Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 242,994	$ 137,737	$ 455,541	$ 298,845
Less: income from continuing operations allocated to participating securities	3,376	2,111	6,308	5,298
Income from continuing operations available to common shareholders	$ 239,618	$ 135,626	$ 449,233	$ 293,547
Basic weighted average common shares outstanding (in shares)	106,475	106,340	106,652	106,039
Basic earnings per share from continuing operations (in dollars per share)	$ 2.25	$ 1.27	$ 4.21	$ 2.77
Diluted Earnings per Share from Continuing Operations
Income from continuing operations	$ 242,994	$ 137,737	$ 455,541	$ 298,845
Less: income from continuing operations allocated to participating securities	3,376	2,111	6,308	5,298
Income from continuing operations available to common shareholders	$ 239,618	$ 135,626	$ 449,233	$ 293,547
Basic weighted average common shares outstanding (in shares)	106,475	106,340	106,652	106,039
Effect of dilutive securities - employee stock options (in shares)	3,399	3,478	3,605	2,899
Diluted weighted average common shares outstanding (in shares)	109,874	109,818	110,257	108,938
Diluted earnings per share from continuing operations (in dollars per share)	$ 2.18	$ 1.24	$ 4.07	$ 2.69