Revenue Recognition - Revenue by Product Class and Timing (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2022	Aug. 31, 2021
Disaggregation Of Revenue [Line Items]
Net sales		$ 1,408,665	$ 1,110,818
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		1,038,880	822,810
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		1,002,135	788,028
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		36,745	34,782
Toll | Steel Processing | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		36,745	34,782
Building Products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	150,323	114,743
Consumer products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	188,703	147,783
Sustainable Energy Solutions
Disaggregation Of Revenue [Line Items]
Net sales	[1]	$ 30,759	$ 25,482

[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 segments are appropriately combined for purposes of the disclosure requirements prescribed by ASC 280 and ASC 606.