Percentage of membership interests.

No definition available.

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Namespace Prefix:	loco_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Related party transaction annual management fee amount.

+ References

No definition available.

+ Details

Name:	loco_RelatedPartyTransactionAnnualManagementFeeAmount
Namespace Prefix:	loco_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of noncontrolling interest which might include background information, terms of the ownership arrangement, and type and terms of equity interest owned by the noncontrolling interest holders.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date of maturity or expiration of arrangements with a related party (for example, but not limited to, leasing and debt arrangements between related parties), in CCYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=loco_TrimaranPolloPartnersLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=loco_TrimaranFundManagementLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
	Nov. 18, 2005	Dec. 28, 2016	Dec. 31, 2014
Trimaran Pollo Partners, LLC [Member]
Related Party Transaction [Line Items]
Company's outstanding common stock owned by Trimaran Pollo Partners, L.L.C.		43.50%
Ownership 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.
Trimaran Pollo Partners, LLC [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Outstanding membership interest, percentage		40.00%
Ownership percentage by stockholders		40.00%
Trimaran Fund Management, LLC [Member]
Related Party Transaction [Line Items]
Date of agreement		Nov. 18, 2005
Annual fees	$ 0.5
General and administrative expenses paid			$ 0.3