Investment in Unconsolidated Affiliate - Schedule of Net Earnings of Unconsolidated Affiliate (Detail) - USD ($) $ in Millions	12 Months Ended
May 31, 2024	May 31, 2023	May 31, 2022
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 22.4	$ 7.7	$ 29.8
Serviacero Worthington
Investments in and Advances to Affiliates [Line Items]
Equity in net income of unconsolidated affiliate	$ 22.4	$ 7.7	$ 29.8

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
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-Name Accounting Standards Codification
-Section S99
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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