Subsequent Events (Details) - Subsequent Event - USD ($) $ in Millions	Apr. 29, 2019	Apr. 05, 2019
Janssen Biotech Inc.
Subsequent Event [Line Items]
Potential milestone payment		$ 15
Everest Medicines II Limited
Subsequent Event [Line Items]
License agreement, upfront payment	$ 65
Everest Medicines II Limited | Minimum
Subsequent Event [Line Items]
Royalty payments, percentage of net sales	14.00%
Everest Medicines II Limited | Maximum
Subsequent Event [Line Items]
Royalty payments, percentage of net sales	20.00%
Everest Medicines II Limited | Upon FDA Approval
Subsequent Event [Line Items]
Potential milestone payment	$ 60
Everest Medicines II Limited | Upon Achievement of Additional Development Milestones
Subsequent Event [Line Items]
Potential milestone payment	180
Everest Medicines II Limited | Upon Achievement of Sales Milestones
Subsequent Event [Line Items]
Potential milestone payment	$ 530