Goodwill and Other Long-Lived Assets - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended									6 Months Ended	12 Months Ended
	Feb. 28, 2015 USD ($)	May 31, 2017 USD ($)	May 31, 2016 USD ($) asset_group	Nov. 30, 2015 USD ($) Facility		Aug. 31, 2015 USD ($)		May 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Nov. 30, 2014 USD ($)	Nov. 30, 2015 USD ($)	May 31, 2017 USD ($)	May 31, 2016 USD ($)	May 31, 2015 USD ($)	May 31, 2014
Goodwill And Other Intangible Assets [Line Items]
Amortization expense												$ 13,525	$ 15,813	$ 20,422
Cash flow projections, discount rate		12.00%
Carrying value long-lived assets		$ 39,990
Number of asset group tested for impairment | asset_group			5
Impairment of long-lived assets				$ 22,962	[1]	$ 3,000	[1]						25,962	100,129
Goodwill		247,673	$ 246,067					$ 238,999				$ 247,673	246,067	238,999
DHybrid Systems LLC
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets								2,344
Minimum
Goodwill And Other Intangible Assets [Line Items]
Definite-lived intangible assets, estimated useful lives												1 year
Maximum
Goodwill And Other Intangible Assets [Line Items]
Definite-lived intangible assets, estimated useful lives												20 years
Pressure Cylinders
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets													22,962	11,911
Goodwill		234,123	233,371					226,761				$ 234,123	233,371	226,761
Pressure Cylinders | Aluminum High Pressure Cylinder Business
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets										$ 3,221
Pressure Cylinders | Oil and Gas Equipment
Goodwill And Other Intangible Assets [Line Items]
Cash flow projections, discount rate				13.00%
Carrying value long-lived assets				$ 59,895
Number of equipment facilities | Facility				2
Impairment of long-lived assets				$ 22,962
Goodwill				25,982							$ 25,982
Pressure Cylinders | Worthington Nitin Cylinders | Joint Venture Transactions
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets											6,346
Percent of controlling interest by the Company															60.00%
Pressure Cylinders | Long-lived Assets Held and Used | Oil and Gas Equipment
Goodwill And Other Intangible Assets [Line Items]
Asset measured at fair value on nonrecurring basis				$ 36,933							36,933
Engineered Cabs
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets						3,000				2,389			3,000	83,989
Goodwill	$ 0								$ 0
Goodwill written-off	$ 44,933
Gain (loss) on sale of business									332
Engineered Cabs | Florence Facility
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets									14,311
Engineered Cabs | Customer relationships
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets									$ 22,356
Engineered Cabs | Long-lived Assets Held and Used
Goodwill And Other Intangible Assets [Line Items]
Asset measured at fair value on nonrecurring basis						1,059
Carrying value long-lived assets						$ 4,059
Other Business Segment | Military Construction Business
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets										$ 1,179
Steel Processing
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets														3,050
Goodwill		$ 7,899	$ 7,045					$ 6,587				$ 7,899	$ 7,045	$ 6,587
Steel Processing | Closure of Precision Specialty Metals, Inc
Goodwill And Other Intangible Assets [Line Items]
Impairment of long-lived assets											$ 3,050

[1] For additional information regarding the Company's impairment activity, refer to "Note C - Goodwill and Other Long-Lived Assets."