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)

v2.4.0.6
Operating Segment Information and Concentrations of Risk - Operating Segments and Geographical Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2011
Segment Reporting Information [Line Items]      
Net sales $ 1,321.3 $ 1,237.5 $ 1,167.0
Total operating income (loss) 29.5 155.5 104.7
Net interest income (expense) 2.4 (7.4) (4.4)
Other income(expense) 1.8 3.0 (3.7)
Total Identifiable Assets 2,107.6 2,310.0  
USA and Europe Fibre Cement [Member]
      
Segment Reporting Information [Line Items]      
Net sales 951.4 862.0 814.0
Total operating income (loss) 145.6 148.4 160.3
Total Identifiable Assets 725.0 749.1  
Asia Pacific Fibre Cement [Member]
      
Segment Reporting Information [Line Items]      
Net sales 369.9 375.5 353.0
Total operating income (loss) 61.7 80.3 79.4
Total Identifiable Assets 230.7 238.4  
Research and Development [Member]
      
Segment Reporting Information [Line Items]      
Total operating income (loss) (26.0) (20.7) (20.1)
Total Identifiable Assets 20.9 15.6  
General Corporate [Member]
      
Segment Reporting Information [Line Items]      
Total operating income (loss) (151.8) (52.5) (114.9)
Total Identifiable Assets 1,131.0 1,306.9  
Segments total [Member]
      
Segment Reporting Information [Line Items]      
Total operating income (loss) 181.3 208.0 219.6
Total Identifiable Assets 976.6 1,003.1  
Worldwide total [Member]
      
Segment Reporting Information [Line Items]      
Net sales 1,321.3 1,237.5 1,167.0
Total operating income (loss) 33.7 151.1 96.6
Total Identifiable Assets 2,107.6 2,310.0  
USA [Member]
      
Segment Reporting Information [Line Items]      
Net sales 923.8 833.9 789.2
Total Identifiable Assets 734.2 748.5  
Australian [Member]
      
Segment Reporting Information [Line Items]      
Net sales 272.0 282.4 266.4
Total Identifiable Assets 156.3 160.5  
New Zealand [Member]
      
Segment Reporting Information [Line Items]      
Net sales 56.1 54.4 52.9
Total Identifiable Assets 39.8 43.7  
Other Countries [Member]
      
Segment Reporting Information [Line Items]      
Net sales 69.4 66.8 58.5
Total Identifiable Assets $ 46.3 $ 50.4