Quarterly report pursuant to Section 13 or 15(d)

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

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Property and Equipment - Components of Property and Equipment (Detail) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Property, Plant and Equipment [Line Items]        
Total property and equipment   $ 2,922   $ 2,872
Less: accumulated depreciation   (803)   (475)
Property and equipment, net $ 14,163 2,119 $ 9,513 2,397
Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment 13,718   8,287  
Less: accumulated depreciation (1,674)   (1,171)  
Property and equipment, net 12,044   7,116  
Computer equipment [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 648   543  
Useful Life (Years) 3 years      
Furniture and fixtures [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment   291   284
Useful Life (Years) 5 years      
Furniture and fixtures [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 1,128   1,009  
Useful Life (Years) 5 years      
Machinery and equipment [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 1,897   143  
Useful Life (Years) 5 years      
Leasehold improvements [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment   $ 1,011   $ 1,006
Leasehold improvements [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment $ 9,181   5,351  
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 process [Member] | Fortress Biotech Inc [Member]        
Property, Plant and Equipment [Line Items]        
Total property and equipment [1] $ 864   $ 1,241  
[1] Relates to the Mustang cell processing facility