Revenue Recognition - Revenue by Product Class and Timing (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2021	Aug. 31, 2020
Disaggregation Of Revenue [Line Items]
Net sales		$ 1,110,818	$ 702,909
Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		34,782	33,911
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		822,810	431,020
Other
Disaggregation Of Revenue [Line Items]
Net sales			22,307
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		788,028	404,808
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales		34,782	26,212
Toll | Steel Processing | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales		34,782	26,212
Building Products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	114,743	88,103
Consumer products
Disaggregation Of Revenue [Line Items]
Net sales	[1]	147,783	133,622
Sustainable Energy Solutions
Disaggregation Of Revenue [Line Items]
Net sales	[1]	$ 25,482	27,857
Oil & gas equipment | Other
Disaggregation Of Revenue [Line Items]
Net sales			9,897
Engineered Cabs | Other
Disaggregation Of Revenue [Line Items]
Net sales			985
Other | Other
Disaggregation Of Revenue [Line Items]
Net sales			11,425
Certain oil & gas equipment contracts | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales			$ 7,699

[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 O - Segment Operations for information regarding the reorganization of our pressure cylinders business and the resulting new reportable segments.