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Stock Repurchase - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
May 31, 2016
May 31, 2015
Dec. 31, 2008
Stock Repurchase Program [Line Items]      
Shares authorized to purchase     1,125,000
Cumulative number of shares repurchased 112,026    
Cost of repurchased shares, including commissions $ 923    
Number of shares repurchased 0 0