Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - Collaborative Arrangement [Member] - USD ($) $ in Millions	1 Months Ended
	Feb. 29, 2016	Jan. 31, 2016
Technology Access Fee [Member] | Medivation Inc And Astellas Pharma Inc Member
Subsequent Event [Line Items]
Collaboration agreement upfront payment		$ 6.0
Pre-Clinical Milestone Payment Member | Medivation Inc And Astellas Pharma Inc Member
Subsequent Event [Line Items]
Collaboration arrangements, revenue		6.0
Development Funding [Member] | Medivation Inc And Astellas Pharma Inc Member
Subsequent Event [Line Items]
Collaboration arrangements, revenue		$ 10.0
Pre-Clinical Milestone Payments [Member] | Merck And Co Inc [Member]
Subsequent Event [Line Items]
Collaboration arrangements, revenue	$ 12.0
Technology Access Fees and Development Funding [Member] | Merck And Co Inc [Member]
Subsequent Event [Line Items]
Collaboration agreement upfront payment	$ 12.0