XML 23 R32.htm IDEA: XBRL DOCUMENT v2.4.0.8
Commitments and Contingencies - Additional Information (Detail) (USD $)
 3 Months Ended
Aug. 31, 2014
May 31, 2014
Commitments and Contingencies Disclosure [Line Items]    
Environmental remediation expense, period of remediation, years 5 years  
Estimated liability costs of remediation $ 916,000 $ 916,000
Estimated liability, measurement period, years 15 years  
Minimum
    
Commitments and Contingencies Disclosure [Line Items]    
Environmental remediation expense 47,000  
Maximum
    
Commitments and Contingencies Disclosure [Line Items]    
Environmental remediation expense $ 79,000