Quarterly report pursuant to Section 13 or 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
 3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Property, Plant and Equipment [Line Items]      
Total property and equipment   $ 2,917 $ 2,872
Less: accumulated depreciation   (644) (475)
Property and equipment, net $ 12,278 9,513 2,397
Fortress Biotech Inc [Member]      
Property, Plant and Equipment [Line Items]      
Total property and equipment 11,372 8,287  
Less: accumulated depreciation (1,367) (1,171)  
Property and equipment, net 10,005 7,116  
Computer equipment [Member] | Fortress Biotech Inc [Member]      
Property, Plant and Equipment [Line Items]      
Total property and equipment $ 594 543  
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 $ 1,015 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 $ 143 143  
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 $ 5,383 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] $ 4,237 $ 1,241  
[1] Relates to the Mustang cell processing facility