Contract Revenue - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		398 Months Ended	1 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended			1 Months Ended	3 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Nov. 30, 2012 European Union SKIP-NMD Agreement	Sep. 30, 2013 European Union SKIP-NMD Agreement	Sep. 30, 2013 July 2010 Contract (Ebola and Marburg IV)	Sep. 30, 2012 July 2010 Contract (Ebola and Marburg IV)	Sep. 30, 2013 July 2010 Contract (Ebola and Marburg IV) Segment	Sep. 30, 2012 July 2010 Contract (Ebola and Marburg IV)	Sep. 30, 2013 Phase two three four Marburg	Aug. 29, 2012 August 2012 Contract (Intramuscular administration)	Sep. 30, 2013 Other Agreements	Sep. 30, 2012 Other Agreements	Sep. 30, 2013 Other Agreements	Sep. 30, 2012 Other Agreements	Jul. 31, 2013 Children's National Medical Center	Sep. 30, 2013 Children's National Medical Center	Sep. 30, 2013 Children's National Medical Center
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of segments										4
Period of performance spanning								4 years		4 years
Estimated funding												$ 84,400,000
Advance payments received on contracts awarded							1,300,000						3,900,000
U.S. governments contract revenue	4,168,000	7,574,000	11,593,000	29,993,000	185,141,000			2,444,000	7,511,000	7,134,000	29,844,000				13,000	427,000	99,000		674,000	674,000
Aggregate amount for research granted						2,500,000	600,000											1,300,000
Aggregate potential funding period						3 years
Deferred revenue							$ 700,000