2. STOCK-BASED COMPENSATION - Option Activity (Details 2) $ / shares in Units, $ in Thousands	3 Months Ended
	Aug. 31, 2015 USD ($) $ / shares shares
Number of Options Outstanding, Ending (in thousands)	3,434
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.63
Options exercisable shares, ending (in thousands)	2,174
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.41
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 2,062
Stock Options
Available Shares, Beginning (in thousands)	845
Options granted (in thousands)	0
Options terminated (in thousands)	122
Available Shares, Ending (in thousands)	967
Options Outstanding, Beginning (in thousands)	3,686
Options Granted (in thousands)	0
Options terminated (in thousands)	(122)
Options exercised (in thousands)	(130)
Number of Options Outstanding, Ending (in thousands)	3,434
Weighted Average Exercise Price Outstanding, Beginning | $ / shares	$ 1.66
Weighted Average Exercise Price Granted | $ / shares	0
Weighted Average Exercise Price Terminated | $ / shares	2.04
Weighted Average Exercise Price Exercised | $ / shares	1.72
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.63
Aggregate Intrinsic Value, beginning balance | $	$ 2,946
Aggregate Intrinsic Value, ending balance | $	$ 2,587
Options fully vested and expected to vest, ending (in thousands)	3,366
Options exercisable shares, ending (in thousands)	2,174
Weighted Average Exercise Price for Options fully vested and expected to vest, ending | $ / shares	$ 1.63
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.41
Aggregate Intrinsic Value for Options fully vested and expected to vest, ending | $	$ 2,535
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 2,062