U.S. Government Contracts (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenue for U.S Government Contract
U.S. government contract revenue	$ 11,207	$ 11,585	$ 22,419	$ 25,881
June 2010 Agreement (H1N1) [Member]
Revenue for U.S Government Contract
U.S. government contract revenue		883		3,207
July 2010 Agreement (Ebola and Marburg) [Member]
Revenue for U.S Government Contract
U.S. government contract revenue	11,171	10,585	22,334	22,490
Other Agreements [Member]
Revenue for U.S Government Contract
U.S. government contract revenue	$ 36	$ 117	$ 85	$ 184