Revenue Recognition - Revenue by Product Class and Over Time (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Disaggregation Of Revenue [Line Items]
Net sales	$ 763,996	$ 874,381	$ 2,447,492	$ 2,820,714
Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales	66,608	48,460	189,755	143,919
Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	491,136	555,871	1,531,448	1,851,401
Pressure Cylinders
Disaggregation Of Revenue [Line Items]
Net sales	270,995	290,690	865,527	885,490
Other
Disaggregation Of Revenue [Line Items]
Net sales	1,865	27,820	50,517	83,823
Direct | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	450,413	527,970	1,425,117	1,756,842
Toll | Steel Processing
Disaggregation Of Revenue [Line Items]
Net sales	40,723	27,901	106,331	94,559
Toll | Steel Processing | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales	40,723	27,901	106,331	94,559
Industrial products | Pressure Cylinders
Disaggregation Of Revenue [Line Items]
Net sales	129,042	148,018	411,994	452,883
Consumer products | Pressure Cylinders
Disaggregation Of Revenue [Line Items]
Net sales	113,258	118,006	360,803	352,023
Oil & gas equipment | Pressure Cylinders
Disaggregation Of Revenue [Line Items]
Net sales	28,695	24,666	92,730	80,584
Engineered Cabs | Other
Disaggregation Of Revenue [Line Items]
Net sales	1,830	27,817	50,446	83,798
Other | Other
Disaggregation Of Revenue [Line Items]
Net sales	35	3	71	25
Certain oil & gas contracts | Pressure Cylinders | Over time revenue
Disaggregation Of Revenue [Line Items]
Net sales	$ 25,885	$ 20,559	$ 83,424	$ 49,360