Consolidated Statements of Stockholders' Equity - 9 months ended Sep. 30, 2018 - 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		229,073,517
Increase (Decrease) in Stockholders' Equity
Net loss attributable to the Company					(61,268)	$ (61,268)
Other comprehensive loss			(432)			(432)
Stock-based compensation	$ 5	6,384				6,389
Stock-based compensation (in shares)	450,270
Stock dividend		39			(39)
Stock dividend (in shares)	20,245
Public offerings, common stock, net	$ 26	4,886				4,912
Public offerings, common stock, net (in shares)	2,560,849
Stock option exercises	$ 4	123		$ (35)		92
Stock option exercises (in shares)	406,412			17,606
Equity component of convertible senior notes, net of issuance costs and income tax benefit		30,121				30,121
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		7,932				7,932
Balance at Sep. 30, 2018	$ 2,326	$ 1,284,384	$ 1,762	$ (30,637)	(1,243,430)	$ 14,405
Balance (in shares) at Sep. 30, 2018	232,511,393			15,002,663		232,511,393
Increase (Decrease) in Stockholders' Equity
Cumulative effect from adoption of accounting standard					$ (3,487)	$ (3,487)