Mustang Bio, Inc. Quarterly report pursuant to Section 13 or 15(d)

License, Clinical Trial and Sponsored Research Agreements (City of Hope - Licenses) (Narrative) (Details)

License, Clinical Trial and Sponsored Research Agreements (City of Hope - Licenses) (Narrative) (Details) € in Millions						1 Months Ended				3 Months Ended		9 Months Ended
	Sep. 08, 2021 USD ($)	Apr. 01, 2021 USD ($) Milestone	Aug. 23, 2019 USD ($) Milestone	Jul. 03, 2017 USD ($) Milestone	May 31, 2017 USD ($) Milestone	Oct. 31, 2020 USD ($) Milestone	Oct. 31, 2020 EUR (€) Milestone	May 31, 2017 USD ($) Milestone	Feb. 28, 2017 USD ($) Milestone	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development - licenses acquired										$ 630,000	$ 287,000	$ 1,630,000	$ 1,837,000
License Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development - licenses acquired										630,000	287,000	1,630,000	1,837,000
License Agreements [Member] \| Leiden University Medical Centre [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fees paid	$ 400,000
Research and development - licenses acquired										350,000	0	350,000	0
License Agreements [Member] \| Leiden University Medical Centre [Member] \| Achievement of Certain Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable	$ 31,000,000
License Agreements [Member] \| CD123 (MB-102) [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of milestones \| Milestone									8
Milestones payable									$ 14,500,000
Research and development - licenses acquired										0	0	250,000	334,000
License Agreements [Member] \| IL13Ra2 (MB-101) [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of milestones \| Milestone									8
Milestones payable									$ 14,500,000
Research and development - licenses acquired										0	0	0	333,000
License Agreements [Member] \| Spacer [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development - licenses acquired										0	0	0	333,000
License Agreements [Member] \| PSCA (MB-105) [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual maintenance fee payable								$ 50,000
Upfront fees paid								$ 300,000
Number of milestones \| Milestone								10
Milestones payable								$ 14,900,000
Research and development - licenses acquired										250,000	0	250,000	0
License Agreements [Member] \| XSCID (MB-107 and MB-207) [Member] \| CSL Behring (Calimmune) [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fees paid			$ 200,000
Number of milestones \| Milestone			3
Milestones payable			$ 1,200,000
Research and development - licenses acquired										30,000	170,000	30,000	170,000
License Agreements [Member] \| HER2 (MB 103) [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual maintenance fee payable					$ 50,000
Upfront fees paid					$ 600,000
Number of milestones \| Milestone					10
Milestones payable					$ 14,900,000
Research and development - licenses acquired										0	0	0	250,000
License Agreements [Member] \| CD20 (MB-106) [Member] \| Fred Hutchinson Cancer Research Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual maintenance fee payable				$ 50,000
Upfront fees paid				$ 300,000
Number of milestones \| Milestone				11
Milestones payable				$ 39,100,000
Research and development - licenses acquired										0	0	0	300,000
License Agreements [Member] \| Car T Technology [Member] \| Mayo Clinic [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Annual maintenance fee payable		$ 25,000
Upfront fees paid		$ 800,000
Number of milestones \| Milestone		11
Milestones payable		$ 92,600,000
Research and development - licenses acquired										0	0	750,000	0
License Agreements [Member] \| LentiBOOST Technology [Member] \| SIRION Biotech [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fees paid						$ 100,000	€ 0.1
Research and development - licenses acquired										$ 0	$ 117,000	$ 0	$ 117,000
License Agreements [Member] \| LentiBOOST Technology [Member] \| SIRION Biotech [Member] \| Achievement of Certain Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of milestones \| Milestone						5	5
Milestones payable						$ 5,400,000	€ 4.7
License Agreements [Member] \| LentiBOOST Technology [Member] \| SIRION Biotech [Member] \| Worldwide net Sales of Licensed Products [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of milestones \| Milestone						3	3
Milestones payable						$ 4,000,000.0	€ 3.5