Segment Information - Research and development costs and an allocation of indirect research and development costs to each program (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) segment	Mar. 31, 2025 USD ($)
Segment Information
Number of operating segments | segment	1
Number of reportable segments | segment	1
Total R&D Expense	$ 73,001	$ 52,614
Single reportable segment
Segment Information
Total R&D Expense	73,001	52,614
Single reportable segment | Barzolvolimab/Anti-KIT Program
Segment Information
Total R&D Expense	62,164	39,703
Single reportable segment | CDX-622
Segment Information
Total R&D Expense	4,294	5,451
Single reportable segment | Other Programs
Segment Information
Total R&D Expense	$ 6,543	$ 7,460