Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Detail)

v2.4.1.9
Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Detail) (Restricted Stock Units (Market Condition) [Member], AUD)
12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Restricted Stock Units (Market Condition) [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Date of grant Sep. 16, 2014 Sep. 16, 2013
Dividend yield (per annum) 4.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
3.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
Expected volatility 37.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
43.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
Risk free interest rate 1.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
1.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
Expected life in years 3 years 3 years
JHX stock price at grant date (A$) 12.42jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsGrantDateStockPrice
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
10.17jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsGrantDateStockPrice
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
Number of restricted stock units 459,317jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsNumber
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember
489,888jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsNumber
/ us-gaap_AwardTypeAxis
= jhx_RestrictedStockUnitsMarketConditionMember