STOCK BASED COMPENSATION - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	May 31, 2015
Stock-based compensation
Shares of common stock authorized for issuance outstanding (in shares)	2,835,630		2,326,801
Employee Stock Purchase Plan, Purchase Price Percentage	85.00%
Issuance for employee stock purchase plan, shares	66,785
Proceeds from issuances of common stock from employee stock purchase plans	$ 673
Employee Stock Purchase Plan, Compensation Expense	106	$ 67
Stock options
Stock-based compensation
Unrecognized compensation cost related to outstanding options	$ 20,930
Period over which unrecognized compensation cost is expected to be recognized as expense	3 years
2014 Stock Incentive Plan
Stock-based compensation
Shares of common stock authorized for issuance (in shares)	1,550,276			2,700,000
Increase in number of authorized shares on the first day of each fiscal year, as a percentage of outstanding common stock (as a percent)	4.00%
Vesting period	4 years
Contractual life	10 years
2014 Stock Incentive Plan | Minimum
Stock-based compensation
Period following termination date vested options are exercisable	1 month
2014 Stock Incentive Plan | Maximum
Stock-based compensation
Period following termination date vested options are exercisable	3 months