Summary of Significant Accounting Policies (Detail) $ in Thousands		1 Months Ended			3 Months Ended		7 Months Ended	9 Months Ended
	May. 19, 2014 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)
Components of collaboration revenue
Total collaboration revenue					$ 3,448	$ 39,575		$ 46,723	$ 39,575
Number of categories for milestones | item								3
License revenue
Components of collaboration revenue
Total collaboration revenue						38,373		$ 38,083	38,373
Research and development activity revenue
Components of collaboration revenue
Total collaboration revenue					1,594	1,200		6,768	1,200
API transfer revenue
Components of collaboration revenue
Total collaboration revenue					1,851			1,851
Joint operating committee revenue
Components of collaboration revenue
Total collaboration revenue					3	$ 2		21	$ 2
Novartis Pharma AG
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees received				$ 200,000
Patient enrollment-based milestone revenue achieved		$ 50,000	$ 50,000				$ 100,000
Novartis Pharma AG | Licensing and Commercialization Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees received	$ 200,000
Novartis Pharma AG | Licensing and Commercialization Agreement | Achievement of specified patient enrollment milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Patient enrollment-based milestone revenue achieved		$ 50,000	$ 50,000				$ 100,000
Recognized revenues					$ 3,400			$ 46,700