Revenues from External Customers and Long-Lived Assets, by Geographical Areas (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2014	May 31, 2013	May 31, 2012
Revenues:
Total revenues	$ 61,077	$ 62,016	$ 57,876	$ 60,168	$ 60,366	$ 64,672	$ 65,192	$ 58,501	$ 241,137	$ 248,731	$ 248,554
Net Long Lived Assets:
Total net long-lived assets	235,010				248,682				235,010	248,682	257,044
UNITED STATES
Revenues:
Total revenues									203,806	211,745	214,354
Net Long Lived Assets:
Total net long-lived assets	188,343				198,956				188,343	198,956	207,449
Non-United States [Member]
Revenues:
Total revenues									37,331	36,986	34,200
Net Long Lived Assets:
Total net long-lived assets	$ 46,667				$ 49,726				$ 46,667	$ 49,726	$ 49,595