Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Other Information Pertaining to Stock Option Grants) (Details)

v3.5.0.2
Stock-Based Compensation Plans (Other Information Pertaining to Stock Option Grants) (Details) - Stock Options [Member] - USD ($)
$ in Millions
12 Months Ended
May 31, 2016
May 31, 2015
May 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of stock options exercised $ 14.5 $ 17.6 $ 18.9
Total grant-date fair value of stock options vested $ 4.0 $ 3.6 $ 3.0