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v3.19.1

Product Warranties - Additional Information (Detail) | 12 Months Ended
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Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract] |
Limited warranty period | 30 years

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- Definition Limited warranty period on its products. + References No definition available. + Details
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Namespace Prefix: | jhx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration