Annual report pursuant to Section 13 and 15(d)

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

v3.7.0.1
Stock-Based Compensation Plans (Other Information Pertaining to Stock Option) (Details) - USD ($)
$ in Millions
12 Months Ended
May 31, 2017
May 31, 2016
May 31, 2015
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of stock options exercised $ 23.8 $ 14.5 $ 17.6
Total grant-date fair value of stock options vested 4.1 4.0 3.6
Performance Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of stock options exercised 12.4 $ 1.0 2.7
Total grant-date fair value of stock options vested $ 4.9   $ 2.6