Consolidated Condensed Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010
Cash Flows From Operating Activities:
Net Income	$ 17,201	$ 11,842
Adjustments to reconcile net income to net cash provided by operating activities:
Earnings from unconsolidated affiliates	(848)	(635)
Depreciation and amortization	8,335	6,445
Amortization of deferred loan costs	128	155
Foreign currency loss (gain)	164	(11)
Deferred income taxes	2,029	(1,297)
Non-cash compensation cost	2,620	2,690
(Increase) decrease:
Receivables	(5,380)	2,640
Inventory	(1,361)	(747)
Prepaid expenses and other current assets	1,594	1,087
Increase (decrease):
Accounts payable	(6,057)	(2,103)
Other accrued liabilities	1,704	1,323
Income taxes	(770)	(1,397)
Net Cash Provided By Operating Activities	19,359	19,992
Cash Flows From Investing Activities:
Capital expenditures	(10,739)	(5,074)
Business acquisitions, net of cash acquired	(2,268)	(41,376)
Proceeds from sale of assets	220
Decrease (increase) in other assets, net	64	(82)
Net Cash Used In Investing Activities	(12,723)	(46,532)
Cash Flows From Financing Activities:
(Payments) borrowings under revolving credit agreement, net	(861)	28,700
Payments related to term and auto notes	(179)	(156)
Debt issuance costs	(759)
Corporate tax effect from share-based payment arrangements	609	781
Issuance of common stock from share- based payment arrangements	669	520
Payments related to withholding tax for share-based payment arrangements	(853)	(433)
Purchase of treasury stock		(1,344)
Net Cash (Used In) Provided By Financing Activities	(1,374)	28,068
Effect Of Exchange Rate Changes on Cash	(592)	173
Net Increase In Cash And Cash Equivalents	4,670	1,701
Cash And Cash Equivalents At Beginning Of Period	14,078	12,610
Cash And Cash Equivalents At End Of Period	$ 18,748	$ 14,311