Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Details)

v3.19.3
Stockholders' Equity - Additional Information (Details) - USD ($)
 1 Months Ended 3 Months Ended 9 Months Ended
Apr. 30, 2019
Jul. 13, 2018
Apr. 05, 2018
Apr. 30, 2019
Nov. 30, 2017
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2019
Aug. 06, 2019
Mar. 29, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Stock-based compensation           $ 3,741,000 $ 4,106,000 $ 10,423,000 $ 12,053,000        
Proceeds From Issuance Of Preferred Stock, At The Market Offering               $ 539,000          
Class of Warrant or Right, Exercise Price of Warrants or Rights                       $ 3.47  
Common Stock, Shares, Issued           70,335,534   70,335,534         57,845,447
Common Stock, Par or Stated Value Per Share           $ 0.001   $ 0.001         $ 0.001
Adjustments To Additional Paid In Capital At Market Offering Costs             (99,000)   (240,000)        
Research and Development Expense [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Stock-based compensation           $ 1,200,000 1,800,000 $ 2,600,000 4,900,000        
General and Administrative Expense [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Stock-based compensation           2,500,000 $ 2,300,000 7,800,000 $ 7,100,000        
Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Proceeds from issuance of Common stock               22,500,000          
Proceeds From Issuance Of Common Stock Net of Issuance Costs           $ 22,000,000   $ 22,000,000          
Common Stock, Shares, Issued           3,500,000   3,500,000          
Common Stock, Par or Stated Value Per Share           $ 6.42   $ 6.42          
Adjustments To Additional Paid In Capital At Market Offering Costs           $ 500,000   $ 500,000          
Common Stock [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Common Stock issued in connection with the first ESPP offering               54,221 43,707        
Issuance of Common Stock for At the Market Offering in shares           1,213,643 1,537,921 8,604,469 2,668,756        
Common Stock [Member] | Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Payments for Commissions               $ 16,000          
Common Stock [Member] | Market Offering 2016 [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Average Price Per Share           $ 1.48   $ 1.88          
Proceeds From Issuance Of Preferred Stock, At The Market Offering           $ 900,000   $ 15,100,000          
Common Stock Shares Available For Future Issuance Value                   $ 5,100,000      
Issuance of Common Stock for At the Market Offering in shares           600,000   8.0          
Payments for Commissions               $ 300,000          
Common Stock [Member] | 2019 At The Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Average Price Per Share           $ 1.79   $ 1.79          
Proceeds from issuance of Common stock           $ 1,000,000   $ 1,000,000          
Issuance of Common Stock for At the Market Offering in shares           600,000   600,000          
Agents Commission, Percentage           3.00%   3.00%          
Payments for Commissions               $ 32,000          
Preferred Stock [Member] | Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Average Price Per Share           $ 20.66   $ 20.66          
Preferred Stock [Member] | 2018 Preferred ATM                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Issuance Of Preferred Stock For At Market Offering, In Shares           26,000   26,000          
Proceeds From Issuance Of Preferred Stock, At The Market Offering           $ 500,000   $ 500,000          
Preferred Stock, Dividend Rate, Percentage     9.375%                    
Preferred Stock Shares Available For Future Issuance Value           5,100,000   $ 5,100,000          
Agents Commission, Percentage               7.00%          
Preferred Stock [Member] | 2019 At The Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Preferred Stock Shares Available For Future Issuance Value           48,900,000   $ 48,900,000          
Mustang Bio, Inc [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Common Stock Shares Available For Future Issuance Value           $ 20,900,000   $ 20,900,000          
Marketable Securities   $ 75,000,000                      
Percentage of Placement of Agent Fee   3.00%                      
Maximum Authorized Amount Of Shares To Be Sold                     $ 75,000,000    
Mustang Bio, Inc [Member] | Over-Allotment Option [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Proceeds from issuance of Common stock $ 31,600,000                        
Payments of Stock Issuance Costs       $ 2,100,000                  
Proceeds From Issuance Of Common Stock Net of Issuance Costs       $ 29,500,000                  
Stock Issued During Period, Shares, New Issues 6,875,000                        
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 1,031,250     1,031,250                  
Class of Warrant or Right, Exercise Price of Warrants or Rights $ 4.00     $ 4.00                  
Checkpoint [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Shares Issued, Price Per Share           $ 3.00   $ 3.00          
Average Price Per Share             $ 4.33 $ 3.54 $ 4.33        
Proceeds from issuance of Common stock           $ 3,400,000 $ 8,000,000 $ 7,900,000 $ 8,000,000        
Proceeds From Issuance Of Common Stock Net of Issuance Costs                 $ 7,700,000        
Stock Issued During Period, Shares, New Issues           1,100,000 1,841,774 2,200,000 1,841,774        
Percentage of Placement of Agent Fee         3.00%                
Maximum Authorized Amount Of Shares To Be Sold         $ 100,000,000 $ 61,100,000   $ 61,100,000          
Checkpoint [Member] | Market Offering [Member]                          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                          
Stock Issued During Period, Shares, New Issues           28,555   55,750          
Stock Issued During Period, Value, New Issues             $ 178,292   $ 178,292        
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               5 years          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options           $ 12,700,000   $ 12,700,000          
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               2 years          
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options           $ 1,800,000   $ 1,800,000          
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%   85.00%          
Common Stock issued in connection with the first ESPP offering               410,728          
Common Stock, Capital Shares Reserved for Future Issuance           589,272   589,272          
Stock-based compensation           $ 18,000 $ 52,000 $ 100,000 $ 100,000