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

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended			90 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Apr. 30, 2013 Lease Agreements [Member] sqft	Jul. 31, 2012 Lease Agreements [Member] sqft	Dec. 31, 2013 Lease Agreements [Member]	Dec. 31, 2012 Lease Agreements [Member] sqft
Operating Leased Assets [Line Items]
Land Subject to Ground Leases					1,500	3,200		8,700
Operating Leases, Rent Expense					$ 122,000	$ 94,000		$ 118,000
Operating Leases, Rent Expense, Net, Total	284,000	93,000	165,000	641,000	366,000	470,000		590,000
Contracted Build Out Costs Associated With Lease							$ 373,000