Summary of Significant Accounting Policies - Collaboration Revenue (Details) $ in Thousands	1 Months Ended				3 Months Ended		6 Months Ended		22 Months Ended
	Jun. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2014 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) category	Jun. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)
Components of collaboration revenue
Total collaboration revenue					$ 1,661	$ 28,198	$ 3,323	$ 43,919
Number of categories for milestones | category							3
License revenue
Components of collaboration revenue
Total collaboration revenue					0	22,937	$ 0	22,937
Research and development activity revenue
Components of collaboration revenue
Total collaboration revenue					1,658	5,150	3,316	6,425
API transfer revenue
Components of collaboration revenue
Total collaboration revenue					0	102	0	14,545
Joint operating committee revenue
Components of collaboration revenue
Total collaboration revenue					$ 3	$ 9	$ 7	$ 12
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]
Enrollment-based milestone revenue achieved	$ 30,000	$ 50,000	$ 50,000	30,000					$ 130,000
Milestone payment received				$ 130,000					$ 130,000