Significant Contracts, Grants, License and Royalty Agreements (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008	Dec. 31, 2012 AnGes Research and Development Agreement [Member]	Dec. 31, 2011 AnGes Research and Development Agreement [Member]	Dec. 31, 2010 AnGes Research and Development Agreement [Member]	Dec. 31, 2010 Naval Medical Research Center [Member]	Dec. 31, 2010 US Navy [Member]	Dec. 31, 2010 IPPOX Foundation [Member]	Dec. 31, 2012 National Institute of Allergy And Infectious Diseases [Member]	Dec. 31, 2011 National Institute of Allergy And Infectious Diseases [Member]	Dec. 31, 2010 National Institute of Allergy And Infectious Diseases [Member]	Dec. 31, 2008 National Institute of Allergy And Infectious Diseases [Member]	Dec. 31, 2012 NIAID [Member]	Dec. 31, 2011 NIAID [Member]	Dec. 31, 2010 NIAID [Member]	Dec. 31, 2007 NIAID [Member]	Dec. 31, 2012 CytRx [Member]
Significant Contracts Grants License And Royalty Agreements [Line Items]
Total cash Installments					$ 11.8
Amount related to the license fee and know-how recognized by company	10.7	25.3			0	0	2.0
Contract with NMRC								1.3	0.8	2.4
Revenue related to contract services delivered	3.9	2.7						0.7	0.8	2.4
Amount of grants awarded														2.0				6.0
Period of grant														2 years				3 years
Revenue recognized from grants											0	0.2	0.7		0	0.9	1.5
Extended period of grant															4 years
License fees	2.6	2.0	0.1																3.8
Significant Contracts, Grants, License and Royalty Agreements (Textual) [Abstract]
Paid for Nonrefundable upfront license fee	25.0
Milestone payment upon finalization of the trial design	10.0
Additional cash payments for achievement through commercial launch	95.0
Revenue related to drug product delivered	1.8	0
Purchases of restricted shares of the Company's common stock	10.85
Non-refundable cash payments	11.8
Excess amount of project cost	22.6
Equity installment received by the company upon execution of the R&D Agreement	6.90			3.95
Restricted common stock issued under stock purchase agreement for the first equity installment	1,061,538			1,109,550
Per share in exchange for the first installment	$ 6.50			$ 3.56
Percentage of initial upfront monetary payments	10.00%
Additional milestone payments related to in-license agreements	15.1
Payments related to the Company's independent programs	$ 7.2