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Retirement Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 28, 2018	Dec. 29, 2017	Dec. 30, 2016
Retirement Plan Disclosure [Line Items]
Defined Contribution Plan Employer Contribution Percentage Of Eligible Wages	7.00%
Defined Contribution Plan Employer Contribution Annual Vesting Percentage	20.00%
Defined Contribution Plan Employer Contribution Annual Vesting Period	5 years
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 8,419,000	$ 7,914,000	$ 7,761,000

X

- Definition

Percentage of employer's contributions to a defined contribution plan that vests in a given year.

+ References

No definition available.

+ Details

Name:	expo_DefinedContributionPlanEmployerContributionAnnualVestingPercentage
Namespace Prefix:	expo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of years until employer's contribution to a defined contribution plan fully vest.

+ References

No definition available.

+ Details

Name:	expo_DefinedContributionPlanEmployerContributionAnnualVestingPeriod
Namespace Prefix:	expo_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Defined contribution plan employer contribution percentage of eligible wages.

+ References

No definition available.

+ Details

Name:	expo_DefinedContributionPlanEmployerContributionPercentageOfEligibleWages
Namespace Prefix:	expo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	expo_RetirementPlanDisclosureLineItems
Namespace Prefix:	expo_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of cost (reversal of cost) for pension and other postretirement benefits.

+ References

No definition available.

+ Details

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