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Subsequent Events - Additional Information (Detail) | 12 Months Ended
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Mar. 31, 2015
Subsequent Events [Abstract] |
Date of agreement | May 06, 2015

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- Definition Agreement Date + References No definition available. + Details
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Namespace Prefix: | jhx_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_SubsequentEventsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration