Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Common Stock [Member] February 2011 Financing [Member]	Common Stock [Member] March 2012 Financing [Member]	Common Stock [Member] May 2013 Financing [Member]	Common Stock [Member] November 2013 Financing [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] February 2011 Financing [Member]	Additional Paid-in Capital [Member] March 2012 Financing [Member]	Additional Paid-in Capital [Member] May 2013 Financing [Member]	Additional Paid-in Capital [Member] November 2013 Financing [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] February 2011 Financing [Member]	Accumulated Deficit [Member] March 2012 Financing [Member]	Accumulated Deficit [Member] May 2013 Financing [Member]	Accumulated Deficit [Member] November 2013 Financing [Member]	Treasury Stock [Member]	Treasury Stock [Member] February 2011 Financing [Member]	Treasury Stock [Member] March 2012 Financing [Member]	Treasury Stock [Member] May 2013 Financing [Member]	Treasury Stock [Member] November 2013 Financing [Member]	Total	February 2011 Financing [Member]	March 2012 Financing [Member]	May 2013 Financing [Member]	November 2013 Financing [Member]
Balance at Dec. 31, 2011	$ 25					$ 401,713					$ (397,420)					$ (3,054)					$ 1,264
Balance (in shares) at Dec. 31, 2011	24,603,000															(21,000)
Changes in Stockholders' Equity [Roll Forward]
Net loss	0					0					(37,315)					0					(37,315)
Issuance of common stock, 401(k) Plan employer match	0					763					0					0					763
Issuance of common stock, 401(k) employer match (in shares)	317,000															0					316,543
Issuance of common stock, financing			16					42,074					0					0					42,090
Issuance of common stock, financing (in shares)			16,072,000
Issuance of common stock, ATM financing	1					1,460					0					0					1,461
Issuance of common stock, ATM financing (in shares)	350,000
Exercise of common stock warrants	2					6,875					0					0					6,877
Exercise of common stock warrants (in shares)	2,289,000
Exercise of stock options for cash		0					6					0					0					6
Exercise of stock options for cash (in shares)		3,000
Issuance of common stock, consultants	0					96					0					0					96
Issuance of common stock, consultants (in shares)	40,000
Stock-based compensation expense	0					2,411					0					0					2,411
Stock-based compensation expense (in shares)	0
Balance at Dec. 31, 2012	44					455,398					(434,735)					(3,054)					17,653
Balance (in shares) at Dec. 31, 2012	43,674,000															(21,000)
Changes in Stockholders' Equity [Roll Forward]
Net loss	0					0					(45,215)					0					(45,215)
Issuance of common stock, 401(k) Plan employer match	0					959					0					0					959
Issuance of common stock, 401(k) employer match (in shares)	510,000															0					510,047
Issuance of common stock, financing				11	29				15,102	53,836				0	0				0	0				15,113	53,865
Issuance of common stock, financing (in shares)				10,847,000	28,750,000														0
Issuance of common stock, ATM financing	1					1,795					0					0					1,796
Issuance of common stock, ATM financing (in shares)	714,000
Issuance of common stock warrants, Deerfield	0					11,729					0					0					11,729
Issuance of common stock warrants, Deerfield (in shares)	0
Exercise of common stock warrants	0					290					0					0					290
Exercise of common stock warrants (in shares)	114,000															0
Exercise of stock options for cash	0					34					0					0					34
Exercise of stock options for cash (in shares)	18,000															0
Issuance of common stock, consultants	0					67					0					0					67
Issuance of common stock, consultants (in shares)	32,000															0
Stock-based compensation expense	0					2,210					0					0					2,210
Stock-based compensation expense (in shares)																					0
Balance at Dec. 31, 2013	85					541,420					(479,950)					(3,054)					58,501
Balance (in shares) at Dec. 31, 2013	84,659,000															(21,000)					84,638,219
Changes in Stockholders' Equity [Roll Forward]
Net loss	0					0					(44,058)					0					(44,058)
Issuance of common stock, 401(k) Plan employer match	1					943					0					0					944
Issuance of common stock, 401(k) employer match (in shares)	593,000															0					593,198
Exercise of common stock warrants	0					803					0					0					803
Exercise of common stock warrants (in shares)	285,000															0
Exercise of stock options for cash	0					30					0					0					30
Exercise of stock options for cash (in shares)	17,000															0					17,000
Issuance of common stock, consultants	0					38					0					0					38
Issuance of common stock, consultants (in shares)	18,000															0
Stock-based compensation expense	0					2,941					0					0					2,941
Stock-based compensation expense (in shares)	36,000
Balance at Dec. 31, 2014	$ 86					$ 546,175					$ (524,008)					$ (3,054)					$ 19,199
Balance (in shares) at Dec. 31, 2014	85,608,000															(21,000)					85,586,914