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Stock-Based Compensation - Additional Information (Detail) (USD $)
12 Months Ended
Jan. 02, 2015
Jan. 03, 2014
Dec. 28, 2012
May 29, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted average fair value of options granted $ 24.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 18.78us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 19.51us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue  
Total intrinsic value of options exercised $ 1,975,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 3,177,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 7,484,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue  
Employee Stock Purchase Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted average purchase price $ 71.35expo_WeightedAveragePriceOfSharesPurchasedUnderEmployeeStockPurchasePlan
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
$ 60.64expo_WeightedAveragePriceOfSharesPurchasedUnderEmployeeStockPurchasePlan
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
$ 50.26expo_WeightedAveragePriceOfSharesPurchasedUnderEmployeeStockPurchasePlan
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
 
Maximum Percentage Of Payroll Deductions Related To Purchase Of Common Stock 15.00%expo_PercentageOfPayrolDeductionsRelatedToPurchaseOfCommonStock
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
     
Purchase price of Common Stock as Percentage of Fair Market Value 95.00%expo_PercentageOfCommonSharesValueAtFairMarketValueOfCommonStock
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
     
Total number of shares reserved for issuance 200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
     
Number of Shares Available for Grant 46,533us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_EmployeeStockMember
     
Vested Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock based compensation expense 6,287,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_VestedRestrictedStockMember
6,061,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_VestedRestrictedStockMember
6,089,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_VestedRestrictedStockMember
 
Percentage of annual bonus settled with fully vested restricted stock unit awards 40.00%expo_PercentageOfAnnualBonusSettledWithVestedRestrictedStockUnitAwards
/ us-gaap_AwardTypeAxis
= expo_VestedRestrictedStockMember
     
Recipient age to expense award on grant date 59 years 6 months      
Unvested Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock based compensation expense 6,103,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_UnvestedRestrictedStockMember
6,030,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_UnvestedRestrictedStockMember
5,650,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_UnvestedRestrictedStockMember
 
Unrecognized compensation cost 5,863,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= expo_UnvestedRestrictedStockMember
     
Weighted average period of recognized term 2 years 6 months      
Employee Stock Option        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized compensation cost 352,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
     
Weighted average period of recognized term 2 years 2 months 12 days      
2008 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total number of shares reserved for issuance       2,414,075us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= expo_EquityIncentivePlanMember
Number of Shares Available for Grant 717,671us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= expo_EquityIncentivePlanMember
     
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock based compensation expense 689,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_StockOptionsGrantedPriorToDecember2005Member
1,077,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_StockOptionsGrantedPriorToDecember2005Member
639,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= expo_StockOptionsGrantedPriorToDecember2005Member
 
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value $ 16,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 15,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 11,300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 74.58us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
[1] $ 54.17us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 48.04us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Intrinsic Value, Amount Per Share $ 81.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
     
[1] Does not include employee stock purchase plans or stock option plans.