Earnings per Share - Summary of Buyback Activity by Program (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Equity, Class of Treasury Stock [Line Items]
Purchase Price	$ 20,724	$ 780,151	$ 551,970
Share Repurchase Programs
Equity, Class of Treasury Stock [Line Items]
Shares	39	8,727	6,851
Avg. Price per Share (in dollars per share)	$ 94.09	$ 87.00	$ 78.47
Purchase Price	$ 3,691	$ 759,237	$ 537,572
July 30, 2013
Equity, Class of Treasury Stock [Line Items]
Shares	0	0	3,981
Avg. Price per Share (in dollars per share)	$ 0.00	$ 0.00	$ 75.49
Purchase Price	$ 0	$ 0	$ 300,500
January 13, 2015
Equity, Class of Treasury Stock [Line Items]
Shares	0	3,078	2,870
Avg. Price per Share (in dollars per share)	$ 0.00	$ 85.44	$ 82.60
Purchase Price	$ 0	$ 262,928	$ 237,072
August 4, 2015
Equity, Class of Treasury Stock [Line Items]
Shares	39	5,649	0
Avg. Price per Share (in dollars per share)	$ 94.09	$ 87.85	$ 0.00
Purchase Price	$ 3,691	$ 496,309	$ 0
August 6, 2016
Equity, Class of Treasury Stock [Line Items]
Shares	0	0	0
Avg. Price per Share (in dollars per share)	$ 0.00	$ 0.00	$ 0.00
Purchase Price	$ 0	$ 0	$ 0