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Stock Based Compensation - Additional Information (Detail) (USD $) | 1 Months Ended | 12 Months Ended | 0 Months Ended
--- | --- | --- | ---
Aug. 31, 2013 | Dec. 28, 2014 | Dec. 29, 2013 | Dec. 30, 2012 | Oct. 09, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Non-voting Common stock conversion basis ratio |  | 1 pbpb_CommonStockConversionBasisRatio |  |  |
Weighted average share value of unrestricted common stock | $ 100,000 us-gaap_AllocatedShareBasedCompensationExpense |  | $ 10,000,000 us-gaap_AllocatedShareBasedCompensationExpense |  |
Recognized stock-based compensation expense |  | 2,543,000 us-gaap_ShareBasedCompensation | 11,610,000 us-gaap_ShareBasedCompensation | 2,825,000 us-gaap_ShareBasedCompensation |
Unrecognized stock compensation expense |  | 5,500,000 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions | 5,500,000 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions | 1,600,000 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions |
Unrecognized stock compensation expense, recognition period |  | Through 2018 |  |  |
Unrestricted Common Stock Granted [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Recognized stock-based compensation expense |  | 400,000 us-gaap_ShareBasedCompensation / us-gaap_AwardTypeAxis = pbpb_UnrestrictedCommonsSharesMember |  |  |
IPO [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Issuance of unrestricted common stock |  |  |  |  | 8,625,000 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_SubsidiarySaleOfStockAxis = us-gaap_IPOMember
Recognized stock-based compensation expense |  |  | 7,600,000 us-gaap_ShareBasedCompensation / us-gaap_SubsidiarySaleOfStockAxis = us-gaap_IPOMember |  |
Non-Employee Board Of Directors [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Issuance of unrestricted common stock |  | 28,240 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_TitleOfIndividualAxis = pbpb_NonEmployeeBoardOfDirectorsMember |  |  |
Weighted average grant-date share price |  | $ 15.29 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / us-gaap_TitleOfIndividualAxis = pbpb_NonEmployeeBoardOfDirectorsMember |  |  |
Weighted average share value of unrestricted common stock |  | $ 400,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_TitleOfIndividualAxis = pbpb_NonEmployeeBoardOfDirectorsMember |  |  |
2001 Equity Incentive Plans [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares of common stock reserved for issuance |  | 746,749 us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_PlanNameAxis = pbpb_TwoThousandOnePlanMember |  |  |
2001 Equity Incentive Plans [Member] | Non-Voting Common Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares of common stock issued to key executive |  | 500,000 pbpb_CommonStockOptionsGrantedShares / us-gaap_PlanNameAxis = pbpb_TwoThousandOnePlanMember / us-gaap_StatementClassOfStockAxis = us-gaap_NonvotingCommonStockMember |  |  |
2013 Long-Term Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares of common stock reserved for issuance |  | 840,437 us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_PlanNameAxis = pbpb_LongTermIncentivePlanTwoThousandThirteenMember |  |  |
Options granted |  | 712,767 pbpb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsCumulativeNumber / us-gaap_PlanNameAxis = pbpb_LongTermIncentivePlanTwoThousandThirteenMember |  |  |
2001 and 2004 Equity Incentive Plans and 2013 Long-Term Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Exercise price of options outstanding, lower limit |  | $ 7.00 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / us-gaap_PlanNameAxis = pbpb_TwoThousandOneAndTwoThousandFourEquityIncentivePlansAndTwoThousandThirteenLongTermIncentivePlanMember |  |  |
Exercise price of options outstanding, higher limit |  | $ 20.53 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / us-gaap_PlanNameAxis = pbpb_TwoThousandOneAndTwoThousandFourEquityIncentivePlansAndTwoThousandThirteenLongTermIncentivePlanMember |  |  |
2001 and 2004 Equity Incentive Plans and 2013 Long-Term Incentive Plan [Member] | Maximum [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Exercisable period from the date of grant |  | 10 years |  |  |
Options issued and outstanding, last expiration date |  | Dec. 31, 2024 |  |  |
Options vesting period |  | 5 years |  |  |

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- Definition Common Stock Options Granted Shares + References No definition available. + Details
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- Definition Options granted since inception of the plan. + References No definition available. + Details
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- Definition Fiscal year through which the Company expects to recognize the cost of unvested options awarded to employees that have been granted as of the balance sheet date. + References No definition available. + Details
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Unrecognized cost of unvested options awarded to employees as compensation. + References No definition available. + Details
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Date the equity-based award expires, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of new stock issued during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 + Details
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