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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 | 715,000 jhx_AggregateNumberOfSharesAcquired | 715,000 jhx_AggregateNumberOfSharesAcquired | 0 jhx_AggregateNumberOfSharesAcquired |
Aggregate cost of common stock repurchased and cancelled | $ 9.1 us-gaap_TreasuryStockValueAcquiredCostMethod | 9.8 us-gaap_TreasuryStockValueAcquiredCostMethod | $ 9.1 us-gaap_TreasuryStockValueAcquiredCostMethod | $ 22.1 us-gaap_TreasuryStockValueAcquiredCostMethod
Average price paid per share of common stock repurchased and cancelled | $ 12.73 us-gaap_TreasuryStockAcquiredAverageCostPerShare | 13.69 us-gaap_TreasuryStockAcquiredAverageCostPerShare |  |

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- Definition Aggregate number of shares acquired under a stock repurchase plan. + References No definition available. + Details
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- Definition Percentage of stock repurchase program authorized. + References No definition available. + Details
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- Details
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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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- Definition Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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