License, Collaboration and Other Significant Agreements - Janssen Pharmaceutica NV Research and License Agreement Narrative (Details) - Development And Commercialize Research And License Agreement - USD ($)	Feb. 09, 2017	Mar. 31, 2017
Johnson & Johnson Innovation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrant to purchase common stock (in shares)	509,611
Exercise price (in dollars per share)	$ 9.81
Fair value of warrant at issuance		$ 3,400,000
Janssen Pharmaceutica NV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, term	3 years
Upfront payment made in cash	$ 1,000,000
Warrant to purchase common stock (in shares)	509,611
Potential aggregate payment received	$ 16,500,000
Potential milestone revenue (up to)	$ 215,000,000
Collaboration agreement, expiration period	10 years
Collaboration agreement, notice period for termination	180 days