Consolidated Statements of Cash Flows	12 Months Ended
	May 31, 2016 USD ($)	May 31, 2015 USD ($)	May 31, 2014 USD ($)
Cash flows from operating activities:
Net income	$ 4,784,000	$ 15,432,000	$ 20,408,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	57,164,000	57,562,000	58,286,000
Rental and lease equipment impairment	443,000	0	0
Remeasurement loss on foreign currency	343,000	5,000	152,000
Provision for losses on accounts receivable	679,000	591,000	860,000
Gain on sale of rental and lease equipment	(11,973,000)	(13,622,000)	(14,195,000)
Stock compensation expense	1,372,000	1,292,000	1,356,000
Excess tax benefit for share-based compensation	(100,000)	(358,000)	(183,000)
Deferred income taxes	(1,876,000)	(4,160,000)	(7,928,000)
Change in operating assets and liabilities:
Accounts receivable	9,137,000	(503,000)	(2,366,000)
Other assets	(4,250,000)	(7,532,000)	(6,568,000)
Accounts payable	(1,463,000)	1,195,000	260,000
Accrued expenses	(1,491,000)	4,586,000	(1,125,000)
Deferred revenue	(414,000)	(1,869,000)	229,000
Net cash provided by operating activities	52,355,000	52,619,000	49,186,000
Cash flows from investing activities:
Proceeds from sales of rental and lease equipment	33,066,000	34,261,000	35,224,000
Payments for purchase of rental and lease equipment	(44,071,000)	(70,954,000)	(58,678,000)
Payments for purchase of other property	(384,000)	(986,000)	(384,000)
Net cash used in investing activities	(11,389,000)	(37,679,000)	(23,838,000)
Cash flows from financing activities:
Borrowings under bank lines of credit	11,211,000	45,702,000	56,018,000
Payments under bank lines of credit	(13,598,000)	(43,315,000)	(66,018,000)
Minimum tax withholdings on share-based compensation	(298,000)	(462,000)	(11,000)
Excess tax benefit for share-based compensation	100,000	358,000	183,000
Payment of dividends	(12,328,000)	(19,656,000)	(19,657,000)
Net cash used in financing activities	(14,913,000)	(17,373,000)	(29,485,000)
Effect of exchange rate changes on cash	(52,000)	551,000	(319,000)
Net increase (decrease) in cash and cash equivalents	26,001,000	(1,882,000)	(4,456,000)
Cash and cash equivalents at beginning of year	4,064,000	5,946,000	10,402,000
Cash and cash equivalents at end of year	30,065,000	4,064,000	5,946,000
Supplemental Cash Flow Information [Abstract]
Interest paid, during the period	69,000	31,000	106,000
Income taxes paid, during the period	7,883,000	8,063,000	23,778,000
Dividends accrued during the period, not yet paid	133,000	155,000	211,000
Rental equipment acquisitions, not yet paid	2,854,000	4,430,000	4,479,000
Used equipment sales in accounts receivable and other assets, not yet collected	4,961,000	7,426,000	9,050,000
Transfers from other assets to rental and lease equipment	$ 466,000	$ 14,338,000	$ 4,535,000