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

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

Stockholders' Equity (Capital Raises) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended		9 Months Ended
	Mar. 04, 2022	Apr. 23, 2021	Oct. 23, 2020	Mar. 31, 2021	Nov. 30, 2020	Sep. 30, 2022	Sep. 30, 2021
Journey [Member] \| 8% Cumulative Convertible Class A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued							758,680
Stock offering, price per share							$ 25.00
Stock offering, gross proceeds							$ 19.0
Sale of stock, net proceeds							17.0
Preferred Stock, dividend rate percentage				8.00%
Stock offering other fees paid							0.1
Placement agent fees							$ 1.9
Maximum [Member] \| Journey [Member] \| 8% Cumulative Convertible Class A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement				$ 12.5
Minimum [Member] \| Journey [Member] \| 8% Cumulative Convertible Class A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement				$ 30.0
Runway Note [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of notes	$ 30.0
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						3,700,000	800,000
Stock offering, price per share						$ 1.59
Stock offering, gross proceeds						$ 5.9
Amount available for future stock offerings						$ 11.5
At the Market Offering [Member] \| Checkpoint [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued						5,157,914,000,000	10,900,000
Stock offering, price per share						$ 1.93	$ 3.42
Stock offering, gross proceeds						$ 9.9	$ 37.2
At the Market Offering [Member] \| Checkpoint [Member] \| Common Stock [Member] \| Founders Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued						128,931	271,515
Shares issued (in percent)						2.50%
At the Market Offering [Member] \| Mustang [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued						7,900,000	17,300,000
Stock offering, price per share						$ 0.84	$ 3.87
Stock offering, gross proceeds						$ 6.6	$ 66.9
At the Market Offering [Member] \| Mustang [Member] \| Common Stock [Member] \| Founders Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, number of shares issued						241,260	517,304
Stock offering, price per share						$ 1.16	$ 3.84
Number of Shares issuable for At-the-Market offering						6,987
Shares issued (in percent)						2.50%
Shelf Registration Statement [Member] \| Checkpoint [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount available for future stock offerings						$ 44.7
Shelf Registration Statement [Member] \| Mustang [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount available for future stock offerings						200.0
Shelf Registration Statement [Member] \| Maximum [Member] \| Checkpoint [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement					$ 100.0
Shelf Registration Statement [Member] \| Maximum [Member] \| Mustang [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement		$ 200.0
Mustang 2020 S-3 [Member] \| Mustang [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock offering, aggregate offering permitted by the agreement			$ 100.0
Amount available for future stock offerings						$ 8.0