Earnings per Share - Summary of Buyback Activity by Program (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Equity, Class of Treasury Stock [Line Items]
Purchase Price	$ 127,319	$ 20,724	$ 780,151
Share Repurchase Programs
Equity, Class of Treasury Stock [Line Items]
Shares	518	39	8,727
Avg. Price per Share (in dollars per share)	$ 173.51	$ 94.09	$ 87.00
Purchase Price	$ 89,997	$ 3,691	$ 759,237
January 13, 2015
Equity, Class of Treasury Stock [Line Items]
Shares	0	0	3,078
Avg. Price per Share (in dollars per share)	$ 0.00	$ 0.00	$ 85.44
Purchase Price	$ 0	$ 0	$ 262,928
August 4, 2015
Equity, Class of Treasury Stock [Line Items]
Shares	0	39	5,649
Avg. Price per Share (in dollars per share)	$ 0.00	$ 94.09	$ 87.85
Purchase Price	$ 0	$ 3,691	$ 496,309
August 2, 2016
Equity, Class of Treasury Stock [Line Items]
Shares	518	0	0
Avg. Price per Share (in dollars per share)	$ 173.51	$ 0.00	$ 0.00
Purchase Price	$ 89,997	$ 0	$ 0