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v3.8.0.1

Fair Value of Senior Notes (Parenthetical) (Detail) - 4.5% Senior Unsecured Notes Due 2026 [Member] | 6 Months Ended
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Sep. 30, 2017
Fair Value Of Financial Instruments [Line Items] |
Debt instrument, interest rate | 4.50%
Debt instrument, maturity year | 2026

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- Definition Debt instrument maturity year. + References No definition available. + Details
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Namespace Prefix: | exp_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- Definition Fair value of financial instruments. + References No definition available. + Details
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Namespace Prefix: | exp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |