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Weighted-Average Assumptions Used to Value Option Awards (Detail) (Fiscal 2015 Employee Stock Option and Board of Directors Grant [Member])
12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Fiscal 2015 Employee Stock Option and Board of Directors Grant [Member]
   
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Dividend Yield 2.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
2.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
Expected Volatility 44.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
44.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
Risk Free Interest Rate 1.86%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
2.04%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= exp_BoardOfDirectorGrantsMember
Expected Life 6 years 7 years