Clinical Trial and Sponsored Research Agreements (Sponsored Research and Clinical Trial Agreements) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 15,419	$ 14,083	$ 46,872	$ 36,603
Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	1,836	1,756	4,884	4,858
City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	0	0	0	0
Mayo Clinic [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	269	231	731	464
CD123 (MB-102) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	62	24	165	250
IL13Ra2 (MB-101) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	192	199	654	992
CS1 (MB-104) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	187	138	287	510
HER2 (MB 103) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	691	319	1,233	473
PSCA (MB-105) [Member] | City of Hope National Medical Center ("COH") [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	27		77	69
Research and Development (Income) Expenses		23
CD20 (MB-106) [Member] | Fred Hutchinson Cancer Center [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	132	492	978	1,490
ST. Jude - XSCID [Member] | St. Jude Children's Research Hospital [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	184	330	402	610
RAG1 SCID (MB-110) [Member] | Leiden University Medical Centre [Member] | Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ 92	$ 0	$ 357	$ 0