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Commitments and Contingencies - Additional Information (Detail) - USD ($)
 12 Months Ended
May 31, 2017
May 31, 2016
Loss Contingencies [Line Items]    
Maximum potential repurchase liability for continuing and discontinued operations $ 30,000,000 $ 25,000,000
Other accrued liabilities $ 100,000 $ 100,000
Minimum [Member]    
Loss Contingencies [Line Items]    
Period to potentially repurchase units 12 months 12 months
Maximum [Member]    
Loss Contingencies [Line Items]    
Period to potentially repurchase units 24 months 24 months