Segments and Geographic Information (Details 1) (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
Net Sales by Geography
Net sales	$ 94,065	$ 88,195	$ 88,616	$ 83,579	$ 90,042	$ 81,571	$ 87,007	$ 83,406	$ 354,455	$ 342,026	$ 221,787
United States [Member]
Net Sales by Geography
Net sales									280,191	266,338	188,187
International [Member]
Net Sales by Geography
Net sales									68,219	67,190	33,600
Supply Agreement [Member]
Net Sales by Geography
Net sales									$ 6,045	$ 8,498	$ 0