STOCK-BASED COMPENSATION (Equity Based Compensation Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allocation of stock-based compensation expense
Stock compensation expense	$ 1,627	$ 665	$ 2,590	$ 1,358
Research and development expenses
Allocation of stock-based compensation expense
Stock compensation expense	816	324	1,347	576
Research and development expenses | Employees
Allocation of stock-based compensation expense
Stock compensation expense	767	309	1,303	535
Research and development expenses | Non-employees
Allocation of stock-based compensation expense
Stock compensation expense	49	15	44	41
General and administrative expenses
Allocation of stock-based compensation expense
Stock compensation expense	811	341	1,243	782
General and administrative expenses | Non-employees
Allocation of stock-based compensation expense
Stock compensation expense	84	24	109	98
General and administrative expenses | Employees and directors
Allocation of stock-based compensation expense
Stock compensation expense	$ 727	$ 317	$ 1,134	$ 684