Revenue Recognition - Revenue by Product Class and Timing (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2023	Nov. 30, 2022	Nov. 30, 2023	Nov. 30, 2022
Disaggregation Of Revenue [Line Items]
Net sales	$ 1,086,918	$ 1,175,541	$ 2,280,174	$ 2,584,206
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	788,655	841,947	1,669,993	1,880,827
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	750,622	807,259	1,595,985	1,809,394
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	38,033	34,688	74,008	71,433
Building Products
Disaggregation Of Revenue [Line Items]
Net sales	122,954	141,671	256,822	291,994
Consumer Products
Disaggregation Of Revenue [Line Items]
Net sales	147,738	153,795	297,151	342,497
Sustainable Energy Solutions
Disaggregation Of Revenue [Line Items]
Net sales	27,537	$ 38,128	56,174	$ 68,888
Other
Disaggregation Of Revenue [Line Items]
Net sales	$ 34		$ 34