v3.26.1
Segment and Geographic Information - Summary of Operating Segments (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Segment Reporting Information [Line Items]      
Net sales $ 4,835.8 $ 3,877.5 $ 3,936.3
Cost of goods sold 3,106.2 2,372.5 2,347.9
Gross profit 1,729.6 1,505.0 1,588.4
Selling, general and administrative expenses 946.4 596.2 602.2
Restructuring expenses 16.2 50.3 20.1
Operating income 447.6 655.9 767.4
Reconciliation to Consolidated Net Income [Abstract]      
Operating income 447.6 655.9 767.4
Interest, net (231.1) (10.3) (15.3)
Other expense (income), net (9.8) (0.2) 2.7
Income tax expense (102.7) (221.4) (244.6)
Net income 104.0 424.0 510.2
Operating Segments      
Segment Reporting Information [Line Items]      
Net sales 4,835.8 3,877.5 3,936.3
Cost of goods sold 3,106.2 2,372.5 2,347.9
Gross profit 1,729.6 1,505.0 1,588.4
Selling, general and administrative expenses 775.7 451.7 443.2
Restructuring expenses 40.4 50.3  
Other expenses 63.2 13.1 13.0
Operating income 850.3 989.9 1,132.2
Reconciliation to Consolidated Net Income [Abstract]      
Operating income 850.3 989.9 1,132.2
General Corporate and R&D      
Segment Reporting Information [Line Items]      
Operating income (402.7) (334.0) (364.8)
Reconciliation to Consolidated Net Income [Abstract]      
Operating income (402.7) (334.0) (364.8)
Siding & Trim      
Segment Reporting Information [Line Items]      
Net sales 2,963.1 2,863.3 2,891.4
Siding & Trim | Operating Segments      
Segment Reporting Information [Line Items]      
Net sales 2,963.1 2,863.3 2,891.4
Cost of goods sold 1,844.9 1,721.4 1,674.8
Gross profit 1,118.2 1,141.9 1,216.6
Selling, general and administrative expenses 373.6 291.7 287.1
Restructuring expenses 35.6 0.0  
Other expenses 47.1 9.3 8.4
Operating income 661.9 840.9 921.1
Reconciliation to Consolidated Net Income [Abstract]      
Operating income 661.9 840.9 921.1
Deck, Rail & Accessories      
Segment Reporting Information [Line Items]      
Net sales 795.2 0.0 0.0
Deck, Rail & Accessories | Operating Segments      
Segment Reporting Information [Line Items]      
Net sales 795.2    
Cost of goods sold 579.9    
Gross profit 215.3    
Selling, general and administrative expenses 222.3    
Restructuring expenses 3.4    
Other expenses 7.3    
Operating income (17.7)    
Reconciliation to Consolidated Net Income [Abstract]      
Operating income (17.7)    
Australia & New Zealand      
Segment Reporting Information [Line Items]      
Net sales 520.6 519.9 562.8
Australia & New Zealand | Operating Segments      
Segment Reporting Information [Line Items]      
Net sales 520.6 519.9 562.8
Cost of goods sold 298.1 301.2 335.4
Gross profit 222.5 218.7 227.4
Selling, general and administrative expenses 62.4 56.0 60.0
Restructuring expenses 1.4 50.3  
Other expenses 4.8 1.4 1.3
Operating income 153.9 111.0 166.1
Reconciliation to Consolidated Net Income [Abstract]      
Operating income 153.9 111.0 166.1
Europe      
Segment Reporting Information [Line Items]      
Net sales 556.9 494.3 482.1
Europe | Operating Segments      
Segment Reporting Information [Line Items]      
Net sales 556.9 494.3 482.1
Cost of goods sold 383.3 349.9 337.7
Gross profit 173.6 144.4 144.4
Selling, general and administrative expenses 117.4 104.0 96.1
Restructuring expenses 0.0 0.0  
Other expenses 4.0 2.4 3.3
Operating income 52.2 38.0 45.0
Reconciliation to Consolidated Net Income [Abstract]      
Operating income $ 52.2 $ 38.0 $ 45.0