Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Details Textuals)

v2.4.0.8
Stock-Based Compensation Plans (Details Textuals) (USD $)
In Millions, unless otherwise specified
12 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
May 31, 2014
May 31, 2013
May 31, 2012
May 31, 2014
Employee Stock Option [Member]
May 31, 2013
Employee Stock Option [Member]
May 31, 2014
Performance Stock Options [Member]
May 31, 2013
Performance Stock Options [Member]
May 31, 2014
Officer [Member]
Unearned Performance Shares [Member]
May 31, 2014
Management [Member]
Restricted Stock Unit [Member]
May 31, 2014
Prior to July 2010 [Member]
Officers and Employees [Member]
Employee Stock Option [Member]
May 31, 2014
Prior to July 2010 [Member]
Officer [Member]
Restricted Stock [Member]
May 31, 2014
Prior to October 2010 [Member]
Director [Member]
Employee Stock Option [Member]
May 31, 2014
Beginning in October 2010 [Member]
Director [Member]
Employee Stock Option [Member]
May 31, 2014
Beginning in July 2010 [Member]
Officer [Member]
Employee Stock Option [Member]
May 31, 2014
Beginning in July 2010 [Member]
Officer [Member]
Restricted Stock [Member]
May 31, 2014
October 2006 Broad-based Grant [Member]
Non-management employees [Member]
Employee Stock Option [Member]
Jul. 31, 2014
Subsequent Event [Member]
Officer [Member]
Performance Stock Options [Member]
May 31, 2014
Achievement of Performance Targets for Fiscal 2014 [Member]
Officer [Member]
Performance Stock Options [Member]
Stock Based Compensation Plans (Textual) [Abstract]                                    
Number of shares authorized for issuance under stock plan 39.1                                  
Shares available for future grants 20.2                                  
Stock-based compensation costs $ 26.3 $ 22.8 $ 22.9                              
Income tax benefits related to stock-based compensation 10.1 8.5 8.3                              
Total unrecognized compensation costs related to all unvested stock-based awards $ 52.4                                  
Weighted-average period in years of all unvested stock-based awards 2 years 10 months 25 days                                  
Contractual life of stock option grants 10 years                                  
Number of days of service needed to be eligible for new hire grant, Non-management employee 90 days                                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Achievement of performance targets for fiscal 2014                                 23.50%  
Vesting percentage                 20.00% 0.00% 33.00% 33.00%   25.00% 33.00%     50.00%
Performance period for unearned performance shares               2 years                    
Options outstanding, Ending balance, Shares       5.4 8.0 2.8 2.7                 0.4    
Vesting period               1 year 5 years   3 years   1 year