Segment Data - Additional Information (Detail)		12 Months Ended
	Mar. 31, 2018	May 31, 2018 Segment JointVenture	May 31, 2017	May 31, 2016
Segment Reporting Information [Line Items]
Number of reportable segments | Segment		3
Number of joint ventures		9
Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		37.00%	43.00%	42.00%
Pressure Cylinders | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		34.00%	28.00%	30.00%
Steel Processing | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		63.00%	69.00%	65.00%
AMTROL | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		7.00%
Engineered Cabs Operating Segment | Sales Revenue, Net | Product Concentration Risk
Segment Reporting Information [Line Items]
Concentration risk percentage		3.00%	3.00%	4.00%
Worthington Cylinders | Operating Segments
Segment Reporting Information [Line Items]
Sale of stock, percentage of ownership before transaction	65.00%
Worthington Steel | Steel Processing
Segment Reporting Information [Line Items]
Number of joint ventures		3