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

Fair Value Measurements - Derivative Contingently Issuable Warrant liabilities (Detail)

Fair Value Measurements - Derivative Contingently Issuable Warrant liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Additions	$ 19,089	$ 289
Avenue [Member] \| Contingently Issuable Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value at the beginning of period:	114
Additions	0
Change in fair value	188
Fair value at end of period:	302	114
Mustang [Member] \| Contingently Issuable Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value at the beginning of period:	0
Additions	634
Change in fair value	159
Issuance of Warrants	(793)
Fair value at end of period:	0	0
Mustang [Member] \| Warrant [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value at the beginning of period:	0
Additions	12
Change in fair value	0
Fair value at end of period:	12	0
Checkpoint [Member] \| Contingently Issuable Warrants [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value at the beginning of period:	0	0
Additions		175
Change in fair value		438
Issuance of Warrants		(613)
Fair value at end of period:		0
Helocyte [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value at the beginning of period:	0
Additions	428
Change in fair value	(261)
Fair value at end of period:	$ 167	$ 0