CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Feb. 29, 2016	May. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 439	$ 604
Accumulated depreciation on rental and lease equipment	237,297	241,116
Accumulated depreciation and amortization for other property	17,475	16,749
Accumulated amortization of intangibles	$ 1,849	$ 1,761
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)
Common stock, par value (in dollars per share)
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	24,195,408	24,108,176
Common stock, shares outstanding (in shares)	24,195,408	24,108,176