Liquidity Risks and Management's Plans (Details) $ / shares in Units, $ in Thousands			6 Months Ended
	Jul. 29, 2015 USD ($)	Jul. 22, 2015 USD ($) Amendment $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Jul. 09, 2015 USD ($)	Dec. 31, 2014 USD ($) shares	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Liquidity Risks and Management's Plans [Abstract]
Cash and cash equivalents			$ 26,091		$ 44,711	$ 65,557	$ 86,283
Long-term debt			30,000		$ 30,000
Liquidity Risk and Managements Plans [Line Items]
Prepayment of principal amount of loan outstanding			$ 10,000
Cash interest rate under loan facility (in hundredths)			8.75%
Market price of common stock (in dollars per share) | $ / shares			$ 1.00
Number of days below market price threshold			30 days
Number of days required to remain above market price threshold			10 days
Number of days to achieve compliance after delisting notice			180 days
Number of days of extension based upon criteria met			180 days
Number of warrant shares potentially issuable (in shares) | shares			13,200,000
Common stock, shares authorized (in shares) | shares			250,000,000		250,000,000
Common stock available for future issuance (in shares) | shares			136,000,000
Deerfield Management Company [Member]
Liquidity Risk and Managements Plans [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares			$ 2.81
Number of warrant shares potentially issuable (in shares) | shares			7,000,000
ATM Program [Member]
Liquidity Risk and Managements Plans [Line Items]
Maximum value of potential common stock available for issue			$ 23,000
Percentage sales commission on shares (in hundredths)			3.00%
Battelle - 2014 Collaboration Agreement [Member]
Liquidity Risk and Managements Plans [Line Items]
Research and development, expected planned cost for stage 2 and 3			$ 6,000
Research and development, percentage of expected planned cost for stage 2 and 3 (in hundredths)			50.00%
Deferred payments interest bearing threshold			90 days
Deferred payments, outstanding interest rate (in hundredths)			12.00%
Deferred payments deferment limit, period			30 days
Deferred costs			$ 1,500
Maximum period to defer payment			12 months
Battelle - 2014 Collaboration Agreement [Member] | Maximum [Member]
Liquidity Risk and Managements Plans [Line Items]
Research and development, planned cost for stage 2 and 3			$ 11,850
Expected deferred payments amount			$ 4,000
Subsequent Event [Member]
Liquidity Risk and Managements Plans [Line Items]
Gross proceeds from issuance of common stock		$ 40,250
Net proceeds from issuance of common stock		37,600
Non-cash consideration received		$ 5,000
Common stock, shares authorized (in shares) | shares		250,000,000
Common stock issued and outstanding or reserved for future issuance (in shares) | shares		246,900,000
Subsequent Event [Member] | Deerfield Management Company [Member]
Liquidity Risk and Managements Plans [Line Items]
Prepayment of principal amount of loan outstanding		$ 5,000
Subsequent Event [Member] | Deerfield Debt Restructuring [Member]
Liquidity Risk and Managements Plans [Line Items]
Prepayment of principal amount of loan outstanding	$ 12,500	5,000
Principal amount of loan outstanding payable in February 2018		12,500		$ 12,500
Principal amount of loan outstanding payable in February 2019		12,500		$ 12,500
Investments in public offering		5,000
Prepayment of future interest obligations		$ 5,000
Cash interest rate under loan facility (in hundredths)		8.25%
Number of amendments to loan agreement | Amendment		2
Non-cash consideration received		$ 5,000
Series A and B Units [Member] | Subsequent Event [Member]
Liquidity Risk and Managements Plans [Line Items]
Number of warrants issued (in shares) | shares		67,100,000
Exercise price of warrants (in dollars per share) | $ / shares		$ 0.70
Series A Units [Member] | Subsequent Event [Member]
Liquidity Risk and Managements Plans [Line Items]
Sale of unit price per unit (in dollars per share) | $ / shares		$ 0.60
Series B Units [Member] | Subsequent Event [Member]
Liquidity Risk and Managements Plans [Line Items]
Number of warrants issued (in shares) | shares		42,000,000
Number of warrants required to purchase one share of common stock (in shares) | shares		1
Sale of unit price per unit (in dollars per share) | $ / shares		$ 0.60
February 2011 Warrants [Member]
Liquidity Risk and Managements Plans [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares			$ 1.50
Number of warrant shares potentially issuable (in shares) | shares			4,600,000
Warrants expiration date			Feb. 22, 2016
February 2011 Warrants [Member] | Maximum [Member]
Liquidity Risk and Managements Plans [Line Items]
Potential proceeds of warrants if exercised			$ 900
February 2011 Warrants [Member] | Subsequent Event [Member]
Liquidity Risk and Managements Plans [Line Items]
Exercise price of warrants (in dollars per share) | $ / shares		$ 0.19