Segment Reporting and Related Disclosures (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	May 31, 2012
Revenues:
U.S.	$ 49,114	$ 50,087
Other	9,387	8,563
Total revenues	58,501	58,650
Net Long-Lived Assets:
U.S.	208,045		207,449
Other	49,064		49,595
Total net long-lived assets	$ 257,109		$ 257,044