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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Total licenses acquired expense	$ 200	$ 1	$ 650	$ 98
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member]
Total licenses acquired expense	250	300	500	400
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member] \| UMass - AAV [Member]
Total licenses acquired expense		$ 300		$ 400
Research and clinical trial agreements [Member] \| Aevitas Therapeutics Inc [Member] \| UPenn - AAV [Member]
Total licenses acquired expense	$ 250		$ 500