2. STOCK-BASED COMPENSATION - Options outstanding and exercisable (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013
Range Exercise Prices Options Outstanding Minimum	$ 0.59
Range Exercise Prices Options Outstanding Maximum	$ 2.68
Number of Options Outstanding, Ending (in thousands)	3,150	3,323	2,956
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 5 months 26 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.25	$ 1.27	$ 1.79
Number Exercisable Shares (in thousands)	1,734
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 6 months 4 days
Weighted Average Exercise Price Options Excercisable	$ 1.19
Aggregate Intrinsic Value Options Exercisable	$ 2,837
Options Price Range A
Range Exercise Prices Options Outstanding Minimum	$ 0.59
Range Exercise Prices Options Outstanding Maximum	$ 0.97
Number of Options Outstanding, Ending (in thousands)	1,074
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 9 months 7 days
Weighted Average Exercise Price Outstanding, Ending	$ 0.76
Number Exercisable Shares (in thousands)	853
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 5 months 5 days
Weighted Average Exercise Price Options Excercisable	$ 0.80
Options Price Range B
Range Exercise Prices Options Outstanding Minimum	$ 1.09
Range Exercise Prices Options Outstanding Maximum	$ 1.42
Number of Options Outstanding, Ending (in thousands)	1,449
Weighted Average Remaining Contractual Life (Years) Options Outstanding	5 years 4 months 2 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.28
Number Exercisable Shares (in thousands)	506
Weighted Average Remaining Contractual Life (Years) Options Exercisable	4 years 5 months 5 days
Weighted Average Exercise Price Options Excercisable	$ 1.29
Options Price Range C
Range Exercise Prices Options Outstanding Minimum	$ 1.73
Range Exercise Prices Options Outstanding Maximum	$ 1.95
Number of Options Outstanding, Ending (in thousands)	465
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 3 months 11 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.88
Number Exercisable Shares (in thousands)	315
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 5 months 1 day
Weighted Average Exercise Price Options Excercisable	$ 1.92
Options Price Range D
Range Exercise Prices Options Outstanding Minimum	$ 2.15
Range Exercise Prices Options Outstanding Maximum	$ 2.68
Number of Options Outstanding, Ending (in thousands)	162
Weighted Average Remaining Contractual Life (Years) Options Outstanding	5 years 29 days
Weighted Average Exercise Price Outstanding, Ending	$ 2.50
Number Exercisable Shares (in thousands)	60
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 8 months 16 days
Weighted Average Exercise Price Options Excercisable	$ 2.26