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
	Mar. 31, 2018	Mar. 31, 2017
Research And Development In Process	$ 97	$ 1,294
Checkpoint Therapeutics, Inc [Member]
Research And Development In Process	0	400
Checkpoint Therapeutics, Inc [Member] \| Jubliant Biosys License CK-103 [Member]
Research And Development In Process	0	400
Mustang Therapeutics, Inc [Member]
Research And Development In Process	75	575
Mustang Therapeutics, Inc [Member] \| City of Hope (COH) IL-13 License [Member]
Research And Development In Process	0	250
Mustang Therapeutics, Inc [Member] \| COH IV/ICV Agreement [Member]
Research And Development In Process	0	125
Mustang Therapeutics, Inc [Member] \| University of California License for PSCA [Member]
Research And Development In Process	0	200
Mustang Therapeutics, Inc [Member] \| Manufacturing License [Member]
Research And Development In Process	$ 75	$ 0