Impairment of Long-Lived Assets - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2020		Aug. 31, 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	$ 9,924,000		$ 40,601,000
Operating lease assets	29,251,000			31,557,000
Fair Value, Measurements, Nonrecurring
Impaired Long Lived Assets Held And Used [Line Items]
Fair market value of assets	9,593,000			26,984,000
Cryogenics
Impaired Long Lived Assets Held And Used [Line Items]
Impairment charge	4,333,000
Impairment of long-lived assets	3,662,000
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 long-lived assets			35,194,000
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	9,593,000	[1],[2]		$ 9,277,000	[3],[4],[5],[6],[7],[8]
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

[1] During the quarter, management determined indicators of impairment were present with regard to the cryogenics business primarily operated out of Theodore, Alabama with European distribution in Austria.  As a result, long-lived assets with a carrying value of $13,526,000 were written down to their estimated fair value of $9,193,000.  Additionally, the customer list intangible assets with a carrying value of $3,662,000 were deemed to be fully impaired and written off.

[2] During the quarter, the Company decided to discontinue its operation of the manufacturing line for alternative fuel cylinders at the Jefferson, Ohio facility.  As a result, long-lived assets with a carrying value of $1,823,000 were written down to their estimated fair market value of $400,000.

[3] During the fourth quarter of fiscal 2020, the Company identified an impairment indicator related to the TWB Hermosillo facility operating lease due to the economic impact of COVID-19.  As a result, the lease ROU asset with a net book value of $565,000 was deemed fully impaired and written off.

[4] During the third quarter of fiscal 2020, the Company identified an impairment indicator for the oil & gas equipment business and performed an interim impairment test of the reporting unit.  In accordance with the applicable accounting guidance, the book value of the corresponding goodwill was written off, resulting in an impairment charge of $22,097,000.

[5] In May 2020, the Company committed to a plan to shut down the packaging solutions business in Greensburg, Indiana.  As a result, long-lived assets with a carrying value of $2,810,000 were written down to their estimated fair market value of $266,000.

[6] During the first quarter of fiscal 2020, the Company identified an impairment indicator for the fabricated products business in Stow, Ohio within the former Engineered Cabs operating segment.  As a result, fixed assets with a net book value of $1,469,000 and lease ROU assets with a net book value of $3,938,000 were deemed to be fully impaired and written off.

[7] 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.

[8] During the third quarter of fiscal 2020, in connection with the closure of the oil & gas equipment manufacturing operations in Wooster, Ohio, customer list intangible assets were determined to be fully impaired and written off.  In addition, the remaining fixed assets at Wooster, Ohio were written down to their estimated fair market value of $6,211,000.