Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Narrative) (Details)

v3.10.0.1
Stock-Based Compensation Plans (Narrative) (Details) - USD ($)
shares in Millions, $ 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]      
Shares authorized for grant 44.1    
Shares available for future grants 19.4    
Stock-based compensation expense $ 44.6 $ 35.4 $ 34.6
Income tax benefits related to stock-based compensation 14.5 13.4 12.9
Total unrecognized compensation cost related to all unvested stock-based awards $ 66.6    
Weighted-average period in years of all unvested stock-based awards 2 years 9 months 18 days    
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options granted 0.7    
Contractual life 10 years    
Total intrinsic value of stock options exercised $ 9.1 $ 23.8 14.5
Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance period 2 years    
Service period 1 year    
Director [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 1 year    
Director [Member] | Restricted Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 1 year    
Management [Member] | Restricted Stock Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 5 years    
Tranche One [Member] | Officer [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 33.30% 25.00%  
Tranche One [Member] | Officer [Member] | Restricted Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 33.30%    
Tranche One [Member] | Management [Member] | Restricted Stock Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 20.00%    
Employee Stock Purchase Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense $ 0.0 $ 0.0 $ 0.0
Discount to the market price 5.00% 5.00% 5.00%
Maximum [Member] | Employee Stock Purchase Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Discount to the market price 15.00%