XML 40 R30.htm IDEA: XBRL DOCUMENT v3.3.1.900
2. STOCK-BASED COMPENSATION - Fair values of the ESPP shares (Details 2) - Employee Stock Purchase Plan
$ / shares in Units, $ in Thousands
9 Months Ended
Feb. 28, 2015
USD ($)
$ / shares
Volatility, Minimum 55.00%
Volatility, Maximum 83.00%
Expected dividend | $ $ 0
Risk-free interest rates, Minimum 0.04%
Risk-free interest rates, Maximum 0.53%
Estimated forfeiture rate 0.00%
Weighted average grant date fair value | $ / shares $ 1.47
Minimum  
Expected term (in years) 6 months
Maximum  
Expected term (in years) 2 years