Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)		1 Months Ended	3 Months Ended				9 Months Ended		12 Months Ended
	Jul. 30, 2014	Nov. 30, 2015 restaurant	Dec. 27, 2017 USD ($)	Sep. 27, 2017 USD ($) restaurant Restaurants shares	Dec. 28, 2016 USD ($)	Sep. 28, 2016 USD ($) shares	Sep. 27, 2017 USD ($) restaurant Restaurants supplier segment shares	Sep. 28, 2016 USD ($) shares	Dec. 28, 2016 USD ($) supplier	Oct. 29, 2017	Dec. 30, 2015 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted | shares				1,248		21,453	170,924	29,259
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | shares				0		32,386	17,661	147,726
Stock-based compensation expense				$ 0		$ 0	$ 738,000	$ 244,000
Depreciation				4,700,000		4,100,000	$ 13,600,000	11,800,000
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 $1.0 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 $5.0 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				85,300,000			$ 85,300,000
Cash available				7,062,000	$ 2,168,000	6,529,000	7,062,000	6,529,000	$ 2,168,000		$ 6,101,000
Number of restaurants damaged | restaurant		1
Expenses incurred from fire damage								100,000
Property, Plant and Equipment, Disposals											$ 100,000
Gain On Business Interruption Insurance Recovery Property Equipment And Expenses				0		(148,000)	0	741,000
Property and equipment owned, net				114,903,000	118,470,000		114,903,000		118,470,000
Impairment of property and equipment				15,000,000		2,454,000	15,480,000	2,508,000
Costs incurred directly related to fire (less than $0.1 million)				0		0	0	48,000
Gain on recovery of insurance proceeds, property, equipment and expenses							0	500,000
Amount received from insurance company in cash					400,000			1,000,000
Operating lease obligations				307,500,000			307,500,000
Deferred tax assets				6,317,000	25,905,000		6,317,000		25,905,000
Unrecognized tax benefits, accrual of interest or penalties				0	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%
Recovery of securities class action legal expense				634,000		0	1,145,000	0
Income tax receivable agreement (income) expense				$ (19,000)		$ 182,000	$ 107,000	$ 411,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | shares				0		9,875	128,252	329,673
Indefinite-lived Intangible Assets
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants Impaired | Restaurants				10			11
Asset impairment charges				$ 0		$ 0	$ 0	$ 0
Number of Restaurants Closed | Restaurants				2
Supplier Concentration Risk
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of suppliers | supplier							1		1
Entity Operated Units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants | restaurant				208			208
Franchised Units
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants | restaurant				265			265
Subsequent Event
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Recovery of Securities Class Action Legal Costs			$ 500,000
Recovery of securities class action legal expense			$ (500,000)
2014 Revolver | Senior Secured Revolving Credit Facility
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Debt Instrument, Periodic Payment				$ 9,500,000		$ 9,500,000	$ 19,000,000	$ 16,000,000
Restrictive covenants, maximum annual repurchase or redemption of qualified entity interests							1,000,000
Restrictive covenants, maximum annual payment for stock option plans, employment agreements and incentive plans							2,500,000
Restrictive covenants, maximum annual payment for other restricted payments							$ 5,000,000
Maximum leverage ratio							4.25
Covenant description, coverage ratio							1.75
Amount of borrowings available				$ 106,900,000			$ 106,900,000
Supplier Two | Accounts Payable | Supplier Concentration Risk
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration							17.40%		16.00%
Largest Supplier One | Purchased | Supplier Concentration Risk
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				27.00%		33.00%	30.00%	33.00%
Accounting Standards Update 2015-07 [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Deferred tax assets					$ 21,500,000				$ 21,500,000
Trimaran Pollo Partners L L C [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Noncontrolling Interest, Description							So long as LLC maintains at least 40% ownership, (i) any member of the board of directors may be removed at any time without cause by affirmative vote of a majority of the Company’s common stock, and (ii) stockholders representing 40% or greater ownership may cause special stockholder meetings to be called.
Fair Value, Measurements, Nonrecurring [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Property and equipment owned, net				$ 280,000			$ 280,000
Impairment of property and equipment				15,035,000			15,480,000	$ 2,508,000
Franchisees [Member] | Subsequent Event
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants										1
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Property and equipment owned, net				$ 280,000			$ 280,000
Los Angeles [Member] | Revenue | Geographic Concentration Risk
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				73.00%		75.00%	73.00%	75.00%
Scenario, Actual [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Income tax receivable agreement (income) expense				$ 100,000