CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Revenue:
Government contracts	$ 9,246us-gaap_ContractsRevenue	$ 5,472us-gaap_ContractsRevenue
Research and development collaborations	631	1,990
Total revenue	9,877us-gaap_Revenues	7,462us-gaap_Revenues
Costs and expenses:
Cost of government contracts revenue	2,459us-gaap_ContractRevenueCost	3,021us-gaap_ContractRevenueCost
Research and development	25,888us-gaap_ResearchAndDevelopmentExpense	14,518us-gaap_ResearchAndDevelopmentExpense
General and administrative	5,843us-gaap_GeneralAndAdministrativeExpense	4,308us-gaap_GeneralAndAdministrativeExpense
Total costs and expenses	34,190us-gaap_CostsAndExpenses	21,847us-gaap_CostsAndExpenses
Loss from operations	(24,313)us-gaap_OperatingIncomeLoss	(14,385)us-gaap_OperatingIncomeLoss
Other income (expense):
Investment income	121us-gaap_InvestmentIncomeNet	12us-gaap_InvestmentIncomeNet
Interest expense	(36)us-gaap_InterestExpense	(52)us-gaap_InterestExpense
Other expense	(142)us-gaap_OtherNonoperatingIncomeExpense	0us-gaap_OtherNonoperatingIncomeExpense
Realized gains on marketable securities	0	615
Net loss	$ (24,370)us-gaap_NetIncomeLoss	$ (13,810)us-gaap_NetIncomeLoss
Basic and diluted net loss per share	$ (0.10)us-gaap_EarningsPerShareBasicAndDiluted	$ (0.07)us-gaap_EarningsPerShareBasicAndDiluted
Basic and diluted weighted average number of common shares outstanding (in shares)	241,223	208,927

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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