Revenue Recognition - Additional Information (Details) - USD ($)			3 Months Ended		6 Months Ended
	Apr. 29, 2019	Apr. 05, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Product revenue, net			$ 20,074,000	$ 0	$ 20,074,000	$ 0
Everest Medicines II Limited
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Upfront fees paid	$ 65,000,000.0
Milestone payment, achievement of FDA approval	60,000,000.0				500,000
Revenue recognized			$ 1,200,000
Milestone payment, development	180,000,000.0
Milestone payment, sales	$ 530,000,000.0
Product revenue, net					0	0
Everest Medicines II Limited | Minimum
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Royalty payments percentage	14.00%
Everest Medicines II Limited | Maximum
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Royalty payments percentage	20.00%
Janssen Biotech Inc.
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Milestone payment, sales		$ 15,000,000.0
Product revenue, net					$ 0	$ 0