CONSOLIDATED STATEMENTS OF STOCKHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning Balance at Dec. 31, 2012	$ 293,409	$ 6	$ (10,311)	$ 388,798	$ (85,084)
Net proceeds of public stock offering	118,382	1		118,381
Exercise of stock options	2,549			2,549
Compensation under employee stock compensation plan	9,498			9,498
Exercise of warrants	399			399
Net income (loss)	(69,654)				(69,654)
Ending Balance at Dec. 31, 2013	354,583	7	(10,311)	519,625	(154,738)
Exercise of stock options	1,468	1		1,467
Surrender of stock to satisfy minimum tax withholding	(368)		(368)
Compensation under employee stock compensation plan	8,590			8,590
Net income (loss)	(147,468)				(147,468)
Ending Balance at Dec. 31, 2014	216,805	8	(10,679)	529,682	(302,206)
Exercise of stock options	2			2
Surrender of stock to satisfy minimum tax withholding	(58)		(58)
Issuance of Series A convertible preferred stock and warrants	6,581			6,581
Accrued dividends on preferred stock	(6,120)			(6,120)
Deemed dividends on preferred stock	(3,690)			(3,690)
Compensation under employee stock compensation plan	5,309			5,309
Net income (loss)	(299,707)				(299,707)
Ending Balance at Dec. 31, 2015	$ (80,878)	$ 8	$ (10,737)	$ 531,764	$ (601,913)