Revenue Recognition - Revenue by Product Class and Timing (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Disaggregation Of Revenue [Line Items]
Net sales		$ 1,378,235	$ 759,109	$ 3,721,914	$ 2,193,110
Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		36,846	38,811	108,803	112,255
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		1,052,562	504,477	2,813,214	1,404,220
Other
Disaggregation Of Revenue [Line Items]
Net sales			11,202		50,354
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		1,015,716	469,266	2,704,411	1,307,631
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		36,846	35,211	108,803	96,589
Toll | Steel Processing | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		36,846	35,211	108,803	96,589
Building Products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	132,944	96,256	368,813	278,349
Consumer products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	161,692	115,071	450,268	366,205
Sustainable Energy Solutions
Disaggregation Of Revenue [Line Items]
Net sales	[1]	$ 31,037	32,103	$ 89,619	93,982
Oil & gas equipment | Other
Disaggregation Of Revenue [Line Items]
Net sales			4,407		20,950
Engineered Cabs | Other
Disaggregation Of Revenue [Line Items]
Net sales			(12)		1,058
Other | Other
Disaggregation Of Revenue [Line Items]
Net sales			6,807		28,346
Certain oil & gas equipment contracts | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales			$ 3,600		$ 15,666

[1] The products contained within each of these reportable 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.  See NOTE P - Segment Operations for information regarding the reorganization of our pressure cylinders business and the resulting new reportable segments, effective June 1, 2021.