Segment and Geographic Information - Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 493.5	$ 216.2	$ 185.0
Operating Segments \| Siding & Trim
Segment Reporting Information [Line Items]
Depreciation and amortization	230.9	160.7	133.8
Operating Segments \| Deck, Rail & Accessories
Segment Reporting Information [Line Items]
Depreciation and amortization	202.4	0.0	0.0
Operating Segments \| Australia & New Zealand
Segment Reporting Information [Line Items]
Depreciation and amortization	22.4	19.2	17.0
Operating Segments \| Europe
Segment Reporting Information [Line Items]
Depreciation and amortization	30.0	32.4	29.7
General Corporate and R&D
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 7.8	$ 3.9	$ 4.5

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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