Impairment of Goodwill and Long-Lived Assets - Additional Information (Detail)	3 Months Ended				6 Months Ended	9 Months Ended
	Nov. 30, 2015 USD ($) Facility	Aug. 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Nov. 30, 2014 USD ($)	Nov. 30, 2015 USD ($)	Feb. 29, 2016 USD ($)	Feb. 28, 2015 USD ($)	May. 31, 2015 USD ($)		May. 31, 2014
Impaired Long-Lived Assets Held and Used [Line Items]
Number of equipment facilities | Facility	2
Carrying value long-lived assets	$ 59,895,000				$ 59,895,000
Asset measured at fair value on nonrecurring basis						$ 0		$ 12,403,000
Cash flow projections, discount rate	13.00%
Impairment of long-lived assets	$ 22,962,000		$ 81,600,000			25,962,000	$ 97,785,000
Goodwill						244,144,000		238,999,000
Engineered Cabs
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets				$ 2,389,000
Goodwill			0				0
Goodwill written-off			44,933,000
Gain(loss)on sale of business			313,000
Engineered Cabs | Florence Facility
Impaired Long-Lived Assets Held and Used [Line Items]
Asset measured at fair value on nonrecurring basis			9,803,000				9,803,000
Impairment of long-lived assets			14,311,000
Aluminum High Pressure Cylinder Business [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets				3,221,000
Military Construction Business
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets				$ 1,179,000
Customer relationships | Engineered Cabs
Impaired Long-Lived Assets Held and Used [Line Items]
Asset measured at fair value on nonrecurring basis			2,000,000				2,000,000
Impairment of long-lived assets			22,356,000
Joint Venture Transactions | Worthington Nitin Cylinders
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets					6,346,000
Percent of controlling interest by the Company										60.00%
Long-lived Assets Held and Used
Impaired Long-Lived Assets Held and Used [Line Items]
Asset measured at fair value on nonrecurring basis	36,933,000				36,933,000			$ 12,403,000	[1]
Engineered Cabs
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets		$ 1,059,000	$ 81,600,000			3,000,000	83,989,000
Engineered Cabs | Long-lived Assets Held and Used
Impaired Long-Lived Assets Held and Used [Line Items]
Carrying value long-lived assets		4,059,000
Asset measured at fair value on nonrecurring basis		$ 3,000,000
Pressure Cylinders
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets						$ 22,962,000	$ 9,567,000
Goodwill	$ 25,982,000				25,982,000
Non Core Steel Processing Assets
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets					$ 3,050,000

[1] During the fourth quarter of fiscal 2015, management reviewed certain intangible assets related to our CNG fuel systems joint venture, dHybrid, for impairment. In accordance with the applicable accounting guidance, the intangible assets were written down to their fair value of $600,000, resulting in an impairment charge of $2,344,000. The key assumptions that drove the fair value calculation were projected cash flows and the discount rate.