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 2 (Details)

v3.21.1
Operating Segment Information and Concentrations of Risk - Summary of Geographical Information 2 (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2019
Segment Reporting Information [Line Items]      
Selling, general and administrative expenses $ 389.6 $ 415.8 $ 403.6
Research and development costs 34.3 32.8 37.9
Property, plant and equipment 2.0 64.5 9.1
Right-of-use assets   11.2  
Intangible assets   1.4  
Inventories   2.9  
Goodwill   0.2  
Asset Retirement Obligations   5.8  
Other   1.2  
Asset impairments 11.1 84.4 15.9
Property, Plant and Equipment      
Segment Reporting Information [Line Items]      
Property, plant and equipment   61.7  
General Corporate      
Segment Reporting Information [Line Items]      
Right-of-use assets   0.0  
Intangible assets   1.4  
Inventories   0.0  
Goodwill   0.0  
Asset Retirement Obligations   0.0  
Other   0.0  
Asset impairments   1.4  
General Corporate | Property, Plant and Equipment      
Segment Reporting Information [Line Items]      
Property, plant and equipment   0.0  
North America Fiber Cement      
Segment Reporting Information [Line Items]      
Research and development costs 5.6 5.3 6.5
Property, plant and equipment 2.0 44.0 3.0
North America Fiber Cement | Cost of Sales      
Segment Reporting Information [Line Items]      
Other 2.0 2.8 0.4
North America Fiber Cement | Operating Segments      
Segment Reporting Information [Line Items]      
Right-of-use assets   0.0  
Intangible assets   0.0  
Inventories   0.0  
Goodwill   0.0  
Asset Retirement Obligations   0.0  
Other   0.0  
Asset impairments   41.2  
North America Fiber Cement | Operating Segments | Property, Plant and Equipment      
Segment Reporting Information [Line Items]      
Property, plant and equipment   41.2  
Asia Pacific Fiber Cement      
Segment Reporting Information [Line Items]      
Research and development costs 1.1 1.8 2.1
Property, plant and equipment 0.0 15.0 0.0
Inventories 2.9    
Goodwill   0.2  
Asia Pacific Fiber Cement | Other liabilities - non-current      
Segment Reporting Information [Line Items]      
Asset retirement obligation   8.0  
Asia Pacific Fiber Cement | Operating Segments      
Segment Reporting Information [Line Items]      
Right-of-use assets   11.2  
Intangible assets   0.0  
Inventories   2.9  
Goodwill   0.2  
Asset Retirement Obligations   5.8  
Other   1.2  
Asset impairments   36.3  
Asia Pacific Fiber Cement | Operating Segments | Property, Plant and Equipment      
Segment Reporting Information [Line Items]      
Property, plant and equipment   15.0  
Europe Building Products      
Segment Reporting Information [Line Items]      
Research and development costs 1.6 1.7 2.6
Property, plant and equipment 0.0 5.5 0.0
Goodwill   0.0  
Europe Building Products | Operating Segments      
Segment Reporting Information [Line Items]      
Right-of-use assets   0.0  
Intangible assets   0.0  
Inventories   0.0  
Goodwill   0.0  
Asset Retirement Obligations   0.0  
Other   0.0  
Asset impairments   5.5  
Europe Building Products | Operating Segments | Property, Plant and Equipment      
Segment Reporting Information [Line Items]      
Property, plant and equipment   5.5  
Research and Development      
Segment Reporting Information [Line Items]      
Selling, general and administrative expenses 2.9 3.0 2.3
Research and development costs $ 26.0 $ 24.0 $ 26.7