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, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 295,789	$ 116,954	$ 594,634	$ 375,112
Less: income from continuing operations allocated to participating securities	5,248	2,573	10,546	7,348
Income from continuing operations available to common shareholders	$ 290,541	$ 114,381	$ 584,088	$ 367,764
Basic weighted average common shares outstanding (in shares)	106,558	105,093	106,210	104,842
Basic earnings per share from continuing operations (in dollars per share)	$ 2.73	$ 1.09	$ 5.50	$ 3.51
Diluted Earnings per Share from Continuing Operations
Income from continuing operations	$ 295,789	$ 116,954	$ 594,634	$ 375,112
Less: income from continuing operations allocated to participating securities	5,248	2,573	10,546	7,348
Income from continuing operations available to common shareholders	$ 290,541	$ 114,381	$ 584,088	$ 367,764
Basic weighted average common shares outstanding (in shares)	106,558	105,093	106,210	104,842
Effect of dilutive securities - employee stock options (in shares)	3,617	2,799	3,044	2,666
Diluted weighted average common shares outstanding (in shares)	110,175	107,892	109,254	107,508
Diluted earnings per share from continuing operations (in dollars per share)	$ 2.66	$ 1.06	$ 5.35	$ 3.42