Segment Data - Additional Information (Detail)		12 Months Ended
	Mar. 31, 2018	May 31, 2020 JointVenture Segment	May 31, 2019	May 31, 2018
Segment Reporting Information [Line Items]
Number of reportable segments | Segment		2
Number of joint ventures		9
Joint Venture Transactions
Segment Reporting Information [Line Items]
Number of joint ventures		4
Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		32.00%	38.00%	37.00%
Pressure Cylinders | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		37.00%	32.00%	34.00%
Steel Processing | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		61.00%	65.00%	63.00%
AMTROL | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		8.00%	8.00%
Other
Segment Reporting Information [Line Items]
Sale of stock, percentage of ownership before transaction	75.00%
Sale of stock, percentage of ownership after transaction	65.00%
Worthington Steel | Steel Processing
Segment Reporting Information [Line Items]
Number of joint ventures		4