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

Operating Segment Information and Concentrations of Risk - Summary of Geographical Information (Parenthetical) (Detail)

v3.7.0.1
Operating Segment Information and Concentrations of Risk - Summary of Geographical Information (Parenthetical) (Detail) - USD ($)
$ in Millions
12 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Mar. 31, 2015
Segment Reporting Information [Line Items]      
Research and development costs $ 30.3 $ 29.5 $ 31.7
Selling, general and administrative expenses 291.6 254.2 245.5
Asbestos adjustments (40.4) (5.5) (33.4)
AICF SG&A expenses (1.5) (1.7) (2.5)
Net interest (expense) income (27.5) (25.6) (7.5)
North America Fiber Cement [Member]      
Segment Reporting Information [Line Items]      
Research and development costs 6.2 6.6 6.1
International Fiber Cement [Member]      
Segment Reporting Information [Line Items]      
Research and development costs 1.5 1.2 1.4
New Zealand weathertightness claims (expense)/ benefit   (0.5) 4.3
Research and Development [Member]      
Segment Reporting Information [Line Items]      
Research and development costs 22.6 21.7 24.2
Selling, general and administrative expenses 2.9 2.2 1.8
AICF Funding [Member]      
Segment Reporting Information [Line Items]      
Net interest (expense) income 1.1 0.3 (1.4)
Australian Pipes Business [Member]      
Segment Reporting Information [Line Items]      
Gain on sale of business   1.7  
General Corporate [Member]      
Segment Reporting Information [Line Items]      
Asbestos adjustments 40.4 5.5 $ 33.4
Value of Asbestos-related assets $ 573.8 $ 619.8