Debt refinancing costs.

No definition available.

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

- Definition

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

+ References

No definition available.

+ Details

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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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- 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

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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 applied to principal.

+ References

+ Details

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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

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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

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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

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

- Definition

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ 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 470
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=28361426&loc=d3e1314-112600

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=28361426&loc=d3e1336-112600

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Line-of-Credit Arrangement
-URI http://asc.fasb.org/extlink&oid=6517033

+ Details

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

- Details

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- Details

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- Details

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- Details

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Current Credit Agreements - Additional Information (Detail) - USD ($)		12 Months Ended
	Dec. 11, 2014	Dec. 28, 2016	Dec. 30, 2015
Debt Instrument [Line Items]
Revolving credit facility maturity period		Dec. 11, 2019
Debt instrument basis percentage		1.00%
Debt instrument, interest rate		2.40%	2.00%
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 2.0% to 2.4% during fiscal 2016 and 1.9% to 2.6% during fiscal 2015 and was 2.4% and 2.0% at December 28, 2016 and December 30, 2015, respectively.
Transaction costs	$ 1,500,000	$ 1,200,000	$ 900,000
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal payments prior to maturity		$ 0
Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		2.00%	1.90%
Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		2.40%	2.60%
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		$ 8,100,000
Amount of borrowings available		87,900,000
Revolving line of credit		$ 104,000,000
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