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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	13,644,367	10,154,952	13,767,873	9,757,654
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	392,731	685,061	480,559	685,061
Opus warrants to purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	1,700,000	0	1,700,000	0
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	1,761,032	1,832,499	1,769,426	2,019,219
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	8,705,136	6,884,631	8,763,797	6,795,132
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total of weighted average shares outstanding	1,085,468	752,761	1,054,091	258,242