Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Narrative) (Details)

v3.20.2
Stock-Based Compensation Plans (Narrative) (Details) - USD ($)
shares in Millions, $ in Millions
12 Months Ended
May 31, 2020
May 31, 2019
May 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized for grant 44.1    
Shares available for future grants 17.3    
Stock-based compensation expense $ 47.4 $ 46.2 $ 44.6
Income tax benefits related to stock-based compensation 9.0 8.9 14.5
Total unrecognized compensation cost related to all unvested stock-based awards $ 65.0    
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]      
Contractual life 10 years    
Performance-Based RSUs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance period 2 years    
Service period 1 year    
Time-Based Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 1 year    
Performance-Based Restricted Stock Awards [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    
Non-Executive [Member] | Time-Based RSUs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 5 years    
Executive [Member] | Time-Based RSUs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 3 years    
Tranche One [Member] | Time-Based Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 33.30%    
Tranche One [Member] | Officer [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 33.30%    
Tranche One [Member] | Non-Executive [Member] | Time-Based RSUs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 20.00%    
Tranche One [Member] | Executive [Member] | Time-Based RSUs [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 33.30%    
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%