License Revenue and Reimbursable Expenses (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jul. 23, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License revenue		$ 77,826,000	$ 46,766,000	$ 175,862,000	$ 117,652,000
Reimbursable expenses		15,400,000	0	15,400,000	0
License revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License revenue		$ 27,414,000	$ 0	$ 27,414,000	$ 0
Menarini Group
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reimbursement of cost	$ 111,500,000
License fee	30,000,000.0
Upfront payment received	30,000,000.0
License	27,400,000
Inventory	2,600,000
Menarini Group | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development and regulatory milestone payments receivable	20,000,000.0
Sales milestone payments receivable	$ 300,000,000.0