Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Details)

v3.20.1
Stockholders' Equity - Additional Information (Details) - USD ($)
 3 Months Ended 12 Months Ended
Feb. 14, 2020
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Mar. 23, 2020
Jul. 13, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation   $ 3,400,000 $ 3,309,000      
Payments of Stock Issuance Costs   $ 1,213,000 0      
Common Stock, Shares, Issued   78,572,169   74,027,425    
Common Stock, Par or Stated Value Per Share   $ 0.001   $ 0.001    
Common Stock Shares Available For Future Issuance Value   $ 17,900,000        
Underwriting discounts and commissions and offering expenses   $ 1,213,000 0      
Stock Repurchase Program, Authorized Amount         $ 5.00  
Preferred shares repurchased and held in treasury   5,000        
Preferred shares repurchased and held in treasury   $ 70,000        
Consideration for repurchase of preferred shares   70,000 0      
Fees incurred for repurchase of preferred shares   2,000 0      
Research and Development Expense [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation   900,000 600,000      
General and Administrative Expense [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation   $ 2,500,000 $ 2,700,000      
Common Stock [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Issuance of Common Stock for At the Market Offering in shares   2,341,000 2,927,427      
Common Stock [Member] | Market Offering [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Average Price Per Share   $ 2.59        
Proceeds From Issuance Of Preferred Stock, At The Market Offering   $ 6,100,000        
Payments of Stock Issuance Costs $ 1,300,000          
Common Stock Shares Available For Future Issuance Value   $ 17,900,000        
Issuance of Common Stock for At the Market Offering in shares   2,300,000        
Payments for Commissions   $ 200,000        
Underwriting discounts and commissions and offering expenses $ 1,300,000          
Preferred Stock [Member] | Market Offering [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Average Price Per Share $ 20.00          
Preferred Stock [Member] | 2018 Preferred ATM            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Gross proceeds $ 14,400,000          
Preferred Stock [Member] | IPO [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Issuance Of Preferred Stock For Public Offering 625,000          
Preferred Stock, Dividend Rate, Percentage 9.375%          
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 93,750          
Mustang Bio, Inc [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Share Price   $ 4.00        
Stock Issued During Period, Shares, New Issues   31,220        
Common Stock Shares Available For Future Issuance Value   $ 15,900,000        
Marketable Securities           $ 75,000,000
Mustang Bio, Inc [Member] | Common Stock [Member] | Market Offering [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Average Price Per Share   $ 3.93        
Proceeds from issuance of Common stock   $ 5,000,000        
Proceeds From Issuance Of Common Stock Net of Issuance Costs   $ 4,900,000        
Issuance of Common Stock for At the Market Offering in shares   1,200,000        
Agents Commission, Percentage   3.00%        
Restricted Stock [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition   4 years 2 months 12 days   4 years 2 months 12 days    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options   $ 17,900,000   $ 17,900,000    
Restricted Stock Units (RSUs) [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition   5 years 4 months 24 days   5 years 4 months 24 days    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options   $ 14,800,000   $ 14,800,000    
Restricted Stock Units (RSUs) [Member] | Mustang Bio, Inc [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Adjustments To Additional Paid In Capital At Market Offering Costs   $ 100,000        
Options to Purchase Common Stock [Member] | Employee Stock [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Employee Stock Purchase Plan to eligible employees, Reckoning fair value percentage during offering period   85.00%        
Common Stock issued in connection with the first ESPP offering   454,515        
Common Stock, Capital Shares Reserved for Future Issuance   545,485        
Stock-based compensation   $ 18,000 $ 20,000