Acquisition of Pelican Therapeutics (Future Milestone Payments) (Details) - Pelican Therapeutics, Inc. $ in Millions	Dec. 31, 2019 USD ($)
Future milestone payment upon Pelican's dosing of the first patient in its first Phase 1 trial for an oncology indication	$ 2.0
Future milestone payment upon Pelican's dosing of the first patient in its first Phase 2 trial for an oncology indication	1.5
Future milestone payment upon successful outcome of the first Phase 2 trial for an oncology indication	3.0
Future milestone payment upon Pelican's dosing of the first patient in its first Phase 3 trial for an oncology indication	6.0
Future milestone payment upon Pelican's dosing of the first patient in its first Phase 3 trial for a non- oncology indication	3.0
Future milestone payment upon successful outcome of the first Phase 3 trial for an oncology indication	7.5
Future milestone payment upon successful outcome of the first Phase 3 trial for a non-oncology indication	3.0
Future milestone payment upon acceptance of a Biologics License Application (BLA) submission for an oncology indication	7.5
Future milestone payment upon acceptance of a BLA submission for a non-oncology indication	3.0
Future milestone payment upon first product indication approval in the United States or Europe for an oncology indication	7.5
Future milestone payment upon first product indication approval in the United States or Europe for a non- oncology indication	$ 3.0
Discount rate used for calculation of fair value of contingent consideration	7.83%