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Retirement Plans - Additional Information (Detail) (USD $)
12 Months Ended
Jan. 02, 2015
Jan. 03, 2014
Dec. 28, 2012
Retirement Plan Disclosure [Line Items]      
Defined Contribution Plan Employer Contribution Percentage Of Eligible Wages 7.00%expo_DefinedContributionPlanEmployerContributionPercentageOfEligibleWages    
Defined Contribution Plan Employer Contribution Annual Vesting Percentage 20.00%expo_DefinedContributionPlanEmployerContributionAnnualVestingPercentage    
Defined Contribution Plan Employer Contribution Annual Vesting Period 5 years    
Pension and Other Postretirement Benefit Expense $ 6,954,000us-gaap_PensionAndOtherPostretirementBenefitExpense $ 6,564,000us-gaap_PensionAndOtherPostretirementBenefitExpense $ 6,573,000us-gaap_PensionAndOtherPostretirementBenefitExpense