Annual report pursuant to Section 13 and 15(d)

Property and Equipment - Components of Property and Equipment (Detail)

v3.8.0.1
Property and Equipment - Components of Property and Equipment (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2016
Sep. 30, 2016
Property, Plant and Equipment [Line Items]        
Total property and equipment   $ 2,872   $ 1,200
Less: Accumulated depreciation   (475)   (36)
Property and equipment, net $ 9,513 2,397 $ 7,376 1,164
Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment 8,287   6,657  
Less: Accumulated depreciation (1,171)   (445)  
Property and equipment, net 7,116   6,212  
Computer Equipment [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 543   440  
Useful Life (Years) 3 years      
Furniture and Fixtures [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment   284   65
Useful Life (Years) 5 years      
Furniture and Fixtures [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 1,009   821  
Useful Life (Years) 5 years      
Leasehold Improvements [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment   $ 1,006   $ 259
Leasehold Improvements [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 5,351   5,396  
Leasehold Improvements [Member] | Fortress Biotech Inc [Member] | Maximum [Member]        
Property, Plant and Equipment [Line Items]        
Useful Life (Years) 15 years      
Leasehold Improvements [Member] | Fortress Biotech Inc [Member] | Minimum [Member]        
Property, Plant and Equipment [Line Items]        
Useful Life (Years) 5 years      
Construction in progress [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment [1] $ 1,241   0  
Machinery and Equipment [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 143   $ 0  
Useful Life (Years) 5 years      
[1] For build-out of Mustang’s cell processing facility in Worcester, MA. The total cost of the construction for the Worcester facility is expected to be $3.5 million. The cost of the equipment for the facility is expected to be $2.5 million