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

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

License, Clinical Trial and Sponsored Research Agreements (City of Hope - Sponsored Research and Clinical Trial Agreements) (Narrative) (Details)	1 Months Ended					3 Months Ended
	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Feb. 28, 2017 USD ($)	Mar. 31, 2015 USD ($) installment	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense						$ 11,618,000	$ 9,314,000
Sponsored Research and Clinical Trial Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense						1,842,000	1,349,000
Sponsored Research and Clinical Trial Agreements [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable					$ 2,000,000.0
Number of installments \| installment					4
Research and development expense						0	500,000
Sponsored Research and Clinical Trial Agreements [Member] \| CD123 Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fees paid				$ 19,450
Contribution toward patient costs				200,000
Contribution per patient				$ 97,490
Agreement term				3 years
Research and development expense						205,000	230,000
Sponsored Research and Clinical Trial Agreements [Member] \| IL13Ra2 Product [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fees paid	$ 29,000			$ 9,300
Milestones payable				200,000
Additional milestone payments				$ 100,000
Contribution per patient	100,000
Agreement term				3 years
Research and development expense						514,000	92,000
Annual maintenance fee payable	200,000
Sponsored Research and Clinical Trial Agreements [Member] \| CS1 Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable			$ 800,000
Research and development expense						175,000	0
Sponsored Research and Clinical Trial Agreements [Member] \| CS1 Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable			$ 2,400,000
Sponsored Research and Clinical Trial Agreements [Member] \| HER2 Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable		$ 29,375
Research and development expense						123,000	0
Sponsored Research and Clinical Trial Agreements [Member] \| HER2 Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable		$ 3,000,000.0
Sponsored Research and Clinical Trial Agreements [Member] \| PSCA Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable	33,000
Research and development expense						$ 50,000	$ 0
Sponsored Research and Clinical Trial Agreements [Member] \| PSCA Product or Process [Member] \| City of Hope National Medical Center ("COH") [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestones payable	$ 2,300,000