CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, liquidation value (in dollars)		$ 51,800
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	21,110,506	20,949,679
Common stock, shares outstanding	21,110,506	20,949,679
Series A-1 junior participating preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,500,000	2,500,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Series B 9.375% redeemable preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, dividend rate (as a percent)	9.375%	9.375%
Preferred stock, liquidation value (in dollars)	$ 30,680	$ 30,680
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	665,592	665,592
Preferred stock, shares outstanding	665,592	665,592
Series C 9.125% redeemable preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, dividend rate (as a percent)	9.125%	9.125%
Preferred stock, liquidation value (in dollars)	$ 35,127	$ 35,127
Preferred stock, shares authorized	5,500,000	5,500,000
Preferred stock, shares issued	1,405,086	1,405,086
Preferred stock, shares outstanding	1,405,086	1,405,086