2. STOCK-BASED COMPENSATION - Option Activity (Details 3) $ / shares in Units, $ in Thousands	3 Months Ended
	Aug. 31, 2016 USD ($) $ / shares shares
Options Outstanding, Ending (in thousands) | shares	3,382
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.67
Options exercisable shares, ending (in thousands) | shares	2,379
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.52
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 2,235
Outstanding Options Stock Option Transactions
Options Outstanding, Beginning (in thousands) | shares	3,201
Options granted (in thousands) | shares	318
Options cancelled (in thousands) | shares	(46)
Options exercised (in thousand) | shares	(91)
Options Outstanding, Ending (in thousands) | shares	3,382
Weighted Average Exercise Price Outstanding, Beginning | $ / shares	$ 1.66
Weighted Average Exercise Price Granted | $ / shares	1.68
Weighted Average Exercise Price Cancelled | $ / shares	1.40
Weighted Average Exercise Price Exercised | $ / shares	1.32
Weighted Average Exercise Price Outstanding, Ending | $ / shares	$ 1.67
Aggregate Intrinsic Value, beginning balance | $	$ 189
Aggregate Intrinsic Value, ending balance | $	$ 2,694
Options fully vested and expected to vest, ending (in thousands) | shares	3,314
Options exercisable shares, ending (in thousands) | shares	2,379
Weighted Average Exercise Price for Options fully vested and expected to vest, ending | $ / shares	$ 1.67
Weighted Average Exercise Price for Options exercisable, ending | $ / shares	$ 1.52
Aggregate Intrinsic Value for Options fully vested and expected to vest, ending | $	$ 2,640
Aggregate Intrinsic Value for Options exercisable, ending | $	$ 2,235