Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Details)

v3.20.2
Stockholders' Equity - Additional Information (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 11, 2020
May 29, 2020
Feb. 14, 2020
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Jun. 29, 2020
May 31, 2020
Mar. 23, 2020
Dec. 31, 2019
Aug. 16, 2019
Jun. 17, 2019
Jun. 16, 2019
Jul. 13, 2018
Nov. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Stock-based compensation expense       $ 3,748,000 $ 3,373,000 $ 7,148,000 $ 6,682,000                  
Payments of Stock Issuance Costs           $ 2,283,000                    
Common Stock, Shares, Issued       86,113,331   86,113,331         74,027,425   150,000,000 50,000,000    
Common Stock, Par or Stated Value Per Share       $ 0.001   $ 0.001         $ 0.001   $ 0.001      
Underwriting discounts and commissions and offering expenses           $ 2,283,000                    
Stock Repurchase Program, Authorized Amount                 $ 5,000,000.0 $ 5,000,000.0            
Preferred shares repurchased and held in treasury       5,000   5,000                    
Consideration for repurchase of preferred shares           $ 70,000                    
Fees incurred for repurchase of preferred shares           $ 2,000                    
Stock Incentive Plan 2013 [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Common Stock, Shares, Issued       13,000,000.0   13,000,000.0   3,000,000.0                
Common Stock, Remaining Number of Shares           4,700,000                    
Research and Development Expense [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Stock-based compensation expense       $ 900,000 800,000 $ 1,800,000 1,400,000                  
General and Administrative Expense [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Stock-based compensation expense       $ 2,900,000 $ 2,600,000 $ 5,400,000 $ 5,300,000                  
Maximum [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Capital Units, Authorized       150,000,000   150,000,000                    
Minimum [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Capital Units, Authorized       50,000,000   50,000,000                    
2020 Shelf                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Common Stock Shares Available For Future Issuance Value       $ 64,400,000   $ 64,400,000                    
Common Stock                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Common Stock issued in connection with the first ESPP offering       53,268,000 54,221,000 53,268,000 54,221,000                  
Issuance of Common Stock for At the Market Offering in shares       6,973,020,000 4,463,399,000 9,314,020,000 7,390,826                  
Common Stock | Market Offering [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Average Price Per Share           $ 2.47                    
Proceeds From Issuance Of Preferred Stock, At The Market Offering           $ 23,000,000.0                    
Payments of Stock Issuance Costs   $ 1,100,000 $ 1,300,000                          
Issuance of Common Stock for At the Market Offering in shares           9,300,000                    
Payments for Commissions           $ 700,000                    
Underwriting discounts and commissions and offering expenses   $ 1,100,000 $ 1,300,000                          
Preferred Stock [Member] | Market Offering [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Average Price Per Share   $ 18.00 $ 20.00                          
Preferred Stock [Member] | 2018 Preferred ATM                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Gross proceeds   $ 11,500,000 $ 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   555,556 625,000                          
Preferred Stock, Dividend Rate, Percentage   9.375%                            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights   83,333 93,750                          
Mustang Bio, Inc [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Share Price       $ 3.76 $ 6.42 $ 3.76 $ 6.42                  
Common Stock Shares Available For Future Issuance Value       $ 50,600,000   $ 50,600,000                    
Marketable Securities                       $ 75,000,000.0     $ 75,000,000.0  
Mustang Bio, Inc [Member] | Common Stock | Market Offering [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Average Price Per Share           $ 3.76 $ 6.42                  
Proceeds from issuance of Common stock           $ 8,000,000.0 $ 22,500,000                  
Proceeds From Issuance Of Common Stock Net of Issuance Costs           $ 7,900,000 $ 22,000,000.0                  
Issuance of Common Stock for At the Market Offering in shares           2,100,000 3,500,000                  
Agents Commission, Percentage           3.00%                    
Mustang Bio, Inc [Member] | Common Stock | Market Offering [Member] | Founders Agreement                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Issuance of Common Stock for At the Market Offering in shares           53,390 87,656                  
Mustang Bio, Inc [Member] | Common Stock | Underwritten Offering | Founders Agreement                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Shares Issued, Price Per Share $ 3.25                              
Proceeds from issuance of Common stock $ 37,200,000                              
Payments of Stock Issuance Costs $ 2,300,000                              
Stock Issued During Period, Shares, New Issues 11,455,604                              
Underwriting discounts and commissions and offering expenses $ 2,300,000                              
Checkpoint [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Common Stock, Capital Shares Reserved for Future Issuance       38,800,000   38,800,000                    
Marketable Securities                               $ 100,000,000
Checkpoint [Member] | Common Stock | Market Offering [Member]                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Average Price Per Share           $ 2.05                    
Proceeds from issuance of Common stock           $ 2,700,000                    
Proceeds From Issuance Of Common Stock Net of Issuance Costs           $ 2,600,000                    
Stock Issued During Period, Shares, New Issues           1,303,282                    
Agents Commission, Percentage           3.00%                    
Checkpoint [Member] | Common Stock | Market Offering [Member] | Founders Agreement                                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Weighted average price per share           $ 2.01                    
Stock Issued During Period, Shares, New Issues           32,571                    
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                    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options       $ 17,100,000   $ 17,100,000                    
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 2 months 12 days                  
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options         $ 13,600,000   $ 13,600,000                  
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           $ 100,000 500,000                  
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           507,783                    
Common Stock, Capital Shares Reserved for Future Issuance       492,217   492,217                    
Stock-based compensation expense       $ 25,000 $ 19,000 $ 43,000 $ 39,000