STOCK OPTIONS, SUMMARY OF OPTION ACTIVITY - (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of option activity - Shares
Outstanding at the beginning of year (in shares)	3,193,785
Granted (in shares)	1,439,463
Forfeited (in shares)	(1,174,616)
Exercised (in shares)	(89,387)
Outstanding at the end of period (in shares)	3,369,245	3,193,785
Vested at the end of period (in shares)	2,224,246
Vested and expected to vest at the end of period (in shares)	3,369,245
Summary of option activity - Weighted Average Exercise Price
Outstanding at the beginning of year (in dollars per shares)	$ 7.52
Granted (in dollars per shares)	3.94
Forfeited (in dollars per shares)	6.40
Exercised (in dollars per shares)	0.29
Outstanding at the end of period (in dollars per shares)	6.57	$ 7.52
Vested at the end of period (in dollars per share)	7.54
Vested and expected to vest at the end of period (in dollars per share)	$ 6.57
Option activity disclosures
Weighted Average Remaining Contractual Term - Outstanding	7 years 1 month 21 days
Weighted Average Remaining Contractual Term - Vested	6 years 2 months 19 days
Weighted Average Remaining Contractual Term - Vested and expected to vest	7 years 1 month 21 days
Aggregate Intrinsic Value - Outstanding (in dollars)	$ 22
Aggregate Intrinsic Value - Vested (in dollars)	22
Aggregate Intrinsic Value - Vested and expected to vest (in dollars)	$ 22
Stock Option
Weighted average grant-date fair value of options granted	$ 2.54	$ 5.23	$ 7.37
Total fair value of options vested	$ 3,837	$ 5,179	$ 5,144
Total unrecognized compensation expense	$ 3,516
Period for unrecognized compensation expense is estimated to be recognized	2 years 4 months 17 days