Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

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

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=loco_MarginRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=loco_CreditAgreementTwoThousandFourteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=loco_SwingLineLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
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Credit Agreements - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended
	Dec. 11, 2014	Jun. 29, 2016	Jun. 29, 2016
Debt Instrument [Line Items]
Revolving credit facility maturity period			Dec. 11, 2019
Debt instrument basis percentage			1.00%
Interest rate description			(a) the federal funds rate plus 0.50%, (b) the prime rate of Bank of America, or (c) LIBOR plus 1.00%. For LIBOR loans, the margin is in the range of 1.75% to 2.50%, and for base rate loans the margin is in the range of 0.75% to 1.50%. The margin was initially set at 2.00% for LIBOR loans and at 1.00% for base rate loans until the delivery of financial statements and a compliance certificate for the first quarter of 2015. The interest rate range was 2.19% to 2.20% and 2.02% to 2.20% for the thirteen and twenty-six weeks ended June 29, 2016, respectively.
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal payments prior to maturity			$ 0
Debt instrument, periodic payment			$ 6,500,000
Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		2.19%	2.02%
Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		2.20%	2.20%
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			0.50%
Base Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			0.75%
Base Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			1.50%
Initial Margin Rate [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			2.00%
LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			1.00%
LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			1.75%
LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument basis percentage			2.50%
2014 Credit Agreement [Member]
Debt Instrument [Line Items]
Senior secured revolving facility	$ 200,000,000
Senior secured revolving facility term	5 years
Letters of credit outstanding		$ 7,200,000	$ 7,200,000
Amount of borrowings available		$ 76,300,000	$ 76,300,000
Swing Line Loans [Member] \| 2014 Credit Agreement [Member]
Debt Instrument [Line Items]
Sub limit of revolving facility	$ 15,000,000
Letter of Credit [Member] \| 2014 Credit Agreement [Member]
Debt Instrument [Line Items]
Sub limit of revolving facility	$ 15,000,000