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

Property, Plant and Equipment - Summary of Impairment Charges (Details)

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Property, Plant and Equipment - Summary of Impairment Charges (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2019
Impaired Long-Lived Assets Held and Used [Line Items]      
Impairment of property, plant & equipment $ 2.0 $ 64.5 $ 9.1
North America Fiber Cement      
Impaired Long-Lived Assets Held and Used [Line Items]      
Impairment of property, plant & equipment 2.0 44.0 3.0
Asia Pacific Fiber Cement      
Impaired Long-Lived Assets Held and Used [Line Items]      
Impairment of property, plant & equipment 0.0 15.0 0.0
Europe Building Products      
Impaired Long-Lived Assets Held and Used [Line Items]      
Impairment of property, plant & equipment 0.0 5.5 0.0
Other Businesses      
Impaired Long-Lived Assets Held and Used [Line Items]      
Impairment of property, plant & equipment $ 0.0 $ 0.0 $ 6.1