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

Capital Management and Dividends - Summary of Dividends Declared or Paid (Detail)

v2.4.1.9
Capital Management and Dividends - Summary of Dividends Declared or Paid (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified
 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2013
Dividends Payable [Line Items]      
Dividend, Total Amount $ 390.1us-gaap_PaymentsOfDividendsCommonStock $ 199.1us-gaap_PaymentsOfDividendsCommonStock $ 188.5us-gaap_PaymentsOfDividendsCommonStock
125 Year Anniversary Special Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.28us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember 		$ 0.28us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember 		$ 0.28us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember
Dividend, Total Amount 124.6us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember 		124.6us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember 		124.6us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_OneHundredAndTwentyFiveYearAnniversarySpecialDividendMember
Dividend, Announcement Date Feb. 28, 2014 Feb. 28, 2014 Feb. 28, 2014
Dividend, Record Date Mar. 21, 2014 Mar. 21, 2014 Mar. 21, 2014
Dividend, Payment Date May 30, 2014 May 30, 2014 May 30, 2014
FY 2015 First Half Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember 		$ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember 		$ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember
Dividend, Total Amount 34.2us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember 		34.2us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember 		34.2us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFifteenFirstHalfDividendMember
Dividend, Announcement Date Nov. 19, 2014 Nov. 19, 2014 Nov. 19, 2014
Dividend, Record Date Dec. 23, 2014 Dec. 23, 2014 Dec. 23, 2014
Dividend, Payment Date Feb. 27, 2015 Feb. 27, 2015 Feb. 27, 2015
FY 2014 First Half Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember 		$ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember 		$ 0.08us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember
Dividend, Total Amount 35.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember 		35.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember 		35.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenFirstHalfDividendMember
Dividend, Announcement Date Nov. 14, 2013 Nov. 14, 2013 Nov. 14, 2013
Dividend, Record Date Dec. 19, 2013 Dec. 19, 2013 Dec. 19, 2013
Dividend, Payment Date Mar. 28, 2014 Mar. 28, 2014 Mar. 28, 2014
FY 2014 Special Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.20us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember 		$ 0.20us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember 		$ 0.20us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember
Dividend, Total Amount 89.0us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember 		89.0us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember 		89.0us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSpecialDividendMember
Dividend, Announcement Date May 22, 2014 May 22, 2014 May 22, 2014
Dividend, Record Date Jun. 12, 2014 Jun. 12, 2014 Jun. 12, 2014
Dividend, Payment Date Aug. 08, 2014 Aug. 08, 2014 Aug. 08, 2014
FY 2014 Second Half Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.32us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember 		$ 0.32us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember 		$ 0.32us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember
Dividend, Total Amount 142.3us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember 		142.3us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember 		142.3us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndFourteenSecondHalfDividendMember
Dividend, Announcement Date May 22, 2014 May 22, 2014 May 22, 2014
Dividend, Record Date Jun. 12, 2014 Jun. 12, 2014 Jun. 12, 2014
Dividend, Payment Date Aug. 08, 2014 Aug. 08, 2014 Aug. 08, 2014
FY 2013 Special Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.24us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember 		$ 0.24us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember 		$ 0.24us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember
Dividend, Total Amount 106.1us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember 		106.1us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember 		106.1us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndThirteenSpecialDividendMember
Dividend, Announcement Date May 23, 2013 May 23, 2013 May 23, 2013
Dividend, Record Date Jun. 28, 2013 Jun. 28, 2013 Jun. 28, 2013
Dividend, Payment Date Jul. 26, 2013 Jul. 26, 2013 Jul. 26, 2013
FY 2012 Second Half Dividend [Member]      
Dividends Payable [Line Items]      
Interim ordinary dividend to shareholders $ 0.13us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember 		$ 0.13us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember 		$ 0.13us-gaap_CommonStockDividendsPerShareCashPaid
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember
Dividend, Total Amount $ 57.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember 		$ 57.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember 		$ 57.5us-gaap_PaymentsOfDividendsCommonStock
/ us-gaap_DividendsAxis
= jhx_FiscalYearTwoThousandAndTwelveSecondHalfDividendMember
Dividend, Announcement Date May 23, 2013 May 23, 2013 May 23, 2013
Dividend, Record Date Jun. 28, 2013 Jun. 28, 2013 Jun. 28, 2013
Dividend, Payment Date Jul. 26, 2013 Jul. 26, 2013 Jul. 26, 2013