Investment in Unconsolidated Affiliate - Schedule of Financial Position of Unconsolidated Affiliate (Detail) - USD ($) $ in Millions	May 31, 2024	May 31, 2023
Investments in and Advances to Affiliates [Line Items]
Cash and cash equivalents	$ 40.2	$ 32.7
Total assets	1,866.4	1,764.4
Current liabilities	618.4	478.4
Other noncurrent liabilities	34.3	33.6
Equity	985.3	1,029.0
Total liabilities and equity	1,866.4	1,764.4
Serviacero Worthington
Investments in and Advances to Affiliates [Line Items]
Cash and cash equivalents	5.7	12.2
Other current assets	274.7	238.2
Noncurrent assets	58.3	58.9
Total assets	338.7	309.3
Current liabilities	64.7	70.8
Other noncurrent liabilities	5.2	5.4
Equity	268.8	233.1
Total liabilities and equity	$ 338.7	$ 309.3