Collaborations and License Agreements - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended		58 Months Ended
	May. 31, 2005	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015
Bristol-Myers Squibb Company [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Company made an upfront payment	$ 1,000,000
Company made milestone payment		$ 1,500,000	$ 1,250,000
Company remaining milestone payment				$ 12,000,000
Obliged to make milestone payments				$ 14,750,000		$ 14,750,000
License expiration period				Through the later of ten years after first commercial sale of a licensed product in such country, expiration of the last licensed patent covering a licensed product.
Takeda Pharmaceutical Company Limited [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial term of research program				3 years
Date of termination agreement						Oct. 31, 2014
Takeda Pharmaceutical Company Limited [Member] | Maximum [Member] | Development Milestones [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Aggregate payment upon achievement of certain milestones				$ 500,000,000		$ 500,000,000
Takeda Pharmaceutical Company Limited [Member] | Maximum [Member] | Sales-based Milestones [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Aggregate payment upon achievement of certain milestones				$ 250,000,000		$ 250,000,000
University [Member] | Licensing Agreements [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License expiration period				Upon expiration of the patent rights or 15 years subsequent to the first sale of products developed through this License.
Other payments				$ 0	$ 0
University [Member] | Licensing Agreements [Member] | Minimum [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Annual spending requirements for development and commercialization of technology expense				$ 1,000,000