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Accrued Expenses And Current Portion Of Other Long-Term Liabilities (Narrative) (Details) (USD $)
 3 Months Ended 6 Months Ended
Mar. 28, 2015
Mar. 29, 2014
Mar. 28, 2015
Mar. 29, 2014
Accrued Expenses And Current Portion Of Other Long-Term Liabilities [Abstract]        
Workers' compensation per occurrence covered under insurance cost $ 750,000us-gaap_WorkersCompensationLiabilityCurrent   $ 750,000us-gaap_WorkersCompensationLiabilityCurrent  
General liability 500,000us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent   500,000us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent  
Medical care benefits per person covered under insurance cost 325,000imkta_MedicalCareBenefitsInsuranceLiabilityPerPerson   325,000imkta_MedicalCareBenefitsInsuranceLiabilityPerPerson  
Self insurance reserves 30,300,000us-gaap_SelfInsuranceReserve   30,300,000us-gaap_SelfInsuranceReserve  
Employee insurance expense 8,600,000us-gaap_GeneralInsuranceExpense 5,800,000us-gaap_GeneralInsuranceExpense 16,300,000us-gaap_GeneralInsuranceExpense 12,000,000us-gaap_GeneralInsuranceExpense
Self insurance reserves, current 11,000,000us-gaap_SelfInsuranceReserveCurrent   11,000,000us-gaap_SelfInsuranceReserveCurrent  
Self insurance reserves, noncurrent $ 19,300,000us-gaap_SelfInsuranceReserveNoncurrent   $ 19,300,000us-gaap_SelfInsuranceReserveNoncurrent