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

Net Loss Per Common Share - Computations of Diluted Weighted Average Shares Outstanding (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	10,154,952	9,164,131	9,757,654	8,889,050
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	685,061	685,061	685,061	696,526
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	1,832,499	2,171,032	2,019,219	2,312,461
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	6,884,631	6,308,038	6,795,132	5,880,063
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	752,761	0	258,242	0