Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)					3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 01, 2021 USD ($) restaurant	Aug. 04, 2020 USD ($) item	Aug. 03, 2020 USD ($) item	Jul. 30, 2014	Sep. 29, 2021 USD ($) restaurant	Sep. 23, 2020 USD ($) restaurant	Sep. 29, 2021 USD ($) restaurant item segment	Sep. 23, 2020 USD ($) restaurant	Dec. 30, 2020 USD ($) item
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | segment							1
Leaves of absence and overtime pay due to COVID 19					$ 500,000	$ 900,000	$ 3,500,000	$ 2,000,000.0
Bad debt expense								190,000
Total amount of outstanding debt					40,000,000.0		40,000,000.0
Cash available					24,669,000		24,669,000		$ 13,219,000
Gain on recovery of insurance proceeds						2,000,000		2,000,000
Proceeds from disposition of restaurants							4,556,000
Net loss on sale of restaurants					(10,000)		(1,534,000)
Property Equipment and Certain Rou Assets Impairment					100,000	1,500,000	701,000	3,478,000
Unrecognized tax benefits, accrual of interest or penalties					0		0		0
Interest related to NOPA									100,000
Unrecognized tax benefits, interest or penalties expenses						0		0
Percentage of cash savings in taxes realized as a result of utilizing net operating losses payable to pre-IPO stockholders				85.00%
Tax Receivable Agreement (Income) Expenses					$ (19,000)	$ (144,000)	$ (69,000)	26,000
AMT Credits, CARES Act									400,000
Proceeds from Income Tax Refunds									500,000
Total deferred amount									$ 4,900,000
Percentage of deferred amount due by current fiscal year					50.00%		50.00%
Percentage of deferred amount due by next fiscal year					50.00%		50.00%
Percentage of qualified wages paid for refundable payroll tax credit					70.00%		70.00%
Employee retention credit					$ 3,200,000		$ 3,200,000
Loyalty Rewards Program, Points Needed For One Reward | item		50	100
Loyalty Rewards Program, Award Earned		$ 5	$ 10
Loyalty Rewards Program, Expiration Period For Inactivity							1 year
Loyalty Reward Program, unused reward expiration period							6 months
Loyalty Rewards Program, Expected Loyalty Points Redemption Period							1 year
Maximum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Net loss on sale of restaurants					(100,000)
Tax Receivable Agreement (Income) Expenses					$ (100,000)		$ (100,000)	$ 100,000
Supplier Concentration Risk | Accounts Payable
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number Of Suppliers | item									2
Supplier Concentration Risk | Supplier One | Accounts Payable
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number Of Suppliers | item							0
Percentage of concentration									24.20%
Supplier Concentration Risk | Supplier Two | Accounts Payable
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration									11.40%
Supplier Concentration Risk | Largest Supplier One | Purchased
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration					27.00%	26.70%	28.10%	26.80%
Geographic Concentration Risk | Revenue
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration					100.00%	100.00%	100.00%	100.00%
Assets held for sale | Sacramento Area
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants agreed to sell to a third party | restaurant	8
Texas
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants with ROU asset impairment charges | restaurant					1		1
Number of restaurants closed | restaurant					1		1
California
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant					3	4	3	4
Number of restaurants with ROU asset impairment charges | restaurant					1	1	1	1
Number of restaurants closed | restaurant					1		1
Greater Los Angeles area market | Geographic Concentration Risk | Revenue
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration					71.60%	71.20%	70.80%	71.50%
Closed Store
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Closed-store reserve expense						$ 300,000	$ 400,000	$ 1,100,000
Closed Store | Maximum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Closed-store reserve expense					$ 100,000
Company-operated
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant					190		190
Proceeds from disposition of restaurants	$ 4,600,000
Net loss on sale of restaurants							$ (1,500,000)
Franchised
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant					290		290