INCOME TAXES - NET DEFERRED TAX ASSET (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Significant components of net deferred tax asset | ||
| Net operating loss carryforward | $ 37,245 | $ 30,014 |
| Research and development credit carryforward | 1,065 | 942 |
| Stock-based compensation | 5,235 | 3,307 |
| Depreciation and amortization | 31 | |
| Depreciation and amortization | (48) | |
| Accrued expenses | 264 | 186 |
| Charitable contributions | 63 | 96 |
| Subtotal | 43,903 | 34,497 |
| Valuation allowance | (43,903) | (34,497) |
| Increase in valuation allowance | 9,406 | 8,727 |
| Uncertain tax positions that would affect its effective tax rate | $ 0 | $ 0 |