Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]
Beginning Balances at Dec. 31, 2017	$ 572,354	$ 2,637	$ 1,967,958	$ (2,096)	$ (1,396,145)
Beginning Balance, shares at Dec. 31, 2017		17,516,024
Stock-based compensation	1,981		1,981
Equity issuance costs	(145)		(145)
Shares of common stock issued in asset acquisition, net of equity issuance costs	90,020	$ 378	89,642
Shares of common stock issued in asset acquisition, net of equity issuance costs, shares		2,521,573
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(935)	$ 18	(18)	(935)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(80,477)
Net income (loss)	(2,624)				(2,624)
Ending Balances at Mar. 31, 2018	660,651	$ 3,033	2,059,418	(3,031)	(1,398,769)
Ending Balance, shares at Mar. 31, 2018		20,118,074
Beginning Balances at Dec. 31, 2017	572,354	$ 2,637	1,967,958	(2,096)	(1,396,145)
Beginning Balance, shares at Dec. 31, 2017		17,516,024
Net income (loss)	(17,662)
Ending Balances at Sep. 30, 2018	649,275	$ 3,043	2,063,396	(3,357)	(1,413,807)
Ending Balance, shares at Sep. 30, 2018		20,169,063
Beginning Balances at Mar. 31, 2018	660,651	$ 3,033	2,059,418	(3,031)	(1,398,769)
Beginning Balance, shares at Mar. 31, 2018		20,118,074
Stock-based compensation	1,979		1,979
Equity issuance costs	(25)		(25)
Issuance of restricted stock		$ 2	(2)
Issuance of restricted stock, shares		15,476
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(205)	$ 5	(5)	(205)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(21,452)
Net income (loss)	(19,036)				(19,036)
Ending Balances at Jun. 30, 2018	643,364	$ 3,040	2,061,365	(3,236)	(1,417,805)
Ending Balance, shares at Jun. 30, 2018		20,155,002
Stock-based compensation	2,171		2,171
Equity issuance costs	(137)		(137)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(121)	$ 3	(3)	(121)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(14,061)
Net income (loss)	3,998				3,998
Ending Balances at Sep. 30, 2018	649,275	$ 3,043	2,063,396	(3,357)	(1,413,807)
Ending Balance, shares at Sep. 30, 2018		20,169,063
Beginning Balances at Dec. 31, 2018	687,486	$ 3,043	2,065,119	(3,357)	(1,377,319)
Beginning Balance, shares at Dec. 31, 2018		20,169,063
Stock-based compensation	6,001		6,001
Equity issuance costs	(30)		(30)
Shares of common stock issued in asset acquisition, net of equity issuance costs	275,759	$ 150	275,609
Shares of common stock issued in asset acquisition, net of equity issuance costs, shares		15,013,520
Reverse split		$ (2,833)	2,833
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(5,394)	$ 22	(5)	(5,411)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(499,897)
Net income (loss)	(14,098)				(14,098)
Ending Balances at Mar. 31, 2019	949,724	$ 382	2,349,527	(8,768)	(1,391,417)
Ending Balance, shares at Mar. 31, 2019		35,682,480
Beginning Balances at Dec. 31, 2018	687,486	$ 3,043	2,065,119	(3,357)	(1,377,319)
Beginning Balance, shares at Dec. 31, 2018		20,169,063
Net income (loss)	17,698
Ending Balances at Sep. 30, 2019	982,014	$ 382	2,350,072	(8,819)	(1,359,621)
Ending Balance, shares at Sep. 30, 2019		35,756,088
Beginning Balances at Mar. 31, 2019	949,724	$ 382	2,349,527	(8,768)	(1,391,417)
Beginning Balance, shares at Mar. 31, 2019		35,682,480
Stock-based compensation	552		552
Equity issuance costs	(925)		(925)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(26)			(26)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(4,727)
Net income (loss)	27,512				27,512
Ending Balances at Jun. 30, 2019	976,837	$ 382	2,349,154	(8,794)	(1,363,905)
Ending Balance, shares at Jun. 30, 2019		35,687,207
Stock-based compensation	1,061		1,061
Issuance of restricted stock, shares		50,568
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings	(168)		(143)	(25)
Issuance of common stock upon vesting of equity-based compensation awards, net of shares withheld for income tax withholdings, shares		(18,313)
Net income (loss)	4,284				4,284
Ending Balances at Sep. 30, 2019	$ 982,014	$ 382	$ 2,350,072	$ (8,819)	$ (1,359,621)
Ending Balance, shares at Sep. 30, 2019		35,756,088