Goodwill and Other Long-Lived Assets - Summary of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands		12 Months Ended
		May 31, 2019	May 31, 2018	May 31, 2017
Goodwill [Line Items]
Goodwill, gross		$ 510,800	$ 521,376	$ 414,200
Accumulated impairment losses		(176,193)	(176,193)	(166,527)
Goodwill, net		334,607	345,183	247,673
Acquisitions and purchase accounting adjustments	[1]	777	103,437
Translation adjustments		(4,093)	3,739
Impairment losses	[2]		(9,666)
Divestitures	[3]	(7,260)
Goodwill, period increase (decrease)		(10,576)	97,510
Steel Processing
Goodwill [Line Items]
Goodwill, gross		7,899	7,899	7,899
Goodwill, net		7,899	7,899	7,899
Pressure Cylinders
Goodwill [Line Items]
Goodwill, gross		330,723	341,299	234,123
Accumulated impairment losses		(4,015)	(4,015)
Goodwill, net		326,708	337,284	234,123
Acquisitions and purchase accounting adjustments	[1]	777	103,437
Translation adjustments		(4,093)	3,739
Impairment losses	[2]		(4,015)
Divestitures	[3]	(7,260)
Goodwill, period increase (decrease)		(10,576)	103,161
Engineered Cabs
Goodwill [Line Items]
Goodwill, gross		44,933	44,933	44,933
Accumulated impairment losses		(44,933)	(44,933)	(44,933)
Other
Goodwill [Line Items]
Goodwill, gross		127,245	127,245	127,245
Accumulated impairment losses		$ (127,245)	(127,245)	(121,594)
Goodwill, net				$ 5,651
Impairment losses	[2]		(5,651)
Goodwill, period increase (decrease)			$ (5,651)

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

[2] Fiscal 2018 impairment charges included $4,015,000 of goodwill allocated to oil & gas equipment assets prior to their disposal on July 31, 2018 and $5,651,000 related to the sale of a 65% stake in WEI on March 31, 2018.

[3] Fiscal 2019 divestitures included the sale of the operating assets and real property related to the solder business and certain brazing assets.