Collaborative and Other Research and Development Contracts (Details) (USD $)	1 Months Ended			6 Months Ended	1 Months Ended				6 Months Ended	1 Months Ended		3 Months Ended		1 Months Ended
	Apr. 30, 2013	Nov. 30, 2011	May 31, 2010	Jun. 30, 2013	May 31, 2010 UAB [Member] Agreement	Feb. 24, 2011 U.S. Department of Health and Human Services [Member]	Sep. 30, 2009 U.S. Department of Health and Human Services [Member]	Jan. 31, 2007 U.S. Department of Health and Human Services [Member]	Jun. 30, 2013 U.S. Department of Health and Human Services [Member]	Jun. 30, 2006 Green Cross Corporation [Member]	Feb. 28, 2006 Mundipharma International Holdings Limited [Member]	Mar. 31, 2012 Mundipharma International Holdings Limited [Member]	Nov. 11, 2011 Mundipharma International Holdings Limited [Member]	May 31, 2010 AECOM and IRL [Member]	Jun. 30, 2000 AECOM and IRL [Member]
Collaborative and Other Research and Development Contracts (Textual) [Abstract]
Collaborative agreement contract value								$ 102,661,000
Collaborative agreement period of agreement								4 years
Collaborative agreement additional contract period							12 months
Collaborative agreement additional contract value						55,000,000	77,191,000
Collaborative agreement adjusted contract value									234,852,000
Contract term									24 months
Maximum amount of fund to be used from funding obligation under collaborative and other research and development contracts				12,800,000
License fee received										250,000
Up-front payment receivable amount											10,000,000
Deferred revenue up-front payment receivable											10,000,000
Deferred revenue initiation of clinical trial payment received											5,000,000
Potential milestone payments receivable													15,000,000
Unamortized deferred revenue, related to Amended and Restated Agreement												7,766,000
Unamortized deferred expenses, related to Amended and Restated Agreement												1,864,000
Deferred amount equal reduction to valuation												2,337,000
Milestone payment minimum															1,400,000
Milestone payment maximum															4,000,000
Annual license fees minimum															150,000
Annual license fees maximum															500,000
Advance notice period for termination of agreement															60 days
Reduction in the percentage of future payments			0.5
Stock issued during period value for modification of license agreement														5,911,000
Payments for modification of license agreement														90,000
Royalty reduction percentage of net proceeds		0.5
Number of agreements					2
Period of agreement					25 years
Renewable period of agreement					5 years
Written notice period license agreement termination related to the hepatitis C polymerase				90 days
Write-off of underlying asset				$ 4,995,000
License agreement termination date	Jul. 28, 2013