Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Cash flows from operating activities:
Net income	$ 30,149	$ 32,714	$ 33,068
Adjustments to reconcile net income to net cash provided by operating activities:
Earnings from unconsolidated affiliates	(822)	(992)	(1,183)
Depreciation and amortization	21,468	19,664	17,469
Loss (gain) on asset disposals	78	193	(21)
Amortization of deferred loan costs	223	222	283
Venezuela devaluation	3,962
Foreign currency loss (gain)	223	943	(31)
Deferred income taxes	(1,040)	5,089	(717)
Gain on contingent consideration revaluation	(2,138)
Write-down of property costs			1,658
Non-cash compensation cost	4,239	3,931	4,386
(Increase) decrease:
Receivables	(6,812)	(10,964)	(16,990)
Inventory	822	(1,405)	(3,629)
Prepaid expenses and other current assets	(17)	443	(559)
Increase (decrease):
Accounts payable	(295)	3,210	(5,965)
Other accrued liabilities	(1,208)	7,779	6,871
Income taxes	4,029	(2,184)	2,012
Net cash provided by operating activities	52,861	58,643	36,652
Cash flows from investing activities:
Capital expenditures	(33,016)	(26,068)	(23,924)
Proceeds from sale of assets	357	758	220
Business acquisitions, net of cash acquired	(10,175)	(18,589)	(19,351)
Distributions from joint venture	2,223	1,000	800
Increase in other assets, net	2		(9)
Net cash used in investing activities	(40,609)	(42,899)	(42,264)
Cash flows from financing activities:
Net (payments) borrowings under revolving credit agreement		(13,600)	12,707
Deferred consideration payments	(1,000)
Debt issuance costs			(799)
Payments related to term and auto notes			(235)
Payments related to withholding tax for share-based payment arrangements	(1,710)	(1,534)	(868)
Corporate tax effect from share-based payment arrangements	1,131	2,996	1,533
Issuance of common stock from share-based payment arrangements	5,270	8,275	2,997
Purchase of treasury stock	(13,334)
Net cash (used in) provided by financing activities	(9,643)	(3,863)	15,335
Effect of exchange rate changes on cash	(2,154)	(157)	(1,324)
Net increase in cash and cash equivalents	455	11,724	8,399
Cash and cash equivalents at beginning of year	34,201	22,477	14,078
Cash and cash equivalents at end of year	34,656	34,201	22,477
Cash paid during the year for:
Interest	2,728	2,615	2,315
Income taxes	$ 12,111	$ 12,926	$ 16,474