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

Income Taxes (Narrative) (Details) $ in Millions	9 Months Ended
Income Taxes (Narrative) (Details) $ in Millions	Sep. 30, 2021 USD ($)
Income Tax Disclosure [Line Items]
Minimum ownership interest in subsidiaries for consolidated income tax return	80.00%
Scenario, Forecast [Member]
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 0

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.