INCOME TAXES (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Deferred tax assets: |
|
|
|
| Net operating loss carryforwards |
$ 71,049
|
$ 38,405
|
|
| Research and development credits |
3,712
|
3,421
|
|
| Accruals and other |
1,541
|
144
|
|
| Depreciation and amortization |
261
|
94
|
|
| Deferred tax assets before valuation allowance |
76,563
|
42,064
|
|
| Valuation allowance |
(76,563)
|
(42,064)
|
|
| Deferred tax liabilities: |
|
|
|
| Net deferred tax assets |
0
|
0
|
|
| Valuation allowance |
|
|
|
| Increase to gross deferred tax asset and valuation allowance resulting from adoption of ASU 2016-09 |
406
|
|
|
| Deferred tax asset valuation allowance increase |
(34,499)
|
(10,539)
|
|
| Net operating loss carryforwards |
|
|
|
| Operating Loss Carryforwards |
1,539
|
1,064
|
$ 0
|
| U.S. federal |
|
|
|
| Deferred tax assets: |
|
|
|
| Research and development credits |
3,367
|
3,110
|
2,868
|
| Net operating loss carryforwards |
|
|
|
| Available net operating loss carryforwards as of the end of the year |
190,926
|
104,888
|
78,276
|
| State |
|
|
|
| Deferred tax assets: |
|
|
|
| Research and development credits |
522
|
469
|
226
|
| Net operating loss carryforwards |
|
|
|
| Available net operating loss carryforwards as of the end of the year |
$ 145,902
|
$ 59,875
|
$ 34,184
|