License and Collaboration Agreements - Narrative (Details)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	60 Months Ended	87 Months Ended
	Jul. 31, 2008 USD ($)	Sep. 30, 2015 USD ($) license_agreement	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) license_agreement	Sep. 30, 2014 USD ($)	Dec. 31, 2009 USD ($)	Sep. 30, 2015 USD ($) license_agreement	Sep. 30, 2015 USD ($) license_agreement	Oct. 31, 2010 license_agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development		$ 8,263,000	$ 5,988,000	$ 24,209,000	$ 13,949,000
GLAAS Discovery Platform [Member] | Collaborative Arrangement, Product [Member] | Sanofi [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized		1,000,000	3,500,000	1,000,000
GLAAS Discovery Platform [Member] | Collaborative Arrangement, Product [Member] | Sanofi [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables		167,000,000		167,000,000			$ 167,000,000	$ 167,000,000
GLA [Member] | Collaborative Arrangement, Product [Member] | MedImmune LLC [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized		$ 2,500,000	$ 0	$ 2,500,000	$ 1,000,000		$ 8,000,000
Number of license agreements | license_agreement									3
Number of license agreements in full force and effect | license_agreement		2		2			2	2
GLA [Member] | Collaborative Arrangement, Product [Member] | MedImmune LLC [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables		$ 72,500,000		$ 72,500,000			$ 72,500,000	$ 72,500,000
GLA [Member] | Collaborative Arrangement, Product [Member] | MedImmune LLC [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone receivables		62,900,000		62,900,000			62,900,000	62,900,000
GLA [Member] | Collaborative Arrangement [Member] | Infectious Disease Research Institute [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development								2,300,000
GLA [Member] | Collaborative Arrangement [Member] | Infectious Disease Research Institute [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Value of common stock issued for license	$ 59,000
First GLA Product [Member] | Collaborative Arrangement [Member] | Infectious Disease Research Institute [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments		2,400,000		2,400,000			2,400,000	2,400,000
Subsequent GLA Products [Member] | Collaborative Arrangement [Member] | Infectious Disease Research Institute [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments		1,250,000		1,250,000			1,250,000	1,250,000
Dendritic Cell-targeted Theraputic and Prophylactic Immunization Strategies [Member] | Collaborative Arrangement [Member] | California Institute of Technology [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Value of common stock issued for license						$ 25,000
Dendritic Cell-targeted Theraputic and Prophylactic Immunization Strategies [Member] | Collaborative Arrangement [Member] | California Institute of Technology [Member] | Maximum [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments		1,600,000		1,600,000			1,600,000	1,600,000
Herpes Simplex Virus Immune Therapy [Member] | Collaborative Arrangement, Product [Member] | Sanofi Pasteur [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Outstanding receivable		177,000		177,000			$ 177,000	$ 177,000
Herpes Simplex Virus Immune Therapy [Member] | Collaborative Arrangement, Product [Member] | Sanofi Pasteur [Member] | Collaboration Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized		$ 329,000		$ 3,900,000