Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 05, 2016 USD ($) Restaurants	Jul. 30, 2014	Nov. 30, 2015 Restaurants	Sep. 28, 2016 USD ($) Restaurants	Sep. 30, 2015 USD ($)	Sep. 28, 2016 USD ($) Segment Restaurants Supplier	Sep. 30, 2015 USD ($)	Dec. 30, 2015 USD ($) Supplier	Nov. 01, 2016 USD ($)	Oct. 03, 2016 Restaurants	Sep. 29, 2016 USD ($) Restaurants	Dec. 31, 2014 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment						1
Restricted dividend payments, description						Under the 2014 Revolver, Holdings may not make certain payments such as cash dividends, except that it may, inter alia, (i) pay up to $1 million per year to repurchase or redeem qualified equity interests of Holdings held by past or present officers, directors, or employees (or their estates) of the Company upon death, disability, or termination of employment, (ii) pay under its income tax receivable agreement (the “TRA”), and, (iii) so long as no default or event of default has occurred and is continuing, (a) make non-cash repurchases of equity interests in connection with the exercise of stock options by directors and officers, provided that those equity interests represent a portion of the consideration of the exercise price of those stock options, (b) pay up to $2.5 million per year pursuant to stock option plans, employment agreements, or incentive plans, (c) make up to $5 million in other restricted payments per year, and (d) make other restricted payments, provided that such payments would not cause, in each case, on a pro forma basis, (x) its lease-adjusted consolidated leverage ratio to equal or exceed 4.25 times and (y) its consolidated fixed charge coverage ratio to be less than 1.75 times.
Total amount of outstanding debt				$ 107,500,000		$ 107,500,000
Cash available				6,529,000	$ 8,207,000	6,529,000	$ 8,207,000	$ 6,101,000				$ 11,499,000
Number of restaurants damaged | Restaurants			1
Costs incurred directly related to fire						48,000
Disposition of assets related to fire				87,000		87,000		111,000
Gain on recovery of insurance proceeds, related to the reimbursement of property and equipment and expenses incurred				(148,000)		741,000
Gain on recovery of insurance proceeds, related to the reimbursement of lost profits				502,000		502,000
Amount received from insurance company in cash						1,000,000
Asset impairment charges				2,400,000		2,400,000
Unrecognized tax benefits, accrual of interest or penalties				0		0		$ 0
Unrecognized tax benefits, interest or penalties expenses				0	$ 0	0	$ 0
Percentage of cash savings in taxes realized as a result of utilizing net operating losses payable to pre-IPO stockholders		85.00%
Indefinite-lived Intangible Assets [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Asset impairment charges				$ 0		$ 0
Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of suppliers | Supplier						0		2
Supplier Two [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration								12.00%
Supplier Three [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration								11.00%
Largest Supplier One [Member] | Purchased [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				33.00%	37.00%	33.00%	37.00%
The Greater Los Angeles Area [Member] | Revenue [Member] | Geographic Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				75.00%	79.00%	75.00%	79.00%
Subsequent Event [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants											4
Number of restaurants damaged | Restaurants	1
Amount received from insurance company in cash	$ 354,000
Insurance deductible	$ 10,000
Letters of credit, Increased outstanding amount									$ 8,000,000
Accounts and Other Receivables [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash received from insurance company included in the accounts and other receivables				$ 354,000		$ 354,000
Senior Secured Revolving Credit Facility [Member] | Subsequent Event [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Pre-payment for new restaurant											$ 3,000,000
2013 First Lien Credit Agreement [Member] | Senior Secured Revolving Credit Facility [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Amount of borrowings available				$ 85,800,000		$ 85,800,000
Entity Operated Units [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants				193		193
Franchised Units [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants				253		253
Franchised Units [Member] | Subsequent Event [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants										2