Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Performance Share Activity) (Details)

v3.10.0.1
Stock-Based Compensation Plans (Performance Share Activity) (Details) - Performance Shares [Member] - $ / shares
shares in Millions
12 Months Ended
May 31, 2018
May 31, 2017
May 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested, Beginning balance, Awards 0.4    
Granted, Awards [1] 0.2    
Vested, Awards (0.2)    
Forfeited, Awards    
Nonvested, Ending balance, Awards 0.4 0.4  
Nonvested, Beginning balance, Weighted-average grant-date fair value per share $ 45.66    
Granted, Weighted-average grant-date fair value per share 53.08 [1] $ 54.97 $ 42.48
Vested, Weighted-average grant-date fair value per share 38.68    
Forfeited, Weighted-average grant-date fair value per share 48.89    
Nonvested, Ending balance, Weighted-average grant-date fair value per share $ 51.53 $ 45.66  
[1] Performance shares granted assuming achievement of performance goals at target. Actual amount of shares to be earned may differ from this amount.