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Stock-Based Compensation - Total Stock-Based Compensation Expense (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Nov. 30, 2013
Nov. 30, 2012
Nov. 30, 2013
Nov. 30, 2012
Common Stock and Stock-based Compensation [Abstract]        
Accelerated stock option expense $ 4 $ 6 $ 8 $ 10