SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Non-Cash Share-Based Compensation Expense (Detail) - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
$ 498
|
$ 611
|
| Research and Development Expense |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
139
|
167
|
| Research and Development Expense | Employee Stock Option |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
136
|
167
|
| Research and Development Expense | Restricted Stock Units (RSUs) |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
3
|
0
|
| Selling, General and Administrative |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
359
|
444
|
| Selling, General and Administrative | Employee Stock Option |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
203
|
301
|
| Selling, General and Administrative | Restricted Stock Units (RSUs) |
|
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |
|
|
| Total share-based compensation expense |
$ 156
|
$ 143
|