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Operating Segment Information and Concentrations of Risk - Additional Information (Detail)	12 Months Ended
	Mar. 31, 2015 Customer	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting [Abstract]
Percentage of net sales individually account for two major customers	10.00%jhx_PercentageOfNetSalesPerCustomerMaximum	10.00%jhx_PercentageOfNetSalesPerCustomerMaximum	10.00%jhx_PercentageOfNetSalesPerCustomerMaximum
Number of major customers	2jhx_NumberOfCustomer
Accounts receivable major customer percentage	14.00%jhx_EntityWideAccountsReceivableMajorCustomerPercentage	14.00%jhx_EntityWideAccountsReceivableMajorCustomerPercentage
Percentage of net sales	25.00%jhx_SalesOutsideDomesticCountryAsPercentageOfNetSales	27.00%jhx_SalesOutsideDomesticCountryAsPercentageOfNetSales	30.00%jhx_SalesOutsideDomesticCountryAsPercentageOfNetSales

X

- Definition

Entity wide accounts receivable major customer percentage.

+ References

No definition available.

+ Details

Name:	jhx_EntityWideAccountsReceivableMajorCustomerPercentage
Namespace Prefix:	jhx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Number Of Customer

+ References

No definition available.

+ Details

Name:	jhx_NumberOfCustomer
Namespace Prefix:	jhx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage Of Net Sales Per Customer Maximum

+ References

No definition available.

+ Details

Name:	jhx_PercentageOfNetSalesPerCustomerMaximum
Namespace Prefix:	jhx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Sales outside the United States as a percentage of net sales.

+ References

No definition available.

+ Details

Name:	jhx_SalesOutsideDomesticCountryAsPercentageOfNetSales
Namespace Prefix:	jhx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

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