Quarterly report pursuant to Section 13 or 15(d)

Clinical Trial and Sponsored Research Agreements (Other - Sponsored Research and Clinical Trial Agreements) (Narrative) (Details)

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Clinical Trial and Sponsored Research Agreements (Other - Sponsored Research and Clinical Trial Agreements) (Narrative) (Details) - USD ($)
$ in Thousands
1 Months Ended 3 Months Ended
Sep. 08, 2021
Jul. 03, 2017
Jan. 31, 2022
Jun. 30, 2021
Nov. 30, 2020
Mar. 31, 2022
Mar. 31, 2021
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Research and development expense           $ 16,289 $ 11,618
Sponsored Research and Clinical Trial Agreements [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Research and development expense           1,592 1,842
Fred Hutchinson Cancer Research Center [Member] | Sponsored Research and Clinical Trial Agreements [Member] | CD20 (MB-106) [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Milestones payable   $ 5,300          
Additional milestone payments     $ 2,200   $ 1,800    
Research and development expense           488 671
St. Jude Children's Research Hospital [Member] | Sponsored Research and Clinical Trial Agreements [Member] | ST. Jude - XSCID [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Research and development expense           124 104
Mayo Clinic [Member] | Sponsored Research and Clinical Trial Agreements [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Research and development expense           231 0
Mayo Clinic [Member] | Sponsored Research and Clinical Trial Agreements [Member] | Car T Technology [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Milestones payable       $ 2,100      
Agreement term       2 years      
Leiden University Medical Centre [Member] | Sponsored Research and Clinical Trial Agreements [Member] | RAG1 SCID (MB-110) [Member]              
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]              
Annual maintenance fee payable $ 500            
Research and development expense           $ 127 $ 0
Agreement term 5 years