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

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

v2.4.0.8
Operating Segment Information and Concentrations of Risk - Operating Segments and Geographical Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Mar. 31, 2012
Segment Reporting Information [Line Items]      
Net Sales $ 1,493.8 $ 1,321.3 $ 1,237.5
Total operating income 53.1 29.5 155.5
Net interest expense (1.1) 2.4 (7.4)
Other income 2.6 1.8 3.0
Total Identifiable Assets 2,106.5 2,113.2  
General Corporate [Member]
      
Segment Reporting Information [Line Items]      
Total operating income (240.6) (151.8) (52.5)
Total Identifiable Assets 1,066.6 1,131.0  
USA [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 1,094.6 923.8 833.9
Total Identifiable Assets 785.8 739.8  
Australia [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 259.2 272.0 282.4
Total Identifiable Assets 176.3 156.3  
New Zealand [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 63.0 56.1 54.4
Total Identifiable Assets 29.4 39.8  
Other Countries [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 77.0 69.4 66.8
Total Identifiable Assets 48.4 46.3  
Segments Total [Member]
      
Segment Reporting Information [Line Items]      
Total operating income 293.7 181.3 208.0
Total Identifiable Assets 1,039.9 982.2  
Worldwide Total [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 1,493.8 1,321.3 1,237.5
Total operating income 54.6 33.7 151.1
Total Identifiable Assets 2,106.5 2,113.2  
USA & Europe Fibre Cement [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 1,127.6 951.4 862.0
Total operating income 237.0 145.6 148.4
Total Identifiable Assets 782.6 730.6  
Asia Pacific Fibre Cement [Member]
      
Segment Reporting Information [Line Items]      
Net Sales 366.2 369.9 375.5
Total operating income 81.1 61.7 80.3
Total Identifiable Assets 237.6 230.7  
Research and Development [Member]
      
Segment Reporting Information [Line Items]      
Total operating income (24.4) (26.0) (20.7)
Total Identifiable Assets $ 19.7 $ 20.9