Condensed Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in-Capital	Accumulated Other Comprehensive Income	Treasury Stock	Accumulated Deficit	Total
Balance at Dec. 31, 2017	$ 2,291	$ 1,250,899	$ 2,194	$ (3,102)	$ (1,178,636)	$ 73,646
Balance (in shares) at Dec. 31, 2017	229,073,517			587,151
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(45,703)	(45,703)
Other comprehensive income/loss			(350)			(350)
Stock-based compensation	$ 2	4,323				4,325
Stock-based compensation (in shares)	202,523
Stock dividend		26			(26)
Stock dividend (in shares)	13,273
Stock option exercises	$ 4	98		$ (35)		67
Stock option exercises (in shares)	366,412			17,606
Equity component of convertible senior notes, net of issuance costs and income tax benefit		31,837				31,837
Purchase of capped call		(16,000)				(16,000)
Purchase of common stock forward				$ (27,500)		(27,500)
Purchase of common stock forward (in shares)				14,397,906
Exercise of warrants (in shares)	100
Provision for common stock warrants		5,806				5,806
Balance at Jun. 30, 2018	$ 2,297	1,276,989	1,844	$ (30,637)	(1,224,365)	26,128
Balance (in shares) at Jun. 30, 2018	229,655,825			15,002,663
Balance at Dec. 31, 2018	$ 2,342	1,289,714	1,584	$ (30,637)	(1,260,290)	$ 2,713
Balance (in shares) at Dec. 31, 2018	234,160,661			15,002,663		234,160,661
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(52,499)	$ (52,499)
Other comprehensive income/loss			(124)			(124)
Stock-based compensation	$ 8	5,115				5,123
Stock-based compensation (in shares)	780,985
Stock dividend		26			(26)
Stock dividend (in shares)	10,147
Issuance of common stock, net	$ 119	28,146				28,265
Issuance of common stock, net (in shares)	11,881,637
Stock option exercises	$ 1	248		$ (44)		205
Stock option exercises (in shares)	141,743			17,774
Provision for common stock warrants		5,662				5,662
Balance at Jun. 30, 2019	$ 2,470	$ 1,328,911	$ 1,460	$ (30,681)	$ (1,312,815)	$ (10,655)
Balance (in shares) at Jun. 30, 2019	246,975,173			15,020,437		246,975,173