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

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

v3.7.0.1
Operating Segment Information and Concentrations of Risk - Summary of Operating Segments (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Mar. 31, 2015
Segment Reporting Information [Line Items]      
Net sales $ 1,921.6 $ 1,728.2 $ 1,656.9
Total operating income 393.2 354.0 335.0
Net interest expense (27.5) (25.6) (7.5)
Total Identifiable Assets 2,012.7 2,029.4  
Other income (expense) 1.3 2.1 (4.9)
General Corporate [Member]      
Segment Reporting Information [Line Items]      
Total operating income (13.6) (43.6) (19.0)
Total Identifiable Assets 718.9 774.4  
North America Fiber Cement [Member]      
Segment Reporting Information [Line Items]      
Net sales 1,493.4 1,335.0 1,224.7
Total operating income 343.9 352.2 290.0
Total Identifiable Assets 917.4 889.7  
International Fiber Cement [Member]      
Segment Reporting Information [Line Items]      
Net sales 411.8 379.4 418.4
Total operating income 95.1 77.9 94.5
Total Identifiable Assets 335.7 324.0  
Other Businesses [Member]      
Segment Reporting Information [Line Items]      
Net sales 16.4 13.8 13.8
Total operating income (6.7) (8.6) (4.5)
Total Identifiable Assets 28.4 27.7  
Research and Development [Member]      
Segment Reporting Information [Line Items]      
Total operating income (25.5) (23.9) (26.0)
Total Identifiable Assets 12.3 13.6  
Segments Total [Member]      
Segment Reporting Information [Line Items]      
Total operating income 406.8 397.6 354.0
Total Identifiable Assets 1,293.8 1,255.0  
Worldwide Total [Member]      
Segment Reporting Information [Line Items]      
Net sales 1,921.6 1,728.2 1,656.9
Total operating income 367.0 330.5 $ 322.6
Total Identifiable Assets $ 2,012.7 $ 2,029.4