CONSOLIDATED BALANCE SHEETS [Parenthetical] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
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	8,200,000	8,200,000
Redeemable Convertible Preferred Stock, shares outstanding	8,200,000	8,200,000
Redeemable Convertible Preferred Stock, liquidation preference (in dollars)	$ 39,570	$ 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	18,079,522	17,552,139
Common Stock, shares outstanding	16,253,426	15,922,321
Treasury Stock, shares at cost	1,826,096	1,629,818