Fortress Biotech, Inc. Annual report pursuant to Section 13 and 15(d)

Licenses Acquired (Journey and Other - Narrative) (Details)

Licenses Acquired (Journey and Other - Narrative) (Details) $ / shares in Units, $ in Thousands					12 Months Ended
	Nov. 16, 2021 D $ / shares shares	Sep. 29, 2021 USD ($)	Jun. 29, 2021 USD ($)	Jun. 29, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired					$ 15,625	$ 2,834
Licensing Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired					15,625	2,834
Journey [Member] \| Dr. Reddy's Laboratories, Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones				$ 4,000
Journey [Member] \| Dr. Reddy's Laboratories, Ltd [Member] \| Achievement of Certain Sales Milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones				$ 17,000
Journey [Member] \| Licensing Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development - licenses acquired					13,819	$ 0
Journey [Member] \| Licensing Agreements [Member] \| Dr. Reddy's Laboratories, Ltd [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees payment			$ 10,000
Payments of milestones		$ 8,000	2,000
Maintenance fees			24,000
Shares issued, price per share \| $ / shares	$ 9.1721
Stock Issued During Period, Shares, New Issues \| shares	545,131
Number of trading days for calculating volume weighted average price per share \| D	15
Journey [Member] \| Licensing Agreements [Member] \| Dr. Reddy's Laboratories, Ltd [Member] \| Contingent Payment Warrant [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Warrants, fair value					$ 3,800
Journey [Member] \| Licensing Agreements [Member] \| Dr. Reddy's Laboratories, Ltd [Member] \| Achievement of Certain Clinical Development, Regulatory and First Commercial Sale milestones [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments of milestones			$ 163,000
Journey [Member] \| Licensing Agreements [Member] \| Minimum [Member] \| Dr. Reddy's Laboratories, Ltd [Member] \| Payable on Net Sales of the DFD-29 Product [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Sales royalties (as a percent)			10.00%
Journey [Member] \| Licensing Agreements [Member] \| Maximum [Member] \| Dr. Reddy's Laboratories, Ltd [Member] \| Payable on Net Sales of the DFD-29 Product [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Sales royalties (as a percent)			15.00%