Goodwill and Other Long-Lived Assets - Summary of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands		12 Months Ended
		May 31, 2021	May 31, 2020	May 31, 2019
Goodwill [Line Items]
Goodwill, gross		$ 549,346	$ 519,724	$ 510,800
Impairment losses		(198,290)	(198,290)	(176,193)
Goodwill, net		351,056	321,434	334,607
Acquisitions and purchase accounting adjustments	[1]	37,876	11,744
Divestitures	[2]	(13,556)	(2,511)
Translation adjustments		5,302	(309)
Impairment losses	[3]		(22,097)
Goodwill, period increase (decrease)		29,622	(13,173)
Steel Processing
Goodwill [Line Items]
Goodwill, gross		20,218	19,695	7,899
Goodwill, net		20,218	19,695	7,899
Acquisitions and purchase accounting adjustments	[1]	523	11,796
Goodwill, period increase (decrease)		523	11,796
Pressure Cylinders
Goodwill [Line Items]
Goodwill, gross		356,950	327,851	330,723
Impairment losses		(26,112)	(26,112)	(4,015)
Goodwill, net		330,838	301,739	326,708
Acquisitions and purchase accounting adjustments	[1]	37,353	(52)
Divestitures	[2]	(13,556)	(2,511)
Translation adjustments		5,302	(309)
Impairment losses	[3]		(22,097)
Goodwill, period increase (decrease)		29,099	(24,969)
Other
Goodwill [Line Items]
Goodwill, gross		172,178	172,178	172,178
Impairment losses		$ (172,178)	$ (172,178)	$ (172,178)

[1] For additional information regarding the Company’s acquisitions, refer to “Note Q – Acquisitions.”

[2] Fiscal 2020 divestitures related to the sale of the Company’s cryogenics business in Turkey. Fiscal 2021 divestitures related to the sale of the Company’s Structural Composites Industries, LLC business located in Pomona, California and the sale of its cryogenic and hydrogen trailer business, including the Theodore, Alabama site, and the cryo-science and microbulk storage unit business.

[3] Fiscal 2020 impairment losses included $22,097,000 of goodwill impairment related to the oil & gas equipment reporting unit.