Fair Value Measurements - Assets Measured at Fair Value on Non-Recurring Basis (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2019		Aug. 31, 2018		May 31, 2018		Nov. 30, 2017	[1]	May 31, 2019	May 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charge	$ 5,436	[1]	$ 2,381	[1]	$ 52,919	[1]	$ 8,289		$ 7,817	$ 61,208
Oil And Gas Equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charge					10,497
Zhejiang Nisshin Worthington Precision Specialty Steel Co
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percent of ownership interest held in unconsolidated affiliates	10.00%								10.00%
Assets estimated fair value	$ 3,700								$ 3,700
Impairment charge	4,017								4,017
Worthington Aritas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charge			2,381		42,422
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value	11,938				30,000				11,938	30,000
Fair Value, Measurements, Nonrecurring | CNG Fuel Systems
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value	238								238
Impairment charge									2,167
Fair Value, Measurements, Nonrecurring | Oil And Gas Equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value					21,000					21,000
Fair Value, Measurements, Nonrecurring | Zhejiang Nisshin Worthington Precision Specialty Steel Co
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value	3,700								3,700
Fair Value, Measurements, Nonrecurring | Worthington Specialty Processing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value	$ 1,000								1,000
Impairment charge									$ 3,269
Fair Value, Measurements, Nonrecurring | Worthington Aritas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets estimated fair value			$ 7,000		$ 9,000					$ 9,000

[1] For additional information regarding the Company’s impairment activity, refer to “Note D – Goodwill and Other Long-Lived Assets.”