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

Stock-Based Compensation - Summary of Stock Options Available for Grant and Outstanding Options Activity (Detail)

v2.4.1.9
Stock-Based Compensation - Summary of Stock Options Available for Grant and Outstanding Options Activity (Detail) (AUD)
12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Shares Available for Grant, Beginning balance 23,947,127us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 24,503,783us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Granted (1,192,225)jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantedInPeriod (1,266,656)jhx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantedInPeriod
New Shares Authorized 2,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized 710,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Shares Available for Grant, Ending balance 24,754,902us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 23,947,127us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Outstanding Options, Number, Beginning balance 1,099,276us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 5,156,136us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Exercised, Outstanding Options, Number (587,496)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (4,056,860)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Outstanding Options, Number, Ending balance 511,780us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,099,276us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Outstanding Options, Weighted Average Exercise Price, Beginning balance 8.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice 7.94us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Exercised, Outstanding Options, Weighted Average Exercise Price 8.06us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice 7.89us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Outstanding Options, Weighted Average Exercise Price, Ending balance 8.17us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice 8.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice