Segment Operations - Financial Information for Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2023		Aug. 31, 2022		May 31, 2023
Segment Reporting Information [Line Items]
Net sales	$ 1,193,256		$ 1,408,665
Impairment of long-lived assets	1,401		312
Separation costs	6,035
Restructuring and other expense (income), net			(1,100)
Miscellaneous income (expense), net	1,011		(5,086)
Loss on extinguishment of debt	1,534
Equity income	54,381		31,712
Adjusted EBIT	128,480		84,742
Total assets	3,476,692				$ 3,650,918
Steel Processing
Segment Reporting Information [Line Items]
Net sales	881,339		1,038,880
Impairment of long-lived assets	1,401		312
Restructuring and other expense (income), net			78
Miscellaneous income (expense), net	712		184
Equity income	8,957		1,770
Adjusted EBIT	78,002	[1]	34,913	[2]
Total assets	1,786,067				1,758,981
Consumer products
Segment Reporting Information [Line Items]
Net sales	149,412		188,703
Miscellaneous income (expense), net	31		(35)
Adjusted EBIT	8,991	[1]	20,934	[2]
Total assets	615,223				615,430
Building Products
Segment Reporting Information [Line Items]
Net sales	133,868		150,323
Miscellaneous income (expense), net	57		222
Equity income	45,043		43,866
Adjusted EBIT	54,016	[1]	52,734	[2]
Total assets	619,794				635,650
Sustainable Energy Solutions
Segment Reporting Information [Line Items]
Net sales	28,637		30,759
Miscellaneous income (expense), net	281		(86)
Adjusted EBIT	(4,722)	[1]	(1,393)	[2]
Total assets	139,147				129,872
Other
Segment Reporting Information [Line Items]
Separation costs	6,035
Restructuring and other expense (income), net			(1,178)
Miscellaneous income (expense), net	(70)		(5,371)
Loss on extinguishment of debt	1,534
Equity income	381		(13,924)
Adjusted EBIT	132	[1]	5,145	[2]
Total assets	316,461				$ 510,985
Consolidated
Segment Reporting Information [Line Items]
Loss on extinguishment of debt	(1,534)
Adjusted EBIT	$ 136,419	[1]	$ 112,333	[2]

[1] Excludes the following: • Impairment of long-lived assets resulted from a revision of the estimated fair value, less selling costs of certain production equipment at our consolidated Samuel joint venture that has been classified as held for sale since August 2022; • Separation costs reflect direct and incremental costs in connection with the anticipated Separation and are held at the corporate level. These costs include fees paid to third-party parties for audit, advisory and legal services to effect the Separation, nonrecurring employee-related costs, such as retention bonuses, and nonrecurring functional costs associated with the separation of shared corporate functions; • Loss on extinguishment of debt resulted from the redemption of the 2026 Notes, in full, on July 28, 2023, and consisted primarily unamortized debt issuance costs and the remaining loss deferred in AOCI associated with an interest rate swap executed prior to the issuance of the 2026 Notes; and • Noncontrolling interest portion of impairment of long-lived assets of $517 within Steel Processing.

[2] Excludes the following: • Impairment of long-lived assets resulted from the reclassification of the net assets of the Samuel toll processing facility in Cleveland, Ohio, to assets held for sale during August 2022; • Restructuring and other income, net was driven primarily by a gain on the sale of the remaining real property of our former oil & gas equipment business on June 14, 2022; • A non-cash settlement charge of $4,774 in miscellaneous income (expense), net within Other related to the pension lift-out transaction associated with the Gerstenslager Company Bargaining Unit Employees’ Pension Plan; • A loss of $15,759 within equity income related to the August 31, 2022, sale of our 50% noncontrolling interest in ArtiFlex; • Incremental compensation expense of $525 within Consumer Products related to the Level5 earnout agreement; and • Noncontrolling interest portion of impairment of long-lived assets of $115 within Steel Processing