NET LOSS PER SHARE - Reconciliation of basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Earnings Per Share [Abstract] | ||||
| Net loss attributable to common stockholders | $ (2,618) | $ (2,692) | $ (5,638) | $ (7,692) |
| Weighted average common shares - basic and diluted (in shares) | 14,451,979 | 12,549,226 | 14,409,752 | 12,312,814 |
| Net loss per share attributable to common stockholders - basic and diluted (in dollars per share) | $ (0.18) | $ (0.21) | $ (0.39) | $ (0.62) |