Fortress Biotech, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Capital Raises) (Narrative) (Details)

Stockholders' Equity (Capital Raises) (Narrative) (Details)									1 Months Ended					3 Months Ended		6 Months Ended
	May 05, 2023 USD ($)	Feb. 10, 2023 USD ($) item $ / shares shares	Jan. 27, 2023 $ / shares shares	Dec. 30, 2022 USD ($) shares	Dec. 16, 2022 USD ($)	Oct. 11, 2022 USD ($) $ / shares shares	Apr. 23, 2021 USD ($)	Oct. 23, 2020 USD ($)	May 31, 2023 USD ($) $ / shares shares	Apr. 30, 2023 USD ($) $ / shares shares	Feb. 28, 2023 USD ($) $ / shares shares	Nov. 30, 2020 USD ($)	Jul. 31, 2018	Jun. 30, 2023 USD ($) $ / shares shares	Feb. 28, 2023 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 13, 2023 $ / shares	Apr. 11, 2023 USD ($)	Dec. 31, 2022 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares				4,900,000							1,180,000
Number of shares called by warrants \| shares											1				1
Stock offering, price per share \| $ / shares											$ 5.25				$ 5.25
Common Stock, par value \| $ / shares														$ 0.001		$ 0.001				$ 0.001
Exercise price of warrants \| $ / shares																		$ 0.5424
Sale of stock, net proceeds				$ 150,000,000							$ 6,700,000
Proceeds from Issuance of Common Stock																$ 1,168,000	$ 5,527,000
Gain (loss) on common stock warrant liabilities														$ 512,000		(6,166,000)
Pre-Funded Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued \| shares											248,572
Stock offering, price per share \| $ / shares											$ 5.2499				$ 5.2499
Series A Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares											1,428,572
Series B Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares											1,428,572
Checkpoint \| Common Stock Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Gain (loss) on common stock warrant liabilities					$ (1,200,000)											$ 7,200,000
Net proceeds					$ 6,700,000
Checkpoint \| Series A Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration term										5 years
Checkpoint \| Series B Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration term										18 months
Avenue Therapeutics, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares			448,000
Shares issued \| shares						3,636,365
Number of warrants to purchase shares \| shares						545,454
Unit Price Per Share \| $ / shares			$ 1.55
Number of common stock (in units)						1
Number of warrants (in units)						1
Proceeds from Issuance of Common Stock						$ 10,400,000
Avenue Therapeutics, Inc [Member] \| InvaGen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares repurchased						100.00%
Purchase price of shares repurchased						$ 3,000,000
Avenue Therapeutics, Inc [Member] \| Pre-Funded Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of warrants \| $ / shares			0.0001			$ 0.0001
Unit Price Per Share \| $ / shares			$ 1.5499			3.2999
Avenue Therapeutics, Inc [Member] \| Common Stock and Pre-funded Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit Price Per Share \| $ / shares						$ 3.30
Number of warrants (in units)						1
Urica \| Convertible Class B Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares															135,494
Stock offering, price per share \| $ / shares											$ 25.00				$ 25.00
Stock offering, gross proceeds															$ 3,400,000
Stock offering, aggregate fees paid															$ 500,000
Preferred Stock, dividend rate percentage															8.00%
Runway Note [Member] \| Mustang
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Debt instrument face amount																			$ 75,000,000.0
At the Market Offering [Member] \| MLV & Co. and FBR Capital Markets & Co [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares																1,600,000	3,500,000
At the Market Offering [Member] \| Common Stock [Member] \| Cantor Fitzgerald & Co., Oppenheimer & Co., Inc., H.C. Wainwright & Co. Inc., Jones Trading Institutional Services LLC. B. Riley and Dawson James Securities, Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, price per share \| $ / shares														$ 0.75		$ 0.75	$ 1.63
Stock offering, gross proceeds																$ 1,200,000	$ 5,700,000
At the Market Offering [Member] \| Checkpoint \| Common Stock [Member] \| Founders Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares																159,620
Share Price \| $ / shares														$ 3.50		$ 3.50
Shares issued (in percent)																2.50%
At the Market Offering [Member] \| Mustang \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares																0	500,000
Stock offering, price per share \| $ / shares																	$ 13.10
Stock offering, gross proceeds																	$ 5,900,000
Stock offering, aggregate fees paid																$ 1,200,000
At the Market Offering [Member] \| Mustang \| Common Stock [Member] \| Founders Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares																	11,906
Stock offering, price per share \| $ / shares																	$ 26.67
Number of Shares issuable for At-the-Market offering \| shares																	2,777
Shelf Registration Statement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount available for future stock offerings														$ 108,300,000		108,300,000
Shelf Registration Statement [Member] \| Checkpoint \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued \| shares										1,700,000
Shelf Registration Statement [Member] \| Mustang
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, commission rate													3.00%
Shelf Registration Statement [Member] \| Maximum \| Mustang
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement							$ 200,000,000
Shelf Registration 2020 Statement [Member] \| Checkpoint
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount available for future stock offerings														8,700,000		8,700,000
Shelf Registration 2020 Statement [Member] \| Maximum \| Checkpoint
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement												$ 100,000,000
Shelf Registration 2023 Statement [Member] \| Checkpoint
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount available for future stock offerings														120,900,000		120,900,000
Shelf Registration 2023 Statement [Member] \| Maximum \| Checkpoint
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement	$ 150,000,000
Mustang 2020 S-3 [Member] \| Mustang
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement								$ 100,000,000.0
Amount available for future stock offerings														$ 8,000,000.0		$ 8,000,000.0
Direct Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares		16,642,894
Stock offering, price per share \| $ / shares		$ 0.835
Proceeds from Issuance of Common Stock		$ 13,200,000
Percentage of company subsidiaries		3.50%
Number of new operating subsidiaries \| item		20
Threshold period of corporate development transaction		5 years
Exercisable period		10 years
Shares Exercisable Fair Market Value Number Of Shares Equivalent \| shares		1
Direct Offering [Member] \| Checkpoint
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of warrants \| $ / shares										$ 3.35
Direct Offering [Member] \| Checkpoint \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares									1,650,000	1,700,000
Stock offering, price per share \| $ / shares									$ 3.071	$ 3.60
Stock offering, gross proceeds									$ 10,000,000.0
Net proceeds									9,100,000
Placement agent fees									$ 900,000
Direct Offering [Member] \| Checkpoint \| Common Stock [Member] \| Pre-Funded Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrants to purchase shares \| shares									1,606,269
Stock offering, price per share \| $ / shares									$ 3.0709
Number of common stock warrants exercised \| shares														459,269		459,269
Direct Offering [Member] \| Checkpoint \| Common Stock [Member] \| Common Stock and Pre-funded Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Per share price of warrants \| $ / shares									$ 2.821
Direct Offering [Member] \| Checkpoint \| Common Stock [Member] \| Series A Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrants to purchase shares \| shares									3,256,269
Warrant expiration term									5 years
Direct Offering [Member] \| Checkpoint \| Common Stock [Member] \| Series B Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of warrants to purchase shares \| shares									3,256,269
Warrant expiration term									18 months
Concurrent Private Placement [Member] \| Checkpoint \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, gross proceeds										$ 6,100,000
Net proceeds										5,500,000
Placement agent fees										$ 600,000
Concurrent Private Placement [Member] \| Checkpoint \| Common Stock [Member] \| Series A Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares										1,700,000
Concurrent Private Placement [Member] \| Checkpoint \| Common Stock [Member] \| Series B Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued \| shares										1,700,000