STOCK‑BASED COMPENSATION - Summary Of RSU Activity (Details) - Non-vested restricted stock units - $ / shares			12 Months Ended
	Mar. 22, 2017	Sep. 30, 2013	Dec. 31, 2017
Number of Shares
Outstanding at Beginning of Period (in shares)			372,335
Granted (in shares)	372,335	372,335	691,585
Vested (in shares)			0
Exercised (in shares)			0
Forfeited (in shares)			(2,841)
Expired (in shares)			0
Canceled (in shares)			(372,335)
Outstanding at End of Period (in shares)			688,744
Weighted Average Grant Date Fair Value
Outstanding at Beginning of Period (in dollars per share)			$ 3.89
Granted (in dollars per share)			13.65
Vested (in dollars per share)			0.00
Exercised (in dollars per share)			0.00
Forfeited (in dollars per share)			13.25
Expired (in dollars per share)			0.00
Canceled (in dollars per share)			3.89
Outstanding at End of Period (in dollars per share)			$ 13.66