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Operating Segment Information and Concentrations of Risk - Summary of Gross Sales by Major Customers (Detail) - Customer A [Member] - USA & Europe Fiber Cement [Member] - USD ($) $ in Millions | 12 Months Ended
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Mar. 31, 2016 | Mar. 31, 2015 | Mar. 31, 2014
Segment Reporting Information [Line Items] |  |  |
Gross Sales of Major Customers | $ 197.0 | $ 177.4 | $ 174.2
Gross sales percentage | 10.10% | 10.70% | 11.70%

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- Definition Gross sales of the Company's major customers that individually account for over 10% of the Company's net sales in one or all of the past three fiscal years. + References No definition available. + Details
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Namespace Prefix: | jhx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Major customer percentage of the Company's total gross sales. + References No definition available. + Details
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Namespace Prefix: | jhx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

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