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

Sponsored Research and Clinical Trial Agreements - Summary of Mustang expense related to its sponsored research agreements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Total Research and Development - Licenses Acquired	$ 250	$ 450
Mustang [Member]
Total Research and Development - Licenses Acquired	250	450
Research and clinical trial agreements [Member] \| Mustang [Member]
Total Research and Development - Licenses Acquired	1,349	1,595
Research and clinical trial agreements [Member] \| Mustang [Member] \| City of Hope (COH) [Member]
Total Research and Development - Licenses Acquired	500	500
Research and clinical trial agreements [Member] \| Mustang [Member] \| COH - CD123 (MB-102) [Member]
Total Research and Development - Licenses Acquired	230	303
Research and clinical trial agreements [Member] \| Mustang [Member] \| COH - IL13Ra2 (MB-101) [Member]
Total Research and Development - Licenses Acquired	92	342
Research and clinical trial agreements [Member] \| Mustang [Member] \| City of Hope - Manufacturing [Member]
Total Research and Development - Licenses Acquired		114
Research and clinical trial agreements [Member] \| Mustang [Member] \| Fred Hutch-CD20 (MB-106) [Member]
Total Research and Development - Licenses Acquired	$ 527	267
Research and clinical trial agreements [Member] \| Mustang [Member] \| Beth Israel Deaconess Medical Center - CRISPR (multiple programs)[Member]
Total Research and Development - Licenses Acquired		$ 69