpb_LetterOfCreditInterestPercentage