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Estimated Fair Value Stock Option Granted, Estimated using Weighted-Average Assumptions (Detail)
6 Months Ended 12 Months Ended
Nov. 30, 2012
May 31, 2012
Schedule of Weighted Average Assumptions for Fair Values of Stock Options[Line Items]    
Risk-free interest rate 1.20% 1.20%
Expected dividend yield 0.00% 0.00%
Expected stock price volatility 39.20% 36.40%
Expected option life (in years) 4 years 4 years