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

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	Dec. 30, 2022	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sale of stock, net proceeds	$ 150,000
Stock offering, number of shares issued	4,900,000
Common stock warrant liabilities		$ 689	$ 886
Sale of National Holding's stock, proceeds received	$ 150,000
Placement Agent Warrants \| Checkpoint Common Stock Warrants \| December 2022 Offering
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liabilities		100
Contingent Payment Warrants \| Urica
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liabilities		$ 200	$ 200