STATEMENTS OF CHANGES IN PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital Common Stock	Accumulated Deficit	Series 1 Preferred Stock - Mezzanine
Balance at Dec. 31, 2014	$ 33,841	$ 104	$ 406,349	$ (372,612)
Balance (in shares) at Dec. 31, 2014		104,452,105
Exercise of employee stock options	$ 4,568	$ 3	4,566
Exercise of employee stock options (in shares)	3,249,160	2,519,267
Stock-based compensation	$ 7,997		7,997
Issuance of restricted common stock		$ 2	(2)
Issuance of restricted common stock (in shares)		1,590,574
Issuance of common stock in licensing agreement	67,285	$ 12	67,273
Issuance of stock in a license agreement (in shares)		11,722,163
Repurchase of shares of restricted common stock	(518)		(518)
Repurchase of shares of restricted common stock (in shares)		(61,819)
Repurchase of common stock	(34)		(34)
Repurchase of common stock (Shares)		(3,711)
Issuance of common stock, net of commissions and expenses	94,320	$ 12	94,309
Issuance of common stock, net of commissions and expenses (in shares)		11,500,000
Net loss	(120,088)			(120,088)
Balance at Dec. 31, 2015	87,371	$ 132	579,939	(492,700)
Balance (in shares) at Dec. 31, 2015		131,718,579
Exercise of employee stock options	$ 714	$ 2	712
Exercise of employee stock options (in shares)	234,833	189,696
Stock-based compensation	$ 8,452		8,452
Issuance of restricted common stock		$ 712	(712)
Issuance of restricted common stock (in shares)		711,770
Issuance of common stock in licensing agreement	87		87		$ 118,242
Issuance of stock in a license agreement (in shares)					100,000
Repurchase of shares of restricted common stock	(1,500)	$ (2)	(1,498)
Repurchase of shares of restricted common stock (in shares)		(243,207)
Repurchase of common stock	(2)		(2)
Repurchase of common stock (Shares)		(168)
Preferred stock dividends					$ 7,079
Preferred stock dividends	(7,123)		(7,123)
Preferred stock dividends (in shares)					6,184
Net loss	(165,297)			(165,297)
Balance at Dec. 31, 2016	(77,298)	$ 132	580,567	(657,997)	$ 125,321
Balance (in shares) at Dec. 31, 2016		132,376,670			106,184
Exercise of employee stock options	$ 88	$ 1	87
Exercise of employee stock options (in shares)	180,000	59,864
Stock-based compensation	$ 8,454		8,454
Issuance of restricted common stock		$ 1	(1)
Issuance of restricted common stock (in shares)		907,032
Repurchase of common stock	(2,059)	$ (1)	(2,058)
Repurchase of common stock (Shares)		(394,267)
Issuance of common stock, net of commissions and expenses	47,270	$ 10	47,260
Issuance of common stock, net of commissions and expenses (in shares)		9,708,738
Preferred stock dividends					$ 18,672
Preferred stock dividends	(18,938)		(18,938)
Preferred stock dividends (in shares)					13,460
Net loss	(54,323)			(54,323)
Balance at Dec. 31, 2017	$ (96,806)	$ 143	615,493	(712,442)	$ 143,993
Balance (in shares) at Dec. 31, 2017		142,658,037			119,644
Cumulative effect adjustment (Note 3)			$ 122	$ (122)