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

Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Narrative) (Details)

Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 11, 2020	Jul. 22, 2016	Jun. 30, 2020	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value of securities available for future issuance				$ 32,600		$ 32,600
Common stock, shares authorized				85,000,000		85,000,000		85,000,000
Common stock par value (in dollars per share)				$ 0.0001		$ 0.0001		$ 0.0001
Common stock, shares issuable				65,810		65,810		1,206,667
Aggregate value of shares subscribed				$ 235		$ 235		$ 4,923
Common stock, shares issued				60,164,539		60,164,539		39,403,519
Proceeds from issuance of common shares						$ 37,230	$ 31,625
Aggregate fees of stock issuance						$ 2,282	$ 2,088
Predetermined offering period, lower fair market value percentage						85.00%
Number of shares purchased under ESPP				72,505		140,856
Shares available for future sale under ESPP				259,144		259,144
Proceeds from employee stock purchase plan				$ 200		$ 300
Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share of equity or debt financing used to calculate equity fee or stock issuance to maintain parity (as a percent)		2.50%
At the Market Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum value of shares authorized to sell at offering									$ 75,000
Agent commission (as a percent)									3.00%
Issuance of common shares (in shares)						7,200,000	3,500,000
Share price				$ 3.56		$ 3.56	$ 6.42
Proceeds from issuance of common shares						$ 25,600	$ 22,500
Aggregate fees of stock issuance						500	500
Proceeds from issuance of Common Stock, net of offering costs						$ 25,100	$ 22,000
At the Market Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares (in shares)						183,215	87,656
Share price				3.56		$ 3.56	$ 6.42
March 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares - Founders Agreement (in shares)					31,220
Share of equity or debt financing used to calculate equity fee or stock issuance to maintain parity (as a percent)					2.50%
Proceeds from issuance of common shares					$ 5,000
June 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares - Founders Agreement (in shares)			22,170
Share of equity or debt financing used to calculate equity fee or stock issuance to maintain parity (as a percent)			2.50%
Proceeds from issuance of common shares			$ 3,000
September 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares - Founders Agreement (in shares)						64,015	64,015
Share of equity or debt financing used to calculate equity fee or stock issuance to maintain parity (as a percent)						2.50%	2.50%
Common stock, shares issuable							65,810
Proceeds from issuance of common shares						$ 18,000	$ 18,000
Public Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares (in shares)	10,769,231
Share price				$ 3.25		$ 3.25
Proceeds from issuance of common shares						$ 37,200
Aggregate fees of stock issuance						2,300
Proceeds from issuance of Common Stock, net of offering costs						$ 34,900
Number of stock options exercised						686,373
Public Offering [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares that can be purchased under an agreement	1,615,384
Public Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common shares - Founders Agreement (in shares)			286,390
Share of equity or debt financing used to calculate equity fee or stock issuance to maintain parity (as a percent)			2.50%
Proceeds from issuance of common shares			$ 37,200
Class A Common Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares converted							(137,608)
Common stock, shares issued				845,385		845,385		845,385
General and Administrative [Member] \| March 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses from related party transaction					$ 100	$ 100
General and Administrative [Member] \| June 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses from related party transaction						100
General and Administrative [Member] \| September 2020 Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses from related party transaction						500	$ 500
General and Administrative [Member] \| Public Offering [Member] \| Fortress Biotech, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses from related party transaction						$ 900