Segment Information - Schedule of Significant Expenses Provided to CODM for Reportable Segment (Details) - USD ($) $ in Millions		3 Months Ended
		Aug. 31, 2025	Aug. 31, 2024
Segment Reconciliation [Abstract]
Net sales		$ 872.9	$ 834.0
Cost of goods sold:
Material cost		583.5	576.3
Direct labor, manufacturing expenses, and other	[1]	174.2	157.3
Total cost of goods sold		757.7	733.6
Gross margin		115.2	100.4
Selling, general and administrative expense		67.9	57.0
Restructuring and other (income), net		(1.0)	0.0
Operating income		48.3	43.4
Other income (expense):
Miscellaneous income (expense), net		0.2	(5.9)
Interest expense, net		(2.9)	(2.6)
Equity in net income of unconsolidated affiliate		6.4	1.3
Earnings before income taxes		52.0	36.2
Income tax expense		13.4	4.0
Net earnings		38.6	32.2
Net earnings attributable to noncontrolling interests		1.8	3.8
Net earnings attributable to Worthington Steel		36.8	28.4
Deemed dividend of redeemable noncontrolling interest		0.5	0.0
Net earnings attributable to Worthington Steel shareholders		$ 36.3	$ 28.4

[1] Includes expenses related to manufacturing profit sharing and bonus.