Potbelly (PBPB) 10-Q 4 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 26, 2021	Oct. 24, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 26, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	PBPB
Security Exchange Name	NASDAQ
Entity Registrant Name	Potbelly Corporation
Entity Central Index Key	0001195734
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-26
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		28,750,836
Entity File Number	001-36104
Entity Tax Identification Number	36-4466837
Entity Address, Address Line One	111 N. Canal Street
Entity Address, Address Line Two	Suite 325
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Incorporation, State or Country Code	DE
Entity Address, Postal Zip Code	60606
City Area Code	312
Local Phone Number	951-0600
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 27, 2020
Current assets
Cash and cash equivalents	$ 9,836	$ 11,126
Accounts receivable, net of allowances of $21 and $47 as of September 26, 2021 and December 27, 2020, respectively	5,732	4,354
Inventories	3,186	2,989
Prepaid expenses and other current assets	4,352	4,839
Total current assets	23,106	23,308
Property and equipment, net	52,578	61,193
Right-of-use assets for operating leases	171,343	189,141
Indefinite-lived intangible assets	3,404	3,404
Goodwill	2,222	2,222
Deferred expenses, net and other assets	4,107	4,089
Total assets	256,760	283,357
Current liabilities
Accounts payable	5,452	6,206
Accrued expenses	29,523	23,742
Short-term operating lease liabilities	30,924	35,325
Current portion of long-term debt	1,833	333
Total current liabilities	67,732	65,606
Long-term debt, net of current portion	13,967	15,953
Long-term operating lease liabilities	170,594	189,146
Other long-term liabilities	4,717	7,157
Total liabilities	257,010	277,862
Commitments and contingencies (Note 11)
Equity
Common stock, $0.01 par value—authorized 200,000 shares; outstanding 28,369 and 24,323 shares as of September 26, 2021 and December 27, 2020, respectively	380	339
Warrants	2,566
Additional paid-in-capital	452,113	438,174
Treasury stock, held at cost, 9,774 and 9,612 shares as of September 26, 2021, and December 27, 2020, respectively	(114,511)	(113,266)
Accumulated deficit	(340,778)	(319,477)
Total stockholders’ equity	(230)	5,770
Non-controlling interest	(20)	(275)
Total equity	(250)	5,495
Total liabilities and equity	$ 256,760	$ 283,357

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 27, 2020
Statement Of Financial Position [Abstract]
Allowances on accounts receivable	$ 21	$ 47
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	200,000,000	200,000,000
Common stock, outstanding	28,369,000	24,323,000
Treasury stock, shares	9,774,000	9,612,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Revenues
Total revenues	$ 101,694	$ 72,663	$ 277,248	$ 216,415
Sandwich shop operating expenses
Labor and related expenses	33,087	25,809	93,662	78,090
Occupancy expenses	13,437	13,904	40,598	43,581
Other operating expenses	16,312	12,126	44,343	35,881
Advertising	896	233	1,740	794
General and administrative expenses	7,612	9,588	24,275	27,300
Depreciation expense	3,610	4,699	12,337	15,110
Pre-opening costs				64
Impairment, loss on disposal of property and equipment and shop closures	1,118	1,721	4,497	9,602
Total expenses	104,297	88,801	297,487	271,425
Loss from operations	(2,603)	(16,138)	(20,239)	(55,010)
Interest expense, net	241	268	713	730
Loss before income taxes	(2,844)	(16,406)	(20,952)	(55,740)
Income tax expense (benefit)	16	(2,917)	230	(6,585)
Net loss	(2,860)	(13,489)	(21,182)	(49,155)
Net income (loss) attributable to non-controlling interest	88	(77)	119	(191)
Net loss attributable to Potbelly Corporation	$ (2,948)	$ (13,412)	$ (21,301)	$ (48,964)
Net loss per common share attributable to common stockholders:
Basic	$ (0.10)	$ (0.56)	$ (0.78)	$ (2.06)
Diluted	$ (0.10)	$ (0.56)	$ (0.78)	$ (2.06)
Weighted average shares outstanding:
Basic	28,264	23,957	27,395	23,792
Diluted	28,264	23,957	27,395	23,792
Product [Member]
Revenues
Total revenues	$ 100,996	$ 72,189	$ 275,274	$ 215,013
Sandwich shop operating expenses
Cost of goods sold, excluding depreciation	28,225	20,721	76,035	61,003
Franchise Royalties And Fees [Member]
Revenues
Total revenues	$ 698	$ 474	$ 1,974	$ 1,402

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]Revision of Prior Period, Adjustment [Member]	Common Stock [Member]	Treasury Stock [Member]	Warrants [Member]	Additional Paid-in-Capital [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]Revision of Prior Period, Adjustment [Member]	Non-Controlling Interest [Member]
Beginning balance at Dec. 29, 2019	$ 69,169		$ 331	$ (112,680)		$ 435,278	$ (254,081)		$ 321
Beginning balance, common shares at Dec. 29, 2019			23,638
Cumulative impact (ASU 2016-13 (Topic 326) [Member]) at Dec. 29, 2019		$ (5)						$ (5)
Net income (loss)	(49,155)						(48,964)		(191)
Stock-based compensation plans	(586)		$ 6	(586)		(6)
Stock-based compensation plans, shares			444
Distributions to non-controlling interest	(344)								(344)
Repurchases of common stock	389		$ 1			388
Repurchases of common stock, shares			130
Contributions from non-controlling interest	143								143
Stock-based compensation expense	2,480					2,480
Ending balance at Sep. 27, 2020	22,091		$ 338	(113,266)		438,140	(303,050)		(71)
Ending balance, common shares at Sep. 27, 2020			24,212
Beginning balance at Jun. 28, 2020	34,653		$ 334	(112,757)		436,536	(289,638)		178
Beginning balance, common shares at Jun. 28, 2020			23,898
Net income (loss)	(13,489)						(13,412)		(77)
Stock-based compensation plans	(509)		$ 4	(509)		(4)
Stock-based compensation plans, shares			314
Distributions to non-controlling interest	(172)								(172)
Stock-based compensation expense	1,608					1,608
Ending balance at Sep. 27, 2020	22,091		$ 338	(113,266)		438,140	(303,050)		(71)
Ending balance, common shares at Sep. 27, 2020			24,212
Beginning balance at Dec. 27, 2020	$ 5,495		$ 339	(113,266)		438,174	(319,477)		(275)
Beginning balance, common shares at Dec. 27, 2020	24,323		24,323
Cumulative impact at Dec. 27, 2020	$ (319,477)
Net income (loss)	(21,182)						(21,301)		119
Stock-based compensation plans	(1,245)		$ 9	(1,245)		(9)
Stock-based compensation plans, shares			796
Proceeds from exercise of stock options	219					219
Issuance of common shares and warrants, net of fees	14,839		$ 32		$ 2,566	12,241
Issuance of common shares and warrants, net of fees, shares			3,250
Contributions from non-controlling interest	136								136
Stock-based compensation expense	1,488					1,488
Ending balance at Sep. 26, 2021	$ (250)		$ 380	(114,511)	2,566	452,113	(340,778)		(20)
Ending balance, common shares at Sep. 26, 2021	28,369		28,369
Beginning balance at Jun. 27, 2021	$ 2,530		$ 378	(113,951)	2,566	451,475	(337,830)		(108)
Beginning balance, common shares at Jun. 27, 2021			28,171
Net income (loss)	(2,860)						(2,948)		88
Stock-based compensation plans	(560)		$ 2	(560)		(2)
Stock-based compensation plans, shares			198
Stock-based compensation expense	640					640
Ending balance at Sep. 26, 2021	$ (250)		$ 380	$ (114,511)	$ 2,566	$ 452,113	$ (340,778)		$ (20)
Ending balance, common shares at Sep. 26, 2021	28,369		28,369

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Equity (Unaudited) (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 27, 2020USD ($)
ASU 2016-13 (Topic 326) [Member]
Cumulative impact tax	$ 2

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020
Cash flows from operating activities:
Net income (loss)	$ (21,182)	$ (49,155)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	12,337	15,110
Noncash lease expense	19,199	20,151
Deferred income tax	14	14
Stock-based compensation expense	1,488	2,480
Impairment, loss on disposal of property and equipment and shop closures	3,944	8,873
Other operating activities	232	582
Changes in operating assets and liabilities:
Accounts receivable, net	(1,378)	(281)
Inventories	(197)	749
Prepaid expenses and other assets	626	49
Accounts payable	(1,130)	1,918
Operating lease liabilities	(24,932)	(10,776)
Accrued expenses and other liabilities	3,841	2,542
Net cash used in operating activities:	(7,138)	(7,744)
Cash flows from investing activities:
Purchases of property and equipment	(7,543)	(8,702)
Net cash used in investing activities:	(7,543)	(8,702)
Cash flows from financing activities:
Borrowings under revolving credit facility	28,000	49,786
Repayments under revolving credit facility	(28,486)	(37,400)
Proceeds from Paycheck Protection Program loan		10,000
Payment of debt issuance costs	(195)	(553)
Proceeds from issuance of common shares and warrants, net of fees	14,839
Proceeds from exercise of stock options	219
Employee taxes on certain stock-based payment arrangements	(1,122)	(585)
Distributions to non-controlling interest		(344)
Contributions from non-controlling interest	136	143
Net cash provided by financing activities:	13,391	21,047
Net increase (decrease) in cash and cash equivalents	(1,290)	4,601
Cash and cash equivalents at beginning of period	11,126	18,806
Cash and cash equivalents at end of period	9,836	23,407
Supplemental cash flow information:
Income taxes paid	185	240
Interest paid	482	468
Supplemental non-cash investing and financing activities:
Unpaid liability for purchases of property and equipment	599	$ 350
Unpaid liability for employee taxes on certain stock-based payment arrangements	$ 124

Organization and Other Matters

Organization and Other Matters	9 Months Ended
	Sep. 26, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Other Matters	(1) Organization and Other Matters Business Potbelly Corporation (the “Company”, “Potbelly”, “we”, “us” or “our”), through its wholly owned subsidiaries, owns and operates 397 company-owned shops in the United States. Additionally, Potbelly franchisees operate 46 shops in the United States. Basis of Presentation The unaudited condensed consolidated financial statements and notes herein should be read in conjunction with the audited consolidated financial statements of Potbelly Corporation and its subsidiaries and the notes thereto included in our Annual Report on Form 10-K for the year ended December 27, 2020. The unaudited condensed consolidated financial statements included herein have been prepared by us without audit, pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to the SEC rules and regulations. In the opinion of management, all adjustments, which are of a normal and recurring nature (except as otherwise noted), that are necessary to present fairly our balance sheet as of September 26, 2021 and December 27, 2020, our statement of operations for the 13 and 39 weeks ended September 26, 2021 and September 27, 2020, the statement of equity for the 13 and 39 weeks ended September 26, 2021 and September 27, 2020, and our statement of cash flows for the 39 weeks ended September 26, 2021 and September 27, 2020 have been included. The condensed consolidated statements of operations for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Any reclassifications made had no impact on the loss from operations, balance sheets or statements of cash flows. We do not have any components of other comprehensive income recorded within our consolidated financial statements and therefore, does not separately present a statement of comprehensive income in our condensed consolidated financial statements. COVID-19 On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus ("COVID-19") and the risks to the international community as the virus spreads globally. On March 11, 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. In response to the pandemic, many states and jurisdictions in which we operate issued stay-at-home orders and other measures aimed at slowing the spread of the coronavirus, resulting in significant changes to our operations and a sudden and drastic decrease in revenues. While the pandemic continues to have an impact on our business, the distribution of COVID-19 vaccines and a decline in positive cases and hospitalizations has resulted in a gradual improvement during 2021. The COVID-19 pandemic has adversely affected, and will continue to adversely affect, our operations and financial results for the foreseeable future. There are many uncertainties regarding the current COVID-19 pandemic, and we continue to closely monitor the impact of the pandemic on all aspects of our business, including how it will impact our customers, employees, suppliers, vendors, business partners, and distribution channels. We are unable to predict the impact that COVID-19 will have on our financial position and operating results due to numerous uncertainties, however, we are continually assessing the evolving impact of the COVID-19 pandemic and intend to make adjustments to our responses accordingly. P rinciples of Consolidation The unaudited condensed 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 (“PSW”); seven of PSW’s wholly owned subsidiaries and PSW’s six 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 seven joint venture investments. Potbelly has ownership interests ranging from 51-80% in these consolidated joint ventures. Fiscal Year We use a 52/53-week fiscal year that ends on the last Sunday of the calendar period. Approximately every five or six years a 53rd week is added. Fiscal year 2021 and 2020 both consist of 52 weeks. The fiscal quarters ended September 26, 2021 and September 27, 2020 each consisted of 13 weeks. Use of Estimates The preparation of financial statements in conformity with 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. Recent Accounting Pronouncements On December 28, 2020, we adopted Accounting Standard Update No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40)

Revenue

Revenue	9 Months Ended
	Sep. 26, 2021
Revenue From Contract With Customer [Abstract]
Revenue	(2) Revenue We primarily earn revenue at a point in time for sandwich shop sales, which can occur in person at the shop, over our online or app platform, or through a third-party platform. 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. We have other revenue generating activities outlined below. Franchise Revenue We earn an initial franchise fee, a franchise development agreement fee and ongoing royalty fees under our franchise agreements. Initial franchise fees are considered highly dependent upon and interrelated with the franchise right granted in the franchise agreement. As such, these franchise fees are recognized over the contractual term of the franchise agreement. We record a contract liability for the unearned portion of the initial franchise fees. 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 us are recorded as deferred revenue in the consolidated balance sheet and amortized over the life of the franchise development agreement. 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. Gift Card Redemptions / Breakage Revenue We sell gift cards to customers, record the sale as a contract liability and recognize the associated revenue as the gift card is redeemed. A portion of these gift cards are not redeemed by the customer, which is recognized by us as revenue as a percentage of customers gift card redemptions. The expected breakage amount recognized is determined by a historical data analysis on gift card redemption patterns. We recognized gift card breakage income of $0.1 million and $0.1 million for the 39 weeks ended September 26, 2021, and September 27, 2020, respectively, which is recorded within net sandwich shop sales in our condensed consolidated statements of operations. Loyalty Program During the second quarter of 2020, we implemented a new customer loyalty program for customers using the Potbelly Perks application at the point of sale. The customer will typically earn 10 points for every dollar spent in addition to any active promotions, and the customer will earn a free entrée after earning 1,000 points. We defer revenue associated with the estimated selling price of points earned by Potbelly Perks members towards free entrées as each point is earned, and a corresponding liability is established in deferred revenue. The deferral is based on the estimated value of the product for which the reward is expected to be redeemed, net of estimated unredeemed points. Once a customer earns a free entrée, that entrée reward will expire after 30 days. Earned but unredeemed points expire after one year of inactivity on that customer’s account. When points are redeemed, we recognize revenue for the redeemed product and reduce deferred revenue. For the 39 weeks ended September 26, 2021 revenue recognized from all revenue sources on point in time sales was $276.8 million, and revenue recognized from sales over time was $0.4 million. For the 39 weeks ended September 27, 2020, revenue recognized from all revenue sources on point in time sales was $216.0 million, and revenue recognized from sales over time was $0.4 million. Contract Liabilities As described above, we record current and noncurrent contract liabilities for upfront franchise fees, gift cards and the loyalty program. There are no other contract liabilities or contract assets recorded by us. The opening and closing balances of our current and noncurrent contract liabilities from contracts with customers were as follows: Current Contract Liability Noncurrent Contract Liability (Thousands) (Thousands) Beginning balance as of December 27, 2020 $ 3,138 $ 1,707 Ending balance as of September 26, 2021 3,357 1,489 Increase (decrease) in contract liability $ 219 $ (218 ) The aggregate value of remaining performance obligations on outstanding contracts was $4.8 million as of September 26, 2021. We expect to recognize revenue related to contract liabilities as follows (in thousands), which may vary based upon franchise activity as well as gift card redemption patterns: Years Ending Amount 2021 $ 1,077 2022 1,834 2023 370 2024 227 2025 314 Thereafter 1,025 Total revenue recognized $ 4,847 For the 13 and 39 weeks ended September 26, 2021, the amount of revenue recognized related to the December 27, 2020 liability ending balance was $0.2 million and $1.1 million, respectively. For the 13 weeks and 39 weeks ended September 27, 2020, the amount of revenue recognized related to the December 31, 2019 liability ending balance was $0.1 million and $0.9 million, respectively. This revenue related to the recognition of gift card redemptions and upfront franchise fees. For the 13 and 39 weeks ended September 26, 2021 and September 27, 2020, we did not recognize any revenue from obligations satisfied (or partially satisfied) in prior periods.

Fair Value Measurement

Fair Value Measurement	9 Months Ended
	Sep. 26, 2021
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 book value of the long-term debt under the Credit Agreement, subsequently amended most recently as of February 26, 2021 and further discussed in Note 7, is considered to approximate its fair value as of September 26, 2021 as the interest rates are considered in line with current market rates. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Assets recognized or disclosed at fair value on the consolidated financial statements on a nonrecurring basis include items such as leasehold improvements, property and equipment, operating lease assets, goodwill, and other intangible assets. These assets are measured at fair value if determined to be impaired. We assess potential impairments to our long-lived assets, which includes property and equipment and lease right-of-use assets, on a quarterly basis or whenever events or circumstances indicate that the carrying amount of an asset may not be recoverable. Shop-level assets and right-of-use assets are grouped at the individual shop-level for the purpose of the impairment assessment. Recoverability of an asset group is measured by a comparison of the carrying amount of an asset group to its estimated undiscounted future cash flows expected to be generated by the asset group. 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 group exceeds the fair value of the asset group. 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. The fair value of right-of-use assets is estimated using market comparative information for similar properties. 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 our shops during the 13 weeks and 39 weeks ended September 26, 2021 , it was determined that indicators of impairment were present for certain shops as a result of continued underperformance, primarily related to the impacts of COVID-19. We performed an impairment analysis related to these shops and recorded an impairment charge of $ 1.0 million and $ million for the 13 and 39 weeks ended September 26, 2021 . T he ultimate severity and longevity of the COVID-19 pandemic is unknown, and therefore, it is possible that impairments could be identified in future periods, and such amounts could be material. During the first quarter of 2021, we amended the lease for our corporate Support Center office in Chicago to relocate to a different office space within the same building. As a result of this relocation, the leasehold improvements of the original office space were disposed, resulting in a loss on disposal of $2.5 million based on the remaining net book value of those assets.

Loss Per Share

Loss Per Share	9 Months Ended
	Sep. 26, 2021
Earnings Per Share [Abstract]
Loss Per Share	(4) Loss Per Share Basic and diluted loss per common share attributable to common stockholders are calculated using the weighted average number of common shares outstanding for the period. Diluted loss per common share attributable to common stockholders is computed by dividing the loss 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 13 and 39 weeks ended September 26, 2021 and September 27, 2020, we had a loss per share, and therefore potentially dilutive shares were excluded from the calculation. The following table summarizes the loss per share calculation: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, 2021 2020 2021 2020 Net loss attributable to Potbelly Corporation $ (2,948 ) $ (13,412 ) $ (21,301 ) $ (48,964 ) Weighted average common shares outstanding-basic 28,264 23,957 27,395 23,792 Plus: Effect of potential stock options exercise — — — — Weighted average common shares outstanding-diluted 28,264 23,957 27,395 23,792 Loss per share available to common stockholders-basic $ (0.10 ) $ (0.56 ) $ (0.78 ) $ (2.06 ) Loss per share available to common stockholders-diluted $ (0.10 ) $ (0.56 ) $ (0.78 ) $ (2.06 ) Potentially dilutive shares that are considered anti-dilutive: Common share options 1,888 3,015 1,994 2,769

Income Taxes

Income Taxes	9 Months Ended
	Sep. 26, 2021
Income Tax Disclosure [Abstract]
Income Taxes	(5) Income Taxes The interim tax provision is determined using an estimated annual effective tax rate and is adjusted for discrete taxable events that occur during the quarter. We regularly assess the need for a valuation allowance related to our deferred tax assets, which includes consideration of both positive and negative evidence related to the likelihood of realization of such deferred tax assets to determine, based on the weight of the available evidence, whether it is more-likely-than-not that some or all of our deferred tax assets will not be realized. In our assessment, we consider recent financial operating results, projected future taxable income, the reversal of existing taxable differences, and tax planning strategies. We recorded a full valuation allowance against our net deferred tax assets during the first quarter of 2019, resulting in a non-cash charge to income tax expense of $13.6 million. We continue to maintain a valuation allowance against all of our deferred tax assets as of September 26, 2021. We did not provide for an income tax benefit on our pre-tax loss for the 13 and 39 weeks ended September 26, 2021 and September 27, 2020. We assess the likelihood of the realization of our deferred tax assets each quarter and the valuation allowance is adjusted accordingly. On March 27, 2020, the CARES Act was enacted into law. The CARES Act is a tax and spending package intended to provide economic relief to address the impact of the COVID-19 pandemic. The CARES Act includes several significant business tax provisions that, among other things, would eliminate the taxable income limit for certain NOLs and allow businesses to carry back NOLs arising in 2018, 2019, and 2020 to the five prior tax years, accelerate refunds of previously generated corporate AMT credits, loosen the business interest limitation under section 163(j), and fix the qualified improvement property regulations in the 2017 Tax Cuts and Jobs Act. As a result of the CARES Act, we received a tax refund of $6.7 million during fiscal year 2020 from the carryback of NOLs and a refund of prior AMT credits.

Leases

Leases	9 Months Ended
	Sep. 26, 2021
Leases [Abstract]
Leases	(6) Leases We determine if a contract contains a lease at inception. We lease retail shops, warehouse and office space under operating leases. For leases with renewal periods at our option, we determine the expected lease period based on whether the renewal of any options are reasonably assured at the inception of the lease. Operating lease assets and liabilities are recognized at the lease commencement date. Operating lease liabilities represent the present value of lease payments not yet paid. Operating lease assets represent our right to use an underlying asset and are based upon the operating lease liabilities adjusted for prepayments or accrued lease payments, initial direct costs, lease incentives, and impairment of operating lease assets. To determine the present value of lease payments not yet paid, we estimate incremental secured borrowing rates corresponding to the maturities of the leases. We estimate this rate based on prevailing financial market conditions, comparable company and credit analysis, and management judgment. We recognize expense for these leases on a straight-line basis over the lease term. Additionally, tenant incentives used to fund leasehold improvements are recognized when earned and reduce our right-of-use asset related to the lease. These are amortized through the right-of-use asset as reductions of expense over the lease term. In fiscal year 2020, as a result of COVID-19, we held discussions with landlords regarding restructuring of our leases in light of various contractual and legal defenses, and we subsequently entered into a total of 350 amendments with our respective landlords through September 26, 2021. The vast majority of these lease amendments were completed during fiscal year 2020, and we are substantially complete with COVID-19-related lease amendments as of September 26, 2021. During the 13 weeks ended September 26, 2021, we did not terminate any leases. During the 39 weeks ended September 26, 2021, we terminated 3 leases. We incurred $0.2 million in lease termination fees related to these leases for the 39 weeks ended September 26, 2021. Upon termination of the leases during the 39 weeks ended September 26, 2021, we derecognized ROU assets of $1.4 million and lease liabilities of $1.5 million that resulted in a net gain of $0.1 million that is recorded in impairment, loss on disposal of property and equipment and shop closures. Operating lease term and discount rate were as follows: September 26, September 27, 2021 2020 Weighted average remaining lease term (years) 7.33 8.02 Weighted average discount rate 7.93 % 7.89 % Certain of our operating lease agreements include variable payments that are passed through by the landlord, such as common area maintenance and real estate taxes, as well as variable payments based on percentage rent for certain of our shops. Pass-through charges and payments based on percentage rent are included within variable lease cost. The components of lease cost were as follows: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, Classification 2021 2020 2021 2020 Operating lease cost Occupancy and General and administrative expenses 10,310 11,112 31,017 34,699 Variable lease cost Occupancy 3,090 2,879 9,565 9,119 Total lease cost $ 13,400 $ 13,991 $ 40,582 $ 43,818 Supplemental disclosures of cash flow information related to leases were as follows: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, 2021 2020 2021 2020 Operating cash flows rent paid for operating lease liabilities 11,688 10,693 36,739 24,200 Operating right-of-use assets obtained in exchange for new operating lease liabilities 2,302 5,264 6,958 18,800 Reduction in operating right-of-use assets due to lease terminations and modifications — 7,973 4,140 12,855 As of September 26, 2021, we had no real estate leases entered into that had not yet commenced. Maturities of lease liabilities were as follows as of September 26, 2021: Operating Leases Remainder of 2021 13,026 2022 42,129 2023 37,972 2024 34,893 2025 31,976 2026 28,199 Thereafter 81,997 Total lease payments 270,192 Less: imputed interest (68,674 ) Present value of lease liabilities $ 201,518

Debt and Credit Facilities

Debt and Credit Facilities	9 Months Ended
	Sep. 26, 2021
Debt Disclosure [Abstract]
Debt and Credit Facilities	(7) Debt and Credit Facilities The components of long-term debt were as follows: September 26, December 27, 2021 2020 Revolving credit facility $ 5,800 $ 6,286 Paycheck Protection Program loan 10,000 10,000 Less: current portion of long-term debt (1,833 ) (333 ) Total long-term debt $ 13,967 $ 15,953 Current portion of debt $ 1,833 $ 333 Revolving credit facility On August 7, 2019, we entered into a second amended and restated revolving credit facility agreement (the "Credit Agreement") with JPMorgan Chase Bank, N.A. (“JPMorgan”). The Credit Agreement amends and restates that certain amended and restated revolving credit facility agreement, dated as of December 9, 2015, and amended on May 3, 2019 (collectively, the "Prior Credit Agreement") with JPMorgan. The Credit Agreement provided, among other things, for a revolving credit facility in a maximum principal amount $40 million, with possible future increases of up to $20 million under an expansion feature. Borrowings under the credit facility generally bear interest at our option at either (i) a eurocurrency rate determined by reference to the applicable LIBOR rate plus a specified margin or (ii) a prime rate as announced by JP Morgan plus a specified margin. The applicable margin was determined based upon our consolidated total leverage ratio. On the last day of each calendar quarter, we were required to pay a commitment fee of 0.20% per annum in respect of any unused commitments under the credit facility. So long as certain total leverage ratios, EBITDA thresholds and minimum liquidity requirements are met and no default or event of default has occurred or would result, there was no limit on the “restricted payments” (primarily distributions and equity repurchases) that we may make, provided that proceeds of the loans under the Credit Agreement may not be used for purposes of making restricted payments. As disclosed in our Annual Report on Form 10-K for the fiscal year ended December 27, 2020, during 2020, we drew on the credit facility to increase our cash position and preserve financial flexibility in light of the uncertainty resulting from the COVID-19 pandemic, and we amended the Credit Agreement throughout fiscal year 2020. Most recently, we entered into Amendment No. 5 (the “Fifth Amendment”) to the Credit Agreement on February 26, 2021. As a result of the Amendment (i) the maturity date was extended from March 31, 2022 to January 31, 2023, (ii) the revolving credit commitment decreased from $40 million to $25 million, (iii) the interest rate margin with respect to any Commercial Bank Floating Rate Loan increased to 2.75%, (iv) the interest rate margin with respect to any Eurodollar Loan increased to 5.00%, (v) the definition of EBITDA was amended to exclude non-cash charges/gains in connection with certain equity interests of the Company, (vi) certain borrowing conditions relating to the Company’s Consolidated Cash Balance were instituted, (vii) the Company is permitted to repurchase/redeem its equity interests under certain conditions and (viii) the minimum monthly EBITDA and Liquidity thresholds the Company must maintain were revised. As of September 26, 2021 , we had $ 5.8 million outstanding under the Credit Agreement. As of December 27 , 2020, we had $ million outstanding under the Credit Agreement. We are currently in compliance with all financial debt covenants. Paycheck Protection Program Loan On August 10, 2020, PSW, an indirect subsidiary of the Company, entered into a loan agreement with Harvest Small Business Finance, LLC in the aggregate amount of $10.0 million (the “Loan”), pursuant to the PPP under the CARES Act. The Loan was necessary to support our ongoing operations due to the economic uncertainty resulting from the COVID-19 pandemic and lack of access to alternative sources of liquidity. The Loan is scheduled to mature five years from the date on which PSW applies for loan forgiveness under the CARES Act, bears interest at a rate of 1% per annum and is subject to the terms and conditions applicable to loans administered by the U.S. Small Business Administration under the CARES Act. The PPP provides that the use of the Loan amount shall be limited to certain qualifying expenses and may be partially or wholly forgiven in accordance with the requirements set forth in the CARES Act. We have used all of the PPP proceeds toward qualifying expenses and are pursuing forgiveness of the full Loan amount, but we are not able to determine the likelihood or the amount of forgiveness that will be obtained. We have recorded the amount of the Loan as long-term debt in our condensed consolidated balance sheet as of September 26, 2021, net of the current portion of the Loan which represents the payments that would be due in the next twelve months if we are not able to obtain forgiveness. The related interest has been recorded to interest expense in our condensed consolidated statement of operations for the 13 and 39 weeks ended September 26, 2021.

Restructuring

Restructuring	9 Months Ended
	Sep. 26, 2021
Restructuring And Related Activities [Abstract]
Restructuring	(8) Restructuring On November 3, 2020, as part of our COVID-related cost reduction efforts and to better align our general and administrative expenses with future strategy, we made the determination to reorganize and restructure our corporate team. We expect that this restructuring plan will result in annual general and administrative expense savings of $3.5 to $4.0 million. This was accomplished through corporate expense optimization, consolidating our shop support services, and through other expense and staff reductions. As a result, we reduced corporate employment levels by approximately 35 employees in the fourth quarter of 2020. We substantially completed our planned restructuring actions during 2020, but we will continue to evaluate our cost structure and seek opportunities for further efficiencies and cost savings as part of our ongoing strategy. As such, we may incur additional restructuring related charges or adjustments to previously recorded charges in the future, however, we are unable to estimate the amount of charges at this time. The accrued restructuring balances as of September 26, 2021 represent expected future cash payments required to satisfy our remaining obligations, nearly all of which are expected to be paid by the end of 2021. Total (Thousands) Balance as of December 27, 2020 $ 1,489 Charges incurred — Payments made (1,107 ) Balance at September 26, 2021 $ 382

Capital Stock

Capital Stock	9 Months Ended
	Sep. 26, 2021
Equity [Abstract]
Capital Stock	(9) Capital Stock On May 8, 2018, we announced that our Board of Directors authorized a stock repurchase program for up to $65.0 million of our outstanding common stock. The program permits us, 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 and Exchange Act of 1934, as amended) or in privately negotiated transactions. The number of common shares actually repurchased, and the timing and price of repurchases, will depend upon market conditions, SEC requirements and other factors. Purchases may be started or stopped at any time without prior notice depending on market conditions and other factors. For the 13 and 39 weeks ended September 26, 2021, we did not repurchase any shares of our common stock under the stock repurchase program. In light of the COVID-19 pandemic, we do not have plans to repurchase any common stock under our stock repurchase program at this time. On February 9, 2021, we closed on a Securities Purchase Agreement (the “SPA”) for the sale by us of 3,249,668 shares of our common stock at a par value of $0.01 per share and the issuance of warrants to purchase 1,299,861 shares of common stock at an exercise price of $5.45 per warrant for gross proceeds of $16.0 million, before deducting placement agent fees and offering expenses of approximately $1.0 million. The warrants are initially exercisable commencing August 13, 2021 through their expiration date of August 12, 2026. The proceeds received from the SPA were allocated between shares and warrants based on their relative fair values at closing. The warrants were valued utilizing the Black-Scholes method.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 26, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	(10) Stock-Based Compensation Stock options We have awarded stock options to certain employees and certain non-employee members of our Board of Directors. The grants generally vest over a four-year A summary of stock option activity for the 39 weeks ended September 26, 2021 is as follows: Options Shares (Thousands) Weighted Average Exercise Price Aggregate Intrinsic Value (Thousands) Weighted Average Remaining Term (Years) Outstanding—December 27, 2020 1,233 $ 10.68 $ — 2.49 Granted — — Exercised (31 ) 7.24 Canceled (664 ) 9.75 Outstanding—September 26, 2021 538 12.03 $ — 2.50 Exercisable—September 26, 2021 535 $ 12.02 $ — 2.48 Stock-based compensation related to stock options 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 13 and 39 weeks ended September 26, 2021, we recognized stock-based compensation expense related to stock options of less than $0.1 million. For the 13 weeks ended September 27, 2020, we recognized stock-based compensation credit of $0.1 million due to forfeiture credits. For the 39 weeks ended September 27, 2020, we recognized stock-based compensation expense related to stock options of $0.2 million. As of September 26, 2021, unrecognized stock-based compensation expense for stock options was less than $0.1 million, which will be recognized through fiscal year 2022. We record stock-based compensation expense within general and administrative expenses in the condensed consolidated statements of operations. Restricted stock units We award restricted stock units (“RSUs”) to certain employees and certain non-employee members of our Board of Directors. Prior to 2021, the Board of Director grants had a vesting schedule of 50% on the first anniversary of the grant date and 50% on the second anniversary of the grant date. Beginning with the annual grant made in the second quarter of 2021, the Board of Director grants fully vest on the first anniversary of the grant date, or upon termination from the Board of Directors for any reason other than for cause, a pro rata portion of the shares vest on the termination date. The employee grants vest in one-third increments over a three-year A summary of RSU activity for the 39 weeks ended September 26, 2021 is as follows: RSUs Number of RSUs (Thousands) Weighted Average Fair Value per Share Non-vested as of December 27, 2020 994 $ 3.35 Granted 649 6.16 Vested (419 ) 7.12 Canceled (13 ) — Non-vested as of September 26, 2021 1,211 $ 4.47 Performance stock units We award performance share units (“PSUs”) to certain of our employees. The PSUs have certain vesting conditions based upon our financial performance or our stock price. We grant PSUs that are subject to service and market vesting conditions. The fair market value of each grant was established using a Monte Carlo simulation model. Participants are entitled to receive a specified number of shares of our common stock contingent on achievement of a stock return on our common stock. For the 13 and 39 weeks ended September 26, 2021, we recognized stock-based compensation expense for PSUs with market vesting conditions of $0.1 million and $0.5 million, respectively. A summary of activity for PSUs with market vesting conditions for the 39 weeks ended September 26, 2021 is as follows: PSUs Number of PSUs (Thousands) Weighted Average Fair Value per Share Non-vested as of December 27, 2020 502 1.38 Granted 130 8.43 Vested (502 ) 6.76 Canceled — — Non-vested as of September 26, 2021 130 $ 8.43

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 26, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	(11) Commitments and Contingencies We are subject to legal proceedings, 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 our financial position or results of operations and cash flows .

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 26, 2021
Related Party Transactions [Abstract]
Related Party Transactions	(12) Related Party Transactions In connection with our sale of common stock and warrants to purchase common stock in February 2021 in a private placement, certain of our stockholders that owned greater than 5% of our outstanding shares prior to the closing of the private placement purchased shares of common stock and warrants to purchase common stock on the same terms as the other shares and warrants that were offered and sold in the offering. The purchasers included the following stockholders, none of which owned more than 8.5% of our outstanding common stock prior to the closing of the private placement: 201,514 shares of common stock and warrants to purchase 80,605 shares of common stock were purchased by 180 Degree Capital Corp., for an aggregate purchase price of approximately $1.0 million and 164,875 shares of common stock and warrants to purchase 65,950 shares of common stock were purchased by B&W Pension Trust (of which 180 Degree Capital Corp. is the investment advisor and may be deemed to be a beneficial owner of such shares), for an aggregate purchase price of approximately $0.8 million; 223,904 shares of common stock and warrants to purchase 89,561 shares of common stock were purchased by Agman Investments LLC, for an aggregate purchase price of approximately $1.1 million; 366,389 shares of common stock and warrants to purchase 146,555 shares of common stock were purchased by funds controlled by Ancora Holdings Inc., for an aggregate purchase price of approximately $1.8 million; 193,372 shares of common stock and warrants to purchase 77,348 shares of common stock were purchased by Chain of Lakes Investment Fund, LLC, for an aggregate purchase price of approximately $0.9 million; and 407,099 shares of common stock were purchased by Intrinsic Investment Holdings, LLC, for an aggregate purchase price of approximately $2.0 million.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 26, 2021
Subsequent Events [Abstract]
Subsequent Events	(13) Subsequent Events On November 3, 2021, we entered into a certain Equity Sales Agreement (the “Sales Agreement”) with William Blair & Company, L.L.C., as agent (“William Blair”) pursuant to which we may sell shares of our common stock having an aggregate offering price of up to $40,000,000 (the “Shares”), from time to time, in our sole discretion, through an “at the market” equity offering program under which William Blair will act as sales agent.

Organization and Other Matters

Organization and Other Matters (Policies)	9 Months Ended
	Sep. 26, 2021
Accounting Policies [Abstract]
Business	Business Potbelly Corporation (the “Company”, “Potbelly”, “we”, “us” or “our”), through its wholly owned subsidiaries, owns and operates 397 company-owned shops in the United States. Additionally, Potbelly franchisees operate 46 shops in the United States.
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements and notes herein should be read in conjunction with the audited consolidated financial statements of Potbelly Corporation and its subsidiaries and the notes thereto included in our Annual Report on Form 10-K for the year ended December 27, 2020. The unaudited condensed consolidated financial statements included herein have been prepared by us without audit, pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) have been condensed or omitted pursuant to the SEC rules and regulations. In the opinion of management, all adjustments, which are of a normal and recurring nature (except as otherwise noted), that are necessary to present fairly our balance sheet as of September 26, 2021 and December 27, 2020, our statement of operations for the 13 and 39 weeks ended September 26, 2021 and September 27, 2020, the statement of equity for the 13 and 39 weeks ended September 26, 2021 and September 27, 2020, and our statement of cash flows for the 39 weeks ended September 26, 2021 and September 27, 2020 have been included. The condensed consolidated statements of operations for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Any reclassifications made had no impact on the loss from operations, balance sheets or statements of cash flows. We do not have any components of other comprehensive income recorded within our consolidated financial statements and therefore, does not separately present a statement of comprehensive income in our condensed consolidated financial statements.
COVID-19	COVID-19 On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus ("COVID-19") and the risks to the international community as the virus spreads globally. On March 11, 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. In response to the pandemic, many states and jurisdictions in which we operate issued stay-at-home orders and other measures aimed at slowing the spread of the coronavirus, resulting in significant changes to our operations and a sudden and drastic decrease in revenues. While the pandemic continues to have an impact on our business, the distribution of COVID-19 vaccines and a decline in positive cases and hospitalizations has resulted in a gradual improvement during 2021. The COVID-19 pandemic has adversely affected, and will continue to adversely affect, our operations and financial results for the foreseeable future. There are many uncertainties regarding the current COVID-19 pandemic, and we continue to closely monitor the impact of the pandemic on all aspects of our business, including how it will impact our customers, employees, suppliers, vendors, business partners, and distribution channels. We are unable to predict the impact that COVID-19 will have on our financial position and operating results due to numerous uncertainties, however, we are continually assessing the evolving impact of the COVID-19 pandemic and intend to make adjustments to our responses accordingly.
Principles of Consolidation	P rinciples of Consolidation The unaudited condensed 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 (“PSW”); seven of PSW’s wholly owned subsidiaries and PSW’s six 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 seven joint venture investments. Potbelly has ownership interests ranging from 51-80% in these consolidated joint ventures.
Fiscal Year	Fiscal Year We use a 52/53-week fiscal year that ends on the last Sunday of the calendar period. Approximately every five or six years a 53rd week is added. Fiscal year 2021 and 2020 both consist of 52 weeks. The fiscal quarters ended September 26, 2021 and September 27, 2020 each consisted of 13 weeks.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements On December 28, 2020, we adopted Accounting Standard Update No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40)

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 26, 2021
Revenue From Contract With Customer [Abstract]
Summary of Current and Noncurrent Contract Liabilities from Contracts with Customers	The opening and closing balances of our current and noncurrent contract liabilities from contracts with customers were as follows: Current Contract Liability Noncurrent Contract Liability (Thousands) (Thousands) Beginning balance as of December 27, 2020 $ 3,138 $ 1,707 Ending balance as of September 26, 2021 3,357 1,489 Increase (decrease) in contract liability $ 219 $ (218 )
Summary of Expected Revenue Recognition Related to Contract Liabilities	We expect to recognize revenue related to contract liabilities as follows (in thousands), which may vary based upon franchise activity as well as gift card redemption patterns: Years Ending Amount 2021 $ 1,077 2022 1,834 2023 370 2024 227 2025 314 Thereafter 1,025 Total revenue recognized $ 4,847

Loss Per Share (Tables)

Loss Per Share (Tables)	9 Months Ended
	Sep. 26, 2021
Earnings Per Share [Abstract]
Summary of Loss Per Share Calculation	The following table summarizes the loss per share calculation: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, 2021 2020 2021 2020 Net loss attributable to Potbelly Corporation $ (2,948 ) $ (13,412 ) $ (21,301 ) $ (48,964 ) Weighted average common shares outstanding-basic 28,264 23,957 27,395 23,792 Plus: Effect of potential stock options exercise — — — — Weighted average common shares outstanding-diluted 28,264 23,957 27,395 23,792 Loss per share available to common stockholders-basic $ (0.10 ) $ (0.56 ) $ (0.78 ) $ (2.06 ) Loss per share available to common stockholders-diluted $ (0.10 ) $ (0.56 ) $ (0.78 ) $ (2.06 ) Potentially dilutive shares that are considered anti-dilutive: Common share options 1,888 3,015 1,994 2,769

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 26, 2021
Leases [Abstract]
Operating Lease Term and Discount Rate	Operating lease term and discount rate were as follows: September 26, September 27, 2021 2020 Weighted average remaining lease term (years) 7.33 8.02 Weighted average discount rate 7.93 % 7.89 %
Components of Lease Cost	The components of lease cost were as follows: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, Classification 2021 2020 2021 2020 Operating lease cost Occupancy and General and administrative expenses 10,310 11,112 31,017 34,699 Variable lease cost Occupancy 3,090 2,879 9,565 9,119 Total lease cost $ 13,400 $ 13,991 $ 40,582 $ 43,818
Supplemental Disclosures of Cash Flow Information Related to Leases	Supplemental disclosures of cash flow information related to leases were as follows: For the 13 Weeks Ended For the 39 Weeks Ended September 26, September 27, September 26, September 27, 2021 2020 2021 2020 Operating cash flows rent paid for operating lease liabilities 11,688 10,693 36,739 24,200 Operating right-of-use assets obtained in exchange for new operating lease liabilities 2,302 5,264 6,958 18,800 Reduction in operating right-of-use assets due to lease terminations and modifications — 7,973 4,140 12,855
Maturities of Lease Liabilities	Maturities of lease liabilities were as follows as of September 26, 2021: Operating Leases Remainder of 2021 13,026 2022 42,129 2023 37,972 2024 34,893 2025 31,976 2026 28,199 Thereafter 81,997 Total lease payments 270,192 Less: imputed interest (68,674 ) Present value of lease liabilities $ 201,518

Debt and Credit Facilities (Ta

Debt and Credit Facilities (Tables)	9 Months Ended
	Sep. 26, 2021
Debt Disclosure [Abstract]
Component of Long-term Debt	The components of long-term debt were as follows: September 26, December 27, 2021 2020 Revolving credit facility $ 5,800 $ 6,286 Paycheck Protection Program loan 10,000 10,000 Less: current portion of long-term debt (1,833 ) (333 ) Total long-term debt $ 13,967 $ 15,953 Current portion of debt $ 1,833 $ 333

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 26, 2021
Restructuring And Related Activities [Abstract]
Schedule Future Cash Payments Required to Satisfy Our Remaining Obligations	The accrued restructuring balances as of September 26, 2021 represent expected future cash payments required to satisfy our remaining obligations, nearly all of which are expected to be paid by the end of 2021. Total (Thousands) Balance as of December 27, 2020 $ 1,489 Charges incurred — Payments made (1,107 ) Balance at September 26, 2021 $ 382

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 26, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	A summary of stock option activity for the 39 weeks ended September 26, 2021 is as follows: Options Shares (Thousands) Weighted Average Exercise Price Aggregate Intrinsic Value (Thousands) Weighted Average Remaining Term (Years) Outstanding—December 27, 2020 1,233 $ 10.68 $ — 2.49 Granted — — Exercised (31 ) 7.24 Canceled (664 ) 9.75 Outstanding—September 26, 2021 538 12.03 $ — 2.50 Exercisable—September 26, 2021 535 $ 12.02 $ — 2.48
Summary of RSU Activity	A summary of RSU activity for the 39 weeks ended September 26, 2021 is as follows: RSUs Number of RSUs (Thousands) Weighted Average Fair Value per Share Non-vested as of December 27, 2020 994 $ 3.35 Granted 649 6.16 Vested (419 ) 7.12 Canceled (13 ) — Non-vested as of September 26, 2021 1,211 $ 4.47
Summary of PSU Activity	A summary of activity for PSUs with market vesting conditions for the 39 weeks ended September 26, 2021 is as follows: PSUs Number of PSUs (Thousands) Weighted Average Fair Value per Share Non-vested as of December 27, 2020 502 1.38 Granted 130 8.43 Vested (502 ) 6.76 Canceled — — Non-vested as of September 26, 2021 130 $ 8.43

Organization and Other Matter_2

Organization and Other Matters - Additional Information (Detail)	9 Months Ended
	Sep. 26, 2021ShopSubsidiaryJointVenture
Nature Of Business And Basis Of Presentation [Line Items]
Number of shops franchisees operate	46
Number of wholly owned subsidiaries | Subsidiary	7
Number of joint ventures | JointVenture	6
Minimum [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Number of shops Potbelly Corporation owns or operates	397
Ownership interest rate	51.00%
Maximum [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Ownership interest rate	80.00%

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Disaggregation Of Revenue [Line Items]
Revenue recognized related to prior periods			$ 100,000	$ 100,000
Amount of revenue recognized	$ 101,694,000	$ 72,663,000	277,248,000	216,415,000
Aggregate value of remaining performance obligation on outstanding contracts	4,847,000		4,847,000
Revenue recognized related to prior periods	0	0	0	0
December 27, 2020 and December 31, 2019 Liability Ending Balance [Member]
Disaggregation Of Revenue [Line Items]
Amount of revenue recognized	$ 200,000	$ 100,000	1,100,000	900,000
Point in Time Sales [Member]
Disaggregation Of Revenue [Line Items]
Amount of revenue recognized			276,800,000	216,000,000
Over Time Sales [Member]
Disaggregation Of Revenue [Line Items]
Amount of revenue recognized			$ 400,000	$ 400,000

Revenue - Summary of Current an

Revenue - Summary of Current and Noncurrent Contract Liabilities from Contracts with Customers (Detail) $ in Thousands	9 Months Ended
	Sep. 26, 2021USD ($)
Revenue From Contract With Customer [Abstract]
Beginning balance of current contract liability	$ 3,138
Ending balance of current contract liability	3,357
Increase (decrease) in contract liability	219
Beginning balance of noncurrent contract liability	1,707
Ending balance of noncurrent contract liability	1,489
Increase (decrease) in contract liability	$ (218)

Revenue - Summary of Expected R

Revenue - Summary of Expected Revenue Recognition Related to Contract Liabilities (Detail1) $ in Thousands	Sep. 26, 2021USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 4,847
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 1,077
Revenue, remaining performance obligation, expected timing of satisfaction, period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 1,834
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 370
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 227
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 314
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligations	$ 1,025
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year

Revenue - Summary of Expected_2

Revenue - Summary of Expected Revenue Recognition Related to Contract Liabilities (Detail) $ in Thousands	Sep. 26, 2021USD ($)
Revenue From Contract With Customer [Abstract]
Revenue, remaining performance obligations	$ 4,847

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 26, 2021	Sep. 26, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charge	$ 1	$ 1.5
Leasehold Improvements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Losses on disposal of property and equipment		$ 2.5

Loss Per Share - Additional Inf

Loss Per Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 27, 2021	Jun. 28, 2020	Jun. 27, 2021	Jun. 28, 2020
Common Share Options [Member]
Loss Per Share [Line Items]
Potential common shares included in diluted shares outstanding	0	0	0	0

Loss Per Share - Summary of Los

Loss Per Share - Summary of Loss Per Share Calculation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Loss Per Share [Line Items]
Net loss attributable to Potbelly Corporation	$ (2,948)	$ (13,412)	$ (21,301)	$ (48,964)
Weighted average common shares outstanding-basic	28,264	23,957	27,395	23,792
Weighted average common shares outstanding-diluted	28,264	23,957	27,395	23,792
Loss per share available to common stockholders-basic	$ (0.10)	$ (0.56)	$ (0.78)	$ (2.06)
Loss per share available to common stockholders-diluted	$ (0.10)	$ (0.56)	$ (0.78)	$ (2.06)
Common Share Options [Member]
Loss Per Share [Line Items]
Potentially dilutive shares that are considered anti-dilutive	1,888	3,015	1,994	2,769

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020	Mar. 27, 2020
Deferred tax assets, valuation allowance	$ 13,600		$ 13,600
Income tax expense (benefit)	$ 16	$ (2,917)	$ 230	$ (6,585)
COVID 19 [Member]
Tax refund from net operating loss carry back					$ 6,700

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 26, 2021USD ($)Termination	Sep. 26, 2021USD ($)Termination
Leases [Abstract]
Leases of terminated | Termination	0	3
Lease termination fees		$ 0.2
Right-of-use assets derecognized upon lease termination		1.4
Lease liabilities derecognized upon lease termination		1.5
Gain recognized upon lease termination		0.1
Additional operating leases payments related to shops not yet open, amount	$ 0	$ 0

Leases - Operating Lease Term a

Leases - Operating Lease Term and Discount Rate (Detail)	Sep. 26, 2021	Sep. 27, 2020
Leases [Abstract]
Weighted average remaining lease term (years)	7 years 3 months 29 days	8 years 7 days
Weighted average discount rate	7.93%	7.89%

Leases - Components of Lease Co

Leases - Components of Lease Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Lessee Lease Description [Line Items]
Total lease cost	$ 13,400	$ 13,991	$ 40,582	$ 43,818
Occupancy and General and Administrative Expenses [Member]
Lessee Lease Description [Line Items]
Operating lease cost	10,310	11,112	31,017	34,699
Occupancy Expenses [Member]
Lessee Lease Description [Line Items]
Variable lease cost	$ 3,090	$ 2,879	$ 9,565	$ 9,119

Leases - Supplemental Disclosur

Leases - Supplemental Disclosures of Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Leases [Abstract]
Operating cash flows rent paid for operating lease liabilities	$ 11,688	$ 10,693	$ 36,739	$ 24,200
Operating right-of-use assets obtained in exchange for new operating lease liabilities	$ 2,302	5,264	6,958	18,800
Reduction in operating right-of-use assets due to lease terminations and modifications		$ 7,973	$ 4,140	$ 12,855

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Detail) $ in Thousands	Sep. 26, 2021USD ($)
Operating Leases
Remainder of 2021	$ 13,026
2022	42,129
2023	37,972
2024	34,893
2025	31,976
2026	28,199
Thereafter	81,997
Total lease payments	270,192
Less: imputed interest	(68,674)
Present value of lease liabilities	$ 201,518

Debt and Credit Facilities - Co

Debt and Credit Facilities - Component of Long-term Debt (Detail) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 27, 2020
Debt Instrument [Line Items]
Long-term debt	$ 13,967	$ 15,953
Less: current portion of long-term debt	(1,833)	(333)
Current portion of debt	1,833	333
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	5,800	6,286
Paycheck Protection Program Loan [Member]
Debt Instrument [Line Items]
Long-term debt	$ 10,000	$ 10,000

Debt and Credit Facilities - Ad

Debt and Credit Facilities - Additional Information (Detail) - USD ($)	Feb. 26, 2021	Aug. 10, 2020	Aug. 07, 2019	Sep. 26, 2021	Dec. 27, 2020
CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, maturity date	Mar. 31, 2022
CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, maturity date	Jan. 31, 2023
JPMorgan Chase Bank, N.A. [Member]
Debt Instrument [Line Items]
Commitment fee, percentage			0.20%
Revolving Credit Facility [Member] | JPMorgan Chase Bank, N.A. [Member]
Debt Instrument [Line Items]
Credit facility agreement, maximum principal amount			$ 40,000,000
Revolving Credit Facility [Member] | JPMorgan Chase Bank, N.A. [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility agreement, future increases			$ 20,000,000
Paycheck Protection Program Loan [Member] | CARES Act Of 2020 [Member] | Potbelly Sandwich Works, LLC [Member]
Debt Instrument [Line Items]
Loan maturity period		5 years
Credit facility agreement, interest rate		1.00%
Paycheck Protection Program Loan [Member] | Harvest Small Business Finance L L C | Commercial Loan [Member] | Potbelly Sandwich Works, LLC [Member]
Debt Instrument [Line Items]
Loan amount		$ 10,000,000
Paycheck Protection Program Loan [Member] | Harvest Small Business Finance L L C | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member]
Debt Instrument [Line Items]
Credit facility agreement, amount outstanding				$ 5,800,000	$ 6,300,000
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility agreement, future increases	$ 40,000,000
Revolving Credit Commitment [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility agreement, future increases	$ 25,000,000
Eurodollar Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member]
Debt Instrument [Line Items]
Debt instrument, increase in interest rate	5.00%
CBFR Loan [Member] | CARES Act Of 2020 [Member] | Fifth Credit Agreement Amendment [Member]
Debt Instrument [Line Items]
Debt instrument, increase in interest rate	2.75%

Restructuring - Additional Info

Restructuring - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 03, 2020USD ($)	Sep. 26, 2021USD ($)	Sep. 27, 2020USD ($)	Sep. 26, 2021USD ($)Employee	Sep. 27, 2020USD ($)
Number of employee reduce | Employee				35
General and administrative expenses		$ 7,612,000	$ 9,588,000	$ 24,275,000	$ 27,300,000
Minimum [Member]
General and administrative expenses	$ 3,500,000
Maximum [Member]
General and administrative expenses	$ 4,000,000

Restructuring - Schedule Future

Restructuring - Schedule Future Cash Payments Required to Satisfy Our Remaining Obligations (Detail) $ in Thousands	6 Months Ended
	Jun. 27, 2021USD ($)
Restructuring Reserve Roll Forward
Beginning balance	$ 1,489
Payments made	(1,107)
Ending balance	$ 382

Capital Stock - Additional Info

Capital Stock - Additional Information (Detail) - USD ($)	Feb. 09, 2021	Sep. 26, 2021	Sep. 26, 2021	Dec. 27, 2020	May 08, 2018
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 65,000,000
Common stock, par value		$ 0.01	$ 0.01	$ 0.01
Warrants [Member]
Equity Class Of Treasury Stock [Line Items]
Placement agent fees and offering expenses	$ 1,000,000
Securities Purchase Agreement [Member]
Equity Class Of Treasury Stock [Line Items]
Issuance of common stock	3,249,668
Common stock, par value	$ 0.01
Warrants exercisable commencement date	Aug. 13, 2021
Warrants expiration date	Aug. 12, 2026
Securities Purchase Agreement [Member] | Warrants [Member]
Equity Class Of Treasury Stock [Line Items]
Issuance of common stock	1,299,861
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 5.45
Proceeds From Securities Purchase Agreement	$ 16,000,000
Stock Repurchase Program [Member]
Equity Class Of Treasury Stock [Line Items]
Repurchases of common stock, shares		0	0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020	Sep. 26, 2021	Sep. 27, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation expense			$ 1,488	$ 2,480
Common Share Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation forfeiture credit		$ 100
Recognized stock-based compensation expense				200
Unrecognized stock compensation expense, recognition period			2022
Common Share Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation expense	$ 100		$ 100
Unrecognized stock compensation expense	100		100
Performance Stock Units [Member] | Market Vesting Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized stock-based compensation expense	$ 100		$ 500
Employee and Non Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants vesting period			4 years
Method used to determine fair value of the options			Black-Scholes option pricing model
Stock options granted	0		0
Non-Employee Board Of Directors [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants vesting period			3 years
Recognized stock-based compensation expense	$ 600	$ 1,000	$ 1,000	$ 1,600
Unrecognized stock compensation expense	$ 4,400		$ 4,400
Unrecognized stock compensation expense, recognition period			2024
Vesting description			The employee grants vest in one-third increments over a three-year period.
Non-Employee Board Of Directors [Member] | Restricted Stock Units (RSUs) [Member] | First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			50.00%
Non-Employee Board Of Directors [Member] | Restricted Stock Units (RSUs) [Member] | Second Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			50.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) shares in Thousands	9 Months Ended	12 Months Ended
	Sep. 26, 2021$ / sharesshares	Dec. 27, 2020$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding shares, beginning balance | shares	1,233
Options, exercised | shares	(31)
Options, canceled | shares	(664)
Options outstanding shares, ending balance | shares	538	1,233
Options outstanding shares, exercisable | shares	535
Options outstanding weighted average exercise price, beginning balance | $ / shares	$ 10.68
Options, weighted average exercise price, exercised | $ / shares	7.24
Options, weighted average exercise price, canceled | $ / shares	9.75
Options outstanding weighted average exercise price, ending balance | $ / shares	12.03	$ 10.68
Options outstanding weighted average exercise price, exercisable | $ / shares	$ 12.02
Option outstanding weighted average remaining term	2 years 6 months	2 years 5 months 26 days
Options exercisable weighted average remaining term	2 years 5 months 23 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of RSU Activity (Detail) - Restricted Stock Units (RSUs) [Member] shares in Thousands	9 Months Ended
	Sep. 26, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs, Non-vested, beginning balance | shares | shares	994
Number of shares, Granted	649
Number of RSUs, Vested	(419)
Number of RSUs, Canceled	(13)
Number of RSUs, Non-vested, ending balance | shares | shares	1,211
Weighted Average Fair Value per Share, Non-vested, beginning balance | $ / shares	$ 3.35
Weighted Average Fair Value per Share, Granted | $ / shares	6.16
Weighted Average Fair Value per Share, Vested | $ / shares	7.12
Weighted Average Fair Value per Share, Non-vested, ending balance | $ / shares	$ 4.47

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of PSU Activity (Detail) - Performance Stock Units [Member] shares in Thousands	9 Months Ended
	Sep. 26, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs, Non-vested, beginning balance | shares | shares | shares	502
Number of shares, Granted | shares	130
Number of RSUs, Vested | shares	(502)
Number of RSUs, Non-vested, ending balance | shares | shares | shares	130
Weighted Average Fair Value per Share, Non-vested, beginning balance | $ / shares	$ 1.38
Weighted Average Fair Value per Share, Granted | $ / shares	8.43
Weighted Average Fair Value per Share, Vested | $ / shares	6.76
Weighted Average Fair Value per Share, Non-vested, ending balance | $ / shares	$ 8.43

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Feb. 28, 2021	Sep. 26, 2021
Related Party Transaction [Line Items]
Stock Issued During Period, Value, New Issues		$ 14,839
Warrants [Member]
Related Party Transaction [Line Items]
Stock Issued During Period, Value, New Issues		$ 2,566
Private Placement [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Ownership percentage related party	5.00%
Private Placement [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Ownership percentage related party	8.50%
Private Placement [Member] | 180 Degree Capital Corp [Member]
Related Party Transaction [Line Items]
Issuance of common stock	201,514
Private Placement [Member] | 180 Degree Capital Corp [Member] | Warrants [Member]
Related Party Transaction [Line Items]
Issuance of common stock	80,605
Stock Issued During Period, Value, New Issues	$ 1,000
Private Placement [Member] | B&W Pension Trust [Member]
Related Party Transaction [Line Items]
Issuance of common stock	164,875
Private Placement [Member] | B&W Pension Trust [Member] | Warrants [Member]
Related Party Transaction [Line Items]
Issuance of common stock	65,950
Stock Issued During Period, Value, New Issues	$ 800
Private Placement [Member] | Agman Investments LLC [Member]
Related Party Transaction [Line Items]
Issuance of common stock	223,904
Private Placement [Member] | Agman Investments LLC [Member] | Warrants [Member]
Related Party Transaction [Line Items]
Issuance of common stock	89,561
Stock Issued During Period, Value, New Issues	$ 1,100
Private Placement [Member] | Ancora Holdings Inc [Member]
Related Party Transaction [Line Items]
Issuance of common stock	366,389
Private Placement [Member] | Ancora Holdings Inc [Member] | Warrants [Member]
Related Party Transaction [Line Items]
Issuance of common stock	146,555
Stock Issued During Period, Value, New Issues	$ 1,800
Private Placement [Member] | Lakes Investment Fund, LLC [Member]
Related Party Transaction [Line Items]
Issuance of common stock	193,372
Private Placement [Member] | Lakes Investment Fund, LLC [Member] | Warrants [Member]
Related Party Transaction [Line Items]
Issuance of common stock	77,348
Stock Issued During Period, Value, New Issues	$ 900
Private Placement [Member] | Intrinsic Investment Holdings, LLC [Member]
Related Party Transaction [Line Items]
Issuance of common stock	407,099
Stock Issued During Period, Value, New Issues	$ 2,000

Subsequent Events (Details)

Subsequent Events (Details)	Nov. 03, 2021shares
Subsequent Event [Member] | William Blair [Member]
Subsequent Event [Line Items]
Issuance of common shares and warrants, net of fees, shares	40,000,000