Collaboration Agreement - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized under collaboration agreement		$ 618,000		$ 618,000
Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement upfront payment	5,800,000
Maximum success-based milestone payments	17,000,000
Revenue recognized under collaboration agreement		618,000	0	618,000	0
Deferred revenue recorded under collaboration agreement	5,100,000	5,100,000		5,100,000
Deferred revenue recognized under collaboration agreement as revenue within one year				$ 2,000,000