Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)		6 Months Ended	12 Months Ended
	Mar. 29, 2017 $ / shares shares	Jun. 30, 2015 USD ($)	Dec. 31, 2019 USD ($) Segment renewal restaurant vendor property $ / shares shares	Jan. 01, 2019 USD ($) restaurant $ / shares shares	Jan. 02, 2018 USD ($) $ / shares shares	Mar. 26, 2019 USD ($)	Jan. 02, 2019 USD ($)	Mar. 27, 2018 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Current Fiscal Year End Date			--12-31
Impairment of long-lived assets			$ 7,159,000	$ 3,861,000	$ 0
Deferred income taxes			$ 69,510,000	69,471,000			$ 70,179,000
Document Period End Date			Dec. 31, 2019
DeferredGiftCardIncomeTotal			$ 3,100,000	$ 2,800,000
Share Price | $ / shares			$ 3.59	$ 4.92	$ 4.63
Deferred gift card income			$ 1,474,000	$ 1,290,000
Allowance for doubtful accounts			$ 100,000	76,000
Number of vendors | vendor			1
Noncurrent portion of advanced reimbursements			$ 300,000	700,000
Current portion of advanced reimbursements			400,000	422,000
Depreciation and amortization expense			22,700,000	23,100,000	$ 21,000,000
Property and equipment depreciation expense			81,227,000	69,089,000
Carrying value of capitalized software costs			2,900,000	2,300,000
Capitalized software costs			2,000,000	1,500,000	1,000,000
Capitalized software amortization expense			1,400,000	1,200,000	1,000,000
Interest capitalized in connection with construction			$ 96,000	131,000	100,000
Lease agreement term (in years)			50 years
Lease accumulated amortization				7,200,000
Deductible per occurrence for general liability			$ 350,000
Percentage of net sales for advertising			4.00%
Advertising expenses			$ 18,800,000	19,000,000	18,100,000
Pre-opening costs			$ 1,650,000	1,584,000	1,591,000
Number of operating segments | Segment			1
Number of reportable segments | Segment			1
Partnership monthly rental income		$ 1,400,000
Proceeds from credit facility			$ 41,000,000	31,000,000	31,500,000
Payments of Debt Issuance Costs			1,014,000	0	0
Gift Card Liability, Current			$ 1,585,000	1,531,000
Adjustment for adoption of new lease standard, net of tax							$ 1,912,000
Number of Stores | property			57
Entity operated units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Accrued advertising			$ 800,000	$ 900,000
Number of restaurants | restaurant			300	322
Franchised units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Accrued advertising			$ 600,000	$ 700,000
Number of restaurants | restaurant			296	258
CALIFORNIA
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant			372
CALIFORNIA | Entity operated units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant			233
CALIFORNIA | Franchised units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant			139
Minimum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of lease renewal options | renewal			1
Lease renewal term (in years)			5 years
Insurance coverage deductibles range for claims			$ 250,000
Maximum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of lease renewal options | renewal			4
Lease renewal term (in years)			10 years
Insurance coverage deductibles range for claims			$ 500,000
Capitalized software
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets (in years)			3 years
Buildings under capital leases
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization expense				$ 900,000	1,200,000
Property and equipment depreciation expense				2,200,000	2,500,000
Estimated useful lives of assets (in years)			20 years
assets held under finance leases [Domain]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Depreciation and amortization expense			$ 500,000
Property and equipment depreciation expense			300,000
Construction-in-progress
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Capitalized construction costs			$ 1,800,000	1,625,000
Restaurant and other equipment | Minimum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets (in years)			3 years
Restaurant and other equipment | Maximum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets (in years)			15 years
Adjustments for Prior Revenue Recognition Standards
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Advertising expenses			$ 13,300,000
Franchise revenue
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Revenue			(19,002,000)	(17,569,000)	(16,464,000)
Franchise advertising contributions
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Revenue			$ (14,516,000)	$ (13,300,000)	$ 0
Warrants
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Shares/warrants repurchased (in shares/warrants) | shares	400,000		846,441	47,511	424,439
Average cost per share/warrant (in dollars per share/warrant) | $ / shares	$ 3.75		$ 1.78	$ 2.55	$ 3.72
Discount on repurchase	5.00%
Share Price | $ / shares	$ 3.95
Retained Earnings (Accumulated Deficit)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Adjustment for adoption of new lease standard, net of tax						$ 1,912,000		$ (707,000)