Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Aug. 31, 2020	May 31, 2020
Statement Of Financial Position [Abstract]
Trade accounts receivable, allowances	$ 55,927	$ 55,847
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	50,000,000	50,000,000
Preferred stock, issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	300,000,000	300,000,000
Common stock, issued	143,813,000	143,261,000
Common stock, outstanding	129,975,000	129,511,000