Investment in Unconsolidated Affiliate - Schedule of Net Earnings of Unconsolidated Affiliate (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Nov. 30, 2024	Nov. 30, 2023	Nov. 30, 2024	Nov. 30, 2023
Investments in and Advances to Affiliates [Line Items]
Equity in net income (loss) of unconsolidated affiliate	$ (0.9)	$ 3.8	$ 0.4	$ 12.8
Serviacero Worthington
Investments in and Advances to Affiliates [Line Items]
Equity in net income (loss) of unconsolidated affiliate	$ (0.9)	$ 3.8	$ 0.4	$ 12.8

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

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