Revenue Recognition - Revenue by Product Class and Timing (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Feb. 28, 2023	Feb. 28, 2022	Feb. 28, 2023	Feb. 28, 2022
Disaggregation Of Revenue [Line Items]
Net sales		$ 1,103,322	$ 1,378,235	$ 3,687,528	$ 3,721,914
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		757,007	1,052,562	2,637,834	2,813,214
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		722,328	1,015,716	2,531,722	2,704,411
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		34,679	36,846	106,112	108,803
Toll | Steel Processing | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		34,679	36,846	106,112	108,803
Building Products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	151,876	132,944	443,870	368,813
Consumer products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	162,647	161,692	505,145	450,268
Sustainable Energy Solutions
Disaggregation Of Revenue [Line Items]
Net sales	[1]	$ 31,792	$ 31,037	$ 100,679	$ 89,619

[1] The products contained within each of these operating segments have similar production processes, require substantially the same raw materials, use similar equipment, and serve similar purposes. Therefore, we believe the products within each of these operating segments are appropriately combined for purposes of the disclosure requirements prescribed by Accounting Standards Codification (“ASC”) Topic 280 and Topic 606.