Condensed Consolidated Statements of Income (Unaudited) - Parenthetical - USD ($) $ in Thousands	3 Months Ended
Mar. 28, 2018	Mar. 29, 2017
Income Statement [Abstract]
Interest Income	$ 8	$ 5

Investment Income, Bank Earning Allowance And Miscellaneous Interest

No definition available.

Name:	loco_InvestmentIncomeBankEarningAllowanceAndMiscellaneousInterest
Namespace Prefix:	loco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration