Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 212,547	$ 161,108
Less: income from continuing operations allocated to participating securities	2,945	3,187
Income from continuing operations available to common shareholders	$ 209,602	$ 157,921
Basic weighted average common shares outstanding (in shares)	106,835	105,740
Basic earnings per share from continuing operations (in dollars per share)	$ 1.96	$ 1.50
Diluted Earnings per Share from Continuing Operations
Income from continuing operations	$ 212,547	$ 161,108
Less: income from continuing operations allocated to participating securities	2,945	3,187
Income from continuing operations available to common shareholders	$ 209,602	$ 157,921
Basic weighted average common shares outstanding (in shares)	106,835	105,740
Effect of dilutive securities - employee stock options (in shares)	3,813	2,797
Diluted weighted average common shares outstanding (in shares)	110,648	108,537
Diluted earnings per share from continuing operations (in dollars per share)	$ 1.89	$ 1.45