Investments - Schedule of Net Earnings of Unconsolidated Affiliate (Detail) - USD ($) $ in Millions	12 Months Ended
May 31, 2026	May 31, 2025	May 31, 2024
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 20.3	$ 4.4	$ 22.4
Serviacero Worthington
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 20.3	$ 4.4	$ 22.4

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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