Revenue from United States and European Union Governments Contracts and Other Revenue (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. and E.U. governments contract revenue	$ 4,474	$ 11,212
July 2010 Contract (Ebola and Marburg IV)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. and E.U. governments contract revenue	2,614	11,163
August 2012 Contract (Intramuscular)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. and E.U. governments contract revenue	1,806
November 2012 SKIP-NMD Agreement (DMD)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. and E.U. governments contract revenue	54
Other Agreements
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. and E.U. governments contract revenue		$ 49