Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	May 31, 2019	May 31, 2018
Statement of Financial Position [Abstract]
Allowance on accounts receivable	$ 37,809	$ 33,510
Preferred stock, shares authorized (in shares)	100,000	100,000
Preferred stock, shares outstanding ( in shares)	0	0
Common stock, shares authorized (in shares)	425,000,000	425,000,000
Common stock, shares issued (in shares)	184,790,626	182,723,471
Common stock, shares outstanding (in shares)	103,284,401	106,326,383
Treasury stock, shares (in shares)	81,506,225	76,397,088