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)

v3.19.1
Operating Segment Information and Concentrations of Risk - Summary of Operating Segments (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Segment Reporting Information [Line Items]      
Net sales $ 2,506.6 $ 2,054.5 $ 1,921.6
Total operating income 351.6 229.2 393.2
Net interest expense (50.1) (29.5) (27.5)
Loss on early debt extinguishment (1.0) (26.1) 0.0
Other income 0.1 0.7 1.3
Income before income taxes 300.6 174.3 367.0
Total Identifiable Assets 4,032.6 2,351.0  
Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income 432.4 453.9 406.8
Total Identifiable Assets 2,345.7 1,459.9  
General Corporate      
Segment Reporting Information [Line Items]      
Total operating income (80.8) (224.7) (13.6)
Total Identifiable Assets 1,686.9 891.1  
North America Fiber Cement      
Segment Reporting Information [Line Items]      
Net sales 1,676.9 1,578.1 1,493.4
North America Fiber Cement | Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income 382.5 381.9 343.9
Total Identifiable Assets 1,280.2 1,070.7  
International Fiber Cement | Operating Segments      
Segment Reporting Information [Line Items]      
Total Identifiable Assets 328.8 328.8  
Asia Pacific Fiber Cement      
Segment Reporting Information [Line Items]      
Net sales 446.8 425.4 370.6
Asia Pacific Fiber Cement | Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income 99.8 108.1 93.8
Europe Building Products      
Segment Reporting Information [Line Items]      
Net sales 368.3 36.3 41.2
Europe Building Products | Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income 10.0 0.3 1.3
Total Identifiable Assets 717.7 22.8  
Other Businesses      
Segment Reporting Information [Line Items]      
Net sales 14.6 14.7 16.4
Other Businesses | Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income (30.9) (8.6) (6.7)
Total Identifiable Assets 10.9 30.1  
Research and Development | Operating Segments      
Segment Reporting Information [Line Items]      
Total operating income (29.0) (27.8) $ (25.5)
Total Identifiable Assets $ 8.1 $ 7.5