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

Operating Segment Information and Concentrations of Risk - Summary of Gross Sales by Major Customers (Detail)

v2.4.1.9
Operating Segment Information and Concentrations of Risk - Summary of Gross Sales by Major Customers (Detail) (USA & Europe Fiber Cement [Member], USD $)
In Millions, unless otherwise specified
 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2013
Segment Reporting Information [Line Items]      
Gross Sales of Major Customers $ 320.8jhx_GrossSalesMajorCustomers $ 313.8jhx_GrossSalesMajorCustomers $ 360.7jhx_GrossSalesMajorCustomers
Customer A [Member]      
Segment Reporting Information [Line Items]      
Gross Sales of Major Customers 177.4jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		174.2jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		223.0jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember
Gross sales percentage 10.70%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		11.70%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		16.90%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember
Customer B [Member]      
Segment Reporting Information [Line Items]      
Gross Sales of Major Customers $ 143.4jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		$ 139.6jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		$ 137.7jhx_GrossSalesMajorCustomers
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember
Gross sales percentage 8.70%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		9.30%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember 		10.40%jhx_MajorCustomerPercentageOfGrossSales
/ us-gaap_MajorCustomersAxis
= jhx_CustomerBMember
/ us-gaap_StatementBusinessSegmentsAxis
= jhx_UnitedStatesOfAmericaAndEuropeFiberCementMember