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 | 9 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|
Sep. 30, 2018 |
Jun. 30, 2018 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Earnings Per Share [Abstract] | ||||||||
| Net loss | $ (1,865) | $ (1,865) | $ (1,537) | $ (1,537) | $ (9,557) | $ (4,087) | $ (9,557) | $ (4,087) |
| Accretion of cumulative dividends of redeemable preferred stock to redemption value | 0 | 0 | (1,484) | (1,484) | 0 | (4,364) | 0 | (4,364) |
| Net loss attributable to common stockholders - basic | $ (1,865) | $ (3,021) | $ (9,557) | $ (8,451) | ||||
| Net loss attributable to common stockholders - diluted | $ (1,865) | $ (3,021) | $ (9,557) | $ (8,451) | ||||
| Weighted average number of shares - basic and diluted | 12,624,858 | 1,773,385 | 12,417,972 | 1,754,576 | ||||
| Net loss per share attributable to common stockholders - basic and diluted (in dollars per share) | $ (0.15) | $ (1.70) | $ (0.77) | $ (4.82) | ||||