ACQUISITION - Summary of Unaudited Proforma Financial Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Combinations [Abstract]
Revenues	$ 82,972	$ 80,622	$ 247,260	$ 246,622
Net loss	$ (15,081)	$ (11,708)	$ (44,216)	$ (39,817)
Net Income per share (in dollars per share)	$ (0.75)	$ (0.59)	$ (2.22)	$ (2.14)
Basic and diluted (in shares)	20,206	19,929	19,968	18,645