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Property, Plant and Equipment - Summary of Impairment Charges (Details) - USD ($) $ in Millions | 12 Months Ended
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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

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- Definition The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228 + Details
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