Earnings per Share - Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2019	May 31, 2018	May 31, 2017
Diluted Earnings per Share from Continuing Operations
Income from continuing operations	$ 226,171	$ 200,923	$ 242,994	$ 212,547	$ 189,298	$ 295,789	$ 137,737	$ 161,108	$ 882,635	$ 783,932	$ 457,286
Less: income from continuing operations allocated to participating securities									9,568	11,794	8,168
Income from continuing operations available to common shareholders									$ 873,067	$ 772,138	$ 449,118
Basic weighted average common shares outstanding (shares)	105,018	105,080	106,475	106,835	106,593	106,558	106,340	105,740	106,080	106,593	104,964
Effect of dilutive securities - employee stock options (shares)									3,415	3,217	2,819
Diluted weighted average common shares outstanding (shares)									109,495	109,810	107,783
Diluted earnings per share:
Diluted earnings per share from continuing operations (in dollars per share)	$ 2.06	$ 1.83	$ 2.18	$ 1.89	$ 1.68	$ 2.66	$ 1.24	$ 1.45	$ 7.97	$ 7.03	$ 4.17