Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 118,647	$ 117,279	$ 380,192	$ 338,930
Less: income from continuing operations allocated to participating securities	2,262	1,871	7,217	5,500
Income from continuing operations available to common shareholders	$ 116,385	$ 115,408	$ 372,975	$ 333,430
Basic weighted average common shares outstanding (shares)	105,093	107,843	104,842	108,923
Basic earnings per share from continuing operations (dollars per share)	$ 1.11	$ 1.07	$ 3.56	$ 3.06
Diluted Earnings per Share from Continuing Operations
Income from continuing operations	$ 118,647	$ 117,279	$ 380,192	$ 338,930
Less: income from continuing operations allocated to participating securities	2,262	1,871	7,217	5,500
Income from continuing operations available to common shareholders	$ 116,385	$ 115,408	$ 372,975	$ 333,430
Basic weighted average common shares outstanding (shares)	105,093	107,843	104,842	108,923
Effect of dilutive securities - employee stock options (shares)	2,799	1,620	2,666	1,689
Diluted weighted average common shares outstanding (shares)	107,892	109,463	107,508	110,612
Diluted earnings per share from continuing operations (dollars per share)	$ 1.08	$ 1.05	$ 3.47	$ 3.01