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

Sponsored Research and Clinical Trial Agreements - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	May 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Research and Development Expense (Excluding Acquired in Process Cost)			$ 15,703	$ 18,511	$ 30,570	$ 41,784
Aevitas [Member]
Cost of the SRA			0	0	300	500
Cellvation [Member]
Research and Development Expense (Excluding Acquired in Process Cost)			0	$ 0	100	$ 100
Mustang Bio, Inc [Member]
Maximum cost associated with COH	$ 2,400
Payments for research and development expenses					800
Oncogenuity [Member]
Cost of the SRA					100		$ 0
Funding commitment period		5 years
Payments for research and development expenses			$ 400		$ 400
Oncogenuity [Member] \| Maximum [Member]
Sponsor research agreement funding commitment		$ 4,800