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Restricted Cash and Cash Equivalents - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash and Cash Equivalents [Abstract]
Restricted cash and cash equivalents related to insurance policy	$ 5.0jhx_RestrictedCashAndCashEquivalentsRelatedToInsurancePolicy	$ 5.0jhx_RestrictedCashAndCashEquivalentsRelatedToInsurancePolicy

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- Definition

Restricted cash and cash equivalents related to insurance policy.

+ References

No definition available.

+ Details

Name:	jhx_RestrictedCashAndCashEquivalentsRelatedToInsurancePolicy
Namespace Prefix:	jhx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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- Details

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