Consolidated Statement of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Beginning Balance at May. 31, 2014	$ 536,835,000	$ 353,000	$ 508,354,000	$ 31,501,000	$ (1,269,000)	$ (2,104,000)
Beginning Balance,Treasury Shares at May. 31, 2014	(142,305)
Beginning Balance, Shares at May. 31, 2014		35,442,004
Net income (loss)	(2,454,000)			(2,454,000)
Exercise of stock options	4,195,000	3,000	4,192,000
Exercise of stock options, Shares		321,134
Purchase of common stock under ESPP	1,416,000	2,000	1,414,000
Purchase of common stock under ESPP, Shares		119,001
Issuance of performance shares	2,000	2,000
Issuance of performance shares, Shares		141,274
Stock based compensation	4,389,000		4,389,000
Other comprehensive income, net of tax	(627,000)				(627,000)
Ending Balance at Feb. 28, 2015	$ 543,756,000	$ 360,000	$ 518,349,000	$ 29,047,000	$ (1,896,000)	$ (2,104,000)
Ending Balance,Treasury Shares at Feb. 28, 2015	(142,305)					(142,305.000)
Ending Balance, Shares at Feb. 28, 2015		36,023,413