Stock-Based Compensation - Stock Options Granted and Outstanding (Details) - $ / shares	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014	May 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period (shares)	7,835,570	8,025,794	7,885,638
Granted (shares)	1,739,767	1,590,185	2,111,649
Canceled (shares)	(235,455)	(486,720)	(699,314)
Exercised (shares)	(919,975)	(1,293,689)	(1,272,179)
Outstanding, end of period (shares)	8,419,907	7,835,570	8,025,794
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period, Weighted Average Exercise Price (dollars per share)	$ 51.59	$ 43.12	$ 37.60
Granted, Weighted Average Exercise Price (dollars per share)	93.55	84.59	61.04
Canceled, Weighted Average Exercise Price (dollars per share)	60.01	55.50	42.42
Exercised, Weighted Average Exercise Price (dollars per share)	35.07	38.11	39.03
Outstanding, end of period, Weighted Average Exercise Price (dollars per share)	$ 61.83	$ 51.59	$ 43.12
Number of exercisable options (shares)	1,649,236	1,426,550	1,583,413	1,815,795