Investment in Unconsolidated Affiliate - Schedule of Net Earnings of Unconsolidated Affiliate (Detail) - USD ($) $ in Millions	3 Months Ended
Aug. 31, 2025	Aug. 31, 2024
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 6.4	$ 1.3
Serviacero Worthington
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 6.4	$ 1.3

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

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