SHAREHOLDERS' EQUITY - Deferred Compensation Arrangement (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2015 |
Mar. 31, 2014 |
|
| Employees and Non Employee Members of Scientific Advisory Board [Member] | ||
| Deferred Compensation Arrangement with Employees and Non-Employees, Share-Based Payments [Line Items] | ||
| Shares issued (in shares) | 35,205 | 31,301 |
| Employees [Member] | ||
| Deferred Compensation Arrangement with Employees and Non-Employees, Share-Based Payments [Line Items] | ||
| Fair value of shares issued | $ 967 | $ 746 |
| Shares withheld for tax withholding obligations (in shares) | 9,565 | 8,071 |
| Fair value of shares withheld for tax withholding obligations | $ 346 | $ 271 |
| Non Employee Members of Scientific Advisory Board [Member] | ||
| Deferred Compensation Arrangement with Employees and Non-Employees, Share-Based Payments [Line Items] | ||
| Fair value of shares issued | $ 300 | $ 323 |