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Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Mar. 31, 2015 | Mar. 31, 2014 | Mar. 12, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] |  |  |
Total stock-based compensation expense | $ 12.5 us-gaap_AllocatedShareBasedCompensationExpense | $ 13.0 us-gaap_AllocatedShareBasedCompensationExpense | $ 10.8 us-gaap_AllocatedShareBasedCompensationExpense
Liability Awards Expense [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] |  |  |
Total stock-based compensation expense | 3.3 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_LiabilityAwardsMember | 4.5 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_LiabilityAwardsMember | 3.8 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_LiabilityAwardsMember
Equity Awards Expense [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] |  |  |
Total stock-based compensation expense | $ 9.2 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_EquityAwardsMember | $ 8.5 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_EquityAwardsMember | $ 7.0 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = jhx_EquityAwardsMember

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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