Accounts Receivable (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 1,591,000	$ 6,937,000
MedImmune upfront payment received	5,000,000
Royalties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	1,164,000	781,000
Collaborators [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	227,000	6,125,000
Research grants [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	196,000	12,000
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 4,000	$ 19,000