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

Warrants to Purchase Common Stock - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Warrants To Purchase Common Stock [Line Items]
Proceeds From Issuance Of Common Stock	$ 4,117,000	$ 92,399,000	$ 28,855,000
Non Employee Warrants [Member]
Warrants To Purchase Common Stock [Line Items]
Stock Issued During Period Shares warrants Exercised		78,710
Cashless Exercise Of Warrants		153,415
Investment Warrants, Exercise Price		$ 5.00
Common Stock [Member]
Warrants To Purchase Common Stock [Line Items]
Stock Issued During Period Shares New Issues			5,750,000
Common Stock [Member] \| Warrants to Purchase Series C Shares [Member]
Warrants To Purchase Common Stock [Line Items]
Stock Issued During Period Shares warrants Exercised		78,636
Cashless Exercise Of Warrants		328,510
Investment Warrants, Exercise Price		$ 5.45
Stock Issued During Period Shares New Issues		340
Proceeds From Issuance Of Common Stock		$ 1,098
Class of Warrant or Right, Outstanding	711,895