View Filing Data

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Jan. 28, 2018	Jun. 23, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	PBPB
Entity Registrant Name	Potbelly Corporation
Entity Central Index Key	0001195734
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		25,107,188
Entity Public Float			$ 278.8

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 25, 2016
Current assets
Cash and cash equivalents	$ 25,530	$ 23,379
Accounts receivable, net of allowances of $129 and $78 as of December 31, 2017 and December 25, 2016, respectively	5,087	3,787
Inventories	3,525	3,365
Prepaid expenses and other current assets	11,061	8,020
Total current assets	45,203	38,551
Property and equipment, net	103,859	107,074
Indefinite-lived intangible assets	3,404	3,404
Goodwill	2,222	2,222
Deferred income taxes, non-current	11,202	19,410
Deferred expenses, net and other assets	4,840	4,784
Total assets	170,730	175,445
Current liabilities
Accounts payable	3,903	3,111
Accrued expenses	23,273	23,082
Accrued income taxes	176	1,622
Total current liabilities	27,352	27,815
Deferred rent and landlord allowances	22,987	21,076
Other long-term liabilities	3,153	2,318
Total liabilities	53,492	51,209
Stockholders’ equity
Common stock, $0.01 par value—authorized 200,000,000 shares; outstanding 24,999,688 and 25,139,127 shares as of December 31, 2017 and December 25, 2016, respectively	318	309
Warrants		909
Additional paid-in-capital	421,657	407,622
Treasury stock, held at cost, 6,831,508 and 5,753,412 shares as of December 31, 2017, and December 25, 2016, respectively	(85,262)	(72,321)
Accumulated deficit	(219,990)	(213,034)
Total stockholders’ equity	116,723	123,485
Non-controlling interest	515	751
Total stockholders' equity	117,238	124,236
Total liabilities and equity	$ 170,730	$ 175,445

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 25, 2016
Statement Of Financial Position [Abstract]
Allowances on accounts receivable	$ 129	$ 78
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	200,000,000	200,000,000
Common stock, outstanding	24,999,688	25,139,127
Treasury stock, shares	6,831,508	5,753,412

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Revenues
Sandwich shop sales, net	$ 424,932	$ 404,874	$ 370,954
Franchise royalties and fees	3,179	2,257	1,895
Total revenues	428,111	407,131	372,849
Sandwich shop operating expenses
Cost of goods sold, excluding depreciation	113,426	111,026	105,614
Labor and related expenses	126,337	117,838	106,628
Occupancy expenses	58,562	52,444	46,762
Other operating expenses	49,209	43,738	39,869
General and administrative expenses	44,618	40,411	37,322
Depreciation expense	25,680	22,734	21,476
Pre-opening costs	1,441	1,786	2,160
Impairment and loss on disposal of property and equipment	10,761	4,141	3,589
Total expenses	430,034	394,118	363,420
Income (loss) from operations	(1,923)	13,013	9,429
Interest expense	124	134	221
Income (loss) before income taxes	(2,047)	12,879	9,208
Income tax expense	4,643	4,443	3,466
Net income (loss)	(6,690)	8,436	5,742
Net income attributable to non-controlling interest	266	224	114
Net income (loss) attributable to Potbelly Corporation	$ (6,956)	$ 8,212	$ 5,628
Net income (loss) per common share attributable to common stockholders:
Basic	$ (0.28)	$ 0.32	$ 0.20
Diluted	$ (0.28)	$ 0.31	$ 0.20
Weighted average shares outstanding:
Basic	25,045,427	25,623,809	28,002,005
Diluted	25,045,427	26,231,367	28,634,396

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Warrants [Member]	Additional Paid-in-Capital [Member]	Accumulated Deficit [Member]	Non-Controlling Interest [Member]
Beginning Balance at Dec. 28, 2014	$ 156,325	$ 298	$ (10,246)	$ 909	$ 391,972	$ (226,874)	$ 266
Beginning Balance, Common Shares at Dec. 28, 2014		28,934,700
Net income	5,742					5,628	114
Stock-based compensation plans	$ 4,784	$ 5			4,779
Stock-based compensation plans, shares		576,381
Exercise of stock warrants, shares	576,000
Excess tax benefits associated with exercise of stock options	$ 308				308
Repurchases of common stock	(39,754)		(39,754)
Repurchases of common stock, Shares		(3,206,820)
Distributions to non-controlling interest	(198)						(198)
Contributions from non-controlling interest	607						607
Amortization of stock-based compensation	2,399				2,399
Ending Balance at Dec. 27, 2015	130,213	$ 303	(50,000)	909	399,458	(221,246)	789
Ending Balance, Common Shares at Dec. 27, 2015		26,304,261
Net income	8,436					8,212	224
Stock-based compensation plans	$ 5,776	$ 6			5,770
Stock-based compensation plans, shares		554,368
Exercise of stock warrants, shares	536,000
Excess tax deficiencies associated with exercise of stock options	$ (663)				(663)
Repurchases of common stock	(22,321)		(22,321)
Repurchases of common stock, Shares		(1,719,502)
Distributions to non-controlling interest	(413)						(413)
Contributions from non-controlling interest	151						151
Amortization of stock-based compensation	3,057				3,057
Ending Balance at Dec. 25, 2016	$ 124,236	$ 309	(72,321)	909	407,622	(213,034)	751
Ending Balance, Common Shares at Dec. 25, 2016	25,139,127	25,139,127
Net income	$ (6,690)					(6,956)	266
Stock-based compensation plans	6,487	$ 7			6,480
Stock-based compensation plans, shares		696,953
Exercise of stock warrants	$ 1,972	$ 2		$ (909)	2,879
Exercise of stock warrants, shares	653,000	241,704
Repurchases of common stock	$ (12,941)		(12,941)
Repurchases of common stock, Shares	(1,078,096)	(1,078,096)
Distributions to non-controlling interest	$ (513)						(513)
Contributions from non-controlling interest	11						11
Amortization of stock-based compensation	4,676				4,676
Ending Balance at Dec. 31, 2017	$ 117,238	$ 318	$ (85,262)		$ 421,657	$ (219,990)	$ 515
Ending Balance, Common Shares at Dec. 31, 2017	24,999,688	24,999,688

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Cash flows from operating activities:
Net income (loss)	$ (6,690)	$ 8,436	$ 5,742
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	25,680	22,734	21,476
Deferred income tax	6,096	(1,659)	(72)
Deferred rent and landlord allowances	1,911	3,256	3,808
Amortization of stock-based compensation	4,676	3,057	2,399
Excess tax deficiency (benefit) from stock-based compensation	2,112	(31)	(308)
Asset impairment, store closure and disposal of property and equipment	10,947	4,243	3,818
Amortization of debt issuance costs	37	34	11
Changes in operating assets and liabilities:
Accounts receivable, net	(650)	674	(445)
Inventories	(160)	(188)	(388)
Prepaid expenses and other assets	(3,190)	3,204	(1,155)
Accounts payable	286	(1,899)	1,876
Accrued and other liabilities	764	4,108	3,558
Net cash provided by operating activities	41,819	45,969	40,320
Cash flows from investing activities:
Acquisition of franchise shop		(1,108)	(333)
Purchases of property and equipment	(34,684)	(36,712)	(35,725)
Net cash used in investing activities	(34,684)	(37,820)	(36,058)
Cash flows from financing activities:
Payments on note payable			(1,008)
Proceeds from exercise of stock options	6,487	5,776	4,784
Proceeds from exercise of stock warrants	1,972
Excess tax benefit from stock-based compensation		31	308
Treasury stock repurchase	(12,941)	(22,321)	(39,754)
Contributions from non-controlling interest	11	151	607
Distributions to non-controlling interest	(513)	(413)	(198)
Net cash used in financing activities	(4,984)	(16,776)	(35,261)
Net increase (decrease) in cash and cash equivalents	2,151	(8,627)	(30,999)
Cash and cash equivalents at beginning of period	23,379	32,006	63,005
Cash and cash equivalents at end of period	25,530	23,379	32,006
Supplemental cash flow information:
Income taxes paid	1,656	3,663	2,376
Interest paid	94	108	183
Supplemental non-cash investing and financing activities:
Unpaid liability for purchases of property and equipment	$ 1,741	$ 2,727	$ 3,395

Organization and Other Matters	12 Months Ended
Organization and Other Matters	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Other Matters	(1) Organization and Other Matters Business Potbelly Corporation (the “Company” or “Potbelly”), through its wholly-owned subsidiaries, operates or franchises Potbelly Sandwich Works sandwich shops in 31 states and the District of Columbia. The first domestic franchise locations administered by the Company opened during February 2011. Additionally, in February 2011, the Company opened its first international franchise in the Middle East. In July 2015, the Company opened its first franchise shop in the United Kingdom; in October 2016, the Company opened its first franchise shop in Canada; and in December 2017, the Company opened its first franchise shop in India. Additionally, during each of July 2015 and April 2016, the Company transitioned one franchise shop into a company-operated shop for a purchase price of $0.3 million and $1.1 million, respectively. The Company did not record any goodwill related to the July 2015 transaction and recorded $0.8 million of goodwill related to the April 2016 transaction. The Company believes both acquisitions are immaterial.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

(2) Summary of Significant Accounting Policies

(a) Principles of Consolidation

The consolidated financial statements include the accounts of Potbelly Corporation; its wholly owned subsidiary, Potbelly Illinois, Inc. (“PII”); PII’s wholly owned subsidiaries, Potbelly Franchising, LLC and Potbelly Sandwich Works LLC (“LLC”); nine of LLC’s wholly owned subsidiaries and LLC’s five joint ventures, collectively, the “Company.” All intercompany balances and transactions have been eliminated in consolidation. For consolidated joint ventures, non-controlling interest represents a non-controlling partner’s share of the assets, liabilities and operations related to the five joint venture investments. The Company has ownership interests ranging from 51-80% in these consolidated joint ventures.

The Company does not have any components of other comprehensive income (loss) recorded within its consolidated financial statements, and, therefore, does not separately present a statement of comprehensive income (loss) in its consolidated financial statements.

Certain reclassifications have been made to conform the prior period consolidated financial statements to the current period presentation.

(b) Reporting Period

The Company uses a 52/53-week fiscal year that ends on the last Sunday of the calendar year. Approximately every five or six years a 53rd week is added. Fiscal years 2017, 2016 and 2015 consisted of 53, 52 and 52 weeks, respectively.

The Company owns and operates Potbelly Sandwich Works sandwich shops in the United States. The Company also has domestic and international franchise operations of Potbelly Sandwich Works sandwich shops. The Company’s chief operating decision maker (the “CODM”) is its Chief Executive Officer. As the CODM reviews financial performance and allocates resources at a consolidated level on a recurring basis, the Company has one operating segment and one reportable segment.

(d) Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Significant estimates include amounts for long-lived assets and income taxes. Actual results could differ from those estimates.

(e) Fair Value Measurements

The Company applies fair value accounting for all financial assets and liabilities and nonfinancial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities that are required to be recorded at fair value, the Company assumes the highest and best use of the asset by market participants in which the Company would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as inherent risk, transfer restrictions, and credit risk.

The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels, and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:

•

Level 1 — Quoted prices in active markets for identical assets or liabilities.

•

Level 2 — Observable inputs other than quoted prices in active markets for identical assets or liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•

Level 3 — Inputs that are both unobservable and significant to the overall fair value measurement reflect an entity’s estimates of assumptions that market participants would use in pricing the asset or liability.

(f) Financial Instruments

The Company records all financial instruments at cost, which is the fair value at the date of transaction. The amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, accounts payable and all other current liabilities approximate their fair value because of the short-term maturities of these instruments.

(g) Cash and Cash Equivalents

The Company considers all highly liquid investment instruments with an original maturity of three months or less when purchased to be cash equivalents. The Company maintains its cash in bank deposit accounts that, at times, may exceed federally insured limits; however, the Company has not experienced any losses in these accounts. The Company believes it is not exposed to any significant credit risk. These are valued within the fair value hierarchy as Level 1 measurements.

(h) Accounts Receivable, net

Accounts receivable, net consists of credit card receivables, amounts owed from vendors and miscellaneous receivables. The Company had credit card receivables of $1.9 million and $1.6 million as of December 31, 2017 and December 25, 2016, respectively.

(i) Inventories

Inventories, which consist of food products, paper goods and supplies, and promotional items, are valued at the lower of cost (first-in, first-out) or market. No adjustment is deemed necessary to reduce inventory to the lower of cost or market value due to the rapid turnover and high utilization of inventory.

(j) Property and Equipment

Property and equipment acquired is recorded at cost less accumulated depreciation. Property and equipment is depreciated based on the straight-line method over the estimated useful lives, generally ranging from three to five years for furniture and fixtures, computer equipment, computer software, and machinery and equipment. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the related lease life, generally 10 to 15 years. For leases with renewal periods at the Company’s option, the Company determines the expected lease period based on whether the renewal of any options are reasonably assured at the inception of the lease.

Direct costs and expenditures for refurbishments and improvements that significantly add to the productive capacity or extend the useful life of an asset are capitalized, whereas the costs of repairs and maintenance are expensed when incurred. The Company capitalizes certain internal costs associated with the development, design, and construction of new shop locations as these costs have a future benefit to the Company. The Company capitalized costs of $0.8 million, $0.6 million and $0.6 million for the fiscal years ended December 31, 2017, December 25, 2016 and December 27, 2015, respectively. Capitalized costs are recorded as part of the asset to which they relate, primarily to leasehold improvements, and such costs are amortized over the asset’s useful life. When assets are retired or sold, the asset cost and related accumulated depreciation are removed from the consolidated balance sheet and any gain or loss is recorded in the consolidated statement of operations.

The Company assesses potential impairments to its long-lived assets, which includes property and equipment, on a quarterly basis or whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. Shop-level assets are grouped at the individual shop-level for the purpose of the impairment assessment. Recoverability of an asset is measured by a comparison of the carrying amount of an asset to its estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of the asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized as the amount by which the carrying amount of the asset exceeds the fair value of the asset. The fair value of the shop assets is determined using the discounted future cash flow method of anticipated cash flows through the shop’s lease-end date using fair value measurement inputs classified as Level 3. Level 3 inputs are derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. The Company used a weighted average cost of capital to discount the future cash flows. After performing periodic reviews of the company-operated shops during each quarter of 2017, 2016 and 2015, it was determined that indicators of impairment were present for certain shops as a result of continued underperformance. The Company performed an impairment analysis related to these shops and recorded impairment charges of $10.6 million, $4.0 million and $3.4 million for the fiscal years 2017, 2016 and 2015, respectively. As a result of damage sustained by Hurricane Harvey, the Company recorded a $0.7 million impairment for the fiscal year 2017, with insurance recoveries of $0.7 million also recorded within the same caption.

(k) Intangible Assets

The Company reviews indefinite-lived intangible assets, which includes goodwill and tradenames, annually at fiscal year-end for impairment or more frequently if events or circumstances indicate that the carrying value may not be recoverable. An impaired asset is written down to its estimated fair value based on the most recent information available. The Company assesses the fair values of its intangible assets, and its reporting unit for goodwill testing purposes, using an income-based approach. Under the income approach, fair value is based on the present value of estimated future cash flows. The income approach is dependent on a number of factors, including forecasted revenues and expenses, appropriate discount rates and other variables. The annual impairment review utilizes the estimated fair value of the intangible assets and the overall reporting unit and compares the estimated fair values to the carrying values as of the testing date. If the carrying value of these intangible assets or the reporting unit exceeds the fair values, the Company would then use the fair values to measure the amount of any required impairment charge. No impairment charge was recognized for intangible assets for any of the fiscal periods presented.

(l) Pre-opening Costs

Pre-opening costs consist of costs incurred prior to opening a new shop and are made up primarily of travel, employee payroll and training costs incurred prior to the shop opening, as well as occupancy costs incurred from when the Company takes site possession to shop opening. Shop pre-opening costs are expensed as incurred.

(m) Advertising Expenses

Advertising costs are expensed as incurred and are included in general and administrative expenses in the consolidated statements of operations. Advertising expenses were $3.4 million, $3.0 million and $2.9 million in fiscal years 2017, 2016 and 2015, respectively.

(n) Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are attributed to differences between financial statement and income tax reporting. Deferred tax assets, net of any valuation allowances, represent the future tax return consequences of those differences and for operating loss and tax credit carryforwards, which will be deductible when the assets are recovered. Deferred tax assets are reduced by a valuation allowance if it is deemed more likely than not that some or all of the deferred tax assets will not be realized. In making this assessment of realizability of deferred tax assets, the Company considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. The Company considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies in making this assessment. Deferred tax liabilities are recognized for temporary differences that will be taxable in future years’ tax returns.

The Company accounts for uncertain tax positions under current accounting guidance, which prescribes a minimum probability threshold that a tax position must meet before a financial statement benefit is recognized. The minimum threshold is defined as a tax position that is more likely than not to be sustained upon examination by tax authorities, based on the technical merits of the position. The tax benefit to be recognized is measured as the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement.

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) was enacted into law making significant changes to the U.S. tax code. See Note 7 for additional information on the impact of the Tax Act.

(o) Stock-Based Compensation

The Company has granted stock options under its 2001 Equity Incentive Plan (the “2001 Plan”), 2004 Equity Incentive Plan (the “2004 Plan”) and 2013 Long-Term Incentive Plan, as amended (the “2013 Plan” and together with the 2004 Plan and 2001 Plan, the “Plans”). The Plans permit the granting of awards to employees and non-employee officers, consultants, agents, and independent contractors of the Company in the form of stock appreciation rights, stock awards and units, and stock options. The Plans give broad powers to the Company’s board of directors to administer and interpret the Plans, including the authority to select the individuals to be granted options and rights and to prescribe the particular form and conditions of each option to be granted. In September 2011, the 2001 Plan expired with options outstanding under the plan still available for exercise. On July 31, 2013, the Company’s board of directors approved the adoption of the 2013 Plan, which replaced the 2004 Plan in conjunction with the Company’s IPO. Upon approval of the 2013 Plan, the Company no longer issued awards under the 2004 Plan. The 2004 Plan expired in February 2014, but will continue to govern outstanding awards granted prior to its termination.

The Company accounts for its stock-based employee compensation in accordance with Accounting Standards Codification (“ASC”) 718, Stock Based Compensation. The Company records stock compensation expense on a straight-line basis over the vesting period based on the grant-date fair value of the awards, which is determined using the Black-Scholes option pricing valuation model for stock options and the quoted share price of Potbelly’s common stock on the date of grant for restricted stock units (“RSUs”).

(p) Leases

The Company leases retail shops, warehouse and office space under operating leases. Most lease agreements contain tenant improvement allowances, rent holidays, lease premiums, rent escalation clauses, and/or contingent rent provisions. For purposes of recognizing incentives, premiums, and minimum rental expenses on a straight-line basis over the terms of the leases, the Company uses the date it takes possession of the leased space for construction purposes as the beginning of the term, which is generally two to three months prior to a shop’s opening date. For leases with renewal periods at the Company’s option, the Company determines the expected lease period based on whether the renewal of any options are reasonably assured at the inception of the lease. In addition to rental expense, certain leases require the Company to pay a portion of real estate taxes, utilities, building operating expenses, insurance and other charges in addition to rent.

For tenant improvement allowances, rent escalations, and rent holidays, the Company records a deferred rent liability in its consolidated balance sheets and amortizes the deferred rent over the terms of the leases as reductions to occupancy expense in the consolidated statements of operations.

(q) Revenue Recognition

Revenue from retail shops is presented net of discounts and recognized when food and beverage products are sold. Sales taxes collected from customers are excluded from revenues and the obligation is included in accrued liabilities until the taxes are remitted to the appropriate taxing authorities.

Potbelly sells gift cards to customers and records the sale as a liability. The liability is released once the card is redeemed. Historically a portion of these gift card sales is not redeemed by the customer (“breakage”). Potbelly recognizes breakage two years after the period of sale. The Company monitors the actual patterns of redemption and updates its estimates and assumptions regarding redemption as the pattern changes. The Company recognized gift card breakage income of $396 thousand, $254 thousand and $175 thousand for the fiscal years ended 2017, 2016 and 2015, respectively, which is recorded within other operating expenses in the consolidated statements of operations.

The Company earns an initial franchise fee, a franchise development agreement fee and ongoing royalty fees under the Company’s franchise agreements. Initial franchise fee revenue is recognized at the point a franchise shop opens for business to the public, as this is the point in time when the Company has substantially performed all initial services required under the franchise agreement. The Company recognized franchise fee revenue of $0.7 million, $0.4 million and $0.4 million in fiscal year 2017, 2016 and 2015, respectively. Initial franchise fee payments received by the Company before the shop opens are recorded as deferred revenue in the consolidated balance sheet. The Company has deferred revenue related to initial franchise fees of $0.7 million and $0.7 million included in accrued expenses as of December 31, 2017 and December 25, 2016, respectively. Franchise development agreement fees represent the exclusivity rights for a geographical area paid by a third party to develop Potbelly shops for a certain period of time. Franchise development agreement fee payments received by the Company are recorded as deferred revenue in the consolidated balance sheet and amortized over the life of the franchise development agreement. The Company had deferred revenue related to franchise development agreement fees of $0.5 million and $0.4 million recorded in accrued expenses as of December 31, 2017 and December 25, 2016, respectively. Royalty fees are based on a percentage of sales and are recorded as revenue as the fees are earned and become receivable from the franchisee. The Company recognized royalty fees revenue of $2.5 million, $1.9 million and $1.5 million for fiscal years 2017, 2016, and 2015, respectively.

(r) Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers.” The pronouncement was issued to clarify the principles for recognizing revenue and to develop a common revenue standard and disclosure requirements for U.S. GAAP and International Financial Reporting Standards (IFRS). The FASB approved a one-year deferral of the effective date of ASU 2014-09, such that it will become effective for the annual period beginning after December 15, 2017. In addition, the FASB issued ASU 2016-08, ASU 2016-10 and ASU 2016-12 in March 2016, April 2016 and May 2016, respectively, to help provide interpretive clarifications on the new guidance in Accounting Standards Codification (ASC) Topic 606. Potbelly will adopt the standard effective the first quarter of 2018 and apply the amendments using the modified retrospective method. The Company has determined that the adoption will not have a material impact on sandwich shop sales, but will impact franchise revenue and gift card breakage. Potbelly licenses intellectual property and trademarks to franchisees through franchise arrangements. As part of these agreements, Potbelly receives an initial franchise fee payment which is recognized as revenue when the shop opens. Effective for the annual period beginning January 1, 2018, initial franchise fees will generally be recognized as revenue over the life of the contract. Potbelly sells gift cards to customers and records the sale as a liability. The liability is released once the card is redeemed. Historically a portion of these gift card sales is not redeemed by the customer (“breakage”) and Potbelly recognized breakage two years after the period of sale. Effective for the annual period beginning January 1, 2018, expected breakage will be recognized as customers redeem the gift cards. As a result of these changes, Potbelly expects the accumulated deficit to increase by $0.8 million (net of tax). The franchise revenue adjustment will impact accrued expenses and other long-term liabilities and the breakage adjustment will impact accrued expenses.

In February 2016, the FASB issued ASU No. 2016-02, “Leases,” which will replace the existing guidance in ASC 840, “Leases.” The pronouncement requires a dual approach for lessee accounting under which a lessee would account for leases as finance leases or operating leases. Both finance leases and operating leases will result in the lessee recognizing a right-of-use asset and a corresponding lease liability. For finance leases, the lessee will recognize interest expense and amortization of the right-of-use asset and for operating leases, the lessee will recognize expense on a straight-line basis. The pronouncement is effective for fiscal years beginning after December 15, 2018, including annual and interim periods thereafter. In addition, the pronouncement requires the use of the modified retrospective method, which will require an adjustment to the consolidated financial statements. The Company is currently evaluating the impact ASU 2016-02 will have on its financial position, results of operations and cash flows but expects that it will result in a material increase in its long-term assets and liabilities given the Company has a significant number of leases.

In March 2016, the FASB issued ASU No. 2016-09, “Compensation – Stock Compensation (Topic 718).” The pronouncement simplifies the accounting for the taxes related to stock-based compensation, including the accounting for income taxes, forfeitures and statutory tax withholding requirements, as well as classification within the statement of cash flows. The pronouncement is effective for annual periods beginning after December 15, 2016, including annual and interim periods. Potbelly adopted ASU 2016-09 in the first quarter of 2017. The primary impact of adoption was the recognition of excess tax benefits and deficiencies that arise upon vesting or exercise of share-based payments in the Income Statement as income tax expense instead of a component of equity recorded to paid-in capital. This aspect of the new guidance, which was required to be adopted prospectively, resulted in an additional income tax expense of $2.1 million for the fiscal year 2017. Potbelly has elected to continue to estimate forfeitures expected to occur to determine the amount of compensation cost to be recognized in each period. Excess income tax benefits and deficiencies from stock-based compensation arrangements are now classified as cash flow from operations, instead of as cash flow used in financing activities. The Company elected to apply this change in presentation prospectively and as such prior periods have not been adjusted. Additionally, in accordance with the new standard, the Company now excludes excess tax benefits and deficiencies from the assumed proceeds available to repurchase shares in the computation of the Company’s diluted earnings per share.

(s) Commitments and Contingencies

The Company is subject to legal proceedings including claims and liabilities, such as employment-related claims and slip and fall cases, which arise in the ordinary course of business and are generally covered by insurance. In the opinion of management, the amount of ultimate liability with respect to those actions should not have a material adverse impact on the Company’s financial position or results of operations and cash flows.

In October 2017, plaintiffs filed a purported collective and class action lawsuit in the United States District Court for the Southern District of New York against the Company alleging violations of the Fair Labor Standards Act ("FLSA") and New York Labor Law ("NYLL"). The plaintiffs allege that the Company violated the FLSA and NYLL by not paying overtime compensation to our assistant managers and violated NYLL by not paying spread-of-hours pay. Potbelly believes the assistant managers were properly classified under state and federal law. The Company intends to vigorously defend this action. This case is at an early stage, and Potbelly is therefore unable to make a reasonable estimate of the probable loss or range of losses, if any, that might arise from this matter.

In 2016, the Company received notice of a potential claim alleging that it violated the Fair Labor Standards Act by not paying overtime to its assistant managers, whom the Company had classified as exempt employees. Although the Company believes that its assistant managers were properly classified as exempt under both federal and state laws, the Company agreed to mediate the matter. On February 20, 2017, the parties entered into a Settlement Agreement and Release whereby participating assistant managers agreed to release the Company from all federal and/or state wage and hour claims in exchange for a gross settlement amount of $1.3 million. As part of the settlement process, a complaint was filed on February 17, 2017 in the Circuit Court of the Fifteenth Judicial Circuit in and for Palm Beach County, Florida. A motion seeking the Court’s approval of the settlement was filed on February 21, 2017, which was subsequently approved. In March 2017, the Company paid out the settlement, which was recorded against the previously established liability.

Many of the food products the Company purchases are subject to changes in the price and availability of food commodities, including, among other things, beef, poultry, grains, dairy and produce. The Company works with its suppliers and uses a mix of forward pricing protocols for certain items including agreements with its supplier on fixed prices for deliveries at a time in the future and agreements on a fixed price with its supplier for the duration of those protocols. The Company also utilizes formula pricing protocols under which the prices the Company pays are based on a specified formula related to the prices of the goods, such as spot prices. The Company’s use of any forward pricing arrangements varies substantially from time to time and these arrangements tend to cover relatively short periods (i.e., typically twelve months or less). Such contracts are used in the normal purchases of the Company’s food products and not for speculative purposes, and as such are not required to be evaluated as derivative instruments. The Company does not enter into futures contracts or other derivative instruments.

Fair Value Measurement	12 Months Ended
Fair Value Measurement	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurement	(3) Fair Value Measurement The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and all other current liabilities approximate fair values due to the short maturities of these balances. The Company assesses potential impairments to its long-lived assets, which includes property and equipment, on a quarterly basis or whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. Shop-level assets are grouped at the individual shop-level for the purpose of the impairment assessment. Recoverability of an asset is measured by a comparison of the carrying amount of an asset to its estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of the asset group exceeds its estimated undiscounted future cash flows, an impairment charge is recognized as the amount by which the carrying amount of the asset exceeds the fair value of the asset. The fair value of the shop assets was determined using the discounted future cash flow method of anticipated cash flows through the shop’s lease-end date using fair value measurement inputs classified as Level 3. Level 3 inputs are derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. After performing a periodic review of the Company’s shops during each quarter of 2017, 2016 and 2015, it was determined that indicators of impairment were present for certain shops as a result of continued underperformance. The Company performed an impairment analysis related to these shops and recorded impairment charges of $10.6 million, $4.0 million and $3.4 million for the fiscal years 2017, 2016 and 2015, respectively. As a result of damage sustained by Hurricane Harvey, the Company recorded a $0.7 million impairment for the fiscal year 2017, with insurance recoveries of $0.7 million also recorded within the same caption.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Earnings (Loss) Per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings (Loss) Per Share

(4) Earnings (Loss) Per Share

Basic and diluted income per common share attributable to common stockholders are calculated using the weighted average number of common shares outstanding for the period. Diluted income per common share attributable to common stockholders is computed by dividing the income allocated to common stockholders by the weighted average number of fully diluted common shares outstanding. In periods of a net loss, no potential common shares are included in diluted shares outstanding as the effect is anti-dilutive. For the fiscal year 2017, the Company had a loss per share, therefore, shares were excluded for potential stock option exercises and warrant exercises.

The following table summarizes the earnings (loss) per share calculation:

	Fiscal Year
	2017			2016		2015
Net income (loss) attributable to Potbelly Corporation	$	(6,956	)	$	8,212	$	5,628
Weighted average common shares outstanding-basic		25,045,427			25,623,809		28,002,005
Plus: Effect of potential stock options exercise		—			549,578		577,156
Plus: Effect of potential warrant exercise		—			57,980		55,235
Weighted average common shares outstanding-diluted		25,045,427			26,231,367		28,634,396
Income (loss) per share available to common stockholders-basic	$	(0.28	)	$	0.32	$	0.20
Income (loss) per share available to common stockholders-diluted	$	(0.28	)	$	0.31	$	0.20
Potentially dilutive shares that are considered anti-dilutive:
Shares		3,375,591			1,164,047		898,966

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property Plant And Equipment [Abstract]

Property and Equipment

(5) Property and Equipment

Property and equipment, net consisted of the following (in thousands):

	December 31,			December 25,
	2017			2016
Leasehold improvements	$	174,602		$	170,196
Machinery and equipment		49,427			47,668
Furniture and fixtures		33,893			32,561
Computer equipment and software		29,832			23,162
Construction in progress		3,831			5,601
		291,585			279,188
Less: Accumulated depreciation		(187,726	)		(172,114	)
	$	103,859		$	107,074

Accrued Expenses

12 Months Ended

Dec. 31, 2017

Accrued Liabilities Current [Abstract]

Accrued Expenses

(6) Accrued Expenses

Accrued expenses consisted of the following (in thousands):

	December 31,		December 25,
	2017		2016
Accrued labor and related expenses	$	7,352	$	6,120
Deferred gift card revenue		2,305		2,292
Accrued occupancy expenses		2,387		1,538
Deferred rent—current		1,011		706
Accrued corporate and shop expenses		1,882		2,255
Accrued utilities		1,311		1,094
Accrued sales and use tax		2,760		1,857
Accrued construction		891		2,329
Accrued contract termination costs ^(a)		27		28
Accrued legal and professional fees		177		1,756
Accrued other		3,170		3,107
Total	$	23,273	$	23,082

(a)	The Company incurs expenses associated with exit activity for certain signed lease agreements, which are recognized in general and administrative expenses. Accrued contract termination costs consisted of the following (in thousands):

	December 31,			December 25,
	2017			2016
Accrued contract termination costs—beginning balance	$	28		$	21
Contract termination costs incurred		578			24
Contract termination costs settled and paid		(579	)		(17	)
Accrued contract termination costs—ending balance	$	27		$	28

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

(7) Income Taxes

Income (loss) before income taxes for the Company’s domestic and foreign operations was as follows (in thousands):

	Fiscal Year
	2017			2016		2015
Domestic operations	$	(2,513	)	$	12,411	$	8,660
Foreign operations		466			468		548
Total	$	(2,047	)	$	12,879	$	9,208

Income tax expense consisted of the following (in thousands):

	Fiscal Year
	2017			2016			2015
Federal:
Current	$	(3,728	)	$	4,652		$	2,450
Deferred		8,792			(1,386	)		209
		5,064			3,266			2,659
State and Local:
Current		150			1,426			1,047
Deferred		(584	)		(273	)		(281	)
		(434	)		1,153			766
Foreign:
Current		13			24			41
		13			24			41
Income tax expense	$	4,643		$	4,443		$	3,466

Income tax expense differed from the amounts computed by applying the U.S. federal income tax rates to income (loss) before income taxes as a result of the following (in thousands):

	Fiscal Year
	2017			2016			2015
Computed “expected” tax expense (benefit)	$	(716	)	$	4,508		$	3,223
Increase (reduction) resulting from:
Minority interest		(105	)		(89	)		(45	)
Permanent differences		96			131			51
State and local income taxes, net of federal income tax effect		5			673			533
FICA and other tax credits		(502	)		(556	)		(392	)
Equity Compensation		2,112			—			—
Adjustments		(93	)		(300	)		(72	)
Rate change		3,846			76			236
Change in valuation allowance		—			—			(68	)
	$	4,643		$	4,443		$	3,466

On December 22, 2017, the Tax Act was enacted into law making significant changes to the U.S. tax code, including: (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) implementing bonus depreciation that will allow for full expensing of qualified property; (3) implementing limitations on the deductibility of certain executive compensation; and (4) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017.

On that same date, the SEC staff also issued Staff Accounting Bulletin (SAB) 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. A company must reflect the income tax effects of those aspects of the Act for which accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements.

At December 31, 2017, the Company has not completed the accounting for the tax effects of enactment of the Tax Act; however, the Company made a reasonable estimate of the effects. The Company is still analyzing certain aspects of the Act and refining its calculations, which could potentially affect the measurement of the amounts recorded at December 31, 2017.

In connection with the Company’s initial analysis of the impact of the Tax Act, Potbelly recorded a provisional tax expense of $3.8 million for the fiscal year 2017, the period in which the legislation was enacted. This expense was due to the remeasurement of certain deferred tax assets and liabilities using the lower U.S. corporate tax rate at which the assets are expected to reverse in the future. Consequently, the Company recorded a net decrease to deferred tax assets of $3.8 million with a corresponding adjustment to deferred income tax expense of $3.8 million for the fiscal year 2017.

Due to the adoption of ASU 2016-09 in 2017, all excess tax benefits and deficiencies are recognized as income tax expense in the Company’s Consolidated Statement of Operations.

The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities reflected in the consolidated balance sheets are presented below (in thousands):

	December 31,			December 25,
	2017			2016
Deferred tax assets:
Net operating loss carryforwards	$	11		$	—
Accrued liabilities		842			1,848
Deferred revenue		120			323
Stock-based compensation		4,495			8,104
Property and equipment		3,258			6,293
Deferred rent		4,229			5,656
Tax credits and charitable contribution carryforwards		273			—
Other		127			234
Total deferred tax assets		13,355			22,458
Net deferred tax assets		13,355			22,458
Deferred tax liabilities:
Prepaids		(452	)		(635	)
Intangible assets		(977	)		(1,351	)
Smallwares		(574	)		(801	)
Other		(150	)		(261	)
Total deferred tax liabilities		(2,153	)		(3,048	)
Net deferred tax assets	$	11,202		$	19,410

As of December 31, 2017 and December 25, 2016, the Company has no valuation allowances recorded based on management’s assessment of the amount of its deferred tax assets that are more likely than not to be realized.

In accordance with its accounting policy, the Company recognizes accrued interest and penalties related to unrecognized tax benefits as a component of income tax expense. As of December 31, 2017 and December 25, 2016, the Company had no interest or penalties accrued.

The tax years prior to 2014 are generally closed for examination by the United States Internal Revenue Service. However, certain of these tax years are open for examination as a result of net operating losses generated in these years and utilized in subsequent years. The Company’s last IRS examination was for the 2014 tax year; no IRS audits are currently ongoing. State statutes are generally open for audit for the 2013 to 2017 tax years. Additionally, certain tax years through 2017 are open for examination by certain state tax authorities.

Debt and Credit Facilities	12 Months Ended
Debt and Credit Facilities	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt and Credit Facilities	(8) Debt and Credit Facilities Credit facility JPMorgan Chase Bank, N.A. On December 9, 2015, the Company entered into an amended and restated five-year revolving credit facility agreement that expires in November 2020. The credit agreement provides, among other things, for a revolving credit facility in a maximum principal amount of $50 million, with possible future increases to $75 million under an expansion feature. Borrowings under the credit facility generally bear interest at the Company’s option at either (i) a eurocurrency rate determined by reference to the applicable LIBOR rate plus a margin ranging from 1.00% to 1.75% or (ii) a prime rate as announced by JP Morgan Chase plus a margin ranging from 0.00% to 0.50%. The applicable margin is determined based upon the Company’s consolidated total leverage ratio. On the last day of each calendar quarter, the Company is required to pay a commitment fee ranging from 0.125% to 0.20% per annum in respect of any unused commitments under the credit facility, with the specific rate determined based upon the Company’s consolidated total leverage ratio. So long as certain total leverage ratios are met, there is no limit on the “restricted payments” (primarily distributions and equity repurchases) that the Company may make. As of December 31, 2017, the Company had no amounts outstanding under the credit facility.

Capital Stock and Warrants	12 Months Ended
Capital Stock and Warrants	Dec. 31, 2017
Equity [Abstract]
Capital Stock and Warrants	(9) Capital Stock and Warrants As of December 31, 2017 and December 25, 2016, the Company had authorized an aggregate of 210,000,000 shares of capital stock, of which 200,000,000 shares were designated as common stock and 10,000,000 shares were designated as preferred stock. As of December 31, 2017, the Company had issued and outstanding 31,831,196 and 24,999,688 shares of common stock, respectively. As of December 25, 2016, the Company had issued and outstanding 30,892,539 and 25,139,127 shares of common stock, respectively. Common Stock As of December 31, 2017, each share of common stock has the same relative rights and was identical in all respects to each other share of common stock. Each holder of shares of common stock is entitled to one vote for each share held by such holder at all meetings of stockholders. On September 8, 2016, the Company announced that its Board of Directors authorized a share repurchase program of up to $30.0 million of the Company’s common stock. The Company’s previous $35.0 million share repurchase program, authorized in September 2015, was completed in July 2016. The new program permits the Company, from time to time, to purchase shares in the open market (including in pre-arranged stock trading plans in accordance with the guidelines specified in Rule 10b5-1 under the Securities Exchange Act of 1934, as amended) or in privately negotiated transactions. During the fiscal year 2017, the Company repurchased 1,078,096 shares of its common stock for approximately $12.9 million, including cost and commission, in open market transactions. As of December 31, 2017, the remaining dollar value of authorization under the share repurchase program was $14.8 million, which does not include commission. Repurchased shares are included as treasury stock in the consolidated balance sheets and the consolidated statements of equity. Warrants The Company had zero and 241,704 warrants outstanding as of December 31, 2017 and December 25, 2016, respectively. The remaining outstanding warrants were exercised in June 2017 with proceeds of $2.0 million received by the Company.

Operating Leases

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Operating Leases

(10) Operating Leases

The Company leases office space for its corporate office and commercial spaces for its shops under various long-term operating lease agreements. The leases for the Company’s shop locations generally have initial terms of 10 years and typically provide for two renewal options in five-year increments as well as for rent escalations. These leases expire or become subject to renewal clauses at various dates from 2018 to 2032. Some of the leases provide for base rent, plus additional rent based on gross sales, as defined in each lease agreement. The Company is also generally obligated to pay certain real estate taxes, utilities, building operating expenses, insurance, and various other expenses related to properties.

Rental expense under operating lease agreements were as follows (in thousands):

	Fiscal Year
	2017			2016			2015
Minimum rentals	$	45,334		$	40,252		$	36,955
Contingent rentals		1,408			1,755			1,827
Less: sublease rentals		(33	)		(94	)		(94	)
Total	$	46,709		$	41,913		$	38,688

A schedule by year of future minimum rental payments required under operating leases, excluding contingent rent, that have initial or remaining non-cancelable lease terms in excess of one year, as of December 31, 2017, is as follows (in thousands):

Years Ending	Minimum
2018	$	47,116
2019		43,449
2020		41,315
2021		37,383
2022		32,168
Thereafter		87,582
Total minimum payments required*	$	289,013

*	Minimum payments have not been reduced by minimum sublease rentals of $0.1 million due in the future.

Certain leases have outstanding letters of credit in lieu of rent deposits expiring at various dates through September 2018. The letters of credit were $0.2 million, $0.7 million and $0.6 million in aggregate for the fiscal years ended December 31, 2017, December 25, 2016 and December 27, 2015, respectively. Under the credit facility, outstanding letters of credit are subject to an annual fee of 1.5% and reduce the available borrowing to the Company.

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2017
Postemployment Benefits [Abstract]
Employee Benefit Plan	(11) Employee Benefit Plan The Company sponsors a 401(k) profit sharing plan for all employees who are eligible based upon age and length of service. The Company made matching contributions of $0.4 million for fiscal years 2017, 2016 and 2015.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

(12) Stock-Based Compensation

Stock-Based Compensation Granted Under the 2013 Long-Term Incentive Plan

Stock options and restricted stock units (“RSUs”) are awarded under the 2013 Long-Term Incentive Plan, as amended (the “2013 Plan”) to eligible employees and certain non-employee members of its Board of Directors. The 2013 Plan permits the granting of awards to employees and non-employee officers, consultants, agents, and independent contractors of the Company in the form of stock appreciation rights, stock awards and units, and stock options. The 2013 Plan gives broad powers to the Company’s Board of Directors to administer and interpret the 2013 Plan, including the authority to select the individuals to be granted options and rights and to prescribe the particular form and conditions of each option to be granted.

On July 31, 2013, the Company’s Board of Directors approved the adoption of the 2013 Plan, which replaced the 2004 Equity Incentive Plan (the “2004 Plan” and together with the 2013 Plan, the “Plans”) in conjunction with the Company’s IPO. Upon approval of the 2013 Plan, the Company no longer issued awards under the 2004 Plan. The 2004 Plan expired in February 2014, but will continue to govern outstanding awards granted prior to its termination. As of December 31, 2017, there have been 2,110,681 options, 28,240 shares of common stock and 329,585 shares of restricted stock units granted under the 2013 Plan. As of December 31, 2017, there are 639,175 shares reserved for future issuance.

Stock Options

Under the Plans, the number of shares and exercise price of each option are determined by the committee designated by the Company’s Board of Directors. The options granted are generally exercisable within a 10-year period from the date of grant. The company awards options to certain employees including the senior leadership team. Options outstanding expire on various dates through the year 2027. The range of exercise prices for options outstanding as of December 31, 2017 is $7.00 to $20.53 per option, and the options generally vest in one-fourth and one-fifth increments over four and five-year periods, respectively.

Activity under the Plans and the Agreement is as follows:

Options	Shares (Thousands)			Weighted Average Exercise Price		Aggregate Intrinsic Value (Thousands)		Weighted Average Remaining Term (Years)
Outstanding—December 28, 2014		4,613		$	10.10	$	12,731		5.62
Granted		565			13.21
Exercised		(576	)		8.30
Canceled		(234	)		13.89
Outstanding—December 27, 2015		4,368		$	10.53	$	9,742		5.10
Granted		369			13.65
Exercised		(536	)		10.77
Canceled		(188	)		14.40
Outstanding—December 25, 2016		4,013		$	10.61	$	13,455		4.78
Granted		464			12.09
Exercised		(653	)		9.94
Canceled		(515	)		12.18
Outstanding—December 31, 2017		3,309		$	10.71	$	7,699		4.90
Exercisable—December 31, 2017		2,421		$	9.87	$	7,398		3.57

The following table reflects the average assumptions utilized in the Black-Scholes option-pricing model to value the options granted for each year:

	2017			2016			2015
Risk-free interest rate		2.0	%		1.7	%		1.9	%
Expected life (years)		6.25			7.00			7.00
Expected dividend yield		—			—			—
Volatility		36.0	%		49.4	%		45.3	%
Weighted average grant date fair value	$	4.76		$	7.05		$	6.45

The risk-free rate is based on U.S. Treasury rates in effect at the time of the grant with a similar duration of the expected life of the options. The expected life of options granted is derived from the average of the vesting period and the term of the option. The Company has not paid dividends to date (with exception to the one-time dividend paid to stockholders prior to the initial public offering) and does not plan to pay dividends in the near future. Beginning October 2015, expected volatility of the options was calculated using the Company’s historical data since its initial public offering. Prior to October 2015, the Company calculated expected volatility of the options based on historical data from selected peer public company restaurants.

RSUs

The Company awards restricted stock units (“RSUs”) to certain non-employee members of its Board of Directors and the senior leadership team. In May 2017, the Company issued 153,369 shares of RSUs with a grant date fair value of $11.05 upon issuance. In August 2017, the Company issued 2,608 shares of RSUs with a grant date fair value of $11.15 upon issuance. In November 2017, the Company issued 6,848 and 78,125 shares of RSUs with grant date fair values of $11.50 and $12.80 upon issuance, respectively. The Board of Director grants have a vesting schedule of 50% on the first anniversary of the grant date and 50% on the second anniversary of the grant date. The senior leadership team grants vest in one-third increments over a three-year period.

In May 2016, the Company issued 52,558 shares of RSUs with a grant date fair value of $13.27 upon issuance. In May 2015, the Company issued 30,856 shares of RSUs with a grant date fair value of $14.26 upon issuance. In August 2015, the Company issued 5,221 shares of RSUs with a grant date fair value of $11.88 upon issuance.

Stock-Based Compensation Expense

Stock-based compensation is measured at the grant date, based on the calculated fair value of the award and is recognized as expense over the requisite employee service period, which is generally the vesting period of the grant, with a corresponding increase to additional paid-in-capital. For the fiscal year 2017, the Company recognized stock compensation expense of $4.7 million, of which $0.6 million was related to Chief Executive Officer (CEO) transition costs. For the fiscal years 2016 and 2015, the company recognized stock compensation expense of $3.1 million and $2.4 million, respectively. As of December 31, 2017, unrecognized stock-based compensation expense was $4.7 million, which will be recognized through fiscal year 2021. The Company records stock-based compensation expense within general and administrative expenses in the consolidated statements of operations.

Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

(13) Quarterly Financial Data (Unaudited)

The unaudited quarterly information includes all normal recurring adjustments that the Company considers necessary for the fair presentation of the information shown below. The Company’s quarterly results have been and will continue to be affected by the timing of new shop openings and their associated pre-opening costs. As a result of these and other factors, the financial results for any quarter may not be indicative of the results for any future period.

The following table presents selected unaudited quarterly financial data for periods indicated (in thousands, except per share data):

	Fiscal Year 2017 (1)
	March 26		June 25			September 24			December 31
Total revenues	$	101,699	$	108,136		$	106,127		$	112,149
Income (loss) from operations		1,263		164			(574	)		(2,776	)
Net income (loss) attributable to Potbelly Corporation		683		(138	)		(240	)		(7,261	)
Income (loss) per share available to common stockholders-basic		0.03		(0.01	)		(0.01	)		(0.29	)
Income (loss) per share available to common stockholders-diluted		0.03		(0.01	)		(0.01	)		(0.29	)

	Fiscal Year 2016 (1)
	March 27		June 26		September 25		December 25
Total revenues	$	95,955	$	105,036	$	103,782	$	102,358
Income from operations		1,889		5,512		2,842		2,770
Net income attributable to Potbelly Corporation		1,088		3,373		1,795		1,956
Income per share available to common stockholders-basic		0.04		0.13		0.07		0.08
Income per share available to common stockholders-diluted		0.04		0.13		0.07		0.08

(1)	Fiscal year 2017 was a 53-week year. The first three fiscal quarters consisted of 13 weeks and the fourth fiscal quarter consisted of 14 weeks. Fiscal year 2016 was a 52-week year. Each quarter of the fiscal year consisted of 13 weeks.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	(14) Commitments and Contingencies The Company is subject to legal proceedings including claims and liabilities, such as employment-related claims and slip and fall cases, which arise in the ordinary course of business and are generally covered by insurance. In the opinion of management, the amount of ultimate liability with respect to those actions should not have a material adverse impact on the Company’s financial position or results of operations and cash flows. In October 2017, plaintiffs filed a purported collective and class action lawsuit in the United States District Court for the Southern District of New York against the Company alleging violations of the Fair Labor Standards Act and New York Labor Law. The plaintiffs allege that the Company violated the FLSA and NYLL by not paying overtime compensation to our assistant managers and violated NYLL by not paying spread-of-hours pay. Potbelly believes the assistant managers were properly classified under state and federal law. The Company intends to vigorously defend this action. This case is at an early stage, and Potbelly is therefore unable to make a reasonable estimate of the probable loss or range of losses, if any, that might arise from this matter. In 2016, the Company received notice of a potential claim alleging that it violated the Fair Labor Standards Act by not paying overtime to its assistant managers, whom the Company had classified as exempt employees. Although the Company believes that its assistant managers were properly classified as exempt under both federal and state laws, the Company agreed to mediate the matter. On February 20, 2017, the parties entered into a Settlement Agreement and Release whereby participating assistant managers agreed to release the Company from all federal and/or state wage and hour claims in exchange for a gross settlement amount of $1.3 million. As part of the settlement process, a complaint was filed on February 17, 2017 in the Circuit Court of the Fifteenth Judicial Circuit in and for Palm Beach County, Florida. A motion seeking the Court’s approval of the settlement was filed on February 21, 2017, which was subsequently approved. In March 2017, the Company paid out the settlement, which was recorded against the previously established liability.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Business

Potbelly Corporation (the “Company” or “Potbelly”), through its wholly-owned subsidiaries, operates or franchises Potbelly Sandwich Works sandwich shops in 31 states and the District of Columbia. The first domestic franchise locations administered by the Company opened during February 2011. Additionally, in February 2011, the Company opened its first international franchise in the Middle East. In July 2015, the Company opened its first franchise shop in the United Kingdom; in October 2016, the Company opened its first franchise shop in Canada; and in December 2017, the Company opened its first franchise shop in India. Additionally, during each of July 2015 and April 2016, the Company transitioned one franchise shop into a company-operated shop for a purchase price of $0.3 million and $1.1 million, respectively. The Company did not record any goodwill related to the July 2015 transaction and recorded $0.8 million of goodwill related to the April 2016 transaction. The Company believes both acquisitions are immaterial.

Principles of Consolidation

(a) Principles of Consolidation

Certain reclassifications have been made to conform the prior period consolidated financial statements to the current period presentation.

Reporting Period

(b) Reporting Period

Segment Reporting

Use of Estimates

(d) Use of Estimates

Fair Value Measurements

(e) Fair Value Measurements

•

Level 1 — Quoted prices in active markets for identical assets or liabilities.

•

Financial Instruments

(f) Financial Instruments

Cash and Cash Equivalents

(g) Cash and Cash Equivalents

Accounts Receivable, net

(h) Accounts Receivable, net

Inventories

(i) Inventories

Property and Equipment

(j) Property and Equipment

Intangible Assets

(k) Intangible Assets

Pre-opening Costs

(l) Pre-opening Costs

Advertising Expenses

(m) Advertising Expenses

Income Taxes

(n) Income Taxes

Stock-Based Compensation

(o) Stock-Based Compensation

Leases

(p) Leases

Revenue Recognition

(q) Revenue Recognition

Recent Accounting Pronouncements

(r) Recent Accounting Pronouncements

Commitments and Contingencies

(s) Commitments and Contingencies

Earnings (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Summary of Earnings (Loss) Per Share Calculation

The following table summarizes the earnings (loss) per share calculation:

	Fiscal Year
	2017			2016		2015
Net income (loss) attributable to Potbelly Corporation	$	(6,956	)	$	8,212	$	5,628
Weighted average common shares outstanding-basic		25,045,427			25,623,809		28,002,005
Plus: Effect of potential stock options exercise		—			549,578		577,156
Plus: Effect of potential warrant exercise		—			57,980		55,235
Weighted average common shares outstanding-diluted		25,045,427			26,231,367		28,634,396
Income (loss) per share available to common stockholders-basic	$	(0.28	)	$	0.32	$	0.20
Income (loss) per share available to common stockholders-diluted	$	(0.28	)	$	0.31	$	0.20
Potentially dilutive shares that are considered anti-dilutive:
Shares		3,375,591			1,164,047		898,966

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property Plant And Equipment [Abstract]

Components of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):

	December 31,			December 25,
	2017			2016
Leasehold improvements	$	174,602		$	170,196
Machinery and equipment		49,427			47,668
Furniture and fixtures		33,893			32,561
Computer equipment and software		29,832			23,162
Construction in progress		3,831			5,601
		291,585			279,188
Less: Accumulated depreciation		(187,726	)		(172,114	)
	$	103,859		$	107,074

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Accrued Liabilities Current [Abstract]

Summary of Accrued Expenses

Accrued expenses consisted of the following (in thousands):

	December 31,		December 25,
	2017		2016
Accrued labor and related expenses	$	7,352	$	6,120
Deferred gift card revenue		2,305		2,292
Accrued occupancy expenses		2,387		1,538
Deferred rent—current		1,011		706
Accrued corporate and shop expenses		1,882		2,255
Accrued utilities		1,311		1,094
Accrued sales and use tax		2,760		1,857
Accrued construction		891		2,329
Accrued contract termination costs ^(a)		27		28
Accrued legal and professional fees		177		1,756
Accrued other		3,170		3,107
Total	$	23,273	$	23,082

(a)	The Company incurs expenses associated with exit activity for certain signed lease agreements, which are recognized in general and administrative expenses. Accrued contract termination costs consisted of the following (in thousands):

	December 31,			December 25,
	2017			2016
Accrued contract termination costs—beginning balance	$	28		$	21
Contract termination costs incurred		578			24
Contract termination costs settled and paid		(579	)		(17	)
Accrued contract termination costs—ending balance	$	27		$	28

Summary of Accrued Contract Termination Costs

Accrued contract termination costs consisted of the following (in thousands):

	December 31,			December 25,
	2017			2016
Accrued contract termination costs—beginning balance	$	28		$	21
Contract termination costs incurred		578			24
Contract termination costs settled and paid		(579	)		(17	)
Accrued contract termination costs—ending balance	$	27		$	28

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Income (Loss) Before Income Taxes

Income (loss) before income taxes for the Company’s domestic and foreign operations was as follows (in thousands):

	Fiscal Year
	2017			2016		2015
Domestic operations	$	(2,513	)	$	12,411	$	8,660
Foreign operations		466			468		548
Total	$	(2,047	)	$	12,879	$	9,208

Components of Income Tax Expense

Income tax expense consisted of the following (in thousands):

	Fiscal Year
	2017			2016			2015
Federal:
Current	$	(3,728	)	$	4,652		$	2,450
Deferred		8,792			(1,386	)		209
		5,064			3,266			2,659
State and Local:
Current		150			1,426			1,047
Deferred		(584	)		(273	)		(281	)
		(434	)		1,153			766
Foreign:
Current		13			24			41
		13			24			41
Income tax expense	$	4,643		$	4,443		$	3,466

Reconciliation of Differences Between Federal Statutory and Effective Income (Loss) Tax Rate

Income tax expense differed from the amounts computed by applying the U.S. federal income tax rates to income (loss) before income taxes as a result of the following (in thousands):

	Fiscal Year
	2017			2016			2015
Computed “expected” tax expense (benefit)	$	(716	)	$	4,508		$	3,223
Increase (reduction) resulting from:
Minority interest		(105	)		(89	)		(45	)
Permanent differences		96			131			51
State and local income taxes, net of federal income tax effect		5			673			533
FICA and other tax credits		(502	)		(556	)		(392	)
Equity Compensation		2,112			—			—
Adjustments		(93	)		(300	)		(72	)
Rate change		3,846			76			236
Change in valuation allowance		—			—			(68	)
	$	4,643		$	4,443		$	3,466

Schedule of Deferred Tax Assets and Liabilities

	December 31,			December 25,
	2017			2016
Deferred tax assets:
Net operating loss carryforwards	$	11		$	—
Accrued liabilities		842			1,848
Deferred revenue		120			323
Stock-based compensation		4,495			8,104
Property and equipment		3,258			6,293
Deferred rent		4,229			5,656
Tax credits and charitable contribution carryforwards		273			—
Other		127			234
Total deferred tax assets		13,355			22,458
Net deferred tax assets		13,355			22,458
Deferred tax liabilities:
Prepaids		(452	)		(635	)
Intangible assets		(977	)		(1,351	)
Smallwares		(574	)		(801	)
Other		(150	)		(261	)
Total deferred tax liabilities		(2,153	)		(3,048	)
Net deferred tax assets	$	11,202		$	19,410

Operating Leases (Tables)

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Schedule Of Rental Expenses Under Operating Leases

Rental expense under operating lease agreements were as follows (in thousands):

	Fiscal Year
	2017			2016			2015
Minimum rentals	$	45,334		$	40,252		$	36,955
Contingent rentals		1,408			1,755			1,827
Less: sublease rentals		(33	)		(94	)		(94	)
Total	$	46,709		$	41,913		$	38,688

Schedule of Future Minimum Rental Payments Under Operating Leases

Years Ending	Minimum
2018	$	47,116
2019		43,449
2020		41,315
2021		37,383
2022		32,168
Thereafter		87,582
Total minimum payments required*	$	289,013

*	Minimum payments have not been reduced by minimum sublease rentals of $0.1 million due in the future.

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Activity Under Plans and Agreement

Activity under the Plans and the Agreement is as follows:

Options	Shares (Thousands)			Weighted Average Exercise Price		Aggregate Intrinsic Value (Thousands)		Weighted Average Remaining Term (Years)
Outstanding—December 28, 2014		4,613		$	10.10	$	12,731		5.62
Granted		565			13.21
Exercised		(576	)		8.30
Canceled		(234	)		13.89
Outstanding—December 27, 2015		4,368		$	10.53	$	9,742		5.10
Granted		369			13.65
Exercised		(536	)		10.77
Canceled		(188	)		14.40
Outstanding—December 25, 2016		4,013		$	10.61	$	13,455		4.78
Granted		464			12.09
Exercised		(653	)		9.94
Canceled		(515	)		12.18
Outstanding—December 31, 2017		3,309		$	10.71	$	7,699		4.90
Exercisable—December 31, 2017		2,421		$	9.87	$	7,398		3.57

Schedule of Average Assumptions to Value Options

The following table reflects the average assumptions utilized in the Black-Scholes option-pricing model to value the options granted for each year:

	2017			2016			2015
Risk-free interest rate		2.0	%		1.7	%		1.9	%
Expected life (years)		6.25			7.00			7.00
Expected dividend yield		—			—			—
Volatility		36.0	%		49.4	%		45.3	%
Weighted average grant date fair value	$	4.76		$	7.05		$	6.45

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Summary of Unaudited Quarterly Financial Data

The following table presents selected unaudited quarterly financial data for periods indicated (in thousands, except per share data):

	Fiscal Year 2017 (1)
	March 26		June 25			September 24			December 31
Total revenues	$	101,699	$	108,136		$	106,127		$	112,149
Income (loss) from operations		1,263		164			(574	)		(2,776	)
Net income (loss) attributable to Potbelly Corporation		683		(138	)		(240	)		(7,261	)
Income (loss) per share available to common stockholders-basic		0.03		(0.01	)		(0.01	)		(0.29	)
Income (loss) per share available to common stockholders-diluted		0.03		(0.01	)		(0.01	)		(0.29	)

	Fiscal Year 2016 (1)
	March 27		June 26		September 25		December 25
Total revenues	$	95,955	$	105,036	$	103,782	$	102,358
Income from operations		1,889		5,512		2,842		2,770
Net income attributable to Potbelly Corporation		1,088		3,373		1,795		1,956
Income per share available to common stockholders-basic		0.04		0.13		0.07		0.08
Income per share available to common stockholders-diluted		0.04		0.13		0.07		0.08

(1)	Fiscal year 2017 was a 53-week year. The first three fiscal quarters consisted of 13 weeks and the fourth fiscal quarter consisted of 14 weeks. Fiscal year 2016 was a 52-week year. Each quarter of the fiscal year consisted of 13 weeks.

Organization and Other Matters - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Apr. 30, 2016 USD ($) Store	Jul. 31, 2015 USD ($) Store	Dec. 25, 2016 USD ($)	Dec. 27, 2015 USD ($)	Dec. 31, 2017 USD ($) State
Nature Of Business And Basis Of Presentation [Line Items]
Number of sandwich works and shops operation states \| State					31
Purchase price of transitioned franchise shop	$ 1,100,000	$ 300,000	$ 1,108,000	$ 333,000
Goodwill			$ 2,222,000		$ 2,222,000
Company-Operated Shops [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Number of franchise shop transitioned \| Store	1	1
Franchise-Operated Shops [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Goodwill	$ 800,000	$ 0

Summary of Significant Accounting Policies - Additional Information (Detail)		1 Months Ended	12 Months Ended
	Feb. 21, 2017 USD ($)	Oct. 31, 2017	Dec. 31, 2017 USD ($) Subsidiary JointVenture Segment	Dec. 25, 2016 USD ($)	Dec. 27, 2015 USD ($)	Apr. 01, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of wholly owned subsidiaries \| Subsidiary			9
Number of joint ventures \| JointVenture			5
Number of operating segments \| Segment			1
Number of reportable segments \| Segment			1
Credit card receivables			$ 1,900,000	$ 1,600,000
Capitalized costs			800,000	600,000	$ 600,000
Impairment charges			10,600,000	4,000,000	3,400,000
Recognized impairment for intangible assets			0	0	0
Advertising expenses			3,400,000	3,000,000	2,900,000
Gift card breakage income recognized			396,000	254,000	175,000
Initial franchise fee			700,000	400,000	400,000
Royalty fees revenue			$ 2,500,000	1,900,000	1,500,000
Term of breakage recognized after sale			2 years
Increase in accumulated deficit			$ (219,990,000)	(213,034,000)
Excess tax deficiency (benefit) from stock-based compensation			2,112,000	(31,000)	$ (308,000)
Purported collective and class action lawsuit filed date		October 2017
Gross settlement amount	$ 1,300,000
ASU No.2014-09 [Member] \| Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Scenario Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase in accumulated deficit						$ (800,000)
ASU No. 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Excess tax deficiency (benefit) from stock-based compensation			2,100,000
Initial Franchise Fees [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue			700,000	700,000
Franchise Development Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue			500,000	$ 400,000
Hurricane Harvey [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment charges			700,000
Insurance recoveries			$ 700,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest rate			51.00%
Estimated period of time between Company's possession of leased space and shop opening date			2 months
Minimum [Member] \| Computer Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			3 years
Minimum [Member] \| Computer Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			3 years
Minimum [Member] \| Machinery and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			3 years
Minimum [Member] \| Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			10 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest rate			80.00%
Estimated period of time between Company's possession of leased space and shop opening date			3 months
Maximum [Member] \| Computer Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			5 years
Maximum [Member] \| Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			5 years
Maximum [Member] \| Computer Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			5 years
Maximum [Member] \| Machinery and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			5 years
Maximum [Member] \| Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful life			15 years

Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges	$ 10.6	$ 4.0	$ 3.4
Hurricane Harvey [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges	0.7
Insurance recoveries	$ 0.7

Earnings (Loss) Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Earnings (Loss) Per Share [Line Items]
Potential common shares included in diluted shares outstanding	3,375,591	1,164,047	898,966
Common Share Options [Member]
Earnings (Loss) Per Share [Line Items]
Potential common shares included in diluted shares outstanding	0

Earnings (Loss) Per Share - Summary of Earnings (Loss) Per Share Calculation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 24, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Earnings Per Share [Abstract]
Net income (loss) attributable to Potbelly Corporation	$ (7,261)	$ (240)	$ (138)	$ 683	$ 1,956	$ 1,795	$ 3,373	$ 1,088	$ (6,956)	$ 8,212	$ 5,628
Weighted average common shares outstanding-basic									25,045,427	25,623,809	28,002,005
Plus: Effect of potential stock options exercise										549,578	577,156
Plus: Effect of potential warrant exercise										57,980	55,235
Weighted average common shares outstanding-diluted									25,045,427	26,231,367	28,634,396
Income (loss) per share available to common stockholders-basic	$ (0.29)	$ (0.01)	$ (0.01)	$ 0.03	$ 0.08	$ 0.07	$ 0.13	$ 0.04	$ (0.28)	$ 0.32	$ 0.20
Income (loss) per share available to common stockholders-diluted	$ (0.29)	$ (0.01)	$ (0.01)	$ 0.03	$ 0.08	$ 0.07	$ 0.13	$ 0.04	$ (0.28)	$ 0.31	$ 0.20
Potentially dilutive shares that are considered anti-dilutive									3,375,591	1,164,047	898,966

Property and Equipment - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 25, 2016
Property Plant And Equipment [Abstract]
Leasehold improvements	$ 174,602	$ 170,196
Machinery and equipment	49,427	47,668
Furniture and fixtures	33,893	32,561
Computer equipment and software	29,832	23,162
Construction in progress	3,831	5,601
Property and equipment, gross	291,585	279,188
Less: Accumulated depreciation	(187,726)	(172,114)
Property and equipment, net	$ 103,859	$ 107,074

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Accrued Liabilities And Other Liabilities [Abstract]
Accrued labor and related expenses	$ 7,352	$ 6,120
Deferred gift card revenue	2,305	2,292
Accrued occupancy expenses	2,387	1,538
Deferred rent—current	1,011	706
Accrued corporate and shop expenses	1,882	2,255
Accrued utilities	1,311	1,094
Accrued sales and use tax	2,760	1,857
Accrued construction	891	2,329
Accrued contract termination costs	27	28	$ 21
Accrued legal and professional fees	177	1,756
Accrued other	3,170	3,107
Total	$ 23,273	$ 23,082

Accrued Expenses - Summary of Accrued Contract Termination Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016
Accrued Liabilities And Other Liabilities [Abstract]
Accrued contract termination costs—beginning balance	$ 28	$ 21
Contract termination costs incurred	578	24
Contract termination costs settled and paid	(579)	(17)
Accrued contract termination costs—ending balance	$ 27	$ 28

Income Taxes - Schedule of Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Income Tax Disclosure [Abstract]
Domestic operations	$ (2,513)	$ 12,411	$ 8,660
Foreign operations	466	468	548
Income (loss) before income taxes	$ (2,047)	$ 12,879	$ 9,208

Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Income Tax Disclosure [Abstract]
Federal, Current	$ (3,728)	$ 4,652	$ 2,450
Federal, Deferred	8,792	(1,386)	209
Federal, Total	5,064	3,266	2,659
State and Local, Current	150	1,426	1,047
State and Local, Deferred	(584)	(273)	(281)
State and Local, Total	(434)	1,153	766
Foreign, Current	13	24	41
Foreign, Total	13	24	41
Income tax expense	$ 4,643	$ 4,443	$ 3,466

Income Taxes - Reconciliation of Differences Between Federal Statutory and Effective Income (Loss) Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Income Tax Disclosure [Abstract]
Computed “expected” tax expense (benefit)	$ (716)	$ 4,508	$ 3,223
Minority interest	(105)	(89)	(45)
Permanent differences	96	131	51
State and local income taxes, net of federal income tax effect	5	673	533
FICA and other tax credits	(502)	(556)	(392)
Equity Compensation	2,112
Adjustments	(93)	(300)	(72)
Rate change	3,846	76	236
Change in valuation allowance			(68)
Income tax expense	$ 4,643	$ 4,443	$ 3,466

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 30, 2018	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Income Tax [Line Items]
U.S. federal corporate tax rate		35.00%
Provisional tax expense due to impact of Tax Act		$ 3,800,000
Net decrease to deferred tax assets corresponding adjustment of deferred income tax expense		3,846,000	$ 76,000	$ 236,000
Change in valuation allowance				$ (68,000)
Unrecognized tax benefits, income tax penalties and interest accrued		0	0
Valuation Allowance Tax Credit Carryforward [Member]
Income Tax [Line Items]
Change in valuation allowance		$ 0	$ 0
Scenario Forecast [Member]
Income Tax [Line Items]
U.S. federal corporate tax rate	21.00%

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 25, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 11
Accrued liabilities	842	$ 1,848
Deferred revenue	120	323
Stock-based compensation	4,495	8,104
Property and equipment	3,258	6,293
Deferred rent	4,229	5,656
Tax credits and charitable contribution carryforwards	273
Other	127	234
Total deferred tax assets	13,355	22,458
Net deferred tax assets	13,355	22,458
Deferred tax liabilities:
Prepaids	(452)	(635)
Intangible assets	(977)	(1,351)
Smallwares	(574)	(801)
Other	(150)	(261)
Total deferred tax liabilities	(2,153)	(3,048)
Net deferred tax assets	$ 11,202	$ 19,410

Debt and Credit Facilities - Additional Information (Detail) - J P Morgan Chase Bank N A [Member] - USD ($)		12 Months Ended
	Dec. 09, 2015	Dec. 31, 2017
Minimum [Member]
Debt Instrument [Line Items]
Percentage of commitment fees based on credit facility		0.125%
Maximum [Member]
Debt Instrument [Line Items]
Percentage of commitment fees based on credit facility		0.20%
Senior Credit Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility agreement term period	5 years
Revolving credit facility agreement expiration date	Nov. 30, 2020
Credit facility, Maximum borrowing capacity	$ 50,000,000
Credit facility, possible future maximum borrowing capacity	$ 75,000,000
Credit facility outstanding amount		$ 0
Senior Credit Facility [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Senior Credit Facility [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.75%
Senior Credit Facility [Member] \| Prime Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.00%
Senior Credit Facility [Member] \| Prime Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%

Capital Stock and Warrants - Additional Information (Detail) - USD ($)		12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015	Sep. 08, 2016	Sep. 08, 2015
Equity [Abstract]
Capital stock, authorized		210,000,000	210,000,000
Common stock, authorized		200,000,000	200,000,000
Preferred stock, authorized		10,000,000	10,000,000
Common stock, issued		31,831,196	30,892,539
Common stock, outstanding		24,999,688	25,139,127
Stock repurchase program, authorized amount					$ 30,000,000	$ 35,000,000
Common stock shares repurchased		1,078,096
Common stock repurchased value		$ 12,941,000	$ 22,321,000	$ 39,754,000
Remaining dollar value of authorization under the share repurchase program		$ 14,800,000
Company warrants outstanding		0	241,704
Proceeds from exercise of stock warrants	$ 2,000,000	$ 1,972,000

Operating Leases - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Option	Dec. 25, 2016 USD ($)	Dec. 27, 2015 USD ($)
Operating Leased Assets [Line Items]
Initial operating lease period	10 years
Number of renewal options under operating leases \| Option	2
Operating lease rent increment term	5 years
Letters of credit in lieu of rent deposits \| $	$ 0.2	$ 0.7	$ 0.6
Letters of credit annual fee percentage	1.50%
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease period for expiration or renewal	2018
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease period for expiration or renewal	2032

Operating Leases - Schedule of Rental Expenses Under Operating Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Operating Leases Rent Expense [Abstract]
Minimum rentals	$ 45,334	$ 40,252	$ 36,955
Contingent rentals	1,408	1,755	1,827
Less: sublease rentals	(33)	(94)	(94)
Total	$ 46,709	$ 41,913	$ 38,688

- Definition

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

+ References + Details

Operating Leases - Schedule of Future Minimum Rental Payments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Leases [Abstract]
2018	$ 47,116
2019	43,449
2020	41,315
2021	37,383
2022	32,168
Thereafter	87,582
Total minimum payments required	$ 289,013

Operating Leases - Schedule of Future Minimum Rental Payments Under Operating Leases (Parenthetical) (Detail) $ in Millions	Dec. 31, 2017 USD ($)
Leases [Abstract]
Minimum sublease rentals due in future	$ 0.1

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Contributions made to profit sharing plan	$ 0.4	$ 0.4	$ 0.4

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended						12 Months Ended
	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	May 31, 2016	Aug. 31, 2015	May 31, 2015	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation expense							$ 4,676	$ 3,057	$ 2,399
Unrecognized stock compensation expense							$ 4,700
Unrecognized stock compensation expense, recognition period							2021
Chief Executive Officer (CEO) Transition Costs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation expense							$ 600
Restricted Stock Units (RSUs) [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued		2,608	153,369	52,558	5,221	30,856
Options vesting period							3 years
Restricted stock units issued, grant-date fair value		$ 11.15	$ 11.05	$ 13.27	$ 11.88	$ 14.26
Vesting description							The senior leadership team grants vest in one-third increments over a three-year period.
Restricted Stock Units (RSUs) [Member] \| First Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		50.00%	50.00%	50.00%	50.00%	50.00%
Restricted Stock Units (RSUs) [Member] \| Second Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		50.00%	50.00%	50.00%	50.00%	50.00%
Restricted Stock Units (RSUs) One [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued	6,848
Restricted stock units issued, grant-date fair value	$ 11.50
Restricted Stock Units (RSUs) One [Member] \| First Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Restricted Stock Units (RSUs) One [Member] \| Second Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Restricted Stock Units (RSUs) Two [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued	78,125
Restricted stock units issued, grant-date fair value	$ 12.80
Restricted Stock Units (RSUs) Two [Member] \| First Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Restricted Stock Units (RSUs) Two [Member] \| Second Anniversary [Member] \| Non-Employee Board Of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
2013 Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted							2,110,681
Shares of common stock reserved for issuance							639,175
Exercise price of options outstanding, lower limit							$ 7.00
Exercise price of options outstanding, higher limit							$ 20.53
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, 2027
Options vesting period							5 years
2013 Long-Term Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period							4 years
2013 Long-Term Incentive Plan [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock							28,240
2013 Long-Term Incentive Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued							329,585

Stock-Based Compensation - Summary of Activity Under Plans and Agreement (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding shares, Beginning balance	4,013	4,368	4,613
Options, Granted	464	369	565
Options, Exercised	(653)	(536)	(576)
Options, Canceled	(515)	(188)	(234)
Options Outstanding shares, Ending balance	3,309	4,013	4,368	4,613
Options Outstanding shares, Exercisable	2,421
Options outstanding weighted average exercise price, Beginning balance	$ 10.61	$ 10.53	$ 10.10
Options, Weighted Average Exercise Price, Granted	12.09	13.65	13.21
Options, Weighted Average Exercise Price, Exercised	9.94	10.77	8.30
Options, Weighted Average Exercise Price, Canceled	12.18	14.40	13.89
Options outstanding weighted average exercise price, Ending balance	10.71	$ 10.61	$ 10.53	$ 10.10
Options outstanding weighted average exercise price, Exercisable	$ 9.87
Options Outstanding Aggregate Intrinsic value	$ 7,699	$ 13,455	$ 9,742	$ 12,731
Options Exercisable Aggregate Intrinsic Value	$ 7,398
Option Outstanding Weighted Average Remaining Term	4 years 10 months 24 days	4 years 9 months 10 days	5 years 1 month 6 days	5 years 7 months 13 days
Options Exercisable Weighted Average Remaining Term	3 years 6 months 25 days

Stock-Based Compensation - Schedule of Average Assumptions to Value Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Risk-free interest rate	2.00%	1.70%	1.90%
Expected life (years)	6 years 3 months	7 years	7 years
Expected dividend yield	0.00%	0.00%	0.00%
Volatility	36.00%	49.40%	45.30%
Weighted average grant date fair value	$ 4.76	$ 7.05	$ 6.45

Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 24, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 112,149	$ 106,127	$ 108,136	$ 101,699	$ 102,358	$ 103,782	$ 105,036	$ 95,955	$ 428,111	$ 407,131	$ 372,849
Income (loss) from operations	(2,776)	(574)	164	1,263	2,770	2,842	5,512	1,889	(1,923)	13,013	9,429
Net income (loss) attributable to Potbelly Corporation	$ (7,261)	$ (240)	$ (138)	$ 683	$ 1,956	$ 1,795	$ 3,373	$ 1,088	$ (6,956)	$ 8,212	$ 5,628
Income (loss) per share available to common stockholders-basic	$ (0.29)	$ (0.01)	$ (0.01)	$ 0.03	$ 0.08	$ 0.07	$ 0.13	$ 0.04	$ (0.28)	$ 0.32	$ 0.20
Income (loss) per share available to common stockholders-diluted	$ (0.29)	$ (0.01)	$ (0.01)	$ 0.03	$ 0.08	$ 0.07	$ 0.13	$ 0.04	$ (0.28)	$ 0.31	$ 0.20

Commitment and Contingencies - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended
	Feb. 21, 2017	Oct. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Purported collective and class action lawsuit filed date		October 2017
Gross settlement amount	$ 1.3