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           Stock-Based Compensation - Assumptions Used for Restricted Stock Grants (Detail) (Restricted Stock Units (Market Condition) [Member], AUD) 
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        12 Months Ended | |
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           Mar. 31, 2015 
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           Mar. 31, 2014 
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           Restricted Stock Units (Market Condition) [Member] 
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| 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  | 
      
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- Definition 
          Share based compensation arrangement by share based payment award fair value assumptions date of grant. No definition available. 
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- Definition 
          Share based compensation arrangement by share based payment award fair value assumptions grant date stock price. No definition available. 
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- Definition 
          Share based compensation arrangement by share based payment award restricted stock units number. No definition available. 
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- Definition 
          The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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