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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 | Mar. 31, 2014 | Mar. 31, 2013 | Feb. 28, 2007
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Ownership interest rate percentage |  |  |  | 100.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
Number of directors appointed by Company | 3 jhx_NumberOfDirectorsAppointedToAicfByCompany |  |  |
Directors appointed by NSW Government | 2 jhx_NumberOfDirectorsAppointedToAicfByGovernment |  |  |
Advertising expense | $ 11.5 us-gaap_AdvertisingExpense | $ 9.5 us-gaap_AdvertisingExpense | $ 8.9 us-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 | 1.7 us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 1.9 us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 4.4 us-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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- Definition Number of directors appointed to the AICF by the New South Wales Government. + References No definition available. + Details
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- Definition Service equity awards percentage vested after the first year. + References No definition available. + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Antidilution -URI http://asc.fasb.org/extlink&oid=6505113 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Diluted Earnings Per Share -URI http://asc.fasb.org/extlink&oid=6510752 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Contingent Stock Agreement -URI http://asc.fasb.org/extlink&oid=6508534 + Details
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