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

X

- 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

Name:	us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration