Clinical Trial and Sponsored Research Agreements (Sponsored Research and Clinical Trial Agreements) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	$ 9,477	$ 15,419	$ 34,313	$ 46,872
Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	364	1,836	3,739	4,884
Mayo Clinic [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense		269	551	731
CD123 (MB-102) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	23	63	23	165
IL13Ra2 (MB-101) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	180	192	817	654
CS1 (MB-104) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense		187	188	287
HER2 (MB 103) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense		691	0	1,233
PSCA (MB-105) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense		27	44	77
CD20 (MB-106) [Member] | Fred Hutchinson Cancer Center [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	142	132	1,239	978
RAG1 SCID (MB-110) [Member] | Leiden University Medical Centre [Member] | Sponsored Research and Clinical Trial Agreements [Member]
License, Clinical Trial and Sponsored Research Agreements
Research and development expense	$ 125	$ 92	$ 349	$ 357