SCHEDULE II - Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		May 31, 2018	May 31, 2017	May 31, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period		$ 3,444	$ 4,579	$ 3,085
Charged to Costs and Expenses		11	269	1,556
Charged to Other Accounts - Describe	[1]			394
Deductions - Describe	[2]	2,823	1,404	456
Balance at End of Period		$ 632	$ 3,444	$ 4,579

[1] Miscellaneous amounts.

[2] Uncollectable accounts charged to the allowance. For fiscal 2018, the balance also includes $1,215,000 related to Worthington Aritas that was reclassified to assets held for sale.