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

Sponsored Research and Clinical Trial Agreements - Summary of Aevitas expense related to its sponsored research agreements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Total licenses acquired expense	$ 700	$ 3,706	$ 1,350	$ 3,804
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member]
Total licenses acquired expense	272	438	772	814
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member] \| UMass - AAV [Member]
Total licenses acquired expense		188		564
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member] \| UPenn - AAV [Member]
Total licenses acquired expense	255	$ 250	755	$ 250
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member] \| Duke - AAV [Member]
Total licenses acquired expense	$ 17		$ 17