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Stock Based Compensation - Additional Information (Detail) (Common Class B, USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended
Aug. 31, 2012
Aug. 31, 2011
Employee Stock
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Employee stock purchase plans, payroll deductions 10.00%  
Shares purchased, price as percentage of lower of the fair market value 85.00%  
Stock Incentive Plan 1990
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares available for grant (in shares) 163  
Stock options vesting period (in years) 4 years  
Stock options expiration from the date of grant (in years) 10 years  
Unrecognized compensation costs from stock options, net of estimated forfeitures $ 293  
Unrecognized compensation costs from stock options, net of estimated forfeitures, to be recognized as selling and administrative expense over a weighted average period (in years) 3 years  
Weighted average fair value per share of the options granted (in dollars per share) $ 25.45 $ 22.11