BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment of Property and Equipment and ROU Assets (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 25, 2025	Jun. 26, 2024	Jun. 25, 2025	Jun. 26, 2024
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Asset impairment charges	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Maximum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Closed-store reserve expense	$ 0.1	$ 0.1	$ 0.1	$ 0.1

Basis of presentation and summary of significant accounting policies.

No definition available.

Name:	loco_BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix:	loco_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482130/360-10-45-4

+ Details

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

- Definition

Amount, after cash payment, of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: