Collaboration Agreement - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended
	May 28, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license agreement, nature and purpose	Under this agreement, the Company and ThromboGenics are collaborating to identify protein or peptide therapeutics that directly modulate any of a specified set of targets in a novel pathway in retinal disease.
Collaboration and license agreement, date				May 28, 2013
Collaboration and license arrangement, rights and obligations	The Company has granted ThromboGenics an exclusive, sublicensable, royalty-bearing license under the Company's rights in these patent rights and know-how, as well as under any other patent rights and know-how that the Company controls during the research term that are necessary for ThromboGenics to perform its obligations to research, develop, manufacture and commercialize collaboration products.
Upfront payment received				$ 1,750,000
Milestone payments receivable		25,000,000		25,000,000
Collaboration revenue		761,000	202,000	1,329,000	202,000
Milestone or royalty payments received
Upon the achievement of specified preclinical and clinical development milestone events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable		10,000,000		10,000,000
Upon the achievement of specified regulatory milestone events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable		$ 15,000,000		$ 15,000,000