Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jun. 30, 1998 USD ($)	Dec. 31, 2016 USD ($) Agreement	Dec. 31, 2015 USD ($)
Kowa Pharmaceuticals America Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable up-front payment		$ 5,000,000
Kowa Pharmaceuticals America Inc [Member] \| Initiation or Achievement [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments		$ 200,000,000
Janssen Pharmaceutical NV [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales		8.00%
Janssen Pharmaceuticals, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement date		Jun. 30, 2010
Number of development and license agreements \| Agreement		2
DiaTex, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement date		Jun. 30, 1998
Monthly license fees	$ 2,000
Potential future development payments	$ 800,000
Development payment		$ 0	$ 0
Royalty payment		$ 0	$ 0