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

Summary of Significant Accounting Policies - Schedule of Exchange Rates Used to Convert Australian Dollar into US Dollars (Detail)

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Summary of Significant Accounting Policies - Schedule of Exchange Rates Used to Convert Australian Dollar into US Dollars (Detail)
 12 Months Ended
Mar. 31, 2015
ExchangeRate
Mar. 31, 2014
ExchangeRate
Mar. 31, 2013
ExchangeRate
Foreign Currency [Abstract]      
Assets and liabilities 1.3096jhx_AssetsAndLiabilitiesExchangeRate 1.0845jhx_AssetsAndLiabilitiesExchangeRate 0.9597jhx_AssetsAndLiabilitiesExchangeRate
Statements of operations 1.1419jhx_StatementsOfOperationsExchangeRate 1.0716jhx_StatementsOfOperationsExchangeRate 0.9694jhx_StatementsOfOperationsExchangeRate
Cash flows - beginning cash 1.0845jhx_CashFlowsBeginningCashExchangeRate 0.9597jhx_CashFlowsBeginningCashExchangeRate 0.9614jhx_CashFlowsBeginningCashExchangeRate
Cash flows - ending cash 1.3096jhx_CashFlowsEndingCashExchangeRate 1.0845jhx_CashFlowsEndingCashExchangeRate 0.9597jhx_CashFlowsEndingCashExchangeRate
Cash flows - current period movements 1.1419jhx_CashFlowsCurrentMovementsExchangeRate 1.0716jhx_CashFlowsCurrentMovementsExchangeRate 0.9694jhx_CashFlowsCurrentMovementsExchangeRate