CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Nov. 30, 2015	May. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 635	$ 604
Accumulated depreciation on rental and lease equipment	237,447	241,116
Accumulated depreciation and amortization for other property	17,198	16,749
Accumulated amortization of intangibles	$ 1,820	$ 1,761
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued
Common stock, par value
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	24,127,743	24,108,176
Common stock, shares outstanding	24,127,743	24,108,176