Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ 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	764		764
Unrealized gain (loss) on marketable securities	(12)			$ (12)
Net income (loss)	(17,782)				(17,782)
Balance at Mar. 31, 2018	79,254	$ 1,334	578,485	(12)	(500,553)
Balance (in shares) at Mar. 31, 2018		13,343
Balance at Dec. 31, 2017	96,284	$ 1,334	577,721		(482,771)
Balance (in shares) at Dec. 31, 2017		13,343
Unrealized gain (loss) on marketable securities	(5)
Net income (loss)	(31,562)
Balance at Sep. 30, 2018	67,043	$ 1,334	580,047	(5)	(514,333)
Balance (in shares) at Sep. 30, 2018		13,343
Balance at Mar. 31, 2018	79,254	$ 1,334	578,485	(12)	(500,553)
Balance (in shares) at Mar. 31, 2018		13,343
Stock-based compensation	780		780
Unrealized gain (loss) on marketable securities	11			11
Net income (loss)	(17,769)				(17,769)
Balance at Jun. 30, 2018	62,276	$ 1,334	579,265	(1)	(518,322)
Balance (in shares) at Jun. 30, 2018		13,343
Stock-based compensation	782		782
Unrealized gain (loss) on marketable securities	(4)			(4)
Net income (loss)	3,989				3,989
Balance at Sep. 30, 2018	67,043	$ 1,334	580,047	(5)	(514,333)
Balance (in shares) at Sep. 30, 2018		13,343
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	594		594
Unrealized gain (loss) on marketable securities	9			9
Net income (loss)	(10,458)				(10,458)
Balance at Mar. 31, 2019	48,964	$ 1,334	581,365		(533,735)
Balance (in shares) at Mar. 31, 2019		13,343
Balance at Dec. 31, 2018	58,819	$ 1,334	580,771	$ (9)	(523,277)
Balance (in shares) at Dec. 31, 2018		13,343
Unrealized gain (loss) on marketable securities	9
Net income (loss)	(20,593)
Balance at Sep. 30, 2019	20,102	$ 1,334	562,638		(543,870)
Balance (in shares) at Sep. 30, 2019		13,363
Balance at Mar. 31, 2019	48,964	$ 1,334	581,365		(533,735)
Balance (in shares) at Mar. 31, 2019		13,343
Stock-based compensation	487		487
Exercise of stock options	23		23
Exercise of stock options (in shares)		6
Net income (loss)	(9,430)				(9,430)
Balance at Jun. 30, 2019	40,044	$ 1,334	581,875		(543,165)
Balance (in shares) at Jun. 30, 2019		13,349
Stock-based compensation	703		703
Exercise of stock options	60		60
Exercise of stock options (in shares)		14
Dividend paid	(20,000)		(20,000)
Net income (loss)	(705)				(705)
Balance at Sep. 30, 2019	$ 20,102	$ 1,334	$ 562,638		$ (543,870)
Balance (in shares) at Sep. 30, 2019		13,363