STOCK-BASED COMPENSATION (Equity Based Compensation Schedule) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Allocation of stock-based compensation expense
Stock compensation expense	$ 963	$ 693
Research and development expenses
Allocation of stock-based compensation expense
Stock compensation expense	531	252
Research and development expenses | Employees
Allocation of stock-based compensation expense
Stock compensation expense	536	226
Research and development expenses | Non-employees
Allocation of stock-based compensation expense
Stock compensation expense	(5)	26
General and administrative expenses
Allocation of stock-based compensation expense
Stock compensation expense	432	441
General and administrative expenses | Non-employees
Allocation of stock-based compensation expense
Stock compensation expense	25	74
General and administrative expenses | Employees and directors
Allocation of stock-based compensation expense
Stock compensation expense	$ 407	$ 367