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

X

- Definition

Agreement Date

+ References

No definition available.

+ Details

Name:	jhx_AgreementDate
Namespace Prefix:	jhx_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Details

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