Quarterly Financial Data (Unaudited) (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
Quarterly Financial Data [Abstract]
Revenue	$ 1,619,584	$ 1,810,648	$ 1,843,749	$ 1,811,139	$ 1,793,730	$ 1,682,330	$ 1,718,268	$ 1,697,975
Gross margin	707,820	824,395	852,391	849,142	823,565	755,153	775,158	774,712	$ 3,233,748	$ 3,128,588	$ 2,908,523
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
Basic earnings per share, 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
Diluted earnings per share, continuing operations (in dollars per share)	$ 1.35	$ 2.16	$ 2.27	$ 2.32	$ 2.06	$ 1.83	$ 2.18	$ 1.89	$ 8.11	$ 7.97	$ 7.03
Weighted average number of 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