Astellas In-License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended	6 Months Ended
	Mar. 31, 2015	Jun. 30, 2015	Jun. 30, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase of technology license with common stock		$ 775,000	$ 0
Astellas In-License Agreements [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Restricted stock issued, shares	861,216
Potential future milestone payments		100,000,000
Astellas In-License Agreements [Member] | Collaborative Arrangement [Member] | Research and development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash payment for license agreement	$ 250,000
Purchase of technology license with common stock		$ 775,094