Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Aug. 31, 2012	May 31, 2012
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 428	$ 522
Accumulated depreciation on rental and lease equipment	209,867	204,108
Accumulated depreciation and amortization for other property	18,121	17,832
Amortization of intangibles	$ 1,345	$ 1,304
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	0	23,987,826
Common stock, shares outstanding	0	23,987,826