CONSOLIDATED BALANCE SHEETS [Parenthetical] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Redeemable Convertible Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Redeemable Convertible Preferred Stock, shares authorized	1,000,000,000	1,000,000,000
Redeemable Convertible Preferred Stock, shares issued	10,552,941	8,200,000
Redeemable Convertible Preferred Stock, shares outstanding	10,552,941	8,200,000
Redeemable Convertible Preferred Stock, liquidation preference (in dollars)	$ 51,170	$ 39,570
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares issued	18,517,683	18,079,522
Common Stock, shares outstanding	16,691,587	16,253,426
Treasury Stock, shares at cost	1,826,096	1,826,096