Income Taxes - Earnings before Income Taxes (Detail) - USD ($) $ in Thousands		12 Months Ended
		May 31, 2019	May 31, 2018	May 31, 2017
Income Tax Disclosure [Abstract]
United States based operations		$ 173,200	$ 177,088	$ 266,222
Non – United States based operations		33,256	31,982	30,905
Earnings before income taxes		206,456	209,070	297,127
Net earnings attributable to noncontrolling interests	[1]	9,818	6,056	13,422
Earnings before income taxes attributable to controlling interest		$ 196,638	$ 203,014	$ 283,705

[1] Net earnings attributable to noncontrolling interests are not taxable to Worthington.