Impairment of Long-Lived Assets - Additional Information (Detail) - USD ($)	3 Months Ended					6 Months Ended
	Nov. 30, 2020		Aug. 31, 2020	Nov. 30, 2019	Aug. 31, 2019	Nov. 30, 2020		Nov. 30, 2019	May 31, 2020
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets									$ 2,800,000
Impairment of long-lived assets	$ 3,815,000			$ 0		$ 13,739,000		$ 40,601,000
Impairment charge			$ 9,924,000
Operating lease assets	30,007,000					30,007,000			31,557,000
Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets	6,334,000					6,334,000			26,984,000
Cryogenics
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of long-lived assets			3,662,000
Impairment charge			4,333,000
Jefferson
Impaired Long Lived Assets Held And Used [Line Items]
Impairment charge			1,423,000
Superior Tools
Impaired Long Lived Assets Held And Used [Line Items]
Impairment charge			506,000
Engineered Cabs
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of ROU assets					$ 905,000
Fixed asset net book value					1,469,000
Operating lease assets					3,938,000
Engineered Cabs | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of long-lived assets					35,194,000
Long Lived Assets Held And Used | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets	6,334,000	[1]				6,334,000	[1]		$ 9,277,000	[2]
Long Lived Assets Held And Used | Oil And Gas Equipment Operations
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of long-lived assets	1,441,000
Long Lived Assets Held And Used | Oil And Gas Equipment Operations | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets	7,375,000					7,375,000
Fair market value of fixed assets	5,934,000					5,934,000
Long Lived Assets Held And Used | Cryogenics
Impaired Long Lived Assets Held And Used [Line Items]
Carrying value long-lived assets			13,526,000
Long Lived Assets Held And Used | Cryogenics | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets			9,193,000
Long Lived Assets Held And Used | Jefferson
Impaired Long Lived Assets Held And Used [Line Items]
Carrying value long-lived assets			1,823,000
Long Lived Assets Held And Used | Jefferson | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets			$ 400,000
Long Lived Assets Held And Used | Engineered Cabs | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets					$ 12,860,000
Finite Lived Intangible Assets | Oil And Gas Equipment Operations | Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets	$ 2,374,000					$ 2,374,000

[1] Comprised of our oil & gas equipment assets in Tulsa, Oklahoma with an estimated fair value of $5,934,000, and our alternative fuel cylinders assets at the Jefferson, Ohio facility with an estimated fair market value of $400,000.  Refer to “NOTE E – Impairment of Long-Lived Assets” for additional information.   

[2] During the fourth quarter of 2020, in connection with the annual indefinite lived assets impairment test, certain European tradenames were written down to their estimated fair market value of $2,800,000.