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Fair Value of Stock Options Granted, Estimated using Weighted-Average Assumptions (Detail)
12 Months Ended
May. 31, 2016
May. 31, 2015
Schedule of Weighted Average Assumptions for Fair Values of Stock Options [Line Items]    
Risk-free interest rate   1.20%
Expected dividend yield   0.00%
Expected stock price volatility   36.20%
Expected option life (in years)   4 years
During fiscal 2016    
Schedule of Weighted Average Assumptions for Fair Values of Stock Options [Line Items]    
Risk-free interest rate 1.20%  
Expected dividend yield 0.00%  
Expected stock price volatility 33.30%  
Expected option life (in years) 4 years