Description of Business - Additional Information (Detail)	12 Months Ended
	Dec. 27, 2017 USD ($) restaurant segment	Sep. 27, 2017 restaurant	Jun. 28, 2017 restaurant	Mar. 29, 2017 restaurant	Dec. 28, 2016 restaurant	Sep. 28, 2016 restaurant	Jun. 29, 2016 restaurant	Mar. 30, 2016 restaurant
Debt Instrument [Line Items]
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 $1.0 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.
Number of operating segments | segment	1
Philippines
Debt Instrument [Line Items]
Number of restaurants	2
Company-operated
Debt Instrument [Line Items]
Number of restaurants	212	208	208	204	201	193	188	188
Company-operated | The Greater Los Angeles Area
Debt Instrument [Line Items]
Number of restaurants	141
Franchised
Debt Instrument [Line Items]
Number of restaurants	265	265	264	263	259	253	251	248
Franchised | The Greater Los Angeles Area
Debt Instrument [Line Items]
Number of restaurants	138
Revolving Credit Facility | 2014 Credit Agreement
Debt Instrument [Line Items]
Maximum annual repurchase or redemption of qualified entity interests | $	$ 1,000,000.0
Maximum annual payment for stock option plans, employment agreements and incentive plans | $	2,500,000.0
Maximum annual payment for other restricted payments | $	$ 5,000,000.0
Maximum leverage ratio	4.25
Minimum coverage ratio	1.75
Chicken Acquisition Corp
Debt Instrument [Line Items]
Ownership interest	43.30%