Stock-Based Compensation - Stock Options Granted and Outstanding (Details) - $ / shares	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018	May 31, 2017
Shares
Outstanding, beginning of period (shares)	8,208,934	8,930,186	8,588,050
Granted (shares)	575,813	1,013,005	1,664,867
Canceled (shares)	(5,432)	(3,045)	(7,809)
Forfeited (shares)	(312,391)	(397,304)	(255,627)
Exercised (shares)	(1,361,525)	(1,333,908)	(1,059,295)
Outstanding, end of period (shares)	7,105,399	8,208,934	8,930,186
Weighted Average Exercise Price
Outstanding, beginning of period, Weighted Average Exercise Price (dollars per share)	$ 123.80	$ 96.71	$ 74.77
Granted, Weighted Average Exercise Price (dollars per share)	250.50	219.37	175.86
Canceled, Weighted Average Exercise Price (dollars per share)	72.17	58.03	45.10
Forfeited, Weighed Average Exercise Price (dollars per share)	185.08	155.39	94.73
Exercised, Weighted Average Exercise Price (dollars per share)	70.03	54.14	44.06
Outstanding, end of period, Weighted Average Exercise Price (dollars per share)	$ 145.54	$ 123.80	$ 96.71
Options exercisable (shares)	1,913,374	1,919,976	2,006,922	1,795,898