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, 2017	$ 96,284	$ 1,334	$ 577,721		$ (482,771)
Balance (in shares) at Dec. 31, 2017		13,343
Stock-based compensation	3,050		3,050
Unrealized gain (loss) on marketable securities	(9)			$ (9)
Net income (loss)	(40,506)				(40,506)
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 (loss) on marketable securities	9			$ 9
Exercise of stock options	$ 145		145
Exercise of stock options (shares)	37,000	37
Dividends paid	$ (26,700)		(26,700)
Net income (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