STOCK OPTIONS, SUMMARY OF OPTION ACTIVITY - (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Summary of option activity - Shares
Outstanding at the beginning of year (in shares)		3,193,785
Granted (in shares)		1,114,463
Forfeited (in shares)		(218,089)
Exercised (in shares)		(89,387)
Outstanding at the end of period (in shares)	4,000,772	4,000,772
Vested at the end of period (in shares)		1,963,220
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)		4.34
Forfeited (in dollars per shares)		8.21
Exercised (in dollars per shares)		0.29
Outstanding at the end of period (in dollars per shares)	$ 6.76	6.76
Vested at the end of period (in dollars per share)	$ 7.94	$ 7.94
Option activity disclosures
Weighted Average Remaining Contractual Term - Outstanding		7 years 7 months 24 days
Weighted Average Remaining Contractual Term - Vested		6 years 3 months 15 days
Aggregate Intrinsic Value - Outstanding (in dollars)	$ 116,629	$ 116,629
Aggregate Intrinsic Value - Vested (in dollars)	116,410	$ 116,410
Stock Option
Weighted average grant-date fair value of options granted		$ 3.54
Total fair value of options vested	1,000	$ 2,000
Total unrecognized compensation expense, related to non-vested share-based compensation arrangements	$ 8,700	$ 8,700
Period for unrecognized compensation expense is estimated to be recognized		2 years 6 months 22 days