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

Revenues Revenues (Details)

v3.19.1
Revenues Revenues (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales $ 2,506.6 $ 2,054.5 $ 1,921.6
Fiber cement revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 2,159.5 2,039.8 1,905.2
Fiber gypsum revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 332.5 0.0 0.0
Other revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 14.6 14.7 16.4
North America Fiber Cement      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 1,676.9 1,578.1 1,493.4
North America Fiber Cement | Fiber cement revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 1,676.9 1,578.1 1,493.4
North America Fiber Cement | Fiber gypsum revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
North America Fiber Cement | Other revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Asia Pacific Fiber Cement      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 446.8 425.4 370.6
Asia Pacific Fiber Cement | Fiber cement revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 446.8 425.4 370.6
Asia Pacific Fiber Cement | Fiber gypsum revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Asia Pacific Fiber Cement | Other revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Europe Building Products      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 368.3 36.3 41.2
Europe Building Products | Fiber cement revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 35.8 36.3 41.2
Europe Building Products | Fiber gypsum revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 332.5 0.0 0.0
Europe Building Products | Other revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Other Businesses      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 14.6 14.7 16.4
Other Businesses | Fiber cement revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Other Businesses | Fiber gypsum revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales 0.0 0.0 0.0
Other Businesses | Other revenues      
Segment Reporting, Revenue Reconciling Item [Line Items]      
Net sales $ 14.6 $ 14.7 $ 16.4