Annual report pursuant to Section 13 and 15(d)

Sponsored Research and Clinical Trial Agreements (Schedule of Research and Development for Sponsored Research and Clinical Trial Agreements) (Details)

v3.21.1
Sponsored Research and Clinical Trial Agreements (Schedule of Research and Development for Sponsored Research and Clinical Trial Agreements) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Research and Development Expense $ 64,109 $ 81,326
Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 7,717 6,143
AAV Gene Therapies [Member] | Research and Clinical Trial Agreements [Member] | Aevitas [Member]    
Research and Development Expense 948 1,133
City of Hope (COH) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 500 2,000
City of Hope (COH) [Member] | MB-102 (CD 123 CAR T for AML) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 433 1,202
City of Hope (COH) [Member] | MB-101 (IL13R2 CAR T for Glioblastoma) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 530 876
City of Hope (COH) [Member] | Manufacturing License [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 0 457
City of Hope (COH) [Member] | MB-104 (CS1 CAR T) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 885 0
City of Hope (COH) [Member] | MB-103 (HER2 CAR T) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 1,519 0
City of Hope (COH) [Member] | MB-105 (PSCA CAR T) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 204 0
Beth Israel Deaconess Medical Center Inc. [Member] | CRISPR (multiple programs) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 0 69
St. Jude Children's Research Hospital [Member] | MB-107 (XSCID) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 1,842 777
Fred Hutchinson Cancer Research Center [Member] | MB-106 (CD20 CAR T) [Member] | Research and Clinical Trial Agreements [Member] | Mustang [Member]    
Research and Development Expense 1,804 762
University of Massachusetts [Member] | AAV Gene Therapies [Member] | Research and Clinical Trial Agreements [Member] | Aevitas [Member]    
Research and Development Expense 381 0
University of Pennsylvania [Member] | AAV Gene Therapies [Member] | Research and Clinical Trial Agreements [Member] | Aevitas [Member]    
Research and Development Expense 567 1,067
Duke University School of Medicine [Member] | AAV Gene Therapies [Member] | Research and Clinical Trial Agreements [Member] | Aevitas [Member]    
Research and Development Expense $ 0 $ 66