Fair Value - Assets Measured at Fair Value on Non-Recurring Basis (Detail) - Fair Value, Nonrecurring - USD ($) $ in Thousands		Nov. 30, 2019	May 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis		$ 13,623	$ 11,938
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis			11,938
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis		13,623
Investment In Unconsolidated Affiliate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[1]	13,623	3,700
Investment In Unconsolidated Affiliate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[1]		3,700
Investment In Unconsolidated Affiliate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[1]	$ 13,623
Long Lived Assets Held And Used
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[2]		1,238
Long Lived Assets Held And Used | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[2]		1,238
Long Lived Assets Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[3]		7,000
Long Lived Assets Held For Sale | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset measured at fair value on non-recurring basis	[3]		$ 7,000

[1]   1) On November 1, 2019, in connection with the contribution of substantially all of the net assets of the Engineered Cabs business to a newly-formed Cabs joint venture, we obtained a 20% minority ownership interest.  In accordance with the applicable accounting guidance, our minority ownership interest in the Cabs joint venture was recorded at its acquisition date fair value of $13,623,000.   During the first quarter of fiscal 2020, we determined our 10% minority ownership interest in our steel joint venture in China, Nisshin, was fully impaired based on the estimated recoverability of the related assets.  During the fourth quarter of fiscal 2019, we determined our 10% minority ownership interest in our Nisshin joint venture was other than temporarily impaired due to current and projected operating losses.  As a result, the investment had been written down to its estimated fair value of $3,700,000, resulting in an impairment charge of $4,017,000 within equity income of unconsolidated affiliates.

[2] During the fourth quarter of fiscal 2019, in connection with the closure of the CNG fuel systems facility in Salt Lake City, Utah, long-lived assets consisting primarily of technology-related intangible assets and fixed assets were written down to their estimated fair value of $238,000, resulting in an impairment charge of $2,167,000.  During the fourth quarter of fiscal 2019, certain long-lived assets at our consolidated joint venture, WSP, were written down to their estimated fair value of $1,000,000, resulting in an impairment charge of $3,269,000.

[3] During the first quarter of fiscal 2019, changes in facts and circumstances related to the planned sale of our cryogenics business in Turkey, Worthington Aritas, resulted in our lowering the estimate of fair value less cost to sell to $7,000,000, generating an impairment charge of $2,381,000