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Segment Information - Additional Information (Detail) | 6 Months Ended
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Sep. 30, 2018 Location Facility Terminal Plant Sector Segment JointVentures
Segment Reporting Information [Line Items] |
Number of sectors | Sector | 3
Number of reportable business segments | Segment | 5
Cement plant locations | Location | 7
Slag grinding facility | Facility | 1
Cement distribution terminals | Terminal | 18
Gypsum wallboard plants | Plant | 5
Readymix concrete batch plants | Plant | 17
Aggregates processing plants | Plant | 4
Number of frac sand processing facilities | Facility | 2
Number of frac sand drying facilities | Facility | 3
Number of frac sand trans-load locations | Location | 6
Proportionate consolidation of share of Joint Venture's revenues and operating earnings | 50.00%
Cement [Member] |
Segment Reporting Information [Line Items] |
Number of Joint Venture | JointVentures | 1

X
- Definition Aggregates processing plants. + References No definition available. + Details
Name: | exp_AggregatesProcessingPlants
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Cement distribution terminals. + References No definition available. + Details
Name: | exp_CementDistributionTerminals
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Cement plant locations. + References No definition available. + Details
Name: | exp_CementPlantLocations
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Gypsum wallboard plants. + References No definition available. + Details
Name: | exp_GypsumWallboardPlants
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of frac sand drying facilities. + References No definition available. + Details
Name: | exp_NumberOfFracSandDryingFacilities
Namespace Prefix: | exp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of frac sand processing facilities. + References No definition available. + Details
Name: | exp_NumberOfFracSandProcessingFacilities
Namespace Prefix: | exp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of frac sand trans-load locations. + References No definition available. + Details
Name: | exp_NumberOfFracSandTransloadLocations
Namespace Prefix: | exp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of joint ventures. + References No definition available. + Details
Name: | exp_NumberOfJointVentures
Namespace Prefix: | exp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of sectors. + References No definition available. + Details
Name: | exp_NumberOfSectors
Namespace Prefix: | exp_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Readymix plants. + References No definition available. + Details
Name: | exp_ReadymixPlants
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Segment reporting information proportionate consolidation of joint ventures revenues and operating earnings. + References No definition available. + Details
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Namespace Prefix: | exp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Slag grinding facility. + References No definition available. + Details
Name: | exp_SlagGrindingFacility
Namespace Prefix: | exp_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=exp_CementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |