Revenue from United States Government Contracts and Other Revenue (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended			401 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue	$ 2,626	$ 4,168	$ 2,951	$ 4,474	$ 7,336	$ 7,574	$ 11,207	$ 11,212	$ 14,219	$ 37,329	$ 46,990	$ 187,767
July 2010 Agreement (Ebola and Marburg IV)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue									9,064	36,557	42,875
June 2010 Agreement (H1N1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue									427		3,490
May 2009 Agreement (H1N1)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue											516
August 2012 Agreement (Intramuscular administration)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue									2,791	673
November 2012 SKIP-NMD Agreement (DMD)
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue									1,263
Children's National Medical Center
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue									674
Other Agreements
Accounts, Notes, Loans and Financing Receivable [Line Items]
U.S. government contract revenue										$ 99	$ 109