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Warranty - Additional Information (Detail) - USD ($)
Nov. 30, 2016
May 31, 2016
Nov. 30, 2015
May 31, 2015
Guarantor Obligations [Line Items]        
Estimated warranty obligation $ 7,879,000 $ 7,317,000 $ 7,018,000 $ 6,911,000
Discontinued Operations [Member]        
Guarantor Obligations [Line Items]        
Estimated warranty obligation $ 117,000 $ 150,000