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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
12 Months Ended | |||
|---|---|---|---|---|
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Mar. 31, 2015
Directors
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Mar. 31, 2014
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Mar. 31, 2013
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Feb. 28, 2007
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| Summary Of Significant Accounting Policies [Line Items] | ||||
| Ownership interest rate percentage | 100.00%us-gaap_EquityMethodInvestmentOwnershipPercentage | |||
| Number of directors appointed by Company | 3jhx_NumberOfDirectorsAppointedToAicfByCompany | |||
| Directors appointed by NSW Government | 2jhx_NumberOfDirectorsAppointedToAicfByGovernment | |||
| Advertising expense | $ 11.5us-gaap_AdvertisingExpense | $ 9.5us-gaap_AdvertisingExpense | $ 8.9us-gaap_AdvertisingExpense | |
| Equity awards vested percentage after first year | 25.00%jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageVestedAfterFirstYear | |||
| Equity awards vested percentage after second year | 25.00%jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageVestedAfterSecondYear | |||
| Equity awards vested percentage after third year | 50.00%jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageVestedAfterThirdYear | |||
| Potential diluted common shares outstanding | 1.7us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 1.9us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 4.4us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | |
| AICF Funding [Member] | ||||
| Summary Of Significant Accounting Policies [Line Items] | ||||
| Ownership interest rate percentage |
0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_StatementBusinessSegmentsAxis = jhx_AsbestosInjuriesCompensationFundMember |
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| X | ||||||||||
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- Definition
Number of directors appointed to the AICF by the Company. No definition available.
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- Definition
Number of directors appointed to the AICF by the New South Wales Government. No definition available.
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- Definition
Service equity awards percentage vested after the first year. No definition available.
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| X | ||||||||||
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- Definition
Service equity awards percentage vested after the second year. No definition available.
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| X | ||||||||||
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- Definition
Service equity awards percentage vested after the third year. No definition available.
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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