Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)				3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 12, 2015 USD ($) Store	Jul. 30, 2014 USD ($) $ / shares shares	Jul. 14, 2014 $ / shares shares	Sep. 30, 2015 USD ($) Restaurants Supplier $ / shares shares	Sep. 24, 2014 USD ($) Supplier	Sep. 30, 2015 USD ($) Segment Restaurants Supplier $ / shares shares	Sep. 24, 2014 USD ($) Supplier	Dec. 31, 2014 USD ($) Supplier $ / shares shares	Jul. 24, 2014 $ / shares shares	Dec. 25, 2013 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment						1
Date of reorganization						Apr. 22, 2014
Reorganization terms						(“Old Holdings”) entered into the following reorganization transactions: (i) Old Holdings merged with and into CSC with CSC continuing as the surviving corporation; (ii) CSC merged with and into CAC with CAC continuing as the surviving corporation and (iii) CAC renamed itself El Pollo Loco Holdings, Inc.
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.
Common stock, authorized | shares			200,000,000	200,000,000		200,000,000		200,000,000	200,000,000
Common stock, par value | $ / shares			$ 0.01	$ 0.01		$ 0.01		$ 0.01	$ 0.01
Stock split ratio			8.56381
Preferred stock, authorized | shares				100,000,000		100,000,000		100,000,000	100,000,000
Preferred stock, par value | $ / shares				$ 0.01		$ 0.01		$ 0.01	$ 0.01
Increase in authorized shares | shares									300,000,000
Stock split note						8.56381 for 1
Total amount of outstanding debt				$ 125,700,000		$ 125,700,000
Cash available				8,207,000	$ 41,825,000	8,207,000	$ 41,825,000	$ 11,499,000		$ 17,015,000
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]
Impairment charge				$ 0		$ 0
Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of suppliers | Supplier						2		2
Number of largest suppliers | Supplier				2	2	2	2
Supplier One [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration						19.00%
Supplier Two [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration						9.00%
Supplier Three [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration								6.00%
Supplier Four [Member] | Accounts Payable [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration								5.00%
Largest Supplier One [Member] | Purchased [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				37.00%	36.00%	37.00%	36.00%
Largest Supplier Two [Member] | Purchased [Member] | Supplier Concentration Risk [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration				2.00%	3.00%	3.00%	3.00%
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				78.00%	80.00%
Subsequent Event [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of new store openings completed | Store	4
Letters of credit balance	$ 7,200,000
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				$ 68,000,000		$ 68,000,000
Senior Secured Term Loan [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Repayment of debt		$ 100,000,000
IPO [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Shares issued in in initial public offering | shares		8,214,286
Shares issued, price per share | $ / shares		$ 15.00
Net proceeds from initial public offering		$ 112,300,000
Underwriters [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Shares issued in in initial public offering | shares		1,071,429
Entity Operated Units [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants				175		175
Franchised Units [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | Restaurants				245		245