Assets Measured at Fair Value on Non-recurring Basis (Parenthetical) (Detail) - USD ($)	3 Months Ended				9 Months Ended
	Nov. 30, 2015	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Feb. 29, 2016	Feb. 28, 2015
Fair Value [Line Items]
Impairment of long-lived assets	$ 22,962,000		$ 81,600,000		$ 25,962,000	$ 97,785,000
Assets fair value		$ 12,403,000			$ 0
DHybrid Systems LLC
Fair Value [Line Items]
Impairment of long-lived assets		2,344,000
Assets fair value		$ 600,000
Engineered Cabs
Fair Value [Line Items]
Impairment of long-lived assets				$ 2,389,000
Engineered Cabs | Customer relationships
Fair Value [Line Items]
Impairment of long-lived assets			22,356,000
Assets fair value			2,000,000			2,000,000
Florence Facility | Engineered Cabs
Fair Value [Line Items]
Impairment of long-lived assets			14,311,000
Assets fair value			$ 9,803,000			$ 9,803,000