Revenue from United States and European Union Governments Contracts and Other Revenue (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		404 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Revenue [Line Items]
U.S. and E.U. governments contract revenue	$ 6,088	$ 4,474	$ 193,855
July 2010 Contract (Ebola and Marburg IV)
Revenue [Line Items]
U.S. and E.U. governments contract revenue	4,064	2,614
August 2012 Agreement (Intramuscular administration)
Revenue [Line Items]
U.S. and E.U. governments contract revenue		1,806
November 2012 SKIP-NMD Agreement (DMD)
Revenue [Line Items]
U.S. and E.U. governments contract revenue	1,365	54
Children's National Medical Center
Revenue [Line Items]
U.S. and E.U. governments contract revenue	$ 659