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

Capital Management and Dividends - Additional Information (Detail)

v2.4.1.9
Capital Management and Dividends - Additional Information (Detail)
In Millions, except Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Jun. 30, 2014
USD ($)
Jun. 30, 2014
AUD
Mar. 31, 2015
USD ($)
Mar. 31, 2014
USD ($)
Equity [Abstract]        
Percentage of stock buyback program authorized     5.00%jhx_PercentageOfStockRepurchaseProgramAuthorized 5.00%jhx_PercentageOfStockRepurchaseProgramAuthorized
Aggregate number of common stock repurchased and cancelled 715,000jhx_AggregateNumberOfSharesAcquired 715,000jhx_AggregateNumberOfSharesAcquired 0jhx_AggregateNumberOfSharesAcquired  
Aggregate cost of common stock repurchased and cancelled $ 9.1us-gaap_TreasuryStockValueAcquiredCostMethod 9.8us-gaap_TreasuryStockValueAcquiredCostMethod $ 9.1us-gaap_TreasuryStockValueAcquiredCostMethod $ 22.1us-gaap_TreasuryStockValueAcquiredCostMethod
Average price paid per share of common stock repurchased and cancelled $ 12.73us-gaap_TreasuryStockAcquiredAverageCostPerShare 13.69us-gaap_TreasuryStockAcquiredAverageCostPerShare