Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2018	$ 58,819	$ 1,334	$ 580,771	$ (9)	$ (523,277)
Balance (in shares) at Dec. 31, 2018		13,343
Stock-based compensation	2,371		2,371
Unrealized gain on marketable securities	9			$ 9
Exercise of stock options	145		145
Exercise of stock options (shares)		37
Dividends paid	(26,700)		(26,700)
Net loss	(17,332)				(17,332)
Balance at Dec. 31, 2019	17,312	$ 1,334	556,587		(540,609)
Balance (in shares) at Dec. 31, 2019		13,380
Stock-based compensation	1,722		1,722
Net loss	(3,028)				(3,028)
Balance at Dec. 31, 2020	$ 16,006	$ 1,334	$ 558,309		$ (543,637)
Balance (in shares) at Dec. 31, 2020		13,380