Annual report pursuant to Section 13 and 15(d)

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

v3.20.2
Stock-Based Compensation Plans (Other Information Pertaining to Restricted Stock Awards) (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
May 31, 2020
May 31, 2019
May 31, 2018
Time-Based Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average grant-date fair value per share $ 84.46 $ 69.80 $ 57.50
Total grant-date fair value of shares vested $ 3.2 $ 3.0 $ 3.0
Performance-Based Restricted Stock Awards [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average grant-date fair value per share $ 80.59 [1] $ 65.17 $ 53.08
Total grant-date fair value of shares vested $ 5.8 $ 5.3 $ 6.6
[1] For performance-based shares, granted number assumes achievement of performance goals at target. Actual number of shares to be earned may differ from this amount.