Revenues and Total Assets in United States and Other Countries (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012	May 31, 2012
Revenues
United States, Revenue	$ 116,155	$ 99,132	$ 366,397	$ 301,652
Revenue, Total	150,975	136,523	513,115	435,889
Total Assets
United States, Total Assets	324,801		324,801		296,240
Total assets	447,137		447,137		403,788
Canada
Revenues
Other foreign countries, Revenue	19,946	22,927	98,647	87,724
Total Assets
Other foreign countries, Total Assets	65,081		65,081		60,334
Europe
Revenues
Other foreign countries, Revenue	8,220	9,672	23,586	26,559
Total Assets
Other foreign countries, Total Assets	32,461		32,461		30,352
Other Foreign Countries
Revenues
Other foreign countries, Revenue	6,654	4,792	24,485	19,954
Total Assets
Other foreign countries, Total Assets	$ 24,794		$ 24,794		$ 16,862