Earnings per Share - Basic Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2020	May 31, 2019	May 31, 2018
Basic Earnings per Share from Continuing Operations
Income from continuing operations	$ 144,585	$ 234,520	$ 246,443	$ 250,812	$ 226,171	$ 200,923	$ 242,994	$ 212,547	$ 876,360	$ 882,635	$ 783,932
Less: income from continuing operations allocated to participating securities									8,158	9,568	11,794
Income from continuing operations available to common shareholders									$ 868,202	$ 873,067	$ 772,138
Basic weighted average common shares outstanding (shares)	103,758	104,245	103,959	103,543	105,018	105,080	106,475	106,835	103,816	106,080	106,593
Basic earnings per share:
Basic earnings per share from continuing operations (dollars per share)	$ 1.38	$ 2.23	$ 2.35	$ 2.40	$ 2.13	$ 1.89	$ 2.25	$ 1.96	$ 8.36	$ 8.23	$ 7.24