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

Licenses Acquired - license as recorded in the Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Research And Development In Process	$ 1	$ 1,800	$ 98	$ 3,094
Checkpoint Therapeutics, Inc [Member]
Research And Development In Process	0	0	0	400
Checkpoint Therapeutics, Inc [Member] \| Jubliant Biosys License CK-103 [Member]
Research And Development In Process	0	0	0	400
Mustang Therapeutics, Inc [Member]
Research And Development In Process	0	1,500	75	2,075
Mustang Therapeutics, Inc [Member] \| City of Hope (COH) IL-13 License [Member]
Research And Development In Process	0	0	0	250
Mustang Therapeutics, Inc [Member] \| COH IV/ICV License [Member]
Research And Development In Process	0	0	0	125
Mustang Therapeutics, Inc [Member] \| COH HER2 License [Member]
Research And Development In Process	0	600	0	600
Mustang Therapeutics, Inc [Member] \| COH CS-1 License [Member]
Research And Development In Process	0	600	0	600
Mustang Therapeutics, Inc [Member] \| COH License for PSCA [Member]
Research And Development In Process	0	300	0	500
Mustang Therapeutics, Inc [Member] \| Manufacturing License [Member]
Research And Development In Process	$ 0	$ 0	$ 75	$ 0