License Agreement - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 19, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Acquired in-process research and development		$ 10,000	$ 51,775	$ 215,250	$ 109,975
Milestone payment capitalized as intangible asset		$ 3,340,242		3,340,242			$ 3,292,501
Pharma Mar, S.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalty fees percentage, maximum	30.00%
Upfront Payments | Pharma Mar, S.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Acquired in-process research and development				$ 200,000
Accelerated And/Or Full Regulatory Approval Milestone Payments | Pharma Mar, S.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones not yet incurred	$ 150,000
Commercial Milestone Payments | Pharma Mar, S.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones not yet incurred	$ 550,000
FDA Approval Of Zepzelca
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment capitalized as intangible asset						$ 100,000
FDA Approval Of Zepzelca | Milestone Payment | Pharma Mar, S.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment capitalized as intangible asset						$ 100,000