Fortress Biotech, Inc. Annual report pursuant to Section 13 and 15(d)

Non-Controlling Interests - Summary Of Non-controlling Interests in Consolidated Entities (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
NCI equity share					$ 32,882
Net loss attributed to non-controlling interests	$ 3,039	$ 1,694	$ 243	$ 479	(5,455)	$ 0	$ 0
Non-controlling in interests consolidated entities	27,427				27,427	$ 0
Avenue [Member]
Noncontrolling Interest [Line Items]
NCI equity share					6
Net loss attributed to non-controlling interests					(567)
Non-controlling in interests consolidated entities	(561)				(561)
Coronado SO Co, Inc [Member]
Noncontrolling Interest [Line Items]
NCI equity share					23
Net loss attributed to non-controlling interests					(240)
Non-controlling in interests consolidated entities	(217)				(217)
Mustang Therapeutics, Inc [Member]
Noncontrolling Interest [Line Items]
NCI equity share					14
Net loss attributed to non-controlling interests					(373)
Non-controlling in interests consolidated entities	(359)				(359)
Checkpoint Therapeutics, Inc [Member]
Noncontrolling Interest [Line Items]
NCI equity share					32,760
Net loss attributed to non-controlling interests					(3,855)
Non-controlling in interests consolidated entities	28,905				28,905
JMC [Member]
Noncontrolling Interest [Line Items]
NCI equity share					79
Net loss attributed to non-controlling interests					(420)
Non-controlling in interests consolidated entities	$ (341)				$ (341)