2. STOCK-BASED COMPENSATION - Options outstanding and exercisable (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified			3 Months Ended
	Aug. 31, 2014	May 31, 2014	Aug. 31, 2014 Options Price Range A	Aug. 31, 2014 Options Price Range B	Aug. 31, 2014 Options Price Range C	Aug. 31, 2014 Options Price Range D	Aug. 31, 2014 Options Price Range E
Range Exercise Prices Options Outstanding Minimum			$ 0.59	$ 1.09	$ 1.73	$ 2.15	$ 0.59
Range Exercise Prices Options Outstanding Maximum			$ 0.97	$ 1.42	$ 1.95	$ 2.71	$ 2.71
Number of Options Outstanding, Ending (in thousands)	3,323	3,002	680	1,351	428	864	3,323
Weighted Average Remaining Contractual Life (Years) Options Outstanding			4 years 7 months 2 days	4 years 8 months 3 days	2 years 8 months 5 days	6 years 25 days	4 years 9 months 4 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.59	$ 1.31	$ 0.70	$ 1.28	$ 1.88	$ 2.63	$ 1.59
Options exercisable shares, ending (in thousands)	1,768		536	675	365	192	1,768
Weighted Average Remaining Contractual Life (Years) Options Exercisable			4 years 7 months 28 days	4 years 1 month 28 days	2 years 1 month 10 days	4 years 8 months 23 days	3 years 11 months 8 days
Weighted Average Exercise Price for Options exercisable, ending	$ 1.26		$ 0.73	$ 1.28	$ 1.90	$ 1.47	$ 1.26
Options exercisable at August 31, 2014 Aggregate intrinsic value	$ 2,074