Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Allowances for receivables	$ 39	$ 41
Accumulated depreciation and amortization of equipment and leasehold improvements	26,819	24,955
Amortization of intangibles	4,607	4,357
Restricted cash	$ 0	$ 2,675
Temporary stock, dividend percentage	7.00%	7.00%
Temporary stock, par value	$ 0.01	$ 0.01
Temporary stock, shares authorized	5,000,000	5,000,000
Temporary stock, shares issued	1,637,786	1,637,786
Temporary stock, shares outstanding	1,637,786	1,637,786
Temporary stock, liquidation preference	$ 11,860	$ 11,568
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	35,000,000	35,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	33,326,927	33,083,180
Common stock, shares outstanding	33,216,071	33,039,713
Treasury stock, shares	110,856	43,467